Road Safety 

Fundamentals

Concepts, Strategies, and Practices that 

Reduce Fatalities and Injuries on the Road
Notice

This document is disseminated under the sponsorship of the U.S. Department of Transportation 

(USDOT) in the interest of information exchange. The U.S. Government assumes no liability for the use 

of the information contained in this document. 

The U.S. Government does not endorse products or manufacturers. Trademarks or manufacturers’ names 

appear in this report only because they are considered essential to the objective of the document. 

Quality Assurance Statement

The Federal Highway Administration (FHWA) provides high-quality information to serve Government, 

industry, and the public in a manner that promotes public understanding. Standards and policies are 

used to ensure and maximize the quality, objectivity, utility, and integrity of its information. FHWA 

periodically reviews quality issues and adjusts its programs and processes to ensure continuous quality 

improvement.

This document can be downloaded for free in full or by individual unit at: 

https://rspcb.safety.fhwa.dot.gov/rsf/
1. Report No.

FHWA-SA-18-003

4. Title and Subtitle

Road Safety Fundamentals:

Concepts, Strategies, and Practices that Reduce Fatalities and Injuries

on the Road

7. Author(s)

Lead Editor: Daniel Carter, P.E., Senior Research Associate

Unit Authors: 

Unit 1: Dan Gelinne, Program Coordinator, UNC Highway Safety 

Research Center 

Unit 2: Bevan Kirley, Research Associate, UNC Highway Safety Research 

Center 

Unit 3: Carl Sundstrom, P.E., Research Associate, UNC Highway Safety 

Research Center 

Unit 4: Raghavan Srinivasan, Ph.D., Senior Transportation Research 

Engineer; Daniel Carter 

Unit 5: Daniel Carter; Jennifer Palcher-Silliman, Communications 

Manager, UNC Highway Safety Research Center

Layout and Graphics: Graham Russell, Graphic Designer, UNC Highway 

Safety Research Center

Technical Editors: Jennifer Palcher-Silliman; Patty Harrison, 

Communications Specialist, UNC Highway Safety Research Center; 

Caroline Mozingo, Senior Manager of Communications, Education and 

Outreach, UNC Highway Safety Research Center

9. Performing Organization Name

and Address

University of North Carolina,

Highway Safety Research Center

12. Sponsoring Agency Name and Address

Federal Highway Administration Office of Safety

1200 New Jersey Ave., SE

Washington, DC 20590

14. Sponsoring Agency Code

15. Supplementary Notes

The project manager for the textbook was Felix H. Delgado, P.E., FHWA Office of Safety

16. Abstract

This book provides an introduction to the fundamental concepts of road safety. The book’s goal is to equip

the reader with a broad base of knowledge about road safety. Thus, the focus is in communicating concepts

rather than providing instruction in detailed analysis procedures.

The audience for this book is two-fold. First, this is intended for those whose job addresses some aspect of 

road safety, particularly in a public agency setting. Second, this book is intended for professors and 

students in a university setting.

This book seeks to lay the foundation of road safety knowledge regardless of a particular discipline. 

Professionals with a background in engineering, planning, public health, law enforcement, and other 

disciplines will benefit from the concepts presented here.

17. Key Words

road safety, road safety management process, site-level management, system

level management, human behavior, safety performance measures, road safety

data, multidisciplinary approaches

18. Distribution Statement

No restrictions

19. Security Classif.

(of this report)

Unclassified

20. Security Classif.

(of this report)

Unclassified

21. No. of Pages

188

22. Price

FREE

5. Report Date

November 2017

6. Performing Organization Code

8. Performing Organization Report No.

10. Work No. (TRAIS)

11. Contract or Grant No.

13. Type of Report and Period Covered

Text book

2. Government Accession No. 3. Recipient’s Catalog No.

Form DOT F 1700.7 (8-72) Reproduction of completed pages authorized

UNIT 1 Foundations of Road Safety

 Chapter 1: Context of Road Safety

 Chapter 2: Road Safety Through the Years

 Chapter 3: Multidisciplinary Approaches

 Chapter 4: Road Users

UNIT 2 Human Behavior and Road Safety Chapter 5: Understanding Human Behavior

 Chapter 6: Changing Human Behavior

UNIT 3 Measuring Safety Chapter 7: Importance of Safety Data

 Chapter 8: Types of Safety Data

 Chapter 9: Improving Safety Data Quality

UNIT 4 Solving Safety Problems Chapter 10: Road Safety Management Process

 Chapter 11: Site-Level Safety Management

 Chapter 12: System-Level Safety Management

UNIT 5 Implementing Road Safety Efforts

 Chapter 13: Who Does What

 Chapter 14: Road Safety Research

 Chapter 15: Strategic Communications

 Chapter 16: Advancing Road Safety

TABLE OF CONTENTS

ROAD SAFETY FUNDAMENTALS 1
2 ROAD SAFETY FUNDAMENTALS

INTRODUCTION

This book provides an introduction to many of the fundamental concepts 

of road safety. These concepts cover areas such as the nature of road safety 

issues, human behavior in the road environment, and identifying and 

solving road safety problems. The goal of this book is to equip the reader 

with a broad base of knowledge about road safety. Thus, the focus of the 

text is in communicating concepts rather than providing instruction in 

detailed analysis procedures.

The audience for this book is two-fold. First, this is intended for those 

whose job addresses some aspect of road safety, particularly in a public 

agency setting. This is especially relevant for individuals who have been 

tasked with managing road safety but who do not have formal training in 

road safety management. In order to show practical applications of each 

road safety concept, this book contains many examples that demonstrate 

the concepts in real-world settings. Second, this book is intended for 

professors and students in a university setting who can use individual units 

or this entire book to add an emphasis on road safety as part of graduatelevel work. Each unit provides learning objectives and sample exercises to 

assist professors as they incorporate content into their courses.

As a final note, this book is intended to lay the foundation of road safety 

knowledge regardless of a particular discipline. Professionals with a 

background in engineering, planning, public health, law enforcement, and 

other disciplines will benefit from the concepts presented here.
ROAD SAFETY FUNDAMENTALS 3

ABOUT THIS BOOK

This book is divided into five units according to major topics of road safety 

knowledge. Each unit is divided into multiple chapters that address the 

primary concepts of the unit. The beginning of each unit provides a list of 

learning objectives that indicate what the reader will be able to understand, 

describe, identify, or otherwise do by the end of the unit.

Each chapter presents call-out boxes, glossary definitions, and references 

as shown below.

ROAD SAFETY FUNDAMENTALS UNIT 1: FOUNDATIONS OF ROAD SAFETY 1-13

Secretary Hoover called a second 

conference for March 1926. During 

the interim between the two 

conferences, a special committee 

drew up a model “Uniform Vehicle 

Code” covering registration and 

titling of vehicles, licensing of 

drivers, and operation of vehicles on 

the highways. The code incorporated 

the best features of the numerous 

and varied State laws then on 

the statute books. The second 

conference approved this code 

and recommended it to the State 

legislatures as the basis for uniform 

motor vehicle legislation.

Studies following this 1926 

conference concluded that 

determining the causes of crashes 

was far more difficult than they had 

presumed. The problem warranted 

a sustained program of research 

by a national organization. The 

Conference agreed, and the Highway 

Research Board (HRB) organized 

the Committee on Causes and 

Prevention of Highway Accidents 

to coordinate crash research 

nationwide. The HRB played a major 

part in subsequent efforts to reduce 

the consequences of crashes.8

Federal Government Role 

in Highway Development

The growing use of motor vehicles 

during the 1920s was mirrored 

by the expansion of the Federal 

Government’s role in funding and 

building roads. In its early form, the 

Office of Public Roads was organized 

under the U.S. Department of 

Agriculture, playing a large role in 

funding roadways within national 

parks and forests. 

Following the Federal Aid Road Act 

of 1916, this office would become 

the Bureau of Public Roads (BPR), 

charged with working cooperatively 

with State highway departments on 

road projects. Work continued on 

the expansion of highways across 

the country, and between 1921 and 

1939, the distance of paved roads 

Balanced Design for Safety

In the 1920s and 1930s, it was good 

engineering practice to design new 

highways as much as possible in long 

straight lines or “tangents.” When it 

became necessary to change direction, 

the engineer laid out a circular curve, 

the radius of which he selected to fit 

the ground with the least construction 

cost, but which could not be less than a 

certain minimum fixed by department 

policy. In practice, engineers made the 

curves sharper than this minimum when 

it was cheaper to do so, but with little 

consistency. Engineers expected motorists 

driving these roads to adjust their speeds 

to the varying radii, and on the sharper 

curves safe design speed might be 

considerably lower than the posted 

speed limit.

Increasing concern for road safety led many 

highway engineers to worry about this 

inconsistency between posted speed limits 

and safe design speed on curves. In 1935, 

highway engineer Joseph Barnett of the BPR 

proposed that all new rural roads conform to 

an “assumed design speed,” a comfortable 

top speed for drivers outside of urban areas. 

With its adoption by American Association 

of State Highway Officials in 1938, Barnett’s 

“balanced design” concept became a 

permanent feature of U.S. roadway design. 

Today, standards for designing curves, 

such as design speed, curve radius and 

superelevation (the tilt of the road through 

a curve) are provided in A Policy on 

Geometric Design of Highways and Streets, 

produced by the American Association for 

State Highway Transportation Officials.

Source: America’s 

Highways, 1776-1976: 

A History of the 

Federal-Aid Program. 

Federal Highway 

Administration 

(U.S. Government 

Printing Office, 

Washington D.C., 

1976).

8

Uniform 

Vehicle Code

A code covering 

registration and 

titling of vehicles, 

licensing of 

drivers, and 

operation of 

vehicles on 

the highways.

Call-out 

boxes are 

provided 

throughout the 

book to provide 

examples 

of concepts 

presented in 

the chapter.

Glossary 

definitions are 

provided along 

the side of the 

page. These 

correspond to 

words in bold 

face in the page 

content.

References

to source 

material are 

provided along 

the side of the 

page. These 

are numbered 

consecutively 

through the unit 

and correspond 

to numbers 

in the page 

content.

A

A

B

B

C

C
1-b UNIT 1: FOUNDATIONS OF ROAD SAFETY ROAD SAFETY FUNDAMENTALS

After reading the chapters and completing 

exercises in Unit 1, the reader will be able to:

J DESCRIBE the importance of road 

safety and how it relates to public 

health, economic, environmental 

and demographic trends

J RECOGNIZE roles and responsibilities 

of various disciplines and approaches 

to improving road safety

J DISTINGUISH between nominal 

and substantive safety

J IDENTIFY key points in the history of 

road safety in the U.S., including key 

legislation and agency formation, and 

understand how these decisions have 

shaped today’s roadways

J IDENTIFY different groups of road users 

and challenges unique to each group

LEARNING OBJECTIVES

Foundations 

of Road Safety

UNIT 1
ROAD SAFETY FUNDAMENTALS UNIT 1: FOUNDATIONS OF ROAD SAFETY 1-1

Context of Road Safety

Road safety is an important part 

of everyday life. Across the nation, 

people use roads and sidewalks to 

get to work, school, stores, and 

home. Public agencies work to 

ensure that people arrive at their 

destination without incident. 

However, not every trip is without 

incident. Deaths and injuries 

resulting from motor vehicle crashes 

represent a significant public 

health concern. The World Health 

Organization (WHO) estimates that 

motor vehicle crashes kill more than 1 

million people around the world each 

year, and seriously injure as many as 

20 to 50 million.1

 These crashes affect 

all road users, from vehicle drivers 

and passengers to pedestrians, 

bicyclists, and transit users. 

Though road safety in the U.S. 

has steadily improved over 

time, it remains a priority for 

transportation agencies, legislators, 

and advocacy organizations. Over 

the past 10 years in the U.S., an 

average of approximately 37,000 

people were killed each year and 

an estimated 2.3 million were 

injured in motor vehicle crashes.2

 

While many of these deaths and 

injuries are sustained by motor 

vehicle passengers and drivers, 

CHAPTER 1 FOUNDATIONS OF ROAD SAFETY

http://www.who.int/

features/factfiles/

roadsafety/en

National Highway 

Traffic Safety 

Administration 

(NHTSA). Fatality 

Analysis Reporting 

System (FARS). 

http://www.nhtsa.

gov/FARS

1983

50,000

fatalities

40,000

30,000

20,000

10,000

198819931998200320082013

Vehicle Occupants

Motorcyclists

Other/Unknown

Pedestrians

bicyclists

FIGURE 1-1: Traffic Fatalities in the U.S. by Year, 1983-2013 (Source: NHTSA FARS)

FIGURE 1-2: Traffic Fatalities in the U.S. by 

Person Type, 2013 (Source: NHTSA FARS)

1

2
1-2 UNIT 1: FOUNDATIONS OF ROAD SAFETY ROAD SAFETY FUNDAMENTALS

they also impact motorcyclists, 

pedestrians, bicyclists, and users 

of transit vehicles. This challenge 

requires a comprehensive approach 

to improving safety, involving 

numerous stakeholders and 

decision makers from a variety of 

perspectives and disciplines. 

Defining Safety

In the simplest terms, safety can 

be defined as the absence of risk 

or danger. Focusing this term to 

address transportation, road safety 

can be characterized by the ability 

of a person to travel freely without 

injury or death. A perfectly safe 

transportation system would not 

experience crashes between various 

road users. Though absence of all 

crashes is an optimal condition, and 

many transportation agencies have 

a goal of zero deaths on the road, 

the reality is that people continue 

to get injured or killed on streets 

and highways across the nation. The 

challenge posed to the road safety 

field is to minimize the frequency 

of crashes and the resulting deaths 

and injuries using all currently 

available tools, knowledge, and 

technology. This challenge is made 

more complex due to the multitude 

of factors influencing safety, from 

infrastructure to vehicle design to 

human behavior. 

Road safety professionals typically 

measure safety by the number and 

rate of crashes and by the severity 

of those crashes. Crash frequency, or 

the number of crashes occurring per 

year or other unit of time, is another 

commonly used metric. Crash rates

are numbers of crashes normalized 

by a particular population or metric 

of exposure. Commonly cited crash 

rates include crashes per 100,000 

people living in a particular State, 

city or country. Some crash rates 

present crash numbers per miles 

traveled or licensed drivers. Crash 

outcomes can be measured by 

the types of injuries sustained to 

the people involved in the crash, 

typically categorized by fatalities 

and injury severity. Focusing on 

crashes that result in severe injuries 

and fatalities is one strategy that 

agencies use to prioritize their 

safety activities.

In addition to the measures 

described above, safety professionals 

can use surrogate measures, such as 

Crash 

frequency

The number 

of crashes 

occurring per 

year or other 

unit of time.

Crash rate

The number 

of crashes 

normalized by 

a particular 

population 

or metric of 

exposure.

Crash 

outcome

Measured 

by the types 

of injuries 

sustained to the 

people involved 

in the crash.

1966

3,500

billion Vehicle Miles Traveled (billions)

Fatality Rate per 100 Million 

Vehicle Miles Traveled

6

5

4

3

2

1

3,000

2,000

1,000

1976198619962006

FIGURE 1-3: Fatality Rate and Vehicle Miles Traveled, 1966-2013 (Source: NHTSA FARS)
ROAD SAFETY FUNDAMENTALS UNIT 1: FOUNDATIONS OF ROAD SAFETY 1-3

Nominal 

safety

An absolute 

statement 

about the safety 

of a location 

based only on 

its adherence 

to a particular 

set of design 

standards and 

related criteria.

Substantive 

safety

Historical and 

long-term 

objective safety 

of a location 

based on 

crash data.

conflicts (near misses), avoidance 

maneuvers, and the time to collision 

if no evasive action is taken, to 

determine the level of safety risk 

and identify specific problems. 

Safety problems may exist even 

in locations that do not have a 

demonstrated history of crashes, 

just as someone who smokes is at 

higher risk for lung cancer even if 

no cancer has yet been detected. 

This can be especially true for 

non-motorized road user safety, 

such as pedestrians and bicyclists, 

since crashes involving these 

road users may be infrequent and 

appear random at first sight. In 

such locations where crashes are 

sparse or distributed across the 

system, safety professionals can use 

surrogate measures to fill the gaps 

and assess the road’s level of risk. 

Observing traffic at an intersection, 

for example, may reveal a pattern 

of near misses and other conflicts 

between vehicles and pedestrians. 

This pattern may not appear in 

crash data, but can be a valuable 

source of information to highlight 

the potential for safety risk. 

Safety perception is also an 

important consideration for travel 

choices. There are a number of 

reasons why someone may or may 

not choose a particular route to 

drive, walk or bike. Pedestrians who 

perceive an intersection to be unsafe 

may cross in a midblock location, 

where they are more easily able to 

find a gap in traffic. Motorists may 

feel uneasy about making a left turn 

across multiple lanes of traffic, so 

they may choose to turn right and 

travel out of their way to perform 

a U-turn instead. Safety perception 

impacts road user decisions but is 

not easily understood by looking 

at crash data. Safety professionals 

can use surveys, driving simulators, 

and other modern technologies to 

understand the safety perception of 

road users.

Evaluating the safety of a particular 

network, corridor or intersection 

requires an understanding of both 

nominal and substantive safety. 

Originally introduced by Dr. Ezra 

Hauer,3

 these terms offer a helpful 

framework for assessing the safety 

of a particular location. Decades of 

research and evaluation in the field 

of road safety have revealed a wealth 

of knowledge concerning the proper 

designs and policies that contribute 

to the safety of a particular location. 

Roadways constructed according to 

the best and latest recommended 

research and design standards are 

said to be nominally safe. Nominal 

safety is an absolute statement 

about the safety of a location based 

only on its adherence to a particular 

set of design standards and related 

criteria. A road that was nominally 

safe when it was first opened to 

traffic may become nominally 

unsafe when the roadway design 

standards change, even though 

the road’s crash performance has 

not changed.

While nominal safety considers 

the design of a road, it does not 

incorporate any information about 

the frequency, type and severity of 

crashes occurring on the facility. The 

historical and long-term objective 

safety of a location based on crash 

data is known as substantive safety. 

A particular intersection that has 

experienced fewer than expected 

crashes over an extended period 

will be referred to as a substantively 

safe location, while a corridor with 

a higher than expected number of 

crashes is substantively unsafe. 

Hauer, E. 

Observational 

Before/After Studies 

in Road Safety. 

Estimating the Effect 

of Highway and 

Traffic Engineering 

Measures on Road 

Safety. Pergamon 

Press. 1997.

3
1-4 UNIT 

1: FOUNDATIONS OF ROAD SAFETY ROAD SAFETY FUNDAMENTALS

Unlike nominal safety, substantive 

safety operates on a continuum and 

allows for a range of explanations 

as to why a particular safety 

problem exists. 

Another key distinction is the fact 

that a location can be nominally 

safe – adhering to all standards and 

design criteria – while experiencing 

high rates of crashes, making it 

substantively unsafe. Similarly, a 

substantively safe location (one that 

has a lower than expected crash 

rate) may be nominally unsafe if it 

does not meet the applicable design 

standards. 

Agencies and safety professionals 

should strive to prioritize the 

substantive safety of a facility. 

Simply building a road that meets all 

the current design standards will not 

ensure that the road is substantively 

safe. Using professional judgement 

to prioritize safety improvements 

and select appropriate designs 

within a range of options, based on 

observations of road user behavior 

and other available data, will 

increase the chance that all factors 

are considered. The end result will 

be a road that moves a step closer 

to the ultimate goal of having 

a transportation system free of 

injuries and deaths.

Road Safety Decisions 

and Trade-offs

The goal of improving safety 

exists alongside other goals of the 

transportation system, such as 

mobility, efficient movement of 

people and goods, environmental 

concerns, public health, and 

economic goals. In this way, 

transportation professionals and 

policy makers often refer to 

trade-offs – making a decision to 

favor one goal at the expense of 

another. While those in the field of 

road safety continually look for 

new designs and technologies to 

advance all goals, there continue 

to be many instances where public 

agencies must weigh competing 

goals for a location or portion of 

the road network and decide what 

trade-offs should be made for the 

goal of increasing road safety. 

Below are several examples: J Roundabouts: A city may decide 

to install a roundabout at an 

intersection to decrease the 

potential conflicts between 

various movements at the 

intersection. Safety is improved, 

especially related to left-turns, 

since all turns are now part of the 

circle. However, a roundabout 

does require traffic on the main 

road to slow their speeds and 

navigate through the roundabout. 

During heavy traffic, especially 

Design Dimensions

(LANE WIDTH, RADIUS OF CURVE, 

STOPPING SIGHT DISTANCE, ETC.)

Crash Risk

Nominal 

Safety

Substantive

Safety

FIGURE 1-4: Comparison of nominal 

and substantive concepts of safety http://

safety.fhwa.dot.gov/geometric/pubs/miti-

gationstrategies/chapter1/1_comparnom-

inal.cfm (Source: NCHRP Report 480, 

Transportation Research Board, 2002)
ROAD SAFETY FUNDAMENTALS UNIT 1: FOUNDATIONS OF ROAD SAFETY 1-5

if it is unbalanced among the 

intersection legs, this may 

cause a decrease in the overall 

throughput of the intersection. 

However, this is a trade-off to 

produce fewer crashes.

J Bicycle Helmet Requirements: 

In order to improve bicyclist 

safety, some jurisdictions have 

adopted ordinances that require 

bicyclists to wear helmets. In 

practice, this can reduce the risk 

of head injuries among cyclists, 

but it may also reduce the 

number of people who choose 

to ride a bicycle. Adopting such 

ordinances would prioritize 

safety while potentially reducing 

bicycle ridership.

J Red Light Cameras: Red light 

camera enforcement monitors 

signalized intersections and 

records information about 

those who violate red light 

laws, typically resulting in 

citations through the mail. These 

cameras have been shown to 

improve safety by decreasing 

the types of crashes that result 

in serious injury,4

 but installing 

the cameras can be met with 

significant public opposition. 

J Protected Left Turns: To 

minimize the risk of severe 

left-turn crashes at signalized 

intersections, engineers may 

choose to provide left turning 

drivers an exclusive protected 

left turn phase (green arrow). 

While this minimizes crash risk 

by separating the left turning 

vehicles from other movements, 

it also requires that extra time 

be added specifically for left 

Council, et al. 

Safety Evaluation of 

Red-Light Cameras. 

Federal Highway 

Administration. 

April 2005. https://

www.fhwa.dot.

gov/publications/

research/safety/

05048/05048.pdf 

4
1-6 UNIT 

1: FOUNDATIONS OF ROAD SAFETY ROAD SAFETY FUNDAMENTALS

turns, which can increase delay 

for the rest of the traffic at the 

intersection.

J Rumble Strips: In rural locations, 

rumble strips can be installed as 

a measure to alert drivers when 

they are running off the road. 

However, these rumble strips are 

usually installed on the edge of 

the road or the paved shoulder 

where bicyclists can safely and 

comfortably ride separated 

from traffic. This may result 

in bicyclists riding in the road 

where they are more vulnerable 

to crashes with motor vehicles.

J Trees and Landscaping:

Street trees, shrubs, and 

other vegetation can serve a 

valuable purpose in roadside 

environments – particularly 

creating shade for the sidewalk, 

serving as a buffer between the 

road and sidewalk area, and 

even creating “visual friction” 

that can keep vehicle speeds 

down. However, trees can also 

pose a safety risk for vehicles 

that run off the road and collide 

with them. Vegetation that is 

too close to an intersection 

can restrict sight distance, 

contributing to crashes. Selected 

tree and vegetation removal is an 

excellent example of a 

trade-off between safety and 

other beneficial features of trees.

J Traffic Signal Installation: A 

high-speed, high-volume road 

with multiple traffic lanes may 

separate housing developments 

from an elementary school. In 

order for children living in the 

housing development to safely 

travel to and from school, a 

traffic signal and crosswalk may 

be installed along the busy road. 

Motorists will be delayed since 

they are required to stop for a 

period of time while the students 

cross, but the crossing is safer 

for those students.

J Access Management: Left turns 

in and out of shopping centers, 

especially along multilane roads, 

can result in severe injuries to 

motorists when crashes occur. 

Eliminating these left turns by 

building raised median islands 

and consolidating driveways 
ROAD SAFETY FUNDAMENTALS UNIT 1: FOUNDATIONS OF ROAD SAFETY 1-7

J LIST various ways to measure the safety 

of a road and describe the advantages 

and disadvantages of each. Consider factors such as the type of information each 

safety measure provides as well as other 

issues such as how it can be collected.

J DESCRIBE a change that could be made 

to a road or intersection that would 

improve one transportation goal (e.g., 

traffic operations, public health, mobility and access, environmental quality, or 

economic growth) at the expense of the 

safety of road users.

J DESCRIBE a change that could be made 

to a road or intersection that would 

improve road safety at the expense of 

another transportation goal (e.g., traffic 

operations, public health, mobility and 

access, environmental quality, or economic growth).

J DESCRIBE a change that could be 

made to a road or intersection that 

would improve safety for a road user 

but not at the expense of other users, 

or other goals.

EXERCISES

can eliminate these risky 

movements; however, this 

prevents direct access to the 

stores by potential customers.

Sometimes improving safety 

for one group of road users may 

negatively impact the safety of 

another group. It can also be the 

case that improving mobility for a 

group of road users may negatively 

affect the safety of that same group. 

There is no absolutely correct 

answer to many of these trade-offs, 

as they are all context-specific. 

Transportation professionals need to 

discuss the various trade-offs in the 

context of a particular community’s 

transportation goals. These types of 

trade-offs are made every day, and 

require the cooperation of numerous 

agencies and stakeholders, all 

of whom have a role to play in 

transportation decision-making. 

Despite the temptation to study road 

safety as a self-contained system, 

there are a multitude of factors 

influencing and being influenced by 

road safety and travel behavior. In 

order to make informed decisions 

about the transportation system, 

transportation professionals 

must understand the impacts – 

both positive and negative – that 

design, operations, and policy 

decisions have on the safety of 

the transportation network as 

well as the impacts on other areas 

such as public health, mobility, 

environmental quality, and 

economic growth. 
1-8 UNIT 1: FOUNDATIONS OF ROAD SAFETY ROAD SAFETY FUNDAMENTALS

Road Safety Through the Years

CHAPTER 2 FOUNDATIONS OF ROAD SAFETY

When examining current efforts to 

address road safety, it is useful to 

view them in the context of American 

transportation history. Recent 

decades have witnessed numerous 

advances in the field of road safety. 

This growing national consciousness 

about the need for safer roads 

provides a stark contrast to the first 

half of the twentieth century when 

the focus was on highway expansion. 

The following chapter will provide 

an overview of the major milestones 

and achievements that led to the 

transportation system we have today, 

as well as the policies and practices 

that were implemented to address a 

growing safety problem.

Late Nineteenth Century and 

the Popularity of Bicycling

An exploration of the history of 

road safety in the U.S. can begin at 

many different points – some of 

our roads were developed as precolonial routes and others were 

trails blazed by Native Americans. 

In terms of lasting influence on the 

modern transportation network, 

however, it is most useful to begin 

the discussion in the late nineteenth 

century. 

In the 1880s and 1890s, bicycles 

were the dominant vehicle on 

our nation’s roads. With the 

introduction of the “safety” bicycle, 

with two wheels of the same size, 

and the pneumatic tire in the late 

1880s, the bicycling craze became an 

economic, political, and social force 

in the U.S. By 1890, the U.S. was 

manufacturing more than 1 million 

bicycles each year.

At that time, bicyclist behavior—

particularly careless or risk-taking 

behavior—was a contributing 

factor to bicycle crashes. However, 

the biggest contributor to crashes 

existed outside the cities; the poor 

condition of the nation’s roads made 

cycling a laborious and dangerous 

process. Bicycle groups worked 

at the Federal, State, and local 

levels to secure road improvement 

legislation. The work of these 

advocacy groups became known as 

the Good Roads Movement.

Three men 

with bicycles 

on bridge near 

Pierce Mill, 

Washington, 

D.C., 1885. 

(Source: 

Brady-Handy 

Collection, 

U.S. Library

 of Congress)
ROAD SAFETY FUNDAMENTALS UNIT 1: FOUNDATIONS OF ROAD SAFETY 1-9

To build support, advocates tailored 

their message to farmers with 

the argument that bad roads, 

by increasing transportation 

expenditures, cost more than good 

roads. While engineers, writers, and 

politicians joined the movement, 

bicyclists dominated the Good Roads 

Movement until cars arrived in the 

early twentieth century.5

By the close of century, automobiles 

had slowly begun to share the roads 

with bicyclists and pedestrians, 

benefitting from many of the road 

improvement efforts spearheaded 

by cycling groups. In 1899, a motor 

vehicle struck and killed a New 

York City pedestrian. This event 

marked the first time in the U.S. 

that a person was killed in a crash 

involving a motor vehicle.6

 

Rise of Motor Vehicles in the 

Early Twentieth Century

In 1905, only 78,000 automobiles, 

most of which were confined to the 

cities, traveled the U.S. Ten years 

later, 2.33 million automobiles were 

traveling the country’s roads, and by 

1918, this number had increased to 

5.55 million. Mass production made 

this increase possible as it lowered 

vehicle manufacturing costs, putting 

vehicles within the reach of the 

middle class. As more vehicles 

became available at a lower price, 

the pattern of daily travel in the U.S. 

began to shift. Longer vehicle trips 

replaced shorter trips by foot or 

bicycle, and development patterns 

began to follow suit. The motor age 

had arrived, and with it a new kind 

of highway would evolve, designed 

specifically for motor vehicles.

Expansion of automobile use had 

immediate positive effects on the 

national economy and quality of life 

around the country. Yet proliferation 

of motor vehicles also had a negative 

side. As millions of new drivers 

took to the roads, traffic crashes 

increased rapidly—tripling from 

10,723 in 1918 to 31,215 in 1929.7

 

Consequences of Speeding

As in modern times, in the early days of the 

automobile, posted speed limits were set 

far below the speed of which most motor 

vehicles were capable.

With faster and heavier traffic, it became 

dangerous to drive in the middle of 

the road and the States began painting 

centerlines on the pavements to channel 

traffic in lanes. At 40 miles per hour, these 

lanes appeared uncomfortably narrow to 

most motorists, especially when passing 

trucks. The lane lines also caused trucks 

to run closer to the shoulder, causing the 

slab edges and corners of the road to 

break. To provide greater safety and 

reduce edge damage, State highway 

departments built wider pavements 

and made new roads straighter. 

These improvements along with mechanical

advances in vehicles, such as more 

powerful engines and four-wheel brakes, 

in turn encouraged even faster speeds. 

Thus, after 1918, highway design followed 

a spiral of cause and effect, resulting in 

faster and faster speeds and wider and 

wider pavements. The motivating force 

behind this spiral was the driving speed 

preferences of the great mass of vehicle 

operators. The public authorities were 

never able to impose or enforce speed 

limits for very long if the majority of drivers 

considered the limits unreasonably low. 

Now, many current engineering practices 

use the 85th percentile speed – or the 

speed at which the majority of drivers travel 

– as the method of setting speed limits.

Source: Richard 

F. Weingroff, “A 

Peaceful Campaign 

of Progress and 

Reform: The 

Federal Highway 

Administration at 

100,” Public Roads 

57, no. 2 (Autumn, 

1993), http://www.

fhwa.dot.gov/

publications/

publicroads/93fall/

p93au1.cfm

Soniak, Matt. When 

and Where Was the 

First Car Accident? 

Mental Floss. 

2 December 2012. 

http://mentalfloss.

com/article/31807/

when-and-wherewas-first-caraccident

Source: America’s 

Highways, 1776-1976: 

A History of the 

Federal-Aid Program. 

Federal Highway 

Administration 

(U.S. Government 

Printing Office, 

Washington D.C., 

1976).

5

6

7
1-10 UNIT 1: FOUNDATIONS OF ROAD SAFETY ROAD SAFETY FUNDAMENTALS

Shifting Attention to Safety

Recognizing the rise in crashes and 

resulting injuries and fatalities, 

Secretary of Commerce Herbert 

Hoover convened the First 

National Conference on Street and 

Highway Safety in Washington, 

D.C., in December 1924. Here, for 

the first time, representatives of 

State highway and motor vehicle 

commissions, law enforcement, 

insurance companies, automobile 

associations and a multitude of other 

stakeholders and interest groups 

met in one place to discuss how 

to address the growing number of 

fatalities and serious injuries.

Prior to the conference, committees 

were established to perform 

research into areas such as planning 

and zoning, traffic control, motor 

vehicles, statistics, and other 

areas related to road safety. 

These committees reported wide 

differences in traffic regulations 

from State to State and city to city. 

For instance, twenty States did not 

attempt to collect crash statistics, 

only eight States required reporting 

crashes that resulted in personal 

injury, and 38 required railroads 

and common carriers to report 

highway crashes. Other committees 

devoted their attention to issues like 

traffic control and vehicle speeds, 

infrastructure and maintenance 

concerns, and issues impacting 

vehicles and their drivers. 

Conference participants supported 

a wide range of measures to 

reduce the rate of crashes and 

recommended that legislative, 

administrative, technical, and 

educational bodies adopt them. 

Conference participants also 

recommended that the States take 

the lead by passing adequate motor 

vehicle laws and setting up suitable 

agencies for administering the laws, 

policing the highways, registering 

vehicles, and licensing drivers. 

To the Federal Government, the 

conference assigned the role of 

encouragement, assembly and 

distribution of information, 

and the development of 

recommended practices. Adoption 

and implementation of these 

recommended practices would be 

left to the individual States.

Secretary of Commerce Herbert Hoover, center, with President Calvin Coolidge, right, 

in February 1924. (Source: Harris & Ewing Collection, U.S. Library of Congress)
ROAD SAFETY FUNDAMENTALS UNIT 1: FOUNDATIONS OF ROAD SAFETY 1-11

Secretary Hoover called a second 

conference for March 1926. During 

the interim between the two 

conferences, a special committee 

drew up a model “Uniform Vehicle 

Code” covering registration and 

titling of vehicles, licensing of 

drivers, and operation of vehicles on 

the highways. The code incorporated 

the best features of the numerous 

and varied State laws then on 

the statute books. The second 

conference approved this code 

and recommended it to the State 

legislatures as the basis for uniform 

motor vehicle legislation.

Studies following this 1926 

conference concluded that 

determining the causes of crashes 

was far more difficult than they had 

presumed. The problem warranted 

a sustained program of research 

by a national organization. The 

Conference agreed, and the Highway 

Research Board (HRB) organized 

the Committee on Causes and 

Prevention of Highway Accidents 

to coordinate crash research 

nationwide. The HRB played a major 

part in subsequent efforts to reduce 

the consequences of crashes.8

Federal Government Role 

in Highway Development

The growing use of motor vehicles 

during the 1920s was mirrored 

by the expansion of the Federal 

Government’s role in funding and 

building roads. In its early form, the 

Office of Public Roads was organized 

under the U.S. Department of 

Agriculture, playing a large role in 

funding roadways within national 

parks and forests. 

Following the Federal Aid Road Act 

of 1916, this office would become 

the Bureau of Public Roads (BPR), 

charged with working cooperatively 

with State highway departments on 

road projects. Work continued on 

the expansion of highways across 

the country, and between 1921 and 

1939, the distance of paved roads 

Balanced Design for Safety

In the 1920s and 1930s, it was good 

engineering practice to design new 

highways as much as possible in long 

straight lines or “tangents.” When it 

became necessary to change direction, 

the engineer laid out a circular curve, 

the radius of which he selected to fit 

the ground with the least construction 

cost, but which could not be less than a 

certain minimum fixed by department 

policy. In practice, engineers made the 

curves sharper than this minimum when 

it was cheaper to do so, but with little 

consistency. Engineers expected motorists 

driving these roads to adjust their speeds 

to the varying radii, and on the sharper 

curves safe design speed might be 

considerably lower than the posted 

speed limit.

Increasing concern for road safety led many 

highway engineers to worry about this 

inconsistency between posted speed limits 

and safe design speed on curves. In 1935, 

highway engineer Joseph Barnett of the BPR 

proposed that all new rural roads conform to 

an “assumed design speed,” a comfortable 

top speed for drivers outside of urban areas. 

With its adoption by American Association 

of State Highway Officials in 1938, Barnett’s 

“balanced design” concept became a 

permanent feature of U.S. roadway design. 

Today, standards for designing curves, 

such as design speed, curve radius and 

superelevation (the tilt of the road through 

a curve) are provided in A Policy on 

Geometric Design of Highways and Streets, 

produced by the American Association for 

State Highway Transportation Officials.

Source: America’s 

Highways, 1776-1976: 

A History of the 

Federal-Aid Program. 

Federal Highway 

Administration 

(U.S. Government 

Printing Office, 

Washington D.C., 

1976).

8

Uniform 

Vehicle Code

A code covering 

registration and 

titling of vehicles, 

licensing of 

drivers, and 

operation of 

vehicles on 

the highways.
1-12 UNIT 1: FOUNDATIONS OF ROAD SAFETY ROAD SAFETY FUNDAMENTALS

increased from 387,000 miles to 

nearly 1.4 million miles.9

 The BPR 

recognized that the antiquated 

highway system was one of the 

contributing causes of the high 

crash toll, but did not go so far as 

to identify primary crash causes or 

recommend potential solutions.

During this time, an emphasis was 

placed on expanding the Federal 

role in the process of highway 

design and development. This 

effort culminated in 1944 when 

Congress approved the development 

of a National System of Interstate 

Highways along with that year’s 

Federal Aid Highway Act. Though 

expansive in scope, calling for a 

40,000 mile network, the legislation 

was not accompanied by any funds 

to support the development of 

these highways. Without funding, 

the legislation did not significantly 

expand the highway system.

Road safety continued to present 

a national concern. In May 1946, 

President Harry S. Truman spoke at 

the Highway Safety Conference to 

rally public support to improve State 

motor vehicle laws, driver licensing, 

and education. After summarizing 

his unsuccessful efforts as a U.S. 

senator to enact Federal legislation 

on motor vehicle registration and 

driver licensing, the President 

said Congress was not yet ready to 

interfere with what many perceived 

as State prerogatives. However, he 

noted that the Federal Government 

would not stand aside if the rates of 

highway fatalities continued to rise.10 

Source: Weingroff, 

Richard. A Peaceful 

Campaign Of 

Progress And Reform: 

The Federal Highway 

Administration 

at 100. Public 

Roads Magazine. 

Vol. 57 No. 2. July 

1993. http://www.

fhwa.dot.gov/

publications/

publicroads/93fall/

p93au1.cfm

Source: Richard 

F. Weingroff and 

the assistance of 

Sonquela Seabron, 

President Dwight 

D. Eisenhower and 

the Federal Role 

in Highway Safety, 

accessed May 23, 

2013, http://www.

fhwa.dot.gov/

infrastructure/

safetyin.cfm

9

10

Safety Signs

Before World War I, most States were 

using signs to warn road users of danger 

ahead, particularly at railroad crossings; 

railroad companies themselves were 

required to post warning signs at all public 

road crossings. However, there was little 

agreement between States about the 

specific design of these warning devices, 

and the signs were a variety of shapes, 

sizes, and colors.

In 1929, the American Engineering Council 

surveyed sign practices in all U.S. cities 

with a population of more than 50,000 

and created a document that was, in 

effect, a manual of the best practices 

of the time. Recognizing the need for 

standard practices for signs in rural and 

urban areas, the American Association of 

State Highway Officials and the National 

Conference on Street and Highway 

Safety organized a Joint Committee on 

Uniform Traffic Control Devices in 1931 

and introduced a new manual for national 

use in 1935. The manual of best practices 

changed over time to become the Manual 

on Uniform Traffic Control Devices. 

President Harry S. Truman, 1945. 

(Source: U.S. Library of Congress)
ROAD SAFETY FUNDAMENTALS UNIT 1: FOUNDATIONS OF ROAD SAFETY 1-13

Post War Development 

and Growth

Economic conditions following 

World War II led to even higher 

levels of driving and automobile 

ownership. Personal savings of 

almost $44 billion created a market 

for housing and other types of 

goods, chief among them new 

automobiles. Automobile production 

jumped from a nearly 70,000 in 1945 

to 3.9 million in 1948.

Because of this increase in 

vehicle production, motor vehicle 

registrations spiked and the number 

of drivers on the nation’s roads and 

highways reached unprecedented 

levels. Under wartime rationing of 

rubber, and specifically tires, States 

had implemented speed controls to 

reduce wear and tear and improve 

tire longevity. With the end of 

rationing and emergency speed 

controls at the conclusion of the 

war, highway travel returned to 

pre-war levels and began a steady 

climb of about 6 percent per year, 

which would continue for nearly 

three decades.

While the increasing popularity of 

low density housing development 

(i.e., the suburbs) and the 

availability of motor vehicles created 

perfect conditions for more driving, 

the nation’s roads and highways 

were unprepared for the increase in 

traffic. Under wartime restrictions, 

States were unable to adequately 

maintain their highways. With 

widespread operation of overloaded 

trucks and reduced maintenance, 

the State highway systems were in 

worse structural shape post-war 

than before the war.

Development of the Interstate 

Highway System

Though the National System of 

Interstate Highways had been 

established by legislation in 

1944, little progress was made 

over the next decade. Without 

funding, established routes were 

slow to develop. That changed in 

1956, when President Dwight D. 

Eisenhower signed the FederalAid Highway Act of 1956. This 

legislation linked the development 

of the interstate highway system to 

the interest of national defense and 

assigned funding that would rapidly 

expand the highway network.11 The 

act established a dedicated funding 

stream and a plan for highway 

development that launched the 

nation into an unprecedented era of 

expansion in which new interstate 

corridors linked cities and towns to 

one another.

http://www.

fhwa.dot.gov/

publications/

publicroads/

06jan/01.cfm

11

President 

Dwight D. 

Eisenhower 

speaks to the 

White House 

Conference on 

Highway Safety, 

1954. (Source: 

Eisenhower 

Presidential 

Library)
1-14 UNIT 1: FOUNDATIONS OF ROAD SAFETY ROAD SAFETY FUNDAMENTALS

Despite the enthusiasm of political 

and business leaders, the growth 

of this system was not without 

its critics. These critics primarily 

denounced the destruction of homes 

and separation of communities 

that sometimes resulted from new 

highways bisecting established 

neighborhoods. Though this opposition 

halted projects in some locations, 

it did not stop the expansion of the 

interstate highway system. 

Highway Safety Act of 1966

In 1964, the U.S. faced a sharp rise 

in the number of traffic fatalities. 

An increased number of vehicles 

on the roadways combined with a 

public culture that did not prioritize 

roadway safety consciousness led 

to 47,700 deaths on the nation’s 

highways, an increase of 10 percent 

over the number of fatalities that 

occurred in 1963. These deaths 

prompted the nation to take a hard 

look at road safety efforts and 

resulted in Congressional hearings in 

March 1965 to raise public awareness 

of the growing national crisis.12

To respond to these trends, the 

nation needed a change of direction 

in the design and operation of its 

roads and vehicles. This change 

began with reviewing safety 

standards in these areas and 

conducting research to identify 

effective measures to improve 

safety. The 1960s was a pivotal 

decade for road safety due to the 

passage of laws that provided 

funding and new policies. On 

September 9, 1966, President 

Lyndon B. Johnson signed the 

National Traffic and Motor Vehicle 

Safety Act of 1966 and the Highway 

Safety Act of 1966. The signing 

ceremony in the Rose Garden 

of the White House marked a 

transformation in the role of the 

Federal Government in road safety. 

This role had been growing during 

the Eisenhower administration, but 

became a larger area of emphasis as 

fatalities on the nation’s highways 

climbed toward 50,000. Those in 

the federal government observed 

that the steps taken during the 

previous two decades to reverse the 

climbing number of fatalities had 

failed, and they believed that road 

safety should no longer be left solely 

to the responsibility of the States, 

the automobile industry, and the 

individual drivers.13

This legislation established the 

U.S. Department of Transportation 

(USDOT) and transformed the 

Bureau of Public Roads into the 

Federal Highway Administration 

(FHWA). New bureaus were added to 

address safety in areas of growing 

concern, such as the Bureau of 

Motor Carrier Safety and National 

Highway Safety Bureau (these 

would later become the Federal 

Motor Carrier Safety Administration 

and the National Highway Traffic 

Safety Administration, respectively). 

The USDOT proceeded to develop 

programs and initiatives and 

pave the way for activities still in 

place today.14

Advances in vehicle design 

and policy were also an area of 

emphasis during the 1960s. In 

1968, federal legislation required 

vehicles to provide seat belts. 15 

Federal law also required States to 

begin implementing motorcycle 

helmet laws in order to qualify for 

particular sources of funding.16 

These requirements led to more 

widespread implementation of 

safety policies through the late 

Source: Richard 

F. Weingroff and 

the assistance of 

Sonquela Seabron, 

President Dwight 

D. Eisenhower and 

the Federal Role 

in Highway Safety, 

accessed May 23, 

2013, http://www.

fhwa.dot.gov/

infrastructure/

safetyin.cfm

12 13

http://www.

fhwa.dot.gov/

infrastructure/

50interstate.cfm

Federal Motor 

Vehicle Safety 

Standard (FMVSS) 

No. 218, 

https://www.federal

register.gov/

documents/2015/05/

21/2015-11756/

federal-motorvehicle-safetystandardsmotorcycle-helmets

Title 49 of the 

United States Code, 

Chapter 301, Motor 

Vehicle Safety, 

https://www.gpo.

gov/fdsys/pkg/

USCODE-2009-

title49/html/

USCODE-2009-

title49-subtitleVI.

htm

14

16

15
ROAD SAFETY FUNDAMENTALS UNIT 1: FOUNDATIONS OF ROAD SAFETY 1-15

1960s and 1970s. Section 402 of 

the Highway Safety Act established 

a revenue stream for funding to 

directly support State programs 

aimed at improving road safety. 

Known as the State and Community 

Highway Safety Grant Program, the 

funds originally supported a variety 

of program areas, including many 

many behavioral safety programs 

that are still in existence today. 17

Energy Crises and Safety 

Legislation in the 1970s 

and 1980s

The 1970s and 1980s were 

characterized by energy crises in 

1973 and 1979 that had immediate 

and lasting impacts on travel trends. 

Vehicle Miles Traveled (VMT) 

decreased following each of these 

events, as Americans drove less 

due to rising fuel costs. Strategic 

legislative action by Congress, such 

as the National Maximum Speed 

Law of 1974 which prohibited speeds 

higher than 55 miles per hour also 

helped by decreasing fuel costs. The 

law would later be repealed in 1995, 

allowing States to set their own 

maximum speed limits.

Between 1970 and 2007, there 

were two periods of time when 

VMT decreased from the previous 

year. These years include 1974 and 

1979, each of which saw a roughly 

18 billion mile decrease in VMT 

from the previous year.18 As driving 

decreased, so did traffic fatalities. 

From 1973 to 1974, for example, 

traffic fatalities went down 16 

percent – the largest single year 

decline since 1941-1942.19 Driving 

levels began to increase again 

once fuel costs normalized, so 

the reductions were not sustained 

beyond the period of economic 

stagnation.

The Highway Safety Act of 1973 

established a specific methodology 

for improving roadway safety from 

an engineering perspective. It 

required the States to first survey 

all hazardous locations and examine 

http://www.

fhwa.dot.gov/

policyinformation/

travel_monitoring/

tvt.cfm

Governors Highway 

Safety Association. 

Section 402 State 

and Community 

Highway Safety 

Grant Program. 

http://www.ghsa.

org/about/federalgrant-programs/402

18

17

https://crashstats.

nhtsa.dot.gov/Api/

Public/ViewPub

lication/811346

19

President Lyndon B. Johnson signs the National Traffic and Motor Vehicle Safety Act of 

1966 and the Highway Safety Act of 1966. (Source: LBJ Presidential Library)
1-16 UNIT 1: FOUNDATIONS OF ROAD SAFETY ROAD SAFETY FUNDAMENTALS

the causes of crashes at these sites. 

A benefit/cost analysis was then 

performed to prioritize needed 

improvements. This process set 

the stage for the current safety 

management processes and would be 

refined and improved over the years. 

The Highway Safety Act of 1973 also 

clarified the relationship between 

the Federal Government and the 

States. The Federal Government 

was to direct policy and program 

components, while the States were 

responsible for implementing those 

policies and programs.20

During the 1970s, Congress also 

established the Motor Carrier Safety 

Assistance Program (MCSAP). 

This program provides financial 

assistance to States to reduce the 

number and severity of crashes 

and hazardous materials incidents 

involving commercial motor 

vehicles (CMV) through inspection 

and enforcement programs 

focused on trucks, carriers, 

and driver regulations. 21

Vehicle safety continued to be a 

priority in the 1970s and 1980s, as 

more States began to implement 

laws requiring the use of seat belts 

and motorcycle helmets. New York 

became the first State to adopt a 

mandatory seat belt law in 1984, and 

other States soon followed suit.22 

The Federal Motor Vehicle Safety 

Standard 213 brought attention 

to child passenger safety. This 

standard was the first to outline 

specific requirements for restraint 

systems designed for children. 

Multimodal Shift in the 1990s

The 1990s saw a shift from 

transportation policies that focused 

on motor vehicle safety and 

efficiency to an acknowledgement of 

alternate modes of transportation, 

such as bicycling, walking and use 

of public transit. The Intermodal 

Surface Transportation Efficiency 

Act of 1991 (ISTEA) added a 

multimodal perspective to the 

Federal-aid highway program. 

While ISTEA was not specifically 

focused on transportation safety, it 

created some programs to promote 

safer travel. For example, ISTEA 

enhanced road safety with new 

programs that encouraged the 

use of safety belts and motorcycle 

helmets.23 The legislation also 

required the installation of airbags 

for drivers and front passengers in 

all cars and trucks.24

In 1998, the Transportation Equity 

Act for the 21st Century (TEA-21) 

provided more focus for roadway 

safety planning by establishing 

safety and security as planning 

http://www.iihs.org/

iihs/topics/laws/

safetybeltuse

22

Source: “What is 

the Motor Carrier 

Safety Assistance 

Program (MCSAP)?” 

accessed May 23, 

2013, https://www.

federalregister.gov/

documents/2000/03/

21/00-6819/motorcarrier-safetyassistance-program

21

Source: “HSIP 

History,” accessed 

October 22, 2013, 

http://safety.fhwa.

dot.gov/hsip/gen_

info/hsip_history.cfm 

and “Subchapter J—

Highway Safety: Part

924—Highway Safety 

Improvement Program,” 

accessed October 

21, 2013, http://www.

gpo.gov/fdsys/pkg/CFR2003-title23-vol1/pdf/

CFR-2003-title23-vol1-

chapI-subchapJ.pdf.

20

Source: 

“Intermodal Surface 

Transportation 

Efficiency Act of 1991 

Information,” last 

updated May 16, 2013, 

accessed July 05, 2013, 

http://www.fhwa.

dot.gov/planning/

public_involvement/

archive/legislation/

istea.cfm.

23

1893Office of Road Inquiry is created, 

which would eventually become the 

Federal Highway Administration

1908Ford Model T is released as 

the first automobile available 

to most of the middle class 1916Bureau of 

Public Roads 

is created

1924First national conference 

on highway safety held 

in Washington, DC 1926Uniform Vehicle Code is 

developed during the second 

highway safety conference 1932Revenue Act of 1932 

establishes first national 

gas tax at 1 cent per gallon

ROAD SAFETY TIMELINE

See next page.

24
ROAD SAFETY FUNDAMENTALS UNIT 1: FOUNDATIONS OF ROAD SAFETY 1-17

http://www.history.

com/this-day-inhistory/federallegislation-makesairbags-mandatory

24

priorities. Prior to TEA-21, a State or 

Metropolitan Planning Organization 

(MPO) may have incorporated 

safety in its goals or long-range 

transportation plan, but specific 

strategies to increase safety were 

seldom included in statewide and 

metropolitan planning processes 

or documents.

TEA-21 established the Highway 

Safety Infrastructure program (not 

to be confused with the Highway 

Safety Improvement Program, 

which would be developed several 

years later), which funded safety 

improvement projects to eliminate 

safety problems. 

The TEA-21 legislation also 

encouraged States to adopt and 

implement effective programs to 

improve the quality (e.g. timeliness, 

accuracy, completeness, uniformity 

and accessibility) of State data 

needed to identify safety priorities 

for national, State and local road 

safety programs.25

Not to be lost among the TEA-21 

legislation, another pivotal moment 

in transportation legislation came in 

2000 when an important provision 

related to alcohol was included in 

the USDOT appropriation act. The 

appropriation carried a requirement 

that all States must enact laws to 

limit the legal blood alcohol content

(BAC) of drivers to 0.08 percent.26 

This limit was in line with similar 

limits imposed on drivers in other 

countries, though some European 

countries limit the legal BAC to 0.05 

percent. 

While 19 States and Washington, 

D.C., had already enacted this law, 

the Federal mandate provided a 

further incentive for other States 

to do so: States that did not pass 

the law by 2004 would forego a 

portion of their transportation 

funding. Though specific laws vary, 

each State now recognizes the legal 

limit of 0.08 percent blood alcohol 

content.27

http://www.ghsa.org/

html/stateinfo/laws/

impaired_laws.html

27

Rodriguez-Iglesias, 

C.; Wiliszowski, ClH.; 

Lacey, J.H. Legislative 

History of .08 Per 

Se Laws, National 

Highway Traffic Safety 

Administration, 

Report No. DOT HS 

809 286, June 2001

26

Source: “TEA-21 

– Transportation 

Equity Act for the 21st 

Century Fact Sheets,” 

last modified April 5, 

2011, accessed June 

2, 2013, http://www.

fhwa.dot.gov/tea21/

factsheets/index.htm

25

Blood alcohol 

content

The percentage 

of alcohol in 

a person’s 

blood, used to 

measure driver 

intoxication.

1944Congress approves the 

development of the National 

System of Interstate Highways 1956Federal-Aid Highway Act provides 

dedicated funding stream to support 

the interstate highway system 1966Highway Safety Act and National Traffic and 

Motor Vehicle Safety Acts are signed, creating 

the U.S. Department of Transportation 1968First Federal Motor Vehicle 

Safety Standard requiring 

seat belts is passed

1971First Federal safety 

standard requiring child 

passenger restraints

Officers use specialized devices to 

measure drivers’ blood alcohol content.
1-18 UNIT 1: FOUNDATIONS OF ROAD SAFETY ROAD SAFETY FUNDAMENTALS

Legislation in the 21st Century

Twenty-first century legislation 

continued to move Federal 

transportation funding and 

policy in the direction of focusing 

on multimodal, data-driven 

approaches to improving the 

transportation system. One specific 

area of focus was a move toward 

safety planning. Transportation 

safety planning shifts the focus 

of traditional planning efforts to 

a more comprehensive process 

that integrates safety into 

transportation decision-making. 

Safety planning encompasses 

corridors and entire transportation 

networks at the local, regional, 

and State levels, as well as 

specific sites.28

In 2005, Congress passed the Safe, 

Accountable, Flexible, and Efficient 

Transportation Equity Act—A 

Legacy for Users (SAFETEA-LU). 

SAFETEA-LU raised the stature of 

Federal road safety programs by 

establishing the Highway Safety 

Improvement Program (HSIP) as 

a core Federal-aid program tied 

to strategic safety planning and 

performance. HSIP is one of six 

core Federal-aid programs under 

which funds are apportioned 

directly to the States. One of the 

major elements of the HSIP was 

Source: 

“Transportation 

Safety Planning 

(TSP),” accessed 

August 13, 2013, 

http://safety.fhwa.

dot.gov/hsip/tsp/ 

and “Transportation 

Safety Planning Fact 

Sheet,” accessed 

August 13, 2013, 

http://safety.fhwa.

dot.gov/hsip/tsp/

fact_sheet.cfm.

Title 23 United 

States Code § 148

28

29

1973Oil embargo leads to energy crisis

Highway Safety Act of 1973, 

introduction of National 

Maximum Speed Law 1979Oil crisis in the 

wake of the 

Iranian Revolution

1974Safety standard 

requiring motorcycle 

helmets is passed

1998TEA-21 is passed, along with a call for 

all States to adopt a 0.08 percent 

blood alcohol content limit for drivers 2012MAP-21 

is passed

1984New York becomes first 

State to pass mandatory 

seat belt law

1993Gas tax 

increased to 18.4 

cents per gallon 1995National 

Maximum Speed 

Law is repealed

2005SAFETEALU is 

1991

passed

ISTEA is 

passed

the requirement for each State to 

develop and implement a Strategic 

Highway Safety Plan (SHSP).29

The plans sought to establish 

data-driven approaches that were 

coordinated with a broad range of 

stakeholders and utilized a diverse 

set of disciplines (e.g., engineering, 

enforcement, education and 

emergency response). These datadriven plans had to include clear 

methods for measuring progress 

toward safety goals.

The Moving Ahead for Progress in 

the 21st Century Act (MAP-21) was 

signed into law in 2012. The 2012 

legislation transformed the policy 

and programmatic framework 

for investments in the country’s 

transportation infrastructure, 

enhancing the programs and policies 

established in 1991.

MAP-21 doubled funding for road 

safety improvement projects, 

strengthened the linkage among 

modal safety programs and created a 

positive agenda to make significant 

progress in reducing highway 

fatalities and serious injuries. It 

provided increased focus on the 

importance of high quality data, 

transportation infrastructure and 

the safety of local streets. 
ROAD SAFETY FUNDAMENTALS UNIT 1: FOUNDATIONS OF ROAD SAFETY 1-19

U.S. Department 

of Transportation. 

Strategic Plans. 

November 2015. 

https://www.

transportation.gov/

mission/budget/

dot-budget-andperformancedocuments#

StrategicPlans

30

J RESEARCH a federal transportation law 

addressed in this chapter and write a 

summary about the law, emphasizing 

the safety aspects. 

J FIND a recent news article that involves 

road safety (more than just a local news 

article on a recent crash) and write a 

summary describing the effort undertaken by the public agency, how it was 

received by the public, and whether it 

was shown to be effective in increasing 

road safety.

J USE https://www.govtrack.us to find a 

transportation bill currently proposed 

or under review by Congress. Describe 

how the legislation would be expected 

to affect road safety. 

J RESEARCH the legal driving Blood 

Alcohol Content (BAC) by state in the 

U.S. and create a table showing the 

comparison. Select one state where 

the legal BAC is lower than the federal 

requirement, locate a paper or news 

article describing how that BAC level 

was decided, and write a summary.

EXERCISES

Conclusion

Exploring the history of travel 

trends and safety in the U.S. helps 

illustrate how past decisions have 

led to the transportation system 

seen today. Safety has not always 

been a deciding factor in how roads 

are built. However, today, safety 

is a top priority of the USDOT.30

Most State and local transportation 

agencies share USDOT’s goal; 

some have even set goals to reduce 

total traffic fatalities to zero. 

These “vision zero” and “toward 

zero deaths” goals are guiding 

transportation projects by requiring 

safety to be incorporated into every 

step of project planning, design, 

construction and operation. 

Future safety issues will certainly 

arise as technological advancements 

lead to changes in the vehicle 

fleet. Autonomous and potentially 

driverless vehicles are being 

developed and tested across the 

world. Though safety improvements 

are touted as a benefit of these 

advanced vehicles, safety will 

continue to be a priority as they 

begin to share the roads with older 

vehicles, bicyclists, and pedestrians. 

As can be learned from the history 

of road safety in the U.S., complex 

problems must be met with safety 

advancements, legislative action, 

and collaboration.
1-20 UNIT 1: FOUNDATIONS OF ROAD SAFETY ROAD SAFETY FUNDAMENTALS

Road safety is a complex issue, and 

any efforts to improve safety must 

address not only the roadway but 

also road user behavior, vehicle 

design, interaction between 

road users, and the effect of the 

roadway on all road users. Road 

safety partners include anyone 

who influences road user safety, 

including those in infrastructure 

safety, behavioral roadway safety, 

transportation planning, public 

health, public safety and many other 

disciplines. Each of these disciplines 

is able to provide a unique 

perspective and each has specific 

methods for addressing road safety. 

It is becoming increasingly common 

for these various disciplines to work 

in collaboration with one another 

to address road safety through 

comprehensive programs. Instead 

of focusing on traditional “silos” 

of activity, agencies hope that this 

interaction and collaboration among 

various disciplines will lead to 

continued safety improvements.

This chapter will discuss 

road safety efforts from the 

disciplines of roadway design and 

engineering, public education, 

and enforcement campaigns. 

Working in collaboration with one 

another, as described above, these 

groups can share the burden of 

road safety responsibilities and 

create comprehensive programs to 

address the various factors that may 

contribute to crashes. 

Multidisciplinary Approaches

CHAPTER 3 FOUNDATIONS OF ROAD SAFETY

The E’s

A popular multidisciplinary approach to 

road safety is sometimes referred to as 

the “four E’s”: Engineering, Education, 

Enforcement, and Emergency response. 

These E’s broadly represent the 

various disciplines that bring together 

stakeholders who care about making 

the road safe for all users. Sometimes 

a fifth “E” for evaluation is added to 

this list to represent the important 

role of evaluating what works and what 

doesn’t. This emphasizes the fact that 

good data is crucial to the improvement 

of road safety.
ROAD SAFETY FUNDAMENTALS UNIT 1: FOUNDATIONS OF ROAD SAFETY 1-21

Roadway Design 

and Engineering

Several types of transportation 

professionals are responsible for 

roadway safety engineering. 

Broadly speaking, the roadway 

safety engineering community 

includes transportation planners 

and engineers. 

Transportation planning plays a 

critical role in determining the shape 

of the transportation system and 

provides an early opportunity for 

professionals to address safety needs. 

Before a road project is designed or 

built, it is influenced by any number 

of comprehensive and strategic 

transportation plans that are 

coordinated to ensure that the system 

being developed is one that matches 

the vision of the local community. 

Planners work with stakeholders 

such as the general public, business 

owners, policy makers, and 

advocates to establish plans for how 

the transportation system can best 

serve every group’s needs. 

In the past, the traditional planning 

process focused on economic 

development, environmental quality, 

and mobility as the three primary 

concerns. Most States consider 

infrastructure safety improvements as 

part of preservation or improvements 

projects or within operational 

changes undertaken by traffic 

offices. States are now able to use 

the Highway Safety Improvement 

Program (HSIP) to fund safety 

projects in at high priority locations. 

This program allows development 

of targeted solutions and approaches 

that address the contributing 

factors to collisions, thereby 

seeking to achieve a higher return 

on safety investments. 

Roadway engineers work on the 

design, construction and system 

preservation of the roadways. In 

particular, engineers are charged 

with designing roads that minimize 

the chance that crashes will occur 

while balancing the needs for 

efficiency and mobility. Engineers 

also work to design roads and 

intersection in such a way that 

minimizes crash severity and 

injury risk when crashes do occur. 

Engineers affect the safety of the 

built environment by incorporating 

safety in to the planning process at 

the beginning of a project; selecting 

design alternatives that prioritize 

safety considerations; using 

design elements that maximize 

the safety of each part of the road 

or intersection; ensuring quality 

and safe construction, operation, 

and maintenance of the roads; 

and addressing safety problems at 

existing locations.

Infrastructure improvements such 

as paved shoulders, rumble strips, 

and improved nighttime visibility 

may prevent drivers from veering 

off the roadway, and still other 

opportunities exist for improving 

the roadside and road user behavior. 

For example, when a driver veers 

off the roadway, it is important to 

provide a roadside environment that 

reduces the potential for crashes and 

injury. Roadside slopes and objects 

such as drainage structures, trees, 

and utility poles are examples of 

roadside elements that engineers 

can target for improvements to 

road safety performance. One 

engineering method to increase 

roadside safety is to create a clear 

zone—an unobstructed, traversable 

roadside area that allows a driver to 

stop safely or regain control of the 

vehicle that has left the roadway.
1-22 UNIT 1: FOUNDATIONS OF ROAD SAFETY ROAD SAFETY FUNDAMENTALS

Engineering solutions must 

incorporate the different needs 

and preferences of a variety of user 

groups. As mentioned previously, 

this often means that tough 

decisions and trade-offs must be 

made to arrive at infrastructure 

solutions that balance the needs of 

different users. This trade-off can 

be illustrated with an example of a 

signalized intersection. Improving 

intersection safety for pedestrians 

may involve adding pedestrian 

crossing time to the signal or 

separating turn movements to 

eliminate high risk conflicts. 

Protected left-turn phases can 

also improve safety for vehicles, as 

shown previously. But these new 

or longer signal phases either add 

time to the cycle length or keep 

the same length while reducing 

time for the through movements. 

Regardless, the result is more delay 

to both pedestrians and motorists. 

In such situations, it is necessary 

to consider all of these needs and 

select the appropriate signal timing 

that meets the needs of all users. 

Adhering to design standards – 

creating nominally safe conditions 

– is only one aspect of the complex 

roadway design and engineering 

field. Addressing substantive safety 

through design strategies requires 

an understanding of multiple 

perspectives, trade-offs and 

user needs.

Public Education and 

Enforcement Campaigns

Public education and communications 

campaigns are commonly used 

to improve road user attitudes 

and awareness. The structure 

and delivery methods of these 

campaigns can take many forms. 

However, they generally involve 

materials (media advertisements, 

informational brochures, posters, 

presentations, etc.) to inform 

people of a desired behavior and 

the benefits of such behavior (or 

conversely, the risks of an unwanted 

behavior).

While standalone informational or 

educational campaigns can improve 

awareness or perceptions about road 

safety issues, they are unlikely to 

change road user behavior. Rather, 

campaigns that educate the public 

about increased law enforcement 

efforts aimed at a particular 

behavior have been shown to be 

effective. Generally referred to as 

“high-visibility enforcement” these 

campaigns increase the perceived 

enforcement of a particular law. 

When people believe there is a high 

probability of being caught, they are 

more likely to follow the law. The 

Click it or Ticket campaign is one of 

the most widely known examples 

of high-visibility enforcement. 

In this case, simply enforcing the 

seatbelt law was not sufficient. 

The key to this program’s success 

was the media coverage and other 

informational campaigns telling the 

public that law enforcement officers 

are looking for people who are not 

wearing a seatbelt. In other words, 

for those people who do not typically 

wear a seatbelt, the law itself 

was not sufficient motivation to 

change. The motivation came from a 

Countermeasures That Work

Countermeasures That Work31 is a 

comprehensive guidance document 

providing details of different programs 

and interventions that are effective 

in improving safety. The guide is 

published regularly by NHTSA. 

Countermeasures 

that Work: A 

Highway safety 

Countermeasures 

Guide for State 

Highway Safety 

Offices, 7th edition, 

2013 DOT HS 811 727

31
ROAD SAFETY FUNDAMENTALS UNIT 

1: FOUNDATIONS OF ROAD SAFETY

1-23

perceived threat of being caught and 

ticketed.

When safety professionals analyze 

possible educational campaigns, they 

must consider the factors that affect 

people’s behavior and the probability 

that the campaign will change such 

behavior. Simply communicating 

safety messages and enforcing 

laws may not lead to a change in 

behavior if a road is designed in a 

way that allows (or unintentionally 

encourages) unsafe behaviors. For 

example, to address a speeding 

problem on a wide multilane 

arterial where the posted speed is 

35 miles per hour, enforcement 

and education may not be the only 

solution. Narrowing the roadway 

and creating more “visual friction” 

along the roadside may be needed 

to alter the desired design speed of 

the road. Supplemental education 

and enforcement campaigns can 

then help reinforce the proper 

behavior. This emphasizes the need 

for cooperation and coordination 

between disciplines to accomplish 

Targeted Enforcement

To reinforce pedestrian safety laws, 

police departments can initiate targeted 

enforcement operations at crosswalks. 

Under this approach, a law enforcement 

officer in plain clothes will attempt 

to cross the street at an uncontrolled 

crosswalk. Drivers who do not yield 

to the officer will be pulled over and 

either cited or warned by patrol vehicles 

waiting beyond the crosswalk. More 

info: http://www.nhtsa.gov/staticfiles/

nti/pdf/812059-PedestrianSafetyEnforce

OperaHowToGuide.pdf
1-24 UNIT 1: FOUNDATIONS OF ROAD SAFETY ROAD SAFETY FUNDAMENTALS

meaningful improvements to 

road safety.

While there is evidence to suggest 

some success for well-designed and 

executed safety education campaigns 

when they are targeted at children,32 

the same results have not been 

shown for teens and adults when 

an educational campaign stands 

alone. Though well-intentioned, 

these approaches generally assume 

that people are not performing 

the desired behavior simply 

because they lack the appropriate 

information. However, this idea fails 

to take into account the fact that, 

in general, most human behavior is 

not the result of conscious, rational 

deliberation. People are largely 

influenced by emotions, values, 

social context, and culture, among 

many other factors. Thus, simply 

being presented with information 

or facts alone is unlikely to lead to 

any lasting behavior change. In the 

context of transportation safety, 

most people do not engage in risky 

or undesirable behaviors due to a 

lack of knowledge about the desired 

behavior. Instead, people act based 

on a variety of contributing factors. 

For example, consider the behavior 

of a pedestrian on a multi-lane 

undivided arterial. The goal of 

the pedestrian is to get to a bus 

stop located directly across the 

street from his current location. 

The pedestrian almost certainly 

knows that the desired behavior 

is to walk a quarter mile to the 

signalized intersection, wait and 

cross with the crossing signal, and 

then to backtrack a quarter mile to 

the bus station. However, instead 

the pedestrian chooses to cross in 

the middle of the block. The fact 

is that there are many factors that 

influence the pedestrian’s decision 

to cross mid-block (time, ability, 

weather, etc.), but likely the most 

important factor is that doing so 

just makes sense. People are wired 

to choose the option that makes 

the most intuitive sense. Efforts to 

change this behavior only through 

signs, posters or other educational 

campaigns will likely have only 

minimal effect.

Similar examples can be found 

throughout the transportation safety 

field. Most people already know they 

should wear their seatbelt, obey 

posted speed limit signs, and limit 

distractions while driving. Yet some 

people refuse to wear a seatbelt, 

Bicycle Safer Journey

Bicycle Safer Journey is an educational 

program intended to provide bicycle 

safety skills and education to children. 

The program uses interactive video 

lessons to teach children safe bicycling 

skills and provides resources for 

parents and teachers. The program 

can be accessed online at http://www.

pedbikeinfo.org/bicyclesaferjourney. 

Zegeer, C. V., 

Blomberg, R. D., 

Henderson, D., 

Masten, S. V., 

Marchetti, L., 

Levy, M. M., Fan, 

Y., Sandt, L. S., 

Brown, A., Stutts, 

J., & Thomas, L. J. 

(2008b). Evaluation 

of Miami–Dade 

pedestrian safety 

demonstration 

project. 

Transportation 

Research Record 

2073, 1-10.

32
ROAD SAFETY FUNDAMENTALS UNIT 1: FOUNDATIONS OF ROAD SAFETY 1-25

some people speed, and some people 

text while driving. Knowledge alone 

is not enough.

Successful education and 

enforcement campaigns recognize 

the reality of people’s behaviors and 

apply this knowledge to the safety 

efforts. For example, social norms 

and cultural influences can provide 

some explanation for why certain 

behaviors are common - even those 

behaviors known to be unsafe. 

Marketing interventions based on 

social norms have been applied 

to the areas of distracted driving 

and driving under the influence of 

alcohol. Such methods provide a 

way to examine safety problems and 

Media Campaign Effectiveness

Well planned and executed media 

campaigns centered on reducing 

alcohol-impaired driving can be 

effective in reducing the occurrence of 

alcohol related crashes. A study in 2004 

pointed to a 13 percent decrease in 

alcohol related crashes following these 

types of campaigns.33

Click It or Ticket

Click It or Ticket is a successful seat belt 

enforcement campaign that has helped to 

increase the national seat belt usage rate. 

The program uses public education to 

communicate the law and risks of not 

using seat belts in a variety of settings. 

The campaigns provide waves of education 

and enforcement along with high visibility 

media coverage to publicize and sustain 

the campaign. NHTSA manages this 

campaign annually with assistance from 

the State Highway Safety offices, law 

enforcement agencies, and national- and 

local-paid advertising.

Elder, R.W., et 

al. Effectiveness 

of mass media 

campaigns for 

reducing drinking 

and driving and 

alcohol-involved 

crashes: a 

systematic review. 

July 2004. http://

www.sciencedirect.

com/science/

article/pii/

S0749379704000467

33
1-26 UNIT 1: FOUNDATIONS OF ROAD SAFETY ROAD SAFETY FUNDAMENTALS

what might be done to address them 

through education and enforcement. 

Comprehensive 

Safety Programs

While each discipline has its own 

strengths, significant improvements 

in roadway safety are more likely 

when a program encompasses 

many disciplines rather than 

just one. Interdisciplinary team 

efforts can take on safety problems 

using multiple approaches and 

are therefore greater in scope 

than individual disciplines 

working in isolation. The need 

for this “multiple approach” 

solution requires collaboration 

among many parties. This type of 

collaboration is most clearly seen 

when agencies seek to create a 

comprehensive safety plan. Creating 

a comprehensive safety plan for 

a city, county, or state must be a 

data driven process. In doing so, 

agencies first begin by analyzing 

their safety data to identify 

emphasis areas where concentrated 

efforts are likely to yield the largest 

reduction in fatalities and serious 

injuries. 

A State’s Strategic Highway Safety 

Plan (SHSP) is an example of a 

comprehensive safety plan, and one 

of the best examples of a multidisciplinary, data driven planning 

effort. A State SHSP provides 

a framework for developing a 

coordinated and comprehensive 

approach to addressing road safety 

across a State. In the development of 

a State’s SHSP, safety stakeholders 

from across the State and across 

disciplines will consider all the 

data available (i.e., crash, injury 

surveillance, roadway and traffic, 

vehicle, enforcement, and driver 

data) that will help an agency 

understand where more safety 

emphasis is needed.34 Beyond crash 

records, an agency may choose to 

rely on alternate data sources like 

roadway characteristics and its own 

knowledge of crash risk to pursue 

systemic safety strategies. A systemic 

approach proactively identifies 

locations that may have a high risk 

of crashes but where the risk has 

not yet resulted in actual crashes.35

Strategic 

Highway 

Safety Plan

Provides a 

framework for 

developing a 

coordinated and 

comprehensive 

approach to 

addressing road 

safety across 

a State.

https://safety.

fhwa.dot.gov/shsp/

guidebook/

34

http://safety.fhwa.

dot.gov/systemic

35
ROAD SAFETY FUNDAMENTALS UNIT 1: FOUNDATIONS OF ROAD SAFETY 1-27

Demographic data showing where 

population growth has occurred, 

or where it is expected, can also 

influence an agency’s safety plans. 

One of the most critical components 

of the SHSP is an evaluation of past 

efforts, so that the agency can know 

what strategies are working and so 

that progress toward goals can be 

measured and tracked over time.

Road safety planning, like the field of 

safety itself, is multidisciplinary in 

nature and relies upon the expertise 

and involvement of numerous 

perspectives. Once developed, these 

safety plans influence activities 

ranging from roadway design and 

engineering to law enforcement and 

safety education. 

Each of the agencies and 

organizations involved in 

transportation safety brings a unique 

and valuable perspective to bear on 

the roadway safety problem. Their 

competing philosophies, worldviews 

and problem solving approaches, 

however, can make collaboration 

difficult. Creating a foundation 

for effective collaboration and 

establishing a process to support 

collaborative efforts are two ways 

to overcome these barriers. One 

way to create a foundation for 

collaboration is to ensure that each 

agency understands the impact 

that its actions have on road safety 

and that each makes safety its top 

priority. The example of a State 

Strategic Highway Safety Plan shows 

this type of collaboration. The SHSP 

process brings together all potential 

areas of safety emphasis, including 

intersections, non-motorized 

users, rural crashes, and others, 

and uses a data driven approach 

to identify priorities and areas 

of need. This foundation can be 

further strengthened by identifying 

which agencies or organizations are 

responsible for implementing each of 

the strategies identified in the SHSP. 

In the U.S., no single player manages 

all programs and disciplines that 

impact road safety. Therefore, 

collaboration among all players is 

fundamental to consistently reduce 

serious injuries and fatalities.

J FIND the website for your State or 

local road safety program. Identify 

initiatives that your State or local 

agency is implementing in the areas of 

planning, engineering, education, and 

enforcement.

J CONSIDER a hypothetical situation 

where it is your job to convene a team 

of professionals to visit a high crash 

intersection and explore possible 

solutions to the safety problem. Create 

a list of the people who should be 

included on that team and briefly 

describe each person’s role. Be sure to 

consider the many different types of 

programs and strategies that can be 

used to improve road safety. 

J SELECT an area of concern, either a 

specific type of road user or an unsafe 

behavior, and discuss how road safety 

in this topic area could be addressed or 

improved through multiple disciplines. 

Possible topics include:

J Older drivers

J Underage drinking

J Fatigued or drowsy driving

J Pedestrians

EXERCISES
1-28 UNIT 1: FOUNDATIONS OF ROAD SAFETY ROAD SAFETY FUNDAMENTALS

Drivers of motor vehicles are far 

from the only users of the road, 

despite accounting for the majority 

of trips taken in the U.S. The public 

right-of-way on most roads is 

usually shared by a number of 

different users, traveling by a 

variety of modes for any number of 

different reasons. Transportation 

professionals must understand 

the mobility and safety needs of 

different user groups and how 

they interact with one another to 

gain a better understanding of 

safety problems and their 

potential solutions.

Road user groups include:

J Passenger vehicle drivers 

and occupants

J Drivers of trucks 

and other large vehicles

J Motorcyclists

J Pedestrians

J Bicyclists

Passenger Vehicle Drivers 

and Occupants

Passenger vehicles are typically 

defined as sedans, pickup trucks, 

minivans, and sport utility vehicles 

and represent the primary mode 

of transportation for the majority 

of Americans. Since these vehicles 

account for the vast majority of 

registered vehicles and vehicle 

miles traveled, it is not surprising 

that much of the transportation 

infrastructure prioritizes the needs 

of these drivers. 

However, despite the priority given 

to drivers of passenger vehicle, 

there remain many unresolved 

safety issues for these drivers. At 

the core of most of these issues are 

the driver’s actions while navigating 

the road network. Engineers may 

work to make a road nominally 

safe by ensuring it follows the 

latest recommendations and design 

standards. However, drivers do not 

always interact with the road system 

as road designers expect them to. 

Thus, a nominally safe road may 

be much less safe in a substantive 

sense. While the common reaction 

has been to assume that some 

fault or “driver error” led to the 

crash, this approach fails to take 

into account a common behavioral 

principle known as behavioral 

adaptation. Simply put, behavioral 

adaptation refers to the unconscious 

process by which people react to 

their environment -- people cannot 

be considered to be a constant in 

the system.

Consider a town that wants to 

resurface and widen a two-lane 

collector roadway through an 

older neighborhood with mature 

street trees. The existing road has 

9.5 foot wide lanes, a 30 mi/h (48 

ki/h) speed limit, and street trees 

between the roadway and sidewalk. 

Design guidance may suggest a 

typical lane width of 12 feet and a 

wider roadside clear zone. It is easy 

to assume that the safest choice 

would be to design a road with the 

widest lanes possible and removal 

Road Users

CHAPTER 4 FOUNDATIONS OF ROAD SAFETY
ROAD SAFETY FUNDAMENTALS UNIT 1: FOUNDATIONS OF ROAD SAFETY 1-29

of the roadside hazards. However, 

after this resurfacing and widening 

project was completed, both traffic 

speeds and crash severity along this 

roadway may increase considerably. 

On the surface, this may seem 

counterintuitive.

In essence, most people drive at 

a speed that feels safe to them. 

To reach this “safe speed,” 

people unconsciously assess the 

roadway and its characteristics. 

Navigating a narrow, curvy road 

with significant roadside hazards is 

more challenging than navigating a 

straight, wide road with large clear 

zones, so people unconsciously 

drive slower and more cautiously on 

the narrow road. When the driving 

task is made easier by widening 

the lanes and removing roadside 

hazards, people will not maintain 

their original behavior. In fact, 

the assumption should be that 

people will adapt to this change 

and unconsciously change their 

behavior accordingly, in this case by 

increasing their speed.

Behavioral adaptation is not 

specific to passenger vehicles. 

When designing the transportation 

infrastructure, engineers must 

consider how human behavior plays 

affects all roadway users. Roadway 

designers must design roads not 

for the way in which they would 

like users to behave, but for the 

way in which users actually behave. 

Behavior of drivers and other road 

users will be covered in a greater 

detail in Unit 2.

The intended speed of this road is 35 miles per hour, but the wide design of the road and 

the number of lanes leads drivers to drive much faster.
1-30 UNIT 1: FOUNDATIONS OF ROAD SAFETY ROAD SAFETY FUNDAMENTALS

Drivers of Trucks and 

Other Large Vehicles

Much of the transportation 

network across the country serves 

an important commercial need. 

Truck drivers, in particular, play 

a significant role in the national 

economy and are responsible for 

moving goods between and within 

cities and States. Large trucks 

account for only 4 percent of 

registered vehicles in the U.S., but 

they make up 9 percent of total 

vehicle miles traveled and accounted 

for 12 percent of total traffic fatalities 

in 2013.36 These large trucks share 

space on the roads with passenger 

vehicles, and have their own safety 

needs. Nationally in 2013, there were 

just under 4,000 people killed in 

crashes involving large trucks, and 

71 percent of them were occupants 

of the other vehicle involved in the 

crash. However, large truck safety 

has improved over time. Between 

2004 and 2013, the miles covered by 

large trucks increased by roughly 25 

percent, while fatalities involving 

large trucks decreased by about 20 

percent (from 4,902 to 3,906).37

Commercial trucks are not the 

only large vehicles on the roads. 

Transit vehicles occupy space on 

our roadways as well, though they 

typically serve pedestrians and 

bicyclists. Transit vehicles that share 

space with passenger vehicles also 

have unique needs and challenges. 

Many of the safety issues associated 

with transit vehicles are similar to 

those of large trucks. Bus operators 

have to consider how stopping 

in traffic impacts the flow and 

operation of the transportation 

system, and must also consider the 

safety of their passengers boarding 

and disembarking the vehicle.

Road designs that accommodate 

large vehicles can sometimes be 

directly at odds with designs that 

favor pedestrians and bicyclists. 

For example, a pedestrian is 

more comfortable crossing an 

intersection if the turns are very 

tight, where the distance between 

corners in minimized to shorten 

the walking distance and decrease 

the time in the roadway. Large 

trucks and buses, however, require 

a larger turning radius (when 

compared to passenger vehicles) 

in order to turn safely. When 

designing intersections for large 

trucks, designers are tempted to 

increase the amount of space in an 

intersection and widen the corners. 

This change will make the turn 

easier, but it will also be more 

uncomfortable (and possibly less 

safe) for pedestrians. As described 

previously, these trade-offs need 

to be assessed and discussed when 

planning road projects.

Motorcyclists

In recent years, motorcycling 

has become increasingly popular 

throughout the U.S. Since 2000 the 

number of registered motorcycles 

in the U.S. has nearly doubled. 38 39 

The result was a 71% increase in 

the number of motorcyclist 

fatalities (from 2,897 in 2000 

to 4,957 in 2012). Motorcyclists 

represented 15 percent of all traffic 

fatalities in 2012, compared to 

just 7 percent of fatalities in 2000. 

40 Motorcyclists are significantly 

overrepresented in traffic fatalities 

since they account for only 

3 percent of registered vehicles 

and 0.7 percent of total vehicle 

miles traveled in 2012.41

http://www-nrd.

nhtsa.dot.gov/

Pubs/812150.pdf

http://www.

fhwa.dot.gov/

policyinformation/

statistics/2013/pdf/

mv1.pdf

https://www.fhwa.

dot.gov/ohim/hs00/

pdf/mv1.pdf

http://www-fars.

nhtsa.dot.gov/

Main/index.aspx

http://www-nrd.

nhtsa.dot.gov/

Pubs/812035.pdf

36

38

39

40

41

37
ROAD SAFETY FUNDAMENTALS UNIT 1: FOUNDATIONS OF ROAD SAFETY 1-31

In general, many of the roadway 

modifications done to improve 

safety for passenger vehicles can 

pose a challenge for motorcyclists. 

Rumble strips can be difficult to 

traverse, especially at low speeds. 

Guard rails, in particular cable 

barriers, can present a serious 

hazard to a motorcyclist impacting 

one at a high speed. Within the 

driving environment, motorcyclists 

are small compared to larger 

vehicles and can be difficult to see, 

especially early or late in the day 

when lighting levels are lower. 

Pedestrians

Walking is the most basic form 

of transportation. At some point 

during a typical day, nearly every 

person is a pedestrian. People walk 

to get to a bus station, to go from 

home to school, or to get from a 

parked vehicle to the front door 

of a business. Some walking trips 

are taken out of necessity – not 

all households own a vehicle, 42

and children and individuals with 

disabilities may not have the option 

to drive. Many more walking trips 

are taken by choice, especially for 

exercise or health. A 2012 survey 

found that 39 percent of trips taken 

by foot are done for exercise or 

personal health purposes. 43 Walking 

is also more common in densely 

populated urban areas, due to the 

close proximity of destinations and 

other services like transit stations.

Regardless of the reasons for 

walking, this mode accounts for 

nearly 11 percent of all trips taken 

in the U.S., according to the 2009 

National Household Travel Survey 

(NHTS). 44 The NHTS shows that 

about a third of all trips taken in 

the U.S. are shorter than one mile, 

and 35 percent of these trips are 

taken by foot. In the 2005 Traveler 

Opinion and Perception Survey 

(TOP), conducted by FHWA, data 

showed that about 107.4 million 

Americans (51 percent of the 

traveling public) use walking as a 

regular mode of travel. 45

Pedestrians (along with bicyclists) 

are among the most vulnerable road 

users, and this is reflected in crash 

data. The 4,743 pedestrians killed 

in 2012 represented 14.1 percent 

of total traffic fatalities in the U.S. 

that year. Between 2008 and 2012, 

motor vehicle fatalities decreased 13 

percent, while pedestrian fatalities 

increased 8 percent. Within the 

population of pedestrians, there 

are certain groups which are 

especially vulnerable. These include 

young children, older adults, and 

individuals with disabilities. 

https://info.ornl.gov/

sites/publications/

Files/Pub50854.pdf

http://www.

pedbikeinfo.org/

data/factsheet_

general.cfm

http://www.

pedbikeinfo.org/

cms/downloads/15-

year_report.pdf

http://www.fhwa.

dot.gov/reports/

traveleropinions/

1.htm

42

43

44

45
1-32 UNIT 1: FOUNDATIONS OF ROAD SAFETY ROAD SAFETY FUNDAMENTALS

Road Diet

In 2008, Seattle Department of 

Transportation implemented a road diet 

on a 1.2-mile (1.9-kilometer) section of 

Stone Way North from N 34th Street to N 

50th Street. In addition to serving motor 

vehicles, this segment of Stone Way North 

helps connect a bicycle path with a park. 

Within five blocks are eight schools, two 

libraries, and five parks.

The modified segment was originally 

a four-lane roadway carrying 13,000 

vehicles per day. For this corridor, 

the city’s 2007 bicycle master plan 

recommended climbing lanes and shared 

lane markings (previously known as 

“sharrows”). The cross section reduced 

the number of travel lanes to add bicycle 

lanes and parking on both sides. The 

resulting corridor saw a decrease in the 

85th percentile speed, while the overall 

capacity remained relatively unchanged 

despite the reduction in the number 

of lanes. The number of bicyclists on 

the corridor increased by 35 percent, 

but crashes involving bicyclists did not 

increase. Pedestrian crashes declined by 

80 percent following the project.

Summarized from a 2011 Public Roads 

article: http://www.fhwa.dot.gov/publications/

publicroads/11septoct/05.cfm

Before (left) and after (right) pictures of Stone Way North. (Source: Seattle DOT)

Young children are a vulnerable 

road user group, and may be more 

likely than adults to rely on walking 

as a primary transportation mode 

– especially before they are old 

enough to drive. One area of concern 

is creating a safe environment for 

young children when they walk to 

school. Safety professionals need 

to ensure that sidewalks and street 

crossings have the appropriate 

measures to assist children in 

traveling safely, and educate 

children about safe walking.

Another vulnerable portion of the 

pedestrian population includes 

those who are blind or visually 

impaired. These pedestrians have 

increased challenges in navigating 

the road safely, particularly at 

street crossings. Challenges faced 

by a blind or visually impaired 

pedestrian include finding the 

appropriate crossing point at an 

intersection corner or midblock 

location, determining the appropriate 

time to cross, and crossing quickly 

and accurately. Both crossing and 

traversing a sloped sidewalk can be 

equally difficult for an individual in a 

wheelchair, where even slight cracks 

or bumps in the sidewalk can present 

major obstacles. The difficulties of 

these challenges increase at locations 
ROAD SAFETY FUNDAMENTALS UNIT 1: FOUNDATIONS OF ROAD SAFETY 1-33

with unusual geometry, irregularly 

timed signals, or non-stop vehicle 

flow such as roundabouts and 

channelized turn lanes.

Older adults face many challenges 

as well. There are a number of 

age-related changes that affect the 

functional ability of older adults 

to safely walk and cross the street. 

These changes include diminished 

physical capability, sensory 

perception, cognitive skills and lag 

in reflexive responses. Eyesight 

deterioration can diminish an older 

person’s ability to see and read 

guide signs, slow their reaction time 

and decrease their ability to gauge 

a vehicle’s approaching speed or 

proximity. 46

Drivers and pedestrians share 

responsibility for many pedestrian 

fatalities, as both parties attempt 

to navigate through the same 

space at the same time. Though 

we know that certain factors are 

likely to result in more severe 

pedestrian crashes, such as speed 

47, no single cause stands out as 

the major contributor to pedestrian 

crashes. For this reason, no single 

countermeasure alone would likely 

make a substantial impact on the 

number of pedestrian crashes. A 

successful countermeasure program 

should use a mix of engineering, 

environmental, educational and 

enforcement measures to improve 

pedestrian safety. 48

Source: “Identifying 

Countermeasure 

Strategies to 

Increase Safety to 

Older Pedestrians,” 

National Highway 

Traffic Safety 

Administration, 1.

https://www.

aaafoundation.org/

sites/default/files/

2011Pedestrian

RiskVsSpeed.pdf

Source: “Identifying 

Countermeasure 

Strategies to 

Increase Safety to 

Older Pedestrians,” 

National Highway 

Traffic Safety 

Administration, 36

46

47

48
1-34 UNIT 1: FOUNDATIONS OF ROAD SAFETY ROAD SAFETY FUNDAMENTALS

Bicyclists

Bicyclists were some of the first 

users of U.S. roads, and the group 

that made the earliest push to 

improve road conditions. In recent 

years, bicycling has seen a rise in 

popularity for both recreation 

and transportation. Data from 

the 2009 NHTS showed that while 

only 1 percent of all trips are 

taken by bicycle, the number of 

bicycle trips doubled between 

1990 and 2009.49 

While bicyclists account for only 1 

percent of all trips, the 726 bicyclist 

fatalities in 2012 represented 2 

percent of all traffic fatalities 

that year.50 While the number of 

bicyclists killed has risen only 

slightly since 2008, the decline in 

motor vehicle deaths means that 

bicyclists account for an increasing 

share of total traffic fatalities.

Bicyclists face unique challenges 

as road users. More often than not, 

bicyclists share space with motor 

vehicles and are considered legal 

users of the road in most locations. 

Many potential bicycle riders are 

not comfortable sharing the road 

with heavy vehicular traffic and 

may be deterred from riding their 

bicycles. Intersections can also 

pose a challenge to bicycle riders 

when they include high volumes 

of turning traffic and a large 

number of lanes. These barriers 

to bicycling, busy street segments 

and intersections, often discourage 

potential riders even when the rest 

of a bicycle network is comfortable. 

Many bicyclists are willing to go out 

of their way to use a route that has 

lower vehicle volumes and speeds, or 

bicycle facilities that are separated 

from traffic. Safe bicycle facilities 

can also improve connections to 

shopping, transit, jobs, schools, and 

essential services.

Conclusion

Successful road safety programs 

will consider the needs of all users 

when planning and developing 

transportation projects. Each user 

group plays an important role in 

the transportation system, and 

each has unique safety needs that 

safety professionals must consider. 

Road user decisions are influenced 

by a variety of factors, and the 

combinations of factors that result 

in particular travel behavior cannot 

easily be categorized or understood 

in simple terms.

J PROVIDE an example of a road 

project where the changes resulted in 

improvements for one user group, but 

negatively impacted another group. This 

example could be hypothetical or based 

on a real world experience.

J VISIT the Fatality Analysis Reporting 

System (FARS) Encyclopedia home page 

(http://www-fars.nhtsa.dot.gov/Main/

index.aspx). Use the data available 

for the most recent year to document 

fatality numbers for the different road 

user groups discussed in this chapter 

(e.g. motorists, pedestrians, bicyclists). 

What other information on road user 

safety can you find with the tools 

available in FARS, and what data is 

not included?

EXERCISES

http://www-nrd.

nhtsa.dot.gov/

Pubs/812018.pdf

50

http://www.

pedbikeinfo.org/

cms/downloads/

15-year_report.pdf

49
ROAD SAFETY FUNDAMENTALS UNIT 1: FOUNDATIONS OF ROAD SAFETY 1-35

THIS PAGE INTENTIONALLY LEFT BLANK
After reading the chapters and completing 

exercises in Unit 1, the reader will be able to:

J EXPLAIN the systems that drive human 

behavior and give examples of each

J EXPLAIN why it is important to 

consider the nature of human 

behavior when designing and 

implementing systems or programs

LEARNING OBJECTIVES

Human 

Behavior and 

Road Safety

UNIT 2
ROAD SAFETY FUNDAMENTALS UNIT 2: HUMAN BEHAVIOR AND ROAD SAFETY 2-1

Understanding Human Behavior

Introduction

Guinea worm disease is a parasitic 

infection that occurs in remote 

parts of Africa. Symptoms of Guinea 

worm disease can be debilitating 

and lead to secondary infections, 

both of which can affect an infected 

person’s ability to perform everyday 

tasks including working, harvesting 

food and caring for children. The 

disease is caused by drinking water 

contaminated with Guinea worm 

larvae. When a worm is mature, 

it creates a painful blister on the 

infected person’s skin. If the person 

immerses the affected body part 

in water, it can temporarily relieve 

the pain from the blister. However, 

this also allows the worm to release 

eggs into the water, continuing the 

infection cycle by spreading the 

disease to others1

. 

There were 3.5 million cases of 

Guinea worm disease throughout 

the world in 1986. By 2015, there 

were only 22 cases. In 30 years the 

disease has been nearly eradicated 

— the only human disease to be 

eradicated besides smallpox2,3. How 

were such large advances made in 

only 30 years, and what does this 

have to do with road safety?

Unlike smallpox, there are no known 

medicines or vaccines that prevent 

Guinea worm disease. Eradication, 

therefore, required a different 

approach: changing human 

behavior.

The Human Factor

A report from the National 

Cooperative Highway Research 

Program (NCHRP) defines “human 

factors” as follows:

Human factors is an applied, scientific 

discipline that tries to enhance the 

relationship between devices and 

systems, and the people who are meant 

to use them. As a discipline, human 

factors approaches system design with 

the “user” as its focal point. Human 

factors practitioners bring expert 

CHAPTER 5 HUMAN BEHAVIOR AND ROAD SAFETY

Cairncross, S., 

Muller, R., and 

Zagaria, N. (2002). 

Dracunculiasis 

(Guinea Worm 

Disease) and 

the Eradication 

Initiative. Clinical 

Microbiology 

Reviews, 223-246.

World Health 

Organization and 

the Carter Center, 

Eradication of 

Guinea Worm 

Disease: Case 

Statement, 2016. 

Available at: https://

www.cartercenter.

org/resources/pdfs/

health/guinea_

worm/2016-gw-casestatement.pdf

WHO, 

Dracunculiasis 

Fact Sheet. May 

2016. Available at: 

http://www.who.

int/mediacentre/

factsheets/fs359/en/

1

2

3
2-2 UNIT 2: HUMAN BEHAVIOR AND ROAD SAFETY ROAD SAFETY FUNDAMENTALS

John L. Campbell, 

Monica G. Lichty; et 

al. (2012). National 

Cooperative 

Highway Research 

Program Report 

600: Human 

Factors Guidelines 

for Road Systems 

(Second Edition). 

Washington, D.C.: 

Transportation 

Research Board.

Kahneman, D. (2011) 

Thinking, Fast and 

Slow. Farrar, Straus 

and Giroux

4

5

knowledge concerning the capabilities 

and limitations of human beings that 

are important for the design of devices 

and systems of many kinds.4

In road safety, the term human 

factors is typically used to describe 

how people respond to the 

roadway environment. However, 

people are not simply users of the 

transportation system. Humans 

also design, engineer, build and 

maintain the roadway environment, 

the vehicles using it and the laws 

governing behavior of roadway users 

and vehicle manufacturers. In that 

sense, the entire transportation 

system is a product of human 

factors. The term human factors 

conveys an oversimplified notion 

of the role of human behavior in 

transportation safety. The human 

part of the equation is more complex 

than simply a list of discrete factors. 

Key Principles of 

Human Behavior

To understand human behavior, it is 

important to bear in mind four key 

principles.

J Human behavior is guided by two 

different systems (deliberative 

and intuitive).

J Humans are not exclusively 

logical, rational beings.

J Human behavior is heavily 

influenced by the environment.

J Humans make mistakes.

Let’s discuss these concepts as they 

relate to road safety.

Human behavior is guided 

by two different systems

Human behavior is largely guided by 

two different systems – a deliberate, 

rational system (deliberative) and 

an implicit, unconscious system 

(intuitive)5

.

The deliberative system is a 

conscious system wherein a person 

considers information using rational 

thought, logic and reasoning in 

deciding on an action.

For example:

When driving home after work, 

a driver decides to change routes 

to avoid an area that is usually 

congested at this time of day. 

In this example, the driver 

considered the available information 

(time of day and previous 

experience with that location) 

and made a conscious decision to 

take another route.

The intuitive system is an implicit, 

unconscious process by which 

a person makes nearly 

instantaneous decisions and 

takes a resulting action. 

For example: 

As a driver approaches a signalized 

intersection, the light turns yellow. 

Without conscious thought, the 

driver either proceeds through the 

intersection or comes to a stop.

In this example, the driver receives 

information from the environment 

(the yellow light), combines it with 

an understanding of the specific 

circumstance based on the driver’s 

previous experiences, and takes an 

action almost immediately. It is 

important to realize the intuitive 

system acts nearly instantaneously 

without the driver’s awareness of 

the process.
ROAD SAFETY FUNDAMENTALS UNIT 

2: HUMAN BEHAVIOR AND ROAD SAFETY

2-3

We often incorrectly assume that 

human behavior is largely controlled 

by the deliberative system when, 

in fact, most behaviors are a result 

of the intuitive system. In other 

words, most human behavior is not 

the result of conscious, rational 

deliberation. For most actions, we 

don’t have enough time or available 

information to do a logical analysis 

before acting. The intuitive system 

allows us to act without this timeconsuming conscious decisionmaking process. 

To think of this another way, 

consider the deliberative system 

as similar to the decision making 

process of a computer. Computers 

function exclusively using a 

deliberative system. They take 

in information, process it using 

explicit algorithms and deliver a 

result. However, humans do not 

function this way. They generally 

make decisions that appear to reflect 

instinctual processes rather than 

systematic rational considerations.

Humans are not exclusively 

logical, rational beings 

Although people take in and 

interpret information, they do so in 

the context of a number of factors, 

such as prior experience, emotions, 

cultural norms, moral beliefs, social 

pressures, convenience, habits and 

financial considerations, among 

many others. Rational calculations 

based on objective evidence are 

often not even possible, and when 

they are, they must compete with 

these other influences. This is why 

people often make decisions that are 

not necessarily the most appropriate 

choice for their health and wellbeing. 

We know that cooking dinner 

at home may be healthier, but 

sometimes it is easier and more 

convenient to have a pizza delivered 

instead. We know we should exercise 

more and get the recommended 

amount of sleep each night, but 

work, family and other obligations 

Flossing and human behavior

At some point in your life, you have 

probably been told that regular flossing 

is good for your dental health. Through 

the years, you’ve likely had conversations 

about flossing with your dentist or dental 

hygienist who encouraged you to floss 

more. Perhaps they showed you the proper 

way to floss and sent you home with your 

own floss in an effort to encourage you 

to start. For a few days or weeks after the 

appointment, you may have deliberately 

flossed more regularly. But if you’re like 

most people, you soon reverted to old 

habits, and the floss sat unused in a 

cabinet. Why do we do this?

Typically, programs aimed at influencing 

human behavior take an educational or 

informational approach on the assumption 

that people act a certain way because 

they lack knowledge about the potential 

consequences, benefits or alternatives. 

Surely, if people simply were aware of the 

benefits of flossing or the consequences 

of not flossing, they would change their 

behavior and become regular flossers. This 

approach appeals to the belief that human 

behavior is rational. 

Although commonly used, this approach 

fails to take into account the complexities 

of human behavior. Other factors influence 

our behaviors – flossing is inconvenient, 

takes time and can be uncomfortable. The 

negative consequences of not flossing (e.g., 

gum disease) are not immediately visible. 

Although people repeatedly hear messages 

explaining why flossing is important, rates 

of flossing among the general population 

remain low. 
2-4 UNIT 2: HUMAN BEHAVIOR AND ROAD SAFETY ROAD SAFETY FUNDAMENTALS

can make this difficult. We know we 

should get a flu shot, but a fear of 

needles may keep us away. 

Humans are largely intuitive beings 

which means their actions are rarely 

the result of a systematic, rational 

decision making process. For years, 

many people did not brush their 

teeth daily, even though the benefits 

of brushing were widely known. 

It was not until mint flavoring 

was added to toothpaste that daily 

brushing became the norm. That 

is, information about the benefits 

of brushing did little to change 

behavior; what convinced people 

to brush was a desire for the clean 

feeling they associated with the 

mint.6

 Because the factors that 

affect human behavior are complex 

and interrelated, behavior is not 

easily changed. When attempting 

to change the behavior of others, 

we tend to assume that people are 

entirely logical and rational beings. 

However, experience repeatedly 

shows this is not the case.

This situation is not unique to 

dental hygiene. We regularly do 

things that we generally realize are 

not in our best interest. We don’t eat 

the recommended amounts of fruits 

and vegetables. We don’t get enough 

sleep. We don’t exercise as much as 

we should. Think about examples 

from your own life.

Human behavior is heavily 

influenced by the environment

Often the environment has a much 

stronger influence on a person’s 

behavior than internal conditions 

(e.g., attitudes and personality) 

commonly assumed to be influential. 

The environment includes the 

physical environment, as well as 

social and organizational contexts, 

such as policies and social norms. 

Given that most behavior is 

intuitive, people generally do 

not know the true reasons for 

their actions, nor can they validly 

articulate what might influence their 

actions. People can usually provide 

explanations for their behavior after 

the fact, but research shows people 

are often not aware of the strong 

influence of environmental factors 

on their behavior. An example in 

Unit 1 of this book describes a town 

that aims to resurface and widen a 

Duhigg, Charles. 

The Power of Habit: 

Why We Do What 

We Do in Life and 

Business

Gates TJ, Qin 

X, Noyce DA. 

Effectiveness of 

Experimental 

Transverse-Bar 

Pavement Marking 

as Speed-Reduction 

Treatment on 

Freeway Curves. 

In Transportation 

Research Record: 

Journal of the 

Transportation 

Research Board, No. 

2056, Transportation 

Research Board 

of the National 

Academies, 

Washington, D.C., 

2008, pp. 95–103. 

Federal Highway 

Administration. 

Engineering 

Countermeasures 

for Reducing 

Speeds: A 

Desktop Reference 

of Potential 

Effectiveness. 

http://safety.fhwa.

dot.gov/roadway_

dept/horicurves/

fhwasa07002/ch7.

cfm. 

6

7

8

Optical Speed Bars

Optical Speed Bars (OSBs) have 

shown promise in reducing vehicle 

speeds in advance of hazardous 

locations7

. OSBs are a series of white 

rectangular markings, placed just 

inside both edges of the travel lane 

and spaced progressively closer, to 

create the illusion of increasing speed 

when traveling at a constant rate as 

well as the impression of a narrower 

lane8

. A compelling characteristic of 

optical speed bars is that they operate 

on intuitive, rather than conscious, 

decisions made by drivers/riders. By 

creating a sense of increasing speed 

as riders approach a dangerous curve, 

they should induce riders to slow down 

– as an instinctive reaction rather than 

a conscious decision.
ROAD SAFETY FUNDAMENTALS UNIT 2: HUMAN BEHAVIOR AND ROAD SAFETY 2-5

two-lane collector roadway through 

a neighborhood with mature trees. 

However, after completing the 

project, both speeds and crash 

severity increased. Behavioral 

adaptation refers to the unconscious 

process by which people react to 

their environment. While driving, 

people unconsciously assess the 

roadway and its characteristics and 

modify their behaviors accordingly. 

This may seem counterintuitive, 

but as discussed, human behavior is 

an intuitive process that is heavily 

influenced by the environment. A 

wider road with limited roadside 

hazards feels safer and people 

unconsciously adapt their behavior 

accordingly. You should assume 

people would not maintain their 

original behavior when the driving 

environment is changed. 

Roadway designers must design 

roads not for the way in which they 

would like users to behave, but for 

the way in which users actually 

will behave. In general, people 

don’t just do what they are told to 

do — by a sign, a law or another 

person. Instead, they integrate 

information from many parts of 

their environment along with their 

own historical experience as they 

determine (usually non-consciously) 

what they should do in a given 

situation12. 

Humans make mistakes

Both our deliberative and intuitive 

systems can lead us to make 

mistakes. Actions reached by a 

deliberative process can be mistaken 

if we fail to consider all relevant 

information or if we process it 

incorrectly. Similarly, our intuitive 

system can lead to errors in 

situations with which we have little 

or no experience. Experience helps to 

refine the intuitive processes, so the 

likelihood of mistakes declines with 

exposure to situations. However, 

mistakes are inevitable and the 

transportation infrastructure needs 

to be designed with the recognition 

that road users will make mistakes 

and that they will often make them 

in predictable ways.

Have you ever looked down at your 

speedometer and realized that you 

were driving substantially over the 

speed limit? You probably didn’t 

make a conscious (deliberative) 

decision to exceed the speed limit. 

Instead, you reached that speed by 

taking cues about the proper speed 

from your environment (intuitive). 

Characteristics of the road, such as 

wide lanes, multiple travel lanes, 

Cialdini. R.B. 

(20005). Basic 

Social Influence Is 

Underestimated. 

Psychological 

Inquiry, 16: 158-161

Cialdini, R.B., 

Demaine, L.J., 

Sagarin, B.J., Barrett, 

D.W., Rhoads, 

K., & Winter, P.L. 

(2006). Managing 

social norms for 

persuasive impact. 

Social Influence, 

1: 3-15

Cialdini, R.B. 

(2007). Descriptive 

social norms as 

underappreciated 

sources of 

social control. 

Psychometrika, 72: 

263-268

9

10

11

Etzioni, Amitai. 

Human Beings Are 

Not Very Easy To 

Change After All, 

Saturday Review, 

June, 1972.

12

Environment affects behavior

Research has shown that people are more 

likely to help another person (in a nonemergency situation) if they see someone 

else helping first. Social psychologist 

Robert Cialdini demonstrated this by 

counting donations given to a street 

musician with and without a colleague first 

modeling the behavior by donating money. 

He found that many more people gave the 

musician money when the behavior was 

modeled than in the control condition with 

no behavior modeling (eight donations 

in the modeled condition versus one 

donation in the control condition). Further, 

when people in the modeled condition 

were asked why they donated, no one 

realized that they had been influenced 

by the behavior of another person. 

Instead, they attributed their donations 

to something else, such as enjoyment of 

the song or how they felt about the person 

playing the music9,10,11.
2-6 UNIT 2: HUMAN BEHAVIOR AND ROAD SAFETY ROAD SAFETY FUNDAMENTALS

presence of a median and long 

gentle curves, convey the message 

that the road can accommodate 

high speeds. Additionally, the speed 

of other vehicles is a particularly 

salient indicator of the right speed.

Recall this example from Unit 1 

(Figure 1-1). Although the posted 

speed limit is 35 mph, many people 

drive much faster than that. This is 

not because they all have a blatant 

disregard for safety. Instead, they 

are unconsciously taking cues 

from their environment, which is 

telling them it is safe to travel at a 

higher speed. Add to this the fact 

that modern vehicles have been 

engineered for occupant comfort, so 

many of the auditory and haptic cues 

(e.g., wind noise, bumps, road noise, 

etc.) that previously gave drivers 

feedback about their speed have been 

eliminated. On a road 

with very few other vehicles, the 

only clear clue to one’s speed is 

the speedometer.

Roads constructed according to the 

recommended design standards may 

be considered safe, but in reality, 

they may only be nominally safe. 

The fact that some road designs 

encourage higher speeds can 

make it substantively unsafe. The 

transportation system is designed, 

built, maintained, governed and 

used by humans. It is often cited 

that human error contributes to 

more than 90% of traffic crashes, 

most often referring to a road user 

error. However, it is important to 

remember that errors by road users 

are not the only human errors that 

can occur. 

For example:

On a rural two-lane road, an SUV 

FIGURE 2-1: Example of unconscious clues leading to higher speed
ROAD SAFETY FUNDAMENTALS UNIT 2: HUMAN BEHAVIOR AND ROAD SAFETY 2-7

J MAKE a list of your own driving 

behaviors. What behaviors involve the 

deliberative system? What behaviors 

are intuitive?

J WORK with your state department of 

transportation to identify a crash cluster 

in your area. It’s highly unlikely that many 

drivers have independently made the 

same mistake at the same location. 

What characteristics of the roadway — 

as designed or built — may have 

contributed to this cluster of crashes? 

What modifications might be made that 

would not be offset by 

behavioral adaptation?

EXERCISES

driver over-compensates when a tire 

slips off the roadway causing the 

vehicle to roll over and strike a tree 

on the opposite side of the road.

Where was the human error in 

this example? Was it in the driver 

who didn’t stay on the road and 

overcompensated with steering? Was 

the road maintained improperly or 

inadequately? Could the crash have 

been prevented if edgeline rumble 

strips had been installed, or if the 

road had a paved shoulder instead 

of a soft gravel shoulder? Should the 

tree next to the roadway have been 

removed? Could SUVs be designed so 

they are less susceptible to roll over? 

The answer is that a combination 

of several of these caused the crash, 

not simply the driver’s error. Just as 

in airplane crashes, it is quite rare 

that any single factor in a motor 

vehicle crash was the sole reason for 

the crash or for its severity.

Meeting nominal safety does not 

guarantee that a crash will never 

occur, nor does it guarantee that 

users will behave in the intended 

way. Those in charge of the road 

should use professional judgement 

to prioritize safety improvements 

and select appropriate designs 

within a range of options based on 

consideration of road user behavior. 

Unit 3 discusses how many kinds 

of data, such as crash data and 

behavioral observation, can be used 

to evaluate the substantive safety of 

the road.
2-8 UNIT 2: HUMAN BEHAVIOR AND ROAD SAFETY ROAD SAFETY FUNDAMENTALS

Changing Human Behavior

CHAPTER 6 HUMAN BEHAVIOR AND ROAD SAFETY

Let’s return to the Guinea worm 

disease example. You may be 

wondering why something so 

seemingly unrelated to improving 

safety in a modern transportation 

system was used to introduce this 

unit. The fact that Guinea worm 

disease is nearly extinct in only 30 

years is a tremendous achievement. 

The fact that it was done through 

behavior change alone, without the 

use of vaccines or medication, is 

unprecedented.

Road safety professionals would 

be wise to consider the successful 

approach to eradicate Guinea worm 

disease. Although the desired 

behaviors may be different, the 

general strategies for influencing 

human behavior are the same. Even 

though changing human behavior 

is exceedingly difficult, it is 

possible to achieve behavior change. 

However, this requires that we take 

into account the nature of human 

behavior instead of assuming that 

simply providing information is 

sufficient.

Understanding factors that 

influence human behavior 

To change human behavior, 

it is important to identify and 

understand not only the target 

behavior but also any other factors 

that influence the behavior. 

Attempting to change a behavior 

without a full understanding of 

the many contributing factors will 

almost certainly fail. 

FIGURE 2-2: Guinea worm disease hotspots in Africa
ROAD SAFETY FUNDAMENTALS UNIT 2: HUMAN BEHAVIOR AND ROAD SAFETY 2-9

Doctors knew that Guinea 

worm disease spreads by people 

drinking contaminated water, and 

contamination of the water supply 

occurred when an infected person 

used the water supply to temporarily 

relieve the symptoms of infection. 

Hence, the eradication campaign 

focused on two main behaviors: 

J Drinking contaminated water

J Using drinking water sources 

to temporarily relieve the pain 

caused by the infection

Simply identifying these behaviors 

was not sufficient. In order to be 

successful, public health officials 

considered many other factors 

influencing these behaviors. 

Why were people drinking 

contaminated water?

J Availability - Uncontaminated 

drinking water may not have 

been available in the community.

J Money – People and 

communities lacked financial 

resources to obtain clean 

drinking water.

J Understanding – People did 

not know that the water was 

contaminated and/or how the 

disease was transmitted.

J Lack of immediate consequences

– Guinea worm disease 

symptoms did not appear until 

one year post-infection. 

Why were people using drinking 

water to relieve the pain caused by 

the infection?

J Immediate benefit – Water 

submersion resulted in 

immediate pain relief.

J Limited availability of water – 

Because water is scarce, most 

water sources were used for 

drinking.

J Unavailability of alternative 

treatments – The lack of medical 

infrastructure meant limited 

access to treatment options.

J Money – People lacked financial 

resources to obtain medical 

treatment even when available.

J Understanding – People lacked 

knowledge about how the 

disease is transmitted.

A thorough understanding of the 

factors that influence behavior is 

necessary to develop a plan for 

behavior change. 

Other Factors Behaviors Outcome

Limited water availability 

Money

Lack of understanding

Lack of immediate 

consequences

Drinking 

contaminated 

water

Using drinking 

water sources 

to relieve pain

Guinea worm 

disease spreads

Immediate benefit

Unavailability of other 

treatment

FIGURE 2-3: Guinea worm disease factors, behaviors and outcomes
2-10 UNIT 2: HUMAN BEHAVIOR AND ROAD SAFETY ROAD SAFETY FUNDAMENTALS

To develop a plan, we cannot merely 

look for the cause of the outcome, 

instead we need to look for the 

weak links in the causal chain and 

intervene at these links. In the case 

of Guinea worm disease, the limited 

availability of water and lack of 

understanding about the disease 

and its transmission were factors 

influencing both behaviors. Thus, 

these factors were targeted in the 

intervention.

Public health officials informed the 

people about the dangers of drinking 

contaminated water and how the 

water was becoming contaminated. 

However, they knew that simply 

providing this information would 

not be sufficient. 

In order to make the right behavior 

the easy choice, officials combined 

education with environmental 

change – they educated people on 

guinea worm disease and made 

clean water more accessible. 

Water sources known to be 

contaminated were treated to 

prevent transmission, and new clean 

water sources were created. When 

water sources could not be treated, 

villagers were given cloth filters to 

decontaminate their water before 

drinking. When people had access 

to clean water, they were less likely 

to drink contaminated water, thus 

significantly reducing the chance 

of infection13. This change to the 

environment (i.e., making clean 

water available) proved to be key in 

eliminating the disease.

While this is an oversimplified 

description of the complex and 

multifaceted approach that occurred 

over 30 years, it highlights what can 

be accomplished when principles of 

behavior change are at the core of a 

comprehensive approach.

Approaches to 

Changing Behavior

We are constantly exposed to 

attempts to influence our behavior. 

Consider the following things that 

you may encounter in everyday life:

J A brochure in your doctor’s 

office about the benefits of 

getting a flu shot

J A requirement that restaurants 

include nutritional information 

in their menu

J Stores that charge for plastic 

shopping bags

J Public service announcements 

(PSAs) about bullying

J Cities that provide large recycling 

bins and small garbage bins

J A law requiring that everyone 

wear seatbelts

Most of these attempts either 

provide information (e.g., a brochure 

with information about flu shots 

or a PSA detailing the negative 

impact of bullying), or they change 

the environment in such a way 

to encourage a different behavior 

(e.g., stores that charge for plastic 

shopping bags or cities that provide 

large recycling bins and small 

garbage bins). Understanding the 

nature of the problem is important 

in determining which approach has 

the best chance of success.

Education, safety messages 

and raising awareness

Education and awareness-raising 

campaigns are often the first and 

only tools tried when attempting 

to influence behavior. In general, 

Cairncross, S., 

Muller, R., and 

Zagaria, N. (2002). 

Dracunculiasis 

(Guinea Worm 

Disease) and 

the Eradication 

Initiative. Clinical 

Microbiology 

Reviews, 223-246.

13
ROAD SAFETY FUNDAMENTALS UNIT 2: HUMAN BEHAVIOR AND ROAD SAFETY 2-11

the goal of such campaigns is to 

communicate information with the 

assumption that once the audience 

is aware of the information, they 

will then act in the desired manner. 

In other words, educational 

campaigns appeal to the deliberative 

system and assume that human 

behavior is usually a product of 

rational thought. Because of this, 

information alone almost never 

works. However, information 

can be helpful as part of a more 

comprehensive program. 

Far too often information-based 

approaches are used in isolation, 

without careful consideration 

of whether the problem can be 

effectively addressed through 

raising awareness alone. Is the 

information new to the audience? 

Is it likely that knowing this 

information will produce the desired 

outcome? To draw from a previous 

example: does simply knowing that 

you should floss convince you to 

floss regularly?

Consider the effect of an educational 

campaign on Guinea worm disease. 

Would an educational or awareness 

raising campaign be enough to 

produce lasting and consistent 

behavior change? On the one hand, 

there was a lack of knowledge 

about the disease among those 

affected, especially about how the 

disease was transmitted. However, 

this education cannot influence 

the additional — and likely more 

important — factors contributing to 

the problem. For example, education 

will not improve the availability 

of clean drinking water or access 

to alternative medical resources, 

nor will it provide the financial 

resources necessary to increase 

access to either. Thus, an education 

campaign, on its own, would not 

This tip card from the early 1900s was likely ineffective in changing the crossing habits 

of people since it relied solely on providing information.
2-12 UNIT 2: HUMAN BEHAVIOR AND ROAD SAFETY ROAD SAFETY FUNDAMENTALS

have been a successful tactic. 

Instead, health officials needed a 

more comprehensive approach.

The same considerations can be 

applied to road safety problems. 

Consider the following example:

Your city manager notices an 

increase in pedestrian crashes 

following the placement of a new 

bus stop on Elm Street, a busy 

multi-lane road without a median. 

The bus stop is located in the middle 

of the block across from a large 

shopping center (Figure 2-4). The 

nearby intersections on either side 

are signalized and have street lights, 

crosswalks and pedestrian signals. 

The intersection and crosswalks 

meet all applicable design standards 

and are therefore nominally safe. 

Although city engineers intended 

that people would cross the street 

at the intersections, observations 

show that many people are crossing 

mid-block from the shopping 

center to the bus stop, resulting in 

frequent conflicts with vehicles. The 

city wants to improve safety in this 

area and has decided to undertake a 

media campaign encouraging people 

to cross only at crosswalks.

What behavior is being targeted?

Crossing Elm Street midblock. 

What are the other factors influencing 

this behavior?

J Convenience – Crossing midblock provides a more direct 

route to the bus stop. People 

coming from the shopping center 

are likely carrying shopping 

bags, which could be difficult to 

carry long distances.

J Previous experience – It is likely 

that people have successfully 

crossed similar streets (or even 

the same street) in this manner 

many other times, so their 

limited previous experience 

suggests this is a safe option. (we 

say limited experience because 

people not likely to be aware of 

the location’s crash history).

J Time pressure – Buses run on a 

schedule, and people may want 

to cross as quickly as possible to 

be sure they catch the next bus.

Is an educational or awareness 

raising campaign targeting this 

behavior likely to be effective? No. 

In all likelihood, people who are 

Bus Stop

Shopping Center

FIGURE 2-4: Example of shopping center and bus stop
ROAD SAFETY FUNDAMENTALS UNIT 2: HUMAN BEHAVIOR AND ROAD SAFETY 2-13

crossing the street in this spot know 

there are crosswalks at the nearby 

intersections. They are crossing the 

street here because it is easier and 

more convenient, and their previous 

experiences tell them they will be 

successful. Additional information 

is unlikely to alter these factors; 

therefore an informational or 

awareness-raising campaign alone 

will not be effective. However, that 

does not mean that all hope is lost. 

Improving the safety of pedestrians 

crossing Elm Street is still possible 

with the right approach. 

Changing the environment

A preferred alternative to education 

is changing the environment. 

We know that people act based 

on information gleaned from the 

world around them, and that most 

of our behavior is unconscious and 

driven by the intuitive system. By 

changing the environment, people 

can be moved towards the behavior 

of interest. In other words – if you 

can’t change the person, change the 

world so that the person will follow.

We know that people are crossing 

Elm Street mid-block because it is 

quicker, easier and more convenient 

than using the crosswalks at the 

nearby intersections. Information or 

awareness campaigns are unlikely 

to influence this behavior because 

the behavior is not due to a lack of 

awareness or information. Instead, 

we need to change the environment 

so that the pedestrians are no longer 

crossing somewhere other than a 

marked crosswalk. 

Possible changes to the environment 

include building a wall or putting 

up a fence to deter people from 

crossing at the mid-block, or 

building a pedestrian bridge to keep 

people out of the flow of traffic. 

These solutions might be cost 

prohibitive, and research shows that 

most pedestrians will still cross a 

street at ground level even when a 

pedestrian bridge is available.14,15

Moore, R.L., Older, 

S.J., Pedestrians 

and Motors are 

Compatible in 

Today’s World. 

Traffic Engineering,

Institute of 

Transportation 

Engineers, 

Washington, DC, 

September, 1965.

Rasanen, M, 

T. Lajunen, F. 

Alticafarbay, and C. 

Aydin, Pedestrian 

Self Reports of 

Factors Influencing 

the Use of Pedestrian 

Bridges, Accident 

Analysis and 

Prevention, 39, pp. 

969-973, 2007.

14

15

FIGURE 2-5: Pedestrian hybrid beacon (Source: pedbikeimages.org/Mike Cynecki)
2-14 UNIT 2: HUMAN BEHAVIOR AND ROAD SAFETY ROAD SAFETY FUNDAMENTALS

Another approach would be to move 

the bus stop closer to the existing 

crosswalks, assuming people will 

choose to cross at the crosswalk 

since it is now more convenient. 

Finally, another alternative would 

be to install a marked crosswalk 

with a pedestrian hybrid beacon 

close to the area where people 

are crossing (Figure 2-5). This 

solution recognizes the factors 

influencing people’s behavior and 

provides an alternative that would 

improve safety and be acceptable to 

pedestrians. 

We know that people respond 

in predictable ways to their 

environments — far more than to 

internal conditions like attitudes 

and personality. Environment can 

include both the physical (built) 

environment and things like 

policies, laws and social norms. 

Let’s revisit the speeding example 

from earlier in the unit (Figure 2-1). 

Although the posted speed limit 

is 35 mph, in reality many people 

drive much faster than that. What 

might we do to get drivers to slow 

down on this road? One option is 

to post additional speed limit signs 

or run local PSAs about the dangers 

of speeding. However, consider 

whether informational signs would 

result in lower speeds. Are drivers 

speeding because they are not aware 

of the speed limit? Are drivers 

unaware of the potential dangers of 

high speeds? The answer to both of 

these questions is “not likely.” 

One example of environmental 

change to reduce driver speed is the 

use of traffic calming measures. 

Features such as speed humps and 

mini roundabouts are examples of 

physical alterations to the driving 

environment that influence how 

road users respond. In the previous 

speeding example, the overall 

design of the road has already been 

established, but the lanes could be 

narrowed or even reduced to one 

in each direction to communicate, 

“This is a road where you should 

drive slower.” Traffic calming 

addresses the intuitive system in that 

it results in drivers slowing down 

Pickrell, T. M., & Li, 

R. (2016, February).

Seat Belt Use in 

2015—Overall Results

(Traffic Safety 

Facts Research 

Note. Report No. 

DOT HS 812 243). 

Washington, DC: 

National Highway 

Traffic Safety 

Administration.

Tison, J. & Williams, 

A.F. (2012). 

Analyzing the First 

Years of the Click It or 

Ticket Mobilizations

(DOT HS 811 232). 

Washington, D.C.: 

National Highway 

Traffic Safety 

Administration.

17

16

Seat belt usage in 

the United States

Seat belt use in the United States has 

a remarkably similar, though opposite 

trajectory to that of Guinea worm 

disease. Though seatbelts were required 

in U.S. vehicles starting in the late 

1960s, use of this equipment was low. 

Observational surveys from the early to 

mid-1980s found use of 5-14 percent.16

By 2015, however, observed seatbelt use 

had climbed to 88.5 percent.17

As with Guinea worm disease, no single 

effort was responsible for increasing seat 

belt use in the United States. Instead, 

efforts that focused on changing the 

environment (e.g., enactment of seat belt 

and child passenger safety laws) were 

coupled with high visibility enforcement 

(e.g., Click-it-or-Ticket). Education played 

a role in these efforts, but not in raising 

awareness for the dangers of not wearing 

seat belts. Rather, education was needed 

to inform people that belt use is required 

and, especially, to create the perception 

among the driving public that police 

were actively enforcing seat belt laws. 
ROAD SAFETY FUNDAMENTALS UNIT 2: HUMAN BEHAVIOR AND ROAD SAFETY 2-15

without being aware of doing so.18

Consider behavior in 

addressing travel safety 

Making strides in road safety is 

possible. However, as with the 

near eradication of Guinea worm 

disease, significant achievements 

will not happen overnight. When 

implementing a program or 

intervention aimed at changing 

behavior, it is important to 

remember that any road safety issue 

is likely the result of a combination 

of factors. Consequently, it is 

unlikely that any one program or 

intervention will completely solve 

the problem. However, combining 

behavioral science principles with 

engineering design can help to 

produce significant advances. 

See Unit 4 for a discussion of 

how to identify and address 

road safety problems.

Conclusion

In short, human behavior 

is extraordinarily complex. 

Consequently, it is difficult to 

influence. Simple, common sense 

approaches like merely raising 

awareness or otherwise providing 

information about an issue virtually 

never succeed. 

Humans are not exclusively 

logical, rational beings.

We often assume human behavior is 

controlled by a logical deliberative 

process when, in fact, most 

behaviors are a result of an intuitive 

process. Many factors influence 

behavior including education, 

emotions, cultural norms, 

religious beliefs, social pressures, 

convenience, habits and finances. 

Understanding human behavior 

and the many factors that influence 

behavior is crucial to solving 

safety problems.

People generally don’t simply 

do what they are told to do.

Information and awareness-raising 

campaigns are often the first tools 

used in efforts to influence behavior. 

However, these approaches are 

too often adopted without careful 

consideration of whether the 

behavior is likely to be changed 

merely with information (which the 

public often already has). 

The environment heavily influences 

human behaviors. We are constantly 

processing information and 

adjusting our behaviors accordingly. 

Most of this behavior is unconscious 

and driven by the intuitive system. 

Changing behavior requires 

an understanding of all 

influencing factors.

Before attempting to influence 

behavior, it is essential to identify 

and understand the important 

factors influencing a behavior. 

Targeting a behavior without a full 

understanding of these factors will 

almost certainly be unsuccessful. 

Because so much of what we do is 

intuitive and heavily influenced by 

our environment, we sometimes 

respond to the transportation 

infrastructure in ways not 

anticipated by the engineers who 

designed it. By changing the 

environment, people can be nudged 

towards the behavior of interest.19 

In other words, if you can’t change 

the person (and you usually can’t!), 

change the world so that the person 

will follow.

Thaler, R.H., and 

Sunstein, C.R. 

Nudge: Improving 

Decisions About 

Health, Wealth, and 

Happiness. 

19

Lewis-Evans, B. 

& Charlton, S.G. 

(2006), Explicit and 

implicit processes 

in behavioural 

adaptation to 

road width. 

Accident Analysis 

& Prevention, 38,

610-617.

18
2-16 UNIT 2: HUMAN BEHAVIOR AND ROAD SAFETY ROAD SAFETY FUNDAMENTALS

The transportation system is 

designed, built, maintained, governed 

and used by humans.

Using the term human factors 

to refer exclusively to the 

user perspective (i.e., drivers, 

pedestrians, etc.) can easily convey 

an oversimplified notion of the role 

of humans in the transportation 

system. From design to use, humans 

play a role in every step of the 

transportation system. In that sense, 

the entire transportation system 

is a product of human factors. For 

that reason, safety professionals 

must consider both the role of the 

environment (e.g., transportation 

infrastructure) and the user when 

trying to understand behavior 

and develop solutions to safety 

problems. 

In sum, significant advances in road 

safety are possible, but changes 

will not happen overnight. Human 

behavior is not easy to change. 

With thoughtful, comprehensive 

approaches that take into account 

an understanding of human 

behavior and the environment 

in which people live, we can 

develop programs, policies and 

countermeasures that have a better 

chance of significantly improving 

road safety.

J CREATE a causal diagram to model the 

behavior(s) and environmental factor(s) 

that contribute to the following. 

J The flu

J Unhelmeted motorcyclist fatalities

J Using the causal diagrams from 

exercise 1, IDENTIFY the weak links 

in the causal chain and describe an 

intervention aimed at changing the 

target behavior(s).

EXERCISES

Bus stop with crossing pedestrians in Portland, Ore. (Source: pedbikeimages.org/Laura Sandt)
ROAD SAFETY FUNDAMENTALS UNIT 2: HUMAN BEHAVIOR AND ROAD SAFETY 2-17

THIS PAGE INTENTIONALLY LEFT BLANK
3-b UNIT 3: MEASURING SAFETY ROAD SAFETY FUNDAMENTALS

After reading the chapters and completing 

exercises in Unit 3, the reader will be able to:

J DESCRIBE why measuring safety 

is important

J IDENTIFY the different types 

of available data

J UNDERSTAND the challenges 

and accuracy of data

J SELECT data for different 

road safety objectives

LEARNING OBJECTIVES

Measuring 

Safety

UNIT 3
ROAD SAFETY FUNDAMENTALS UNIT 3: MEASURING SAFETY 3-1

Importance of Safety Data

Good quality safety data are the core 

of any successful effort to improve 

road safety. Local, State, and Federal 

agencies use crash data as well as 

roadway, vehicle, driver history, 

emergency response, hospital, and 

enforcement data to improve road 

safety. All of these data sources can 

be used, in isolation or jointly, to 

produce projects, programs, and 

guide policies that reduce injuries 

and save lives. These types of data 

are collectively categorized as safety 

data in this book. 

Safety professionals in many 

disciplines – highway design, 

transportation planning, 

operations, road maintenance, 

law enforcement, education, 

emergency response services, 

policy makers, infrastructure 

program management, road safety 

management, and public health – 

use safety data to identify problem 

areas, select countermeasures, and 

monitor countermeasure impact.

Road safety management and 

project development has become 

increasingly data-driven and 

evidence-based. This approach 

to road safety emphasizes safety 

performance (i.e., number of 

crashes), rather than solely adhering 

to engineering standards, personal 

experience, beliefs, and intuition. 

For example, in the past, road 

improvements were considered 

“safe” if the improvements met 

the standards contained in the 

Manual on Uniform Traffic Control 

Devices (MUTCD) and A Policy on 

Geometric Design of Highway and 

Streets, also known as the Green 

Book1,2. However, most of these 

standards are engineering based 

(i.e., nominal safety as discussed 

in Unit 1), and were not necessarily 

based on an evaluation of actual 

road safety performance. Presently, 

transportation professionals use 

safety data (such as crash data, 

road characteristics, and traffic 

volume) to evaluate road safety 

performance and inform their 

decisions. This substantive approach 

challenges professionals to quantify 

the expected consequences and 

outcomes of safety strategies in real 

measurements, such as the expected 

number of crashes, injuries, 

and fatalities. 

The selection of road safety 

measures and treatments can 

benefit from an understanding of 

the intricacies and limitations of 

safety data. This unit presents many 

kinds of safety data, explores the 

current process used to collect data, 

and discusses the impact that these 

processes have on data quality (i.e., 

accuracy and reliability). The unit 

also discusses ways to improve data 

quality and analysis.

Relating Nominal and 

Substantive Safety to Data

The concepts of nominal and 

substantive safety were first 

introduced in Unit 1 of this textbook. 

Nominal safety refers to whether 

CHAPTER 7 MEASURING SAFETY

Manual on Uniform 

Traffic Control 

Devices (MUTCD), 

Federal Highway 

Administration, 

2009.

A Policy on 

Geometric Design 

of Highways and 

Streets, American 

Associations of 

State Highway 

Transportation 

Officials, 6th 

edition, 2011.

1

2
3-2 UNIT 3: MEASURING SAFETY ROAD SAFETY FUNDAMENTALS

or not a design (or design element) 

meets minimum design criteria 

based on national or State standards 

and guidance documents, such as 

the AASHTO Green Book or the 

MUTCD. Substantive safety refers to 

the actual safety performance, such 

as expected number of collisions by 

type and severity on a road.

The contrast of these concepts is 

directly linked to this discussion of 

safety data. To determine if a road 

is nominally safe we do not need 

safety data; we only need to know if 

all design standards were followed. 

However, we need high quality 

safety data and data analysis to 

determine if a road is substantively 

safe. Typically, the analysis includes 

estimating the expected number of 

crashes and comparing it against the 

road’s actual safety performance. 

More information on safety analysis 

is presented in Unit 4, Solving Safety 

Problems.

Use of Safety Data in Road 

Safety Management

Data are integral to safety decision 

making, both in prioritizing 

investments and in identifying 

analyzing the most effective 

techniques and interventions. 

The more comprehensive and 

accurate the data, the better the 

resulting decisions. Understanding 

contributing factors to crashes and 

how best to implement potential 

countermeasures is complex, and 

it may involve a variety of agencies 

and historical data challenges. 

Because of this complexity, both 

accurate data and high quality data 

analysis is necessary for road safety 

management. A great database is 

only as useful as the analysis and 

application of that data. Table 3-1 

explores the relationship between 

data quality and data analysis quality 

and shows why agencies should 

strive to improve both of these areas. 
ROAD SAFETY FUNDAMENTALS UNIT 3: MEASURING SAFETY 3-3

Crash data analysis using 

quantifiable metrics and 

scientifically defensible methods can 

help decision makers improve road 

safety by reducing more injuries and 

saving more lives at a lower cost. 

Accurate crash data help determine 

crash and severity trends, such as 

increases or decreases in certain 

types of crashes. Data also help 

safety professionals pinpoint high 

crash locations and identify highrisk users, such as younger drivers, 

older drivers, impaired drivers, 

and motorcyclists. Examining 

the characteristics of crashes 

allows road safety professionals to 

identify contributing crash factors 

related to roadway environment, 

design, or behavioral adaptations. 

This type of analysis will lead 

to a more effective selection of 

countermeasures that will reduce 

future crash occurrences or crash 

severity. Planners and engineers can 

use crash data to show quantitative 

information to decision makers on 

how specific planning guidance, 

design proposals, or engineering 

countermeasures can save lives. 

Safety professionals could seek to 

improve safety by relying merely on 

their gut judgment. The results of 

such an approach, however, would 

be quite unreliable. As shown in 

Table 3-1, safety professionals can 

improve their decision making 

process by using high quality data 

together with robust analysis 

processes. This unit will focus on 

the data itself. The use of the data in 

safety management is presented and 

discussed in Unit 4.

Good quality safety data and 

analysis are the keys to identifying 

real safety issues on roads and 

evaluating the best methods for 

improving safety. The following 

chapters provide an overview of 

different types of safety data and of 

ways in which agencies can improve 

the quality of their data. 

TABLE 3-1: Data and Analysis Quality Comparison

HIGH QUALITY ANALYSIS LOW QUALITY ANALYSIS

HIGH QUALITY DATA

BEST CAS

The agency is likely to reach the best 

safety decisions. Analysts are aware 

of data capabilities and limitations. 

This is the most expensive to achieve, 

due to the need for good data and 

training on how to conduct analyses.

MISSED OPPORTUNITY

The agency needs to invest in high 

quality analysis. Otherwise, the agency 

has wasted money in databases 

that are not being utilized to their 

potential. Good data with poor 

analysis will lead to poor decisions. 

LOW QUALITY DATA

PROMISING

A robust analysis that recognizes 

the limitations of the data can 

still produce useful results. 

The agency should focus on 

improving data quality.

WORST CASE

Poor data and poor analysis will lead 

to bad decisions. The agency may be 

better off relying on judgment.
3-4 UNIT 3: MEASURING SAFETY ROAD SAFETY FUNDAMENTALS

As highway safety analysis 

methods continue to evolve, it 

is equally important to focus on 

quality data to conduct these safety 

analyses. Transportation agencies 

can and should incorporate road 

characteristics, traffic volume, and 

enforcement and citation data, 

and other information into their 

safety analysis processes. This will 

enable them to better identify safety 

problems and prescribe solutions 

that improve safety and make more 

efficient use of safety funds.

Single sources of safety data also 

do not give a complete picture 

of the safety risks on our roads. 

For example, using crash data by 

itself leaves safety practitioners 

with purely reactive approaches—

identifying locations where 

crashes have already happened. 

By combining crash data with 

other types of data, more details 

begin to emerge. For example, by 

combining crash data and detailed 

road inventory information, safety 

practitioners can develop a more 

in-depth understanding of the road 

attributes that contribute to crash 

risk. This will allow them to adopt 

a proactive approach, seeking out 

those factors associated with a high 

risk of crashes and addressing sites 

that share those “elements” before a 

crash occurs.

Crash, roadway, and traffic data 

should be integrated or combined 

using common or “linking” 

reference systems, such as mileposts 

or geospatial position. These data 

should also have the ability to be 

linked to the State’s other road 

safety databases, including citation 

data or injury surveillance systems. 

Additionally, commercial motor 

vehicle data could also be linked 

based upon common data elements 

involved in crashes and inspections. 

Not all types of safety data are 

available or used by all practitioners. 

Safety data exist in distinct 

databases that are maintained by 

different agencies and often are 

accessible only to those agencies. 

One role for safety professionals is 

to bring together safety databases 

Types of Safety Data

CHAPTER 8 MEASURING SAFETY

Roadway 

elements

Physical 

features of the 

road such as 

travel lanes, 

shoulder width, 

pavement 

condition, 

and roadside 

characteristics

Chicago’s Use of Injury Data 

to Benchmark Safety Goals 

and Progress

Chicago DOT completed a 

comprehensive pedestrian crash 

analysis in 2011 to inform the citywide 

Chicago Pedestrian Plan. This analysis 

evaluated various crash types, 

contributing environmental factors, and 

different age groups using the Illinois 

Department of Transportation crash 

data files. The findings present crash 

density citywide, by ward, and around 

schools. The data also highlighted 

key crash conditions and served as a 

benchmark for measuring the City of 

Chicago’s road safety goals.

Reference: City of Chicago 2011 Pedestrian 

Crash Analysis, Summary Report, 

Chicago Department of Transportation, 

Accessed September 2016 at https://www.

cityofchicago.org/city/en/depts/cdot/supp_

info/2011_pedestrian_crashanalysis.html
ROAD SAFETY FUNDAMENTALS UNIT 3: MEASURING SAFETY 3-5

and analyze them using logical and 

statistically robust processes. 

Safety data can be categorized into 

two groups based on criteria of core 

data needs for safety evaluations, 

data availability, accuracy, and 

usefulness to safety practitioners 

and researchers. Some safety data 

are used often and are critical to 

safety analysis for many agencies. 

Other safety data are used less 

often but can be supplemental to 

specific safety analyses. This chapter 

provides general information on 

safety data in these two groups:

Critical data

J Crashes

J Traffic volume

J Road characteristics

Supplemental data

J Conflicts and 

avoidance maneuvers

J Injury surveillance and 

emergency medical systems

J Driver history

J Vehicle registrations

J Citations and enforcement

J Naturalistic

J Driving simulator

J Public opinion

J Behavioral observation 

Crash Data

Description

Crash data is the most widely used 

type of safety data, and it is essential 

in road safety analysis. Crashes 

are currently viewed as the most 

objective and reliable measurements 

of road safety. However, there 

are challenges with crash data, 

such as human error in reporting, 

unreported crashes, and the length 

of time it often takes for crashes to 

be entered into a database. Crash 

data is also the primary measure 

of effectiveness for safety efforts, 

since the goal is to decrease crash 

occurrences and lower the severity of 

crashes that do occur. Crash records 

typically provide details on events 

leading to the crash, vehicles, and 

people involved in crashes, as well as 

the consequences of crashes, such as 

fatalities, injuries, property damage, 

and citations. 

Data collection process

Crash data collection begins when a 

State highway patrol trooper or local 

police officer arrives at the crash 

scene. The officer completes a crash 

report, documenting the specifics 

of the crash. While the specifics 

and level of detail of the crash data 

vary from State to State, in general, 

the most basic crash data consist of 

where and when the crash occurred, 

what type of crash it was, and who 

was involved. The specific data 

collected on crashes is determined 

by State agencies, local government 

agencies, and often a coalition of law 

enforcement agencies. The exact data 

fields and coding differ from State to 

State. The level of detail in a crash 

report may also differ by the severity 

of a crash. For instance, in some 

States property damage only crashes 

(PDO) are self-reported and, thus, 

often have less information than 

injury crashes, which are reported by 

law enforcement officers. 

States also differ in the threshold 

of what is required for a crash to be 

reported. Reporting of crashes can 

vary by threshold requirements, such 

as “only injury crashes” or “PDO 

crashes over an estimated $2,000 

in damage.” These thresholds are 
3-6 UNIT 3: MEASURING SAFETY ROAD SAFETY FUNDAMENTALS

Case identifier: The unique identifier 

within a given year that identifies a 

Crash county: The county or equivalent specific crash within a State.

entity where the crash physically occurred.

A

Contributing 

circumstances, 

road: Apparent 

condition of the 

road that may 

have contributed 

to the crash.

Light 

conditions: 

The type/level of 

light that existed 

at the time of 

the motor 

vehicle crash.

Relation to junction: The coding of 

this data element is based on the location 

of the first harmful event of the crash. It 

identifies the crash’s location with respect 

to presence in a junction or proximity to 

components typically associated with 

junction or interchange areas.

Roadway 

surface 

conditions: The 

roadway surface 

condition at the 

time and place 

of a crash.

Type of intersection: An intersection 

consists of two or more roadways that 

intersect at the same level.

Contributing 

circumstances, 

environment: 

Apparent 

environmental 

conditions 

which may have 

contributed to 

the crash.

Weather 

conditions: 

The prevailing 

atmospheric 

conditions that 

existed at the 

time of the 

crash.

Crash location: The exact location on 

the road where the first harmful event 

of the crash occurred. It is best if this 

information includes a geolocation based 

on a Geographic Information System 

(GIS) or Linear Referencing System (LRS) 

location coordinates.

Crash city/place: City/place (political 

jurisdiction) in which the crash occurred.

Crash date and time: The date (year, 

month, and day) and time (00:00-23:59) 

when the crash occurred. 

Crash classification: Used to identify 

ownership of the land where the crash 

occurred and identify the characteristics of 

the crash with respect to its location on or 

off a trafficway.

D

A

D,E,F,G,H

Driver 

information

Vehicle 

information

E

F

G

H

C

B

B,C

I,J

K,L,M

I

K

M

L

J
ROAD SAFETY FUNDAMENTALS UNIT 3: MEASURING SAFETY 3-7

FIGURE 3-1 (above, left): Data elements on a crash report form. (Source: North Carolina DOT)

First harmful event: The first injury or 

damage-producing event that 

characterizes the crash type.

Location of first harmful event relative 

to the trafficway: The location of the first 

harmful event as it relates to its position 

within or outside the trafficway.

Manner of crash/collision impact: The 

identification of the manner in which two 

motor vehicles in transport initially came 

together without regard to the direction 

of force. This data element refers only 

to crashes where the first harmful event 

involves a collision between two motor 

vehicles in transport.

Work zonerelated: A crash 

that occurs in 

or related to a 

construction, 

maintenance, or 

utility work zone, 

whether or not 

workers were 

actually present 

at the time of 

the crash. Work 

zone-related 

crashes may also 

include those 

involving motor 

vehicles slowed 

or stopped 

because of 

the work zone, 

even if the first 

harmful event 

occurred before 

the first 

warning sign. School bus-related: Indicates whether 

a school bus or motor vehicle functioning 

as a school bus for a school-related 

purpose is involved in the crash. The 

school bus, with or without a passenger 

on board, must be directly involved as 

a contact motor vehicle or indirectly 

involved as a non-contact motor vehicle 

(children struck when boarding or 

alighting from the school bus, two vehicles 

colliding as the result of the stopped 

school bus, etc.).

Source of 

information: 

Affiliation of 

the person 

completing the 

crash report.

O

Q

Q

R

R

S

S

N

P

Crash sketch/

diagram

Crash 

narrative

N,O,P
3-8 UNIT 

3: MEASURING SAFETY ROAD SAFETY FUNDAMENTALS

unrelated to the number of crashes 

that are actually occurring on a road, 

but the reported numbers could look 

quite different. Changes to the crash 

reporting thresholds can happen 

abruptly and may significantly affect 

the crash data. Consider how the 

safety of a road, based on reported 

crashes, would appear in the years 

before and after a crash reporting 

threshold change from $1,000 to 

$4,000. You would expect to see 

fewer reported crashes after the 

change, since crashes with damage 

below $4,000 would no longer be 

reported, even though there may 

be no real change in the number of 

crashes occurring. 

After the crash investigation is 

completed by the officer for the 

investigating agency, it usually 

undergoes an internal quality review. 

Passing the internal review, the 

crash report is sent to the State crash 

database. In some cases, the data is 

transmitted electronically, while in 

other cases the State agency receives 

a paper copy of the crash report. 

The agency that maintains crash 

data for the State may be the State 

department of transportation 

(DOT), the department of motor 

vehicles (DMV), or a State law 

enforcement agency. This agency 

will in turn make the data available 

to various other agencies. Federal, 

State, and local governments, as 

well as metropolitan planning 

organizations, advocacy groups, auto 

and insurance industries, and private 

consultants request crash data to 

conduct various transportation 

planning activities and analysis. 

The agency maintaining the 

data may provide raw or filtered 

datasets to local agencies and to 

national databases, such as the 

National Highway Traffic Safety 

Administration’s (NHTSA’s) Fatality 

Analysis Reporting Systems (FARS). 

The time between the crash 

occurrence and the availability 

of the crash data from the State 

crash database varies and typically 

depends on the type of crash 

reporting system and the State 

and local government capabilities. 

This time period between crash 

occurrence and the report’s 

availability for analysis defines the 

timeliness of the crash data. While 

some agencies can provide complete 

data with a very short turnaround 

(i.e., less than a month), others take 

significantly longer (i.e., up to two 

years) due to backlogs and personnel 

shortages. Agencies who have the 

majority of their crashes reported 

electronically from law enforcement 

typically have shorter turnarounds 

on the crash data.

Common data elements

Common data elements for crash 

data include information on date, 

location, injury severity, types of 

vehicles, and characteristics of 

persons involved. Crash narratives 

and diagrams are typically found in 

the original crash reports, though 

generally not in the crash database. 

Narratives and diagrams are most 

useful when the safety professional 

desires to know the exact location 

of the crash, such as the particular 

approach of an intersection. 

NHTSA developed the Model 

Minimum Uniform Crash Criteria 

(MMUCC) in 1998 as a model set 

of data elements that should 

be collected to enable safety 

professionals to conduct data-driven 

analyses. States are encouraged 

to adopt MMUCC standards, 
ROAD SAFETY FUNDAMENTALS UNIT 

3: MEASURING SAFETY

3-9

though they are not required to 

match these recommendations. 

MMUCC, currently in its fourth 

edition, recommends the crash data 

elements listed below. Chapter 9 

presents further information on 

MMUCC on page 3-30. 

Data sources and custodians

Crash details may be available from 

different sources or systems. State 

agencies and institutions typically 

maintain the State crash database. 

These include State departments 

of transportation, departments of 

motor vehicles, departments of 

public safety, or in some cases, State 

universities under contract to a 

specific department. Local agencies, 

such as cities or metropolitan 

planning organizations, may also 

maintain their own crash databases 

within local record management 

systems. These local systems 

are most frequently housed by 

the local police, public works, or 

transportation departments.

Transportation safety applications

Crash data serve as the primary 

observable measure of safety 

(or lack thereof) on the road. 

Transportation professionals can use 

crash data to analyze a single crash, 

a specific site, an entire corridor, 

or a large area, such as in regional 

or Statewide planning. Crash data 

can be used to provide guidance to 

transportation decision makers and 

to guide the formation of safety 

legislation. 

Coordination or integration with 

other data sets

In transportation departments, 

other data elements frequently used 

along with crash data include road 

characteristics and traffic volume 

data. For example, by combining 

road characteristics with crash 

data, safety professionals are able 

to identify road elements that may 

lead to higher frequency or injury 

severity of crashes, and therefore 

develop a systemic approach to 

reduce that crash risk at many of 

the locations that have those risk 

elements. Using traffic volume, 

agencies can calculate crash rates 

(e.g., crashes per road vehicle) to 

better identify locations requiring 

safety improvements.

Data challenges and gaps 

Some of the most common issues 

found in crash reporting include 

incomplete data (for example a 

driver’s blood alcohol content is 

often missing), delays in entering 

the data into databases, inaccurate 

crash locations, and wrongly 

assigned fault and wrong choice of 

crash type. Some of these issues can 

be fixed by training police officers 

and those who enter the data into 

the database, as well as by using 

technology checks in data collection. 

Agencies should periodically conduct 

independent quality checks on the 

accuracy and reliability of their data.

Caution on the use of crash rates

Crash rate calculation (crashes per 

amount of traffic) is a simplistic 

measure that may be useful when 

comparing sites with similar 

characteristics and traffic volumes. 

However, the relationship between 

crashes and volume is not linear and 

can therefore lead to wrong conclusions 

if that assumption is made when 

considering volume increases on a road 

or comparing roads of different types. 

Unit 4 discusses how an analyst can use 

safety performance functions to avoid 

this error.
3-10 UNIT 3: MEASURING SAFETY ROAD SAFETY FUNDAMENTALS

Traffic Volume Data 

Description

Traffic volume data indicates how 

many road users travel on a road or 

through an intersection. The most 

prevalent type of volume data is 

a count of daily use by motorized 

vehicle traffic. This type of traffic 

volume data can be measured 

in many ways depending on the 

intended use. Volume measurements 

include: 

J Annual average 

daily traffic (AADT)

J Average daily traffic (ADT)

J Total entering vehicles (TEV) 

for intersections

J Turning movement counts

J Vehicle miles traveled (VMT)

J Pedestrian counts

J Bicyclist counts

J Percentage of traffic for specific 

vehicle types (e.g., heavy trucks 

or motorcycles)

AADT is the average number of 

vehicles passing through a segment 

from both directions of the mainline 

route for all days of a specified 

year. As AADT requires continuous 

year-round counting, these data 

are often unavailable for many road 

segments. In these cases, ADT is 

used to estimate AADT by using 

shorter duration counts of that road 

and then adjusting those volumes 

by daily and seasonal factors. Other 

data used for crash analysis include 

turning movement counts and 

TEV at intersections and VMT on a 

road segment, which is a measure 

of segment length and traffic 

volume. VMT are useful for highway 

planning and management, and a 

common measure of road use. Along 

with other data, VMT is often used 

to estimate congestion, air quality, 

and expected gas tax revenues, and 

can serve as a proxy for the level of 

a region’s economic activity. Volume 

data is also occasionally collected 

for bicyclists and pedestrians at road 

segments and crossing locations.

The Oregon DOT identified pedestrian and 

bicycle crashes as one of its primary focus 

areas for infrastructure funding. While 

pedestrians and bicyclists account for more 

than 15% of all traffic fatalities statewide, 

the locations of serious injuries and 

fatalities appear to be random. Therefore, 

in 2013, ODOT set out to develop a 

program that focuses the limited available 

funding for infrastructure countermeasures 

on locations with the greatest crash 

potential. In order to identify these higherrisk locations, ODOT is working to discover 

behavioral patterns and road conditions 

that lead to pedestrian and bicycle crashes. 

While a promising approach, this analysis 

is constrained by the limited availability 

of road information (e.g., bicyclist and 

pedestrian volumes, the presence of 

crosswalks, turn lanes, driveway activity, 

and sight distances). While the lack of 

these data does not preclude such an 

analysis, it does reduce the certainty of the 

findings. An additional benefit from this 

effort is that it has helped ODOT identify 

current data deficiencies which ODOT is 

currently working to fix.

Reference: Pedestrian and Bicycle Safety 

Implementation Plan, Oregon Department 

of Transportation, February 2014. Accessed 

September 2016 at https://www.oregon.gov/

ODOT/HWY/TRAFFIC-ROADWAY/docs/

pdf/13452_report_final_partsA+B.pdf

Challenges with the Use of Crash Data to Systemically Identify High Risk Locations
ROAD SAFETY FUNDAMENTALS UNIT 3: MEASURING SAFETY 3-11

Data collection process

Volume data can be collected 

automatically or manually. Vehicle 

volume data is typically collected 

using automated counters, 

such as magnetic induction 

loops, pneumatic tube counters, 

microwave, radar, or video detection. 

These automated counters can also 

be configured to classify vehicles 

and produce counts by vehicle 

type (e.g., trucks, single passenger 

vehicles, etc.). For shorter durations 

or occasional counts, transportation 

agencies use manual traffic counts 

performed by observers, either in 

the field or through video cameras. 

Manual counting is also used often 

for bicyclist or pedestrian counts, 

although there are a number of 

additional technologies, such as 

infrared beams, that can be used 

to collect non-motorized volume 

data. These manual counts can range 

in length from one-hour counts 

to full-day counts, depending on 

the agency’s needs and practices. 

Fitness tracking apps may also 

provide additional information 

to jurisdictions regarding where 

bicyclist and pedestrian activity is 

occurring. Some care is needed when 

using these data due to the selfselection bias present from users 

having to opt-in to the tracking 

and only using for specific types of 

activities (e.g., fitness cycling rather 

than commuting).

Each State has its own traffic data 

collection needs, priorities, budget, 

and geographic and organizational 

constraints. These differences 

cause agencies to select different 

equipment for data collection, use 

different data collection plans, 

and emphasize different data 

reporting outputs. The FHWA Traffic 

Monitoring Guide (TMG) highlights 

best practices and provides guidance 

to highway agencies in traffic 

volume data collection, analysis, 

and reporting3

. The TMG presents 

recommendations to improve 

and advance current programs 

with a view towards the future of 

traffic monitoring. Traffic data is 

used to assess current and past 

performance and to predict future 

performance. Some States are 

utilizing traffic data from intelligent 

transportation systems (ITS) to 

support coordination of planning 

and operations functions at the 

Federal and State levels. 

Common data elements

Volume data must include the 

counted volume, location, date, and 

duration of the count. Depending 

on the method used, the volume 

data may also contain information 

on vehicle classification, speed, 

or weight; lane position; weather; 

and directional factors. From these 

data, transportation professionals 

can calculate the average number of 

Traffic Monitoring 

Guide, Federal 

Highway 

Administration, 

Office of Highway 

Policy Information, 

September 2013.

3

What’s the difference between 

ADT and AADT?

Short term traffic counts are typically 

collected at a location for a 12-, 18-, or 

24-hour period. Average Daily Traffic 

(ADT) is the count of traffic calculated 

to reflect the 24-hour (daily) volume 

of the date it was collected. The 

Annual Average Daily Traffic (AADT) is 

calculated for an entire year from the 

ADT by adjusting that simple average 

traffic volume to take into account the 

different travel patterns that occur 

during short duration count periods. For 

example, a summer traffic count taken 

in a beach vacation town would need 

to be adjusted downward to reflect the 

average traffic volume for the year, since 

traffic would be much higher in 

the summertime.
3-12 UNIT 3: MEASURING SAFETY ROAD SAFETY FUNDAMENTALS

vehicles that traveled each segment of 

road and daily vehicle miles traveled 

for specific groups of facilities, 

vehicle types, and vehicle speeds.

Data sources and custodians

State highway agencies collect 

and maintain traffic volume data 

for State-controlled roads. These 

data are shared with the U.S. 

Department of Transportation in 

order to monitor road usage and 

safety trends. Local jurisdictions 

also collect and maintain traffic 

volume data; the scope, consistency, 

and quality of these data varies by 

jurisdiction. 

Transportation safety applications

Agencies use volume data to support 

activities in design, maintenance, 

operations, safety, environmental 

analysis, finance, engineering, 

economics, and performance 

management. For instance, total 

traffic volume estimates or forecasts 

on a section of road are used to 

generate State and nationwide 

estimates of total distance traveled. 

Annual traffic volumes are also 

essential in network screening, 

diagnosis, and the selection of 

countermeasures (see further 

presentation of these processes in 

Unit 4). When selecting appropriate 

crash modification factors (CMFs) 

to estimate the benefit of potential 

countermeasures, a safety 

practitioner must use traffic volumes 

to confirm that the CMFs are suitable 

for the site in consideration. 

Coordination or integration with 

other data sets

Other data elements frequently 

used with traffic volume data 

in safety applications include 

road characteristic inventories 

and crash data. For example, an 

agency that uses traffic volume and 

crashes together can identify sites 

with highest potential for safety 

improvements and target specific 

crash types. This allows them to 

better identify and prioritize locations 

for safety improvements.

Spatial Data and Road Safety

Many of the types of data presented in this 

chapter can be stored in a spatial format 

and displayed in a GIS. GIS is a particularly 

powerful tool designed to store, 

manipulate, analyze, and visualize data 

that is linked to a location. This makes it 

valuable to highway safety practitioners 

who can use a common referencing system 

for much of their highway data and link it 

together in GIS. For example, a single GIS 

database can contain road attributes, such 

as number of lanes, pavement condition, 

and lighting; crash information; and 

traffic volumes. This information can then 

be used to analyze crash hotspots and 

trends, such as multi-vehicle crashes in the 

vicinity of signalized intersections. 

This GIS map displays signalized 

intersections as squares and crashes 

as dots and allows the analyst to easily 

identify crashes occurring within 150 feet 

of a signalized intersection (denoted by 

circular areas around each intersection).
ROAD SAFETY FUNDAMENTALS UNIT 3: MEASURING SAFETY 3-13

Data challenges and gaps 

One of the biggest challenges in 

collecting accurate volume data is 

implementing a quality assurance 

process to ensure that counts are 

accurately recorded. Traffic volume 

for most roads is also based on 

sampling, which leads to estimates 

of volume on much of the road. As 

technology continues to develop and 

become more prevalent on our roads 

and in our vehicles, the accuracy will 

improve considerably. Additionally, 

pedestrian and bicyclist counts are 

more susceptible to higher variability 

due to their lower volumes; 

thus, longer count durations and 

additional locations are required for 

accurate data applications. 

Road Characteristics Data 

Description

Road characteristics data is also 

referred to as road inventory data. 

The most basic road characteristics 

data typically includes road name or 

route number, road classification, 

location coordinates, number of 

lanes, lane width, shoulder width, 

and median type. Intersection 

characteristics typically include 

road names, area type, location 

coordinates, traffic control, and 

lane configurations. The collection 

of these data elements supports 

an enhanced safety analysis and 

investment decision making when 

combined with other datasets, such 

as crash information.

Data collection process

Road characteristics data can be 

collected through several methods 

including photo or video logs, field 

surveys, aerial surveys, integrated 

GIS and global positioning systems 

(GPS) mapping, and vehiclemounted Light Detection and 

Ranging (LIDAR) technology. Some 

States find it more cost effective to 

purchase these data from third party 

providers.

Common data elements

Transportation agencies typically 

collect those road characteristics 

that they need or can be collected 

based on the available funds. Road 

characteristics are collected for many 

different purposes, such as road 

maintenance and improvement 

projects. Given that States have 

different priorities and funding 

structures, the elements of road 

characteristics data is not the 

same from State to State or among 

local agencies.

To provide guidance on road 

characteristics that are the most 

needed for safety analysis, the FHWA 

developed the Model Inventory of 

Roadway Elements (MIRE). MIRE 

provides a recommended (but not 

required) list of road characteristics 

elements specifically for safety 

analysis. The elements are divided 

into the categories shown in Table 

3-2. Chapter 9 presents further 

FIGURE 3-2: This image from the FHWA 

Model Inventory of Roadway Elements 

(v. 1.0) illustrates roadway elements.
3-14 UNIT 3: MEASURING SAFETY ROAD SAFETY FUNDAMENTALS

information on MIRE on page 3-32. 

Data sources and custodians

Road characteristics data are 

collected at both the local and 

Statewide levels. At the local level, 

having data on details, such as 

traffic control devices, sidewalks, or 

the number of travel lanes, can be 

beneficial for safety evaluations and 

safety project prioritization. These 

data are maintained by the city or by 

a higher level agency such as a MPO.

State road characteristics data 

include physical road attributes, 

traffic control devices, rail grade 

crossings, and structures, such 

as bridges and tunnels. Each 

State highway agency, some 

local transportation and public 

works departments, and regional 

planning agencies collect and 

maintain road characteristics data. 

In addition, most States also have 

supplemental inventory data for 

bridges as part of the National 

Bridge Inventory and railroad grade 

crossings as part of the Federal 

Railroad Administration’s Railroad 

Grade Crossing Inventory. These 

databases usually can be linked to 

the Statewide road inventory.

Transportation safety applications

Road safety professionals can 

use road characteristics data to 

access data about the physical 

characteristics of crash sites 

or other priority sites. Road 

characteristics data is essential for 

network screening, development 

or calibration of crash prediction 

models, and related applications. 

These data are also valuable on the 

large scale level to estimate where 

crashes are expected to occur on the 

system. 

Coordination with other data sets

Road characteristics data can be 

linked with crash and volume data to 

improve safety analysis and problem 

identification. Combining datasets in 

this way allows safety professionals 

to identify areas with a high 

TABLE 3-2: Categories of MIRE Elements

CATEGORY EXAMPLES OF MIRE DATA ELEMENTS

Roadway Segment Roadway classification

Paved surface characteristics

Number and type of travel lanes

Shoulder, median, and roadside descriptors

Pedestrian and bicyclist facilities

Traffic volumes

Roadway Alignment Curve and grade information

Roadway Junction Traffic control devices

Intersection features

Interchange and ramp descriptors
ROAD SAFETY FUNDAMENTALS UNIT 3: MEASURING SAFETY 3-15

potential for safety improvements 

(by means of a network screening 

process) and identify appropriate 

countermeasures. However, the 

road characteristics data must share 

a common reference system with 

the crash and volume data in order 

to link them together. The most 

common methods of linking road 

data with crash or volume data use 

a linear referencing system, such as 

routes and mileposts, or a spatial 

referencing system, where all files 

share the same coordinate system.

Data challenges and gaps 

Collecting accurate road 

characteristics data can be a timeconsuming and expensive process. 

Data collection that is done only 

for part of a road network results 

in gaps in inventories of road 

features such as the location of 

guardrails, shoulder widths, and 

rumble strips. Transportation 

agencies are continually looking for 

newer technologies to streamline 

the collection of this detailed data. 

Also, it is more common for road 

characteristics data to be fuller 

and more detailed for State system 

roads compared to local roads, 

since local agencies typically have 

less funding, fewer staff, and less 

general prioritization for collecting 

road characteristics data.

CRASH DATA

Determine proportional 

issues from specific 

vehicle types

Calculate 

crash rates

Calculate 

predicted crashes 

from safety 

performance 

functions

Prioritize maintenance 

activities

Prioritize systemic 

improvements

Determine 

risk factors

Develop safety 

performance 

functions for 

predicting crashes

ROAD DATA

VOLUME DATA

FIGURE 3-3: Using Safety Data Together
3-16 UNIT 3: MEASURING SAFETY ROAD SAFETY FUNDAMENTALS

Supplemental Safety Data

In addition to the critical 

transportation safety datasets 

(crashes, road characteristics, and 

traffic volume), there are many 

other datasets that can be used and 

combined to conduct additional 

types of evaluations on the 

effectiveness of programs, human 

behaviors and safe decision making, 

and public opinions.

Conflicts, Avoidance Maneuvers, 

and Other Interactions

Observing conflicts between road 

users, avoidance maneuvers, such as 

swerving or hard braking, and other 

interactions, such as failures to yield 

can provide valuable information 

on road safety. These other 

measures of safety are referred to 

as surrogate measures. They occur 

more frequently than actual crashes 

and therefore enable agencies to 

identify safety risks more quickly 

and in a proactive manner (i.e., 

before the crash occurs). However, 

by their nature of being surrogates, 

there is potential for inaccuracy in 

determining which types of conflicts 

are good indicators of crashes. 

Surrogate safety data is collected 

by in-field observers or through 

recordings that capture the 

behaviors and interactions of road 

users. These recordings can be 

made through stationary cameras or 

dashboard-mounted video cameras. 

Observing interactions between road users, like these drivers and crossing pedestrians, 

can be a good way to gain supplemental data about safety effects.
ROAD SAFETY FUNDAMENTALS UNIT 3: MEASURING SAFETY 3-17

Increasingly, researchers are using 

programs to automatically identify 

potential events. This eliminates the 

need to scan visually through the 

entire video.

Observing interactions between 

road users can provide valuable 

information on the safety effect 

of certain road elements, such 

as signals or signs, and help 

identify the probability of crashes 

under different conditions. If a 

reliable relationship between the 

observations and crashes is known, 

such studies may also provide 

insights into the potential for safety 

issues between road users, such 

as between vehicle drivers and 

pedestrians.

However, one of the biggest 

challenges for using observations of 

road user interactions is that they 

are surrogate measures of safety. 

To date, we lack good research 

that would quantitatively equate 

surrogate measures of safety to 

crash data. If such relationships 

were known, safety professionals 

could conduct evaluations with a 

large number of surrogate measures 

in a relatively short period of time. 

This contrasts with the need to wait 

for years for sufficient crash data to 

support a good analysis.

Injury Surveillance and Emergency 

Medical Systems Data 

Injury surveillance systems 

(ISS) typically provide data on 

emergency medical systems (EMS), 

hospital emergency departments, 

hospital admissions/discharges, 

trauma registry, and long-term 

rehabilitation. This information 

is used to track injury causes, 

severity, costs, and outcomes. 

Although an injury associated with 

a traffic crash is only one type of 

injury in these medical systems, 

traffic crash injuries can be a useful 

source of data in bridging the gap 

between traditional traffic safety 

and public health issues. Hospital 

records are also often the only 

source of information on bicycle 

and pedestrian crashes that are not 

recorded by the police, such as those 

that occur in non-roadway locations 

like parking lots and driveways.

Evaluation of Children Involved 

in Off-Roadway Crashes Using 

Trauma Center Records

Many off-roadway crashes are not 

reported by law enforcement and 

are thus missed when conducting 

safety evaluations using police crash 

reports. One group that is particularly 

affected by this lack of data is young 

children injured by passenger vehicles 

in driveways and parking lots. This 

lack of information provides safety 

professionals with little knowledge 

about crash risk factors and actual 

incident rates that could be used 

to allocate resources and promote 

safety interventions and good design 

and behaviors. A 2010 study (Rice et 

al.) in California used records from 

eight trauma centers to identify the 

frequency and characteristics of these 

crashes. This study highlighted the 

inconsistencies with external causeof-injury codes used by emergency 

departments, but suggests that there 

is value to surveillance of off-roadway 

pedestrian injuries at trauma centers as 

a way of identifying incidents that are 

not captured by other data sources.

Reference: Rice TM, Trent RB, Bernacki 

K, Rice JK, Lovette B, Hoover E, Fennell 

J, Aistrich, AZ, Wiltsek D, Corman E, 

Anderson CL, Sherck J. (2012). Trauma 

center-based surveillance of nontraffic 

pedestrian injury among California 

children. Western Journal of Emergency 

Medicine; 13.2.
3-18 UNIT 3: MEASURING SAFETY ROAD SAFETY FUNDAMENTALS

Hospitals often use the external 

cause of injury classifications to 

code causes of patient injuries, 

including those from traffic crashes. 

These data can provide a description 

of injury severity, type of crash (e.g., 

motor vehicle passenger, bicyclist), 

and, in some cases, the location of 

incident. However, the data is often 

incomplete or non-specific. In order 

to provide a more comprehensive 

understanding of motor vehicle 

crash outcomes, NHTSA developed 

the Crash Outcome Data Evaluation 

System (CODES), which links crash, 

vehicle, and behavior characteristics 

to their specific medical and 

financial outcomes. Hospital injury 

data most often includes date, injury 

severity, cause, and demographic 

information. Personal identifying 

information is not included.

Hospital data can be used by 

a variety of governmental and 

non-governmental agencies to 

investigate the causes of injuries. 

Based on this analysis, the agencies 

can develop a safety campaign 

to reduce injuries to particular 

demographics. It can also be used 

to identify the full magnitude of 

crashes for a specific user group or 

demographic that is not recorded 

or reported by law enforcement. 

For example, hospital data can 

help safety professionals better 

understand the number of bicyclist 

crashes, since many bicycle-related 

crashes are not reported to law 

enforcement.

Hospital data are often difficult 

to use for those who administer 

roads, primarily the State DOT. The 

data is time consuming to acquire 

and may not contain complete 

data. Additionally, since there are 

no personal identifiers relating 

hospital injury data to specific crash 

records, the linkage is difficult and 

is seldom done. For these reasons, 

State DOTs rarely use these data; it 

is most often employed by public 

health researchers. However, there 

continues to be efforts at both 

Federal and State levels to develop 

better ways to integrate injury 

surveillance and emergency medical 

systems data with crash data.

Hospital data 

can be used 

to investigate 

causes of 

injuries, and 

is often the 

only source of 

information on 

some bicycle 

and pedestrian 

crashes.
ROAD SAFETY FUNDAMENTALS UNIT 3: MEASURING SAFETY 3-19

Driver History Data 

Departments of Motor Vehicles 

(DMVs) maintain driver history data 

on all licensed drivers in the State. 

DMVs typically create a driver record 

when a person enters the State 

licensing system to obtain a driver’s 

license or when an unlicensed 

driver commits a violation or is 

involved in a crash. State driver 

history databases interact with the 

National Driver Register (NDR) 

and the Commercial Driver License 

Information Systems (CDLIS) to 

prevent drivers with a history of atfault crashes or inordinate number 

of citations from obtaining multiple 

or subsequent licenses. 

The driver history data contain 

information such as:

J Basic identifiers (e.g., name, 

address, driver license number)

J Demographics (e.g., age, 

birth date, gender)

J Information relevant to license 

and driver improvement actions 

(e.g., license issue, expiration 

and renewal dates, license 

class, violation dates, 

suspension periods) 

One challenge with using these data 

is that they are almost never shared 

outside a DMV. State or local DOTs 

do not have access to these data 

while developing their HSIPs (or 

conducting location specific safety 

studies). Sharing driver history data 

nationally is limited and could be 

improved by creating inter-agency 

data sharing partnerships that 

address privacy concerns and allow 

State DOTs to work with the data.

Vehicle Registration Data

Vehicle registration data includes 

information about registered 

vehicles in a State and is also 

typically maintained by the DMV. 

Vehicle registration systems may 

also contain information regarding 

commercial vehicles and carriers 

registered in a particular State and 

licensed to travel in other States. 

These data can provide information 

on the vehicle population within a 

State or county to be used in large 

scale safety analysis. These data 

can also help identify owners in the 

event of a crash or traffic violation.

Typical vehicle registration data may 

include owner information, license 

plate number, vehicle make, model, 

and year of manufacture, body type, 

vehicle identification number, and 

miles traveled. Common data for 

commercial vehicles may include 

U.S. Department of Transportation 

(DOT) number, carrier information, 

and inspection or out-of-service 

information.

Citations and Enforcement

Citation data refers to data on 

individual drivers that records any 

illegal actions that were cited by a 

law enforcement officer. It includes 

traffic violations, such as reckless 

driving, driving under the influence, 

and not carrying adequate car 

insurance; traffic crashes; driver’s 

license suspensions, revocations, 

and cancellations; and failures to 

appear in court. The data can also 

include the traffic infractions that 

have been adjudicated by the courts.

These data are helpful in identifying 

and tracking those individuals 

with a higher potential for unsafe 

driving behaviors. In an attempt to 

control crash occurrences, States 

may monitor high-risk drivers 

by reviewing their driver history 
3-20 UNIT 3: MEASURING SAFETY ROAD SAFETY FUNDAMENTALS

records, paying particular attention 

to driver citations. Ideally, States 

track a citation from the time it is 

issued by a law enforcement officer 

through its disposition in a court of 

law. Citation information tracked 

and linked to driver history files 

enable States to screen drivers with 

a history of frequent citations for 

actions known to increase crash 

risk. States have found citation 

tracking systems useful in detecting 

repeat traffic offenders prior to 

conviction. It can also be used to 

track the behavior of particular law 

enforcement agencies and the courts 

with respect to dismissals and plea 

bargains. Many law enforcement 

agencies use citations as a method 

of tracking and measuring the 

effectiveness of enforcement efforts.

Some constraints exist with the 

use of citation and enforcement 

data to help prevent crashes. Some 

States have difficulty in maintaining 

accurate citation information 

because local jurisdictions may 

collect different data elements 

from varying citation forms. 

Obtaining and managing judicial 

information is also a challenge 

because of the various levels of court 

administration and jurisdiction. 

Unfortunately, in some States 

judges do not have access to the 

offender’s driver history at the time 

of sentencing, so many offenders 

escape the stricter penalties 

sanctioned for repeat offenses. 

In addition, the traffic safety 

community often lacks access to 

adjudication information due to 

privacy concerns. 

Naturalistic Driving Data

Naturalistic driving data are driver 

behavior data collected during 

actual driving trips through 

technology placed in the vehicle. 

This technology typically includes 

video camera views of the driver, 

speed and vehicle motion sensors, 

and location tracking equipment. 

Data such as video might be 

collected on a continuous basis, or 

only after certain events like hard 

braking. Using data collected by 

this equipment, researchers are 

able to gather information on the 

underlying causes of crashes by 

observing drivers in a natural driving 

situation. Frequently collected 

data include road environment 

information, such as weather; 

driver information, such as eye 

movements; and information 

on vehicle movement including 

location on the road, acceleration, 

deceleration, and speed. 

These data are used to evaluate how 

drivers interact with and react to 

the road, other road users, and other 

environmental features. Driver 

observation is used to understand 

fundamental issues of driver 

behavior and to develop improved 

safety countermeasures. The data 

are primarily used in research 

studies on a variety of topics. The 

data from the SHRP2 program 

have been used to study safety 

Strategic Highway

Research Program 2

The largest naturalistic study in the 

United States to date is the second 

Strategic Highway Research Program 

(SHRP2), which included over 3,400 

drivers participating in the study. 

SHRP2 data includes over 5,400,000 

individual trips and over 36,000 crash, 

near crash, and baseline driving events. 

FHWA provides more information on 

SHRP2 at https://www.fhwa.dot.gov/

goshrp2.
ROAD SAFETY FUNDAMENTALS UNIT 3: MEASURING SAFETY 3-21

issues including prevention of road 

departures, driver reaction to posted 

speed limits, and driver response 

to curves in the road, in addition to 

many non-safety-related topics.

A challenge with collecting a large 

amount of naturalistic data is the 

high cost of recruiting participants, 

instrumenting vehicles, and 

reducing and analyzing the data. 

The process of coding (observing) 

the behaviors of the driver while 

driving is time-consuming and is 

typically conducted on a frame-byframe basis, leading to expensive 

data collection and lengthy study 

periods. The data are highly private 

(i.e., contains videos of driver faces), 

and therefore are typically difficult 

to access or distribute. Despite these 

challenges, naturalistic driving data 

provides a unique and extremely 

insightful look at fundamental 

issues of road safety.

Driving Simulator Data

Due to the high cost of naturalistic 

driving studies and the rarity of 

traffic crashes, driving simulators 

are often used to efficiently and 

safely evaluate driver behavior 

under different conditions. 

Researchers are able to study 

many different conditions and 

complex environments without 

exposing drivers to danger 

through replicating a wide range 

of road, traffic, and environmental 

conditions, as well as driver 

behaviors such as distractions, 

impairment, and fatigue. New types 

of road designs can be guided by 

the use of simulators, particularly 

complex features, such as urban 

highway interchanges.

Driving simulators like this one are often used to evaluate driver behavior under specific 

conditions and in a cost-effective way.
3-22 UNIT 3: MEASURING SAFETY ROAD SAFETY FUNDAMENTALS

Simulators can also be used 

for driver education to teach 

people about the effects of driver 

distractions or to prepare young 

drivers for different conditions 

before they encounter them on the 

road. Truck simulators are used to 

replicate the driving environment 

for different types of commercial 

trucks and used to safely train 

new drivers.

Public Opinion Data 

Feedback from the general 

public can be a useful source of 

information for safety professionals. 

Safety professionals can use 

information on road safety issues 

and concerns from the public to 

identify specific locations or types of 

conditions where people have real or 

perceived traffic safety concerns. 

There are many different ways to 

collect this information, such as a 

phone-based survey, web-based 

tools (pins on maps or online 

forms), meetings, or intercept 

surveys. Common data collected 

are the type of concern, location, 

and type of mode (i.e., walking, 

bicycling, transit user, or driving).

These data are typically collected at 

the local level, frequently as part of 

a transportation planning process 

or as a collaborative effort with law 

enforcement. Bringing residents 

and police officers to join the road 

safety audit teams or diagnosis 

teams during their field visits is also 

a beneficial way to learn about the 

experiences of the road users in the 

study area.

These data may provide valuable 

insights about what the travelling 

public perceives as dangerous; 

however, it may be a biased sample 

based on those who self-select 

to provide the information to the 

researching agencies. Findings 

will be subjective as each person 

perceives a condition based on 

their individual experiences only. 

Different persons perceive different 

issues and recommend different 

“best” solutions for the same 

condition. Conclusions based on 

survey findings should be used with 

care.

Behavioral Observation

Observational surveys of road user 

behaviors are an effective method 

of data collection on information 

that may otherwise be inaccurately 

recorded due to self-reporting bias 

or are difficult to capture through 

other means. Several examples 

of data typically recorded using 

direct observation are the use of 

mobile devices (texting or calling), 

right turn on red, safety belt use, 

motorcycle or bicycle helmet use, 

and traffic control violations, such 

as rolling through stop signs.

0

20

40

60 64.3%

60.7%

2014

DOT-Compliant

Helmets

Noncompliant

Helmets

No

Helmet

2015

4.8%

10.6%

30.9% 28.7%

FIGURE 3-4: Observations of 

motorcyclists showed how many were 

wearing DOT-compliant helmets (Source: 

National Occupant Protection Use Survey)
ROAD SAFETY FUNDAMENTALS UNIT 3: MEASURING SAFETY 3-23

These data are collected through 

observing road users on the road. 

Large scale surveys collecting a high 

number of observations will provide 

the most accurate sample of the road 

user population in the study area. 

Additionally, robust observation data 

will cover differing road types and 

land use characteristics and contain 

observations at different times of 

day, week, and season. An example 

of a large-scale data collection 

effort is the National Occupant 

Protection Use Survey conducted 

annually by NHTSA. In 2013, over 

52,000 occupants were observed in 

nearly 40,000 vehicles. The data, 

summaries, and evaluations from 

this program may be viewed on the 

NHTSA website4

.

Data Users

While many agencies use safety 

data, most of them have different 

goals. For example, a city traffic 

engineer may have a specific scope 

for identifying and treating specific 

high priority sites, whereas a safety 

analysist with a State may be focused 

on safety at the system level. 

Moreover, safety researchers and 

graduate students may be focused on 

a whole range of safety evaluations 

that are not intended to be action 

plans to improve safety at a specific 

site or system. Each type of data user 

may have different levels of access to 

these various types of safety data. 

The following tables provide 

common uses and data needs for 

these different types of data users.

https://crashstats.

nhtsa.dot.gov

4

TABLE 3-3 (above/next page): Data Use by Safety Professionals, Academics and Researchers ACADEMICS AND RESEARCHERS

DATA TYPE USEFULNESS ACCESSIBILITY OFTEN PAIRE

Crash Essential High Road characteristics,

Traffic volumes

Road characteristics Essential High Crash,

Traffic volumes

Traffic volumes Essential High Crash,

Road characteristics

Naturalistic driving Supplemental Moderate

Conflicts/avoidance 

maneuvers Supplemental Low Road characteristics,Traffic volumes

Citations Supplemental Low Crash, Traffic volumes,

Road characteristics

Driving simulator Supplemental Low Road characteristics

Behavior observation Supplemental Low Crash,

Road characteristics

Injury surveillance Supplemental Very low

Driver history Supplemental Very low

Vehicle registration Supplemental Very low

Public opinion Supplemental Very low
3-24 UNIT 

3: MEASURING SAFETY ROAD SAFETY FUNDAMENTALS

SAFETY PROFESSIONALS 

FOR SPECIFIC SITES

DATA TYPE USEFULNESS ACCESSIBILITY OFTEN PAIRE

Crash Essential High Road characteristics,

Traffic volumes

Road 

characteristics Essential High Crash,Traffic volumes

Traffic volumes Essential High Crash,

Road characteristics

Public opinion Supplemental High Crash,

Road characteristics

Conflicts/avoidance 

maneuvers Supplemental Low Road characteristics,

Traffic volumes

Citations Supplemental Low Crash, Traffic volumes,

Road characteristics

Behavior 

observation Supplemental Low Crash,Road characteristics

Injury surveillance Non-essential Very low

Driver history Non-essential Very low

Vehicle registration Non-essential Very low

Naturalistic driving Non-essential Very low

Driving simulator Non-essential Very low

SAFETY PROFESSIONALS 

FOR SYSTEM LEVEL ANALYSIS

DATA TYPE USEFULNESS ACCESSIBILITY OFTEN PAIRE

Crash Essential High Road characteristics,

Traffic volumes

Road 

characteristics Essential High Crash,Traffic volumes

Traffic volumes Essential High Crash,

Road characteristics

Public opinion Supplemental High Crash,

Road characteristics

Conflicts/avoidance 

maneuvers

Non-essential Low Road characteristics,

Traffic volumes

Citations Non-essential Low

Behavior 

observation Non-essential Low

Injury surveillance Non-essential Very low

Driver history Non-essential Very low

Vehicle registration Non-essential Very low

Naturalistic driving Non-essential Very low

Driving simulator Non-essential Very low
ROAD SAFETY FUNDAMENTALS UNIT 3: MEASURING SAFETY 3-25

Insurance data

(e.g., carrier, policy number, expiration 

date, claims cost)

These data can provide insights into 

associations between insurance status and 

safety.

Demographic data

(e.g., population by gender, age, rural/

urban, residence, and ethnicity)

These data can be used for normalizing 

crash data to a state’s general population.

Safety program evaluation data

(e.g., surveys, assessments, inspections)

These data can provide feedback on the 

effectiveness of a new safety program.

Maintenance data

(e.g., guardrail replacement)

These data may indicate where unreported 

crashes are occurring.

J IDENTIFY possible relationships 

between the safety data presented 

in this chapter and census data (e.g., 

traffic safety vs. population density). 

J CONSIDER if, in the future, vehicles 

store pre-crash data in a “black box” 

type of event recording device. What 

types of data would you like it to store 

and how would you use this data (i.e., 

what types of analysis would you 

recommend conducting)?

J EXPLORE what type of safety analysis 

could be made possible using 

communication between vehicles 

(V2V) and also between vehicles 

and infrastructure (V2I - i.e., roads, 

intersections, etc.).

J DETERMINE how safety professionals 

can incorporate operational data, such 

as those from dynamic tolling lanes and 

speed sensors, into a safety analysis 

program.

EXERCISES

Other Types of Road Safety Data 

Additional types of data can also be useful to road safety professionals. These types of 

data may include:
3-26 UNIT 3: MEASURING SAFETY ROAD SAFETY FUNDAMENTALS

Quality Measures Of Data

The previous chapters in this unit 

have made the case that data are 

critical when seeking to improve 

road safety. However, simply having 

data is not enough. Good decisions 

require good data. When collecting, 

recording, maintaining, and 

analyzing safety data, road safety 

professionals must focus on the 

quality of data. Data-driven analysis 

tools are continually advancing and 

can help set priorities and select 

appropriate safety strategies, but 

the need for quality data to drive 

these tools is clear. Professionals 

commonly recognize that data 

quality can be measured on six 

criteria – timeliness, accuracy, 

completeness, uniformity, integration, 

and accessibility. Each of these 

criteria are presented in this chapter. 

Timeliness 

Timeliness is a measure of how 

quickly an event is available within 

a data system. State and local 

agencies can use technologies to 

automate crash data collection and 

quickly process police crash reports 

for analytic use. However, some 

agencies still rely on traditional 

methods, such as paper form data 

collection and manual data entry; 

these data collection methods can 

result in significant time lags. Many 

States, however, are moving closer 

to real-time data collection methods 

by using electronic reporting to 

improve the timeliness of data 

collection and submission.

Accuracy

Accuracy is a measure of how 

reliable the data are and whether 

they correctly represent reality. For 

example, exact crash location is 

an important detail for accuracy. A 

crash occurring at the intersection 

of First Street and Main Street 

should be recorded as occurring at 

that intersection. Accurate data are 

crucial during the analysis phase to 

generate road safety statistics and 

to pinpoint safety problems. Errors 

may occur at any stage of the data 

collection process. Common data 

accuracy errors include:

J Typographic errors (for data 

entered manually )

J Inaccurate and vague 

descriptions of the crash location

J Incorrect descriptions or entry 

of road names, road surface, 

level of accident severity, 

vehicle types, etc.

J Subjectivity on details that rely 

on the opinion of the reporting 

officer (e.g., property damage 

thresholds, excessive speed 

for conditions)

Technology can and is currently 

being used to improve accuracy and 

reduce errors. Automatic internal 

data quality checks are important for 

this purpose. These types of checks 

would determine if two data fields 

contain possibly conflicting data, 

and if so, bring it to the attention 

of the data analyst. An example of 

Improving Safety Data Quality

CHAPTER 9 MEASURING SAFETY
ROAD SAFETY FUNDAMENTALS UNIT 3: MEASURING SAFETY 3-27

conflicting data fields would be a 

crash type recorded as “rear end” 

but the crash report says that one 

car was hit on the “side”.

Completeness

Completeness is a measure of 

missing information. It may range 

from missing data on the individual 

crash forms to missing information 

due to unreported crashes. 

Unreported crashes, particularly 

non-injury crashes, present a 

drawback to crash data analysis. 

Without knowing about these 

crashes, we cannot recognize the 

full magnitude of certain types of 

crashes (e.g., pedestrian involved 

crashes). Non-injury crashes, or 

property damage only (PDO) crashes, 

involve damage less than a specified 

threshold (e.g., $1,000); these 

thresholds vary from State to State. 

The parties involved in PDO crashes 

Many police officers now use in-car computers to complete and submit electronic crash 

reports, increasing the timeliness of data availability. (Source: Town of Hanover, NH)

are typically not required to report 

the crash and often agree to work 

out the financial damages personally 

or through their automobile 

insurance policies. In some States, 

even when PDOs are reported, they 

are not always added into the crash 

database. 

In addition to the limitations from 

absent data due to unreported 

crashes, fluctuations in the 

thresholds (i.e., dollar amounts) can 

make it difficult to compare data 

from previous years. Unreported 

PDO crashes are one of many 

measures of “completeness” 

that road safety professionals 

must consider when collecting 

and analyzing data. A lack of 

complete data hinders the ability to 

measure the effectiveness of safety 

countermeasures (e.g., safety belts, 

helmets, and red light cameras) or 

change in crash severity.
3-28 UNIT 3: MEASURING SAFETY ROAD SAFETY FUNDAMENTALS

Crash Data Improvement Program

The Federal government established 

the Crash Data Improvement Program 

(CDIP) to provide states with a 

means to measure the quality of the 

information within their crash database. 

It is intended to provide the states with 

metrics that can be used to establish 

measures of where their crash data 

stand in terms of its timeliness, the 

accuracy and completeness of the 

data, the consistency of all reporting 

agencies reporting the information in 

the same way, the ability to integrate 

crash data with other safety databases, 

and how the state makes the crash data 

accessible to users. Additionally, CDIP 

was established to help familiarize the 

collectors, processors, maintainers, and 

users with the concepts of data quality 

and how quality data help to improve 

safety decisions. CDIP also included a 

guide that presents information on each 

data quality characteristic and how to 

measure them.

Reference: Crash Data Improvement 

Program, National Highway Traffic Safety 

Administration, https://safety.fhwa.dot.

gov/cdip/summary.cfm

Uniformity

Uniformity is a measure of how 

consistent information is coded in 

the data system or how well it meets 

accepted data standards. Numerous 

law enforcement agencies within 

each State, some of which are not 

the primary users of the crash 

data, are responsible for crash data 

collection. The challenge for States 

is ensuring there is consistency 

among the various agencies when 

collecting and reporting crash data. 

One example of inconsistent or nonuniform data can be the location of 

a crash. If one agency, for example 

the State highway patrol, uses 

GPS to document a crash at one of 

several entrances (driveways) to a 

shopping center, but the city police 

use a linear reference system (e.g., 

distance from an intersection), there 

is a potential for inconsistent crash 

location data. 

The Model Minimum Uniform 

Crash Criteria (MMUCC) is used by 

States to ensure uniform crash data. 

MMUCC is an optional guideline 

that presents a model minimum 

set of uniform variables or data 

elements for describing a motor 

vehicle crash. This uniformity 

assists transportation safety 

professionals and governments in 

making decisions that lead to safety 

improvements. Similarly, MIRE 

provides a recommended list of 

elements to use when reporting road 

and traffic characteristics, thereby 

increasing uniformity of road 

network data. More information on 

MMUCC and MIRE is presented at 

the end of this chapter.

Integration

Data integration is a measure of 

whether different databases can 

be linked together to merge the 

information in each database into 

a combined database. Each State 

maintains its own crash database. 

However, crash data alone do not 

typically provide sufficient details 

on issues like environmental risk 

factors, driver experience, or medical 

consequences. Linking crash data 

to other databases, such as road 

characteristics, driver licensing, 

vehicle registration, and hospital 

outcome data assists analysts 

and planners in evaluating the 

relationship of the circumstances 

of the crash and other factors (e.g., 

human, road, medical treatment) at 

the time of the crash. In addition, 

integrated databases promote 

collaboration among agencies, which 
ROAD SAFETY FUNDAMENTALS UNIT 3: MEASURING SAFETY 3-29

Moving Ahead for 

Progress in the 21st 

Century Act, Section 

1112, §148(f)(2)

5

can lead to improvements in the 

data and the data collection process. 

Some data are more challenging to 

integrate with other data sets. For 

example, hospital data are difficult 

to integrate with crash data due to 

the lack of a common identification 

system (as well as medical privacy 

laws). This is different from crash, 

road characteristics, and volume 

data, which can share a common 

referencing system on the road and 

thus be integrated and linked more 

easily for analysis.

Spatially-located data in a GIS 

system can be integrated simply 

based on spatial position. This 

geographic integration can assist 

agencies in bringing together data 

that were gathered by various 

departments or agencies that may 

use different data storage standards 

and reference systems.

Accessibility

Accessibility is a measure of how 

easy it is to retrieve and manipulate 

safety data in a system, in particular 

by those entities that are not the 

data system owners. Complete, 

accurate, and timely data easily 

made available to localities, MPOs, 

and other safety partners can greatly 

enhance transportation planning 

and safety investments. Agencies 

or departments who house safety 

data, especially crash data, should 

consider how accessible the data 

are to external parties and how the 

process of obtaining data could be 

streamlined.

Data Improvement Strategies 

Local, State, and Federal agencies, 

as well as non-governmental 

organizations, require accurate 

data to be available for analysis and 

problem solving. Thus, programs to 

improve data should be in the work 

programs of all agencies invested in 

road safety. Data could be improved 

by changes in policy, technology, 

assessments, and training.

Policy

With so many agencies and 

organizations involved in the 

data collection process, published 

policy is a necessity. A standard 

set of procedures can provide a 

clear expectation of each agency’s 

roles and responsibilities in data 

collection. Federal guidance and 

State legislation or administrative 

policy and regulations generally 

form a basis for policy. An 

example of Federal guidance 

comes from the provision in the 

MAP-21 transportation legislation 

that requires States to collect a 

comprehensive set of roadway and 

traffic fundamental data elements 

(FDEs) on all public roads5

. 

Technology 

Technology plays an important role 

in data collection improvement. 

Federal legislation provides funds 

that allow States to improve their 

data collection systems with 

the latest technology for quality 

data collection and integration. 

Technology is not static and is 

always changing. Some technology 

examples that help facilitate data 

collection include electronic crash 

reporting systems, GPS location 

devices, barcode or magnetic 

strip technologies, wireless 

communications, error checking, 

and conflicting fields.

Assessments

Assessments are official evaluations 

that government agencies conduct 
3-30 UNIT 3: MEASURING SAFETY ROAD SAFETY FUNDAMENTALS

Federal Highway 

Administration 

Roadway Safety 

Data Program, 

http://safety.fhwa.

dot.gov/rsdp/

technical.aspx

6

to determine the effectiveness of a 

traffic safety process or program. A 

team of outside experts conducts a 

comprehensive assessment of the 

highway safety program using an 

organized, objective approach and 

well-defined procedures that:

J Provide an overview of the 

program’s current status 

in comparison to 

pre-established standards

J Note the program’s strengths 

and weaknesses

J Provide recommendations for 

improvement

Both FHWA and NHTSA provide 

these types of assessments, such 

as the Roadway Data Improvement 

Program (RDIP), which can improve 

the quality of an agency’s data 

through expert technical assistance 

and fresh perspectives. When 

State agencies request an RDIP 

assessment, an FHWA team reviews 

and assesses a State’s roadway 

data system for the content of the 

data collected; for the ability to 

use, manage and share the data; 

and to offer recommendations for 

improving the road data. The RDIP 

also examines the State’s ability to 

coordinate and exchange road data 

with local agencies, such as those in 

cities, counties, and MPOs6

.

Training

Education and training of 

transportation professionals play 

a vital role in improving data 

and data collection. For example, 

law enforcement officers create 

the crash data that is used by 

safety professionals to conduct 

studies and evaluate road safety. 

Thus, law enforcement need to 

understand how crash data are 

used in policy development and 

investment decisions, infrastructure 

improvements, and safety planning. 

Through proper education and 

training programs, law enforcement 

can have a broader perspective 

of their contribution to reducing 

crashes through improved 

data reporting. Other examples 

include training transportation 

professionals on the latest data 

collection tools and technology, 

advising court officials and 

adjudicators on important changes 

to safety legislation and penalties, 

and training personnel on how to 

handle crash reports with inaccurate 

or missing information.

Federal Guidance

The following two sections present 

examples of Federal guidance that 

leads State agencies into improving 

the quality of their safety data.

Model Minimum Uniform Crash 

Criteria

Statewide motor vehicle traffic 

crash data systems provide the 

basic information necessary for 

effective road safety efforts at any 

level of government—local, State, 

or Federal. Unfortunately, the use of 

State crash data is often hindered by 

the lack of uniformity between and 

within States. Data definitions, the 

number and type of data elements, 

and the threshold for collecting 

data varies from jurisdiction to 

jurisdiction. The Model Minimum 

Uniform Crash Criteria (MMUCC) 

was developed to help bring greater 

uniformity to crash data collection 

and provide national guidance to 

data collectors. MMUCC represents 

a voluntary and collaborative effort 

to generate uniform, accurate, 

reliable, and credible crash data to 
ROAD SAFETY FUNDAMENTALS UNIT 3: MEASURING SAFETY 3-31

MMUCC Example Element

The following is the MMUCC format for 

“Person Data Element Derived from 

Collected Data.” 

PD1. Age 

Definition: The age in years of the person 

involved in the crash 

Source: This data element is derived from 

Date of Birth (P2) and Crash Date and 

Time (C3).

Attribute: 

• Age in years 

Rationale: Age is necessary to 

determine the effectiveness of safety 

countermeasures appropriate for various 

age groups.

support data-driven highway safety 

decisions at a State and a national 

level. MMUCC serves as a foundation 

for State crash data systems. 

Since MMUCC is a minimum set of 

recommended crash data, States 

and localities may choose to collect 

additional motor vehicle crashrelated data elements if they feel 

the data are necessary to enhance 

decision-making. Implementation 

of MMUCC is a collaborative effort 

involving the Governors Highway 

Safety Association, FHWA, NHTSA, 

and the Federal Motor Carrier Safety 

Administration (FMCSA). 

The MMUCC Guideline is updated 

every four or five years to address 

emerging highway safety issues, 

simplify the list of recommended 

data elements, and clarify 

definitions of each data element.

MMUCC Data Elements

MMUCC consists of data elements 

recommended to be collected by 

investigators at the crash scene. 

From the crash scene information, 

additional data elements can be 

derived to assist law enforcement. 

Additional data elements are 

available through linkage to driver 

history, hospital and other health/

injury data, and road inventory data. 

Each group of data elements has a 

unique identifier that describes the 

type of data element and whether it 

is derived or linked data.

MMUCC data elements are divided 

into four major groups that describe 

various aspects of a crash: crash, 

vehicle, person, and roadway. Each 

data element includes a definition, 

a set of specific attributes, and a 

rationale for the specific attribute. 

For the entire list of MMUCC data 

elements, refer to the latest edition 

of the MMUCC Guideline located at 

www.mmucc.us.

The MMUCC data elements represent 

a core set of data elements. The 

fourth edition (2012) of the MMUCC 

Guideline contains 110 data elements 

and recommends that States collect 

all 110 data elements. To reduce the 

data collection burden, MMUCC 

recommends that law enforcement 

at the scene should collect 77 of the 

110 data elements. From crash scene 

information, 10 data elements can 

be derived, while the remaining 23 

data elements should be obtained 

after linkage to other State data 

files. States unable to link to other 

State data to obtain the MMUCC 

linked data elements should collect, 

at a minimum, those linked data 

elements feasible for collecting on 

the crash report. At the same time, 

States should work to develop data 

linkage capabilities so they eventually 

are able to obtain, via linkage, all of 

the information to be generated by 

the MMUCC linked data elements.
3-32 UNIT 3: MEASURING SAFETY ROAD SAFETY FUNDAMENTALS

FIGURE 3-5: MIRE Data Elements Category Descriptors (Source: MIRE version 1.0)

ROADWAY SEGMENT ROADWAY ALIGNMENT

Segment location/linkage elements

Segment classification

Segment cross section

Segment roadside descriptors

Other segment descriptors

Segment traffic flow data

Segment traffic operations/control data

Other supplemental segment descriptors

Horizontal curve data

Vertical curve data

ROADWAY JUNCTION

At-grade intersection/junctions

Interchange and ramp descriptors

Model Inventory of Roadway Elements

Critical safety data include not 

only crash data, but also road 

inventory data, traffic data, and 

other information. State DOTs need 

accurate and detailed data on road 

characteristics as they develop 

and implement strategic highway 

safety plan (SHSPs) and look toward 

making more data driven safety 

investments.

With the need for and availability of 

so many types of data, the question 

becomes “How can transportation 

agencies be sure that they are 

collecting the necessary roadway 

data to make effective road safety 

decisions?” MIRE is a vitally 

important resource that defines the 

data needed to help transportation 

agencies build a road characteristics 

database that will lead to good 

safety analysis. MIRE defines 202 

individual characteristics of the road 

system that should be collected. 

These characteristics are referred to 

as data elements. The elements fall 

into three broad categories: 

J Roadway segment descriptors

J Roadway alignment descriptors

J Roadway junction descriptors

Most State and local transportation 

agencies do not have all the data 

needed to use analysis tools such 

as SafetyAnalyst, the Interactive 

Highway Safety Design Model, and 

other tools and procedures identified 

in the Highway Safety Manual. 

MIRE provides a structure for road 

inventory data that allows State and 

local transportation agencies to use 

these analysis tools with their own 

data rather than relying on default 

values that may not reflect local 

conditions. 

As the need for road inventory 

information has increased, new and 

more efficient technologies to collect 

road characteristics have emerged. 

However, the collected data need a 

framework for common information 

sharing. Just as MMUCC provides 

guidance for consistent crash data 

elements, MIRE provides a structure 

for roadway inventory data elements 

using consistent definitions and 

attributes. It defines each element, 

provides a list of attributes for 

coding, and assigns a priority status 

rating of “critical” or “value added” 

based on the element’s importance 

for use in analytic tools, such as 
ROAD SAFETY FUNDAMENTALS UNIT 3: MEASURING SAFETY 3-33

SafetyAnalyst. 

The latest version of MIRE can be 

viewed and downloaded from the 

FHWA Office of Safety site, http://

safety.fhwa.dot.gov/tools/data_tools/

mirereport/.

Figure 3-5 displays a breakdown of 

the major data element categories 

and subcategories contained in 

MIRE. MIRE further breaks down 

each subcategory into individual 

data elements. For a complete listing 

of MIRE data elements, refer to the 

MIRE publication. 

While the complete list of MIRE 

elements is rather extensive, there 

are a basic set of elements within 

MIRE called the Fundamental Data 

Elements (FDE) that an agency 

needs to conduct safety analyses 

regardless of the specific analysis 

tools used or methods applied. As 

discussed, the need for improved 

and more robust safety data is 

increasing due to the development 

of a new generation of safety data 

analysis tools and methods. 

Linking Data Through A 

Referencing System

The types of road safety data 

presented in this unit are only useful 

as much as they are capable of being 

linked through a common geospatial 

relational location referencing 

system. States recognize that they 

must have a common relational 

location referencing system (i.e., 

geographic information system or 

linear referencing system) for all 

public roads if they are going 

to integrate different types of 

safety data. If all safety data are 

referenced to the same system, the 

road characteristics data can be 

linked with the crash data, which 

would permit the State to identify 

locations on all public roads where 

crash patterns are occurring that 

can be reduced through known 

countermeasures. 

In most States, development of a 

common referencing system for all 

public roads will require significant 

effort and cooperation with local 

agencies. The Federal Highway 

Performance Monitoring System 

requires GIS-based referencing for 

all roads in the Federal-aid highway 

system, interstate highways, and 

public roads not classified as local 

roads or rural minor collectors.7

However, significant travel occurs 

on local roads and rural minor 

collectors. Some local agencies 

have or are developing, their own 

GIS-based referencing systems for 

roads in their inventory data. Light 

detection and ranging (LIDAR) 

systems are often used to accurately 

survey the road network. The State 

should work with local agencies 

to incorporate these referencing 

systems into the State base map. 

Once the referencing systems 

are combined, attribute data for 

additional mileage can be added 

when either State or local agencies 

develop or expand inventories. 

Moreover, as stated above, this will 

lead to the ability to link crashes 

with inventory and traffic data, 

enabling the State to use the more 

advanced problem identification 

methods on more and more miles of 

public roads.

Memorandum on 

Geospatial Network 

for All Public Roads, 

Office of Highway 

Policy Information, 

August 7, 2012. 

Accessed October 

2017 at https://

www.fhwa.dot.gov/

policyinformation/

hpms/arnold.pdf

7
3-34 UNIT 3: MEASURING SAFETY ROAD SAFETY FUNDAMENTALS

J SELECT a scenario below. Assume that 

you are using crash data as your primary 

data to inform your decisions. Explain 

how each of the six quality criteria 

discussed in this chapter could affect 

your evaluation of the current safety 

situation and your recommendations. 

J You are prioritizing intersections in 

a city to be treated with enhanced 

visibility treatments, such as 

larger signs, wider markings, and 

additional signal heads. 

J You are developing a public 

outreach effort to communicate 

the need to yield to pedestrians at 

crosswalks. You wish to focus your 

efforts to the areas of the city where 

failing to yield to pedestrians is the 

most rampant.

J You are recommending safety 

improvements to an interchange 

that was identified based on having 

a higher number of expected 

crashes than other interchanges of 

the same type.

Given the scenario you selected above, 

how do you think the availability of 

other types of data could affect your 

recommendations? Such data may 

include any of the data types covered 

in Chapter 3.2. (e.g., EMS and hospital 

injury data, enforcement citations, 

public complaints, or other data). What 

additional information could this reveal?

J IDENTIFY programs or policies that exist 

in your state or local agency to improve 

data. This may include any of the types 

of safety data covered in Chapter 3.2.

EXERCISES

Conclusion

Data are crucial to improving road 

safety. Safety data consist of various 

kinds of data that can be used 

to identify safety problems and 

priorities so that safety partners 

in many agencies can address 

important issues. Data such as crash 

data, traffic volume data, and road 

characteristics data are often used 

and are critical for safety analysis 

by many agencies. Other data, such 

as conflict observations, emergency 

medical data, and citation data, can 

be useful in a supplemental role for 

specific studies. Regardless of the 

type of safety data, the quality of the 

data is vitally important. Agencies 

that collect safety data should 

strive to improve their timeliness, 

accuracy, completeness, uniformity, 

integration, and accessibility to 

maximize their potential to drive 

good decisions.
ROAD SAFETY FUNDAMENTALS UNIT 3: MEASURING SAFETY 3-35

THIS PAGE INTENTIONALLY LEFT BLANK
4-b UNIT 4: SOLVING SAFETY PROBLEMS ROAD SAFETY FUNDAMENTALS

After reading the chapters and completing 

exercises in Unit 4, the reader will be able to:

J IDENTIFY three major components 

of road safety management

J DEFINE the process of conducting 

site-level and system-level 

safety management

J USE safety data to identify safety 

issues and develop strategies to 

solving those issues

LEARNING OBJECTIVES

Solving Safety 

Problems

UNIT 4
ROAD SAFETY FUNDAMENTALS UNIT 4: SOLVING SAFETY PROBLEMS 4-1

Road Safety Management

Road safety management refers to 

the process of identifying safety 

problems, devising potential 

strategies to combat those safety 

problems, and selecting and 

implementing the strategies. 

Effective safety management is 

also proactive and looks for ways 

to prevent safety problems before 

they arise. High quality safety data 

should be used to determine the 

nature of the road safety problems 

and how best to solve them. As 

discussed in Unit 3, the clearest and 

most readily available indicators of 

road safety problems are crash data. 

These data can be used to identify 

safety problems on a large or a small 

scale. Other data, such as roadway 

characteristics, traffic volume, 

citations, and driver history, can be 

integrated with crash data to assist 

in identifying safety trends and high 

priority locations.

Data quality issues should not 

prevent a data-driven process

Every transportation agency will 

acknowledge that it does not have 

perfect data. All data have issues 

related to accuracy, coverage, 

timeliness, and other factors. One 

agency’s crash data may have an 

incomplete record of low severity 

crashes. Another agency may 

have very little data on the traffic 

volume on low volume rural roads. 

However, data quality issues should 

not prevent a transportation agency 

from using the data to drive its 

safety management efforts. Even 

while the agency strives to improve 

its data, the data on hand should be 

used in the process of identifying 

safety problems and devising 

solutions to those problems.

Data needs for safety analysis

High quality safety analysis 

demands high quality data. 

Unfortunately, poor data availability 

and low quality limit the types of 

analyses that can be conducted. 

The data requirements depend on 

the type of analysis and what safety 

questions are being asked. Table 

4-1 provides examples of various 

categories of safety analysis and lists 

the data that would be needed to 

conduct them.1

CHAPTER 10 UNIT 4: SOLVING SAFETY PROBLEMS

Applying Safety 

Data and Analysis to 

Performance-Based 

Transportation 

Planning, 

e-Guidebook, 

FHWA, http://safety.

fhwa.dot.gov/tsp/

fhwasa15089/

appb.cfm

1
4-2 UNIT 

4: SOLVING SAFETY PROBLEMS ROAD SAFETY FUNDAMENTALS

TABLE 4-1: Safety analysis categories, questions, tools and data needs. SAFETY ANALYS

QUESTIONDTA NEED

BENCHMARKI

How many fatalities 

and serious injuries are 

occurring in my area? 

How does this 

compare to other 

areas of my State?

Total crashes

Total fatalities and serious injuries

High-level roadway data — roadway ownership, 

functional classification Agency geographic boundary informatio

CRASH TRENDS ANCONTRIBUTING FACTO

What type of road users 

are involved in crashes? 

When are the 

crashes occurring? 

What are the major 

contributing factors 

to crashes?

Crash severity — fatality, injury type, 

property damage only

Crash incidence data — time of day, day, 

month, weather, etc. 

Crash type — road departure, intersection, 

head-on, angle, etc. 

Contributing factors — age, impairment, 

seatbelt usage, speed, etc.

SITES FOR SAFETY IMPROVEMEN

What locations 

(intersections or 

segments) show the 

most potential for 

safety improvements?

Crash severity

Crash location

Roadway and roadside characteristics — intersection 

control, number of lanes, presence and type of 

shoulder, presence and type of median, posted 

speed, horizontal and vertical alignment, etc. 

Traffic volume data — intersection total entering 

traffic volume, roadway segment volume per 

million vehicle miles. 

Calibrated safety performance functions, 

if predictive methods are used

SAFETY RISK FACTO

What are the common 

characteristics of 

locations with crashes? 

What are the 

countermeasures 

to address these 

characteristics? 

How should we prioritize 

system-wide 

implementation?

Crash severity

Crash location

Roadway and roadside characteristics — intersection 

control, number of lanes, presence and type of 

shoulder, presence and type of median, posted 

speed, horizontal and vertical alignment, etc. 

Traffic volume data — intersection total entering 

traffic volume, roadway segment volume per 

million vehicle miles.
ROAD SAFETY FUNDAMENTALS UNIT 4: SOLVING SAFETY PROBLEMS 4-3

Safety data as 

performance measures

A transportation agency has many 

types of data at its disposal for 

identifying safety problems, but the 

agency must select which type(s) 

of data will be the performance 

measures used to identify the road 

safety emphasis areas. Federal 

legislation has focused increasingly 

on fatal crashes and serious injury 

crashes as performance measures 

for road safety.

Table 4-2 provides examples of 

performance measures developed 

by the National Highway Traffic 

Safety Administration (NHTSA) 

and the Governors Highway Safety 

Association (GHSA) that could be 

used to identify safety priorities.2

The sources of the data could be 

State crash data files, the Fatality 

Analysis Reporting System (FARS), 

surveys conducted by the State, 

or grant applications from law 

enforcement and other departments. 

The section on Network Screening 

in Chapter 11 presents a more 

detailed discussion of crash-based 

performance measures and how they 

can be used to identify sites that are 

high priority for safety treatment. 

TABLE 4-2: Safety performance measures and data sources (Source: NHTSA 2007)

DESCRIPTION SOURCES

Number of traffic fatalities (three-year or five-year moving averages) FARS 

Number of serious injuries in traffic crashes State crash 

data files

Fatalities/VMT (including rural, urban, and total fatalities) FARS, FHWA 

Number of unrestrained passenger vehicle occupant fatalities, seat positions FARS 

Number of fatalities in crashes involving a driver or motorcycle operator 

with a blood alcohol concentration of .08 g/dL or higher FARS 

Number of speeding-related fatalities FARS 

Number of motorcyclist fatalities FARS 

Number of unhelmeted motorcyclist fatalities FARS 

Number of drivers 20 or younger involved in fatal crashes FARS 

Number of pedestrian fatalities FARS 

Observed seat belt use for passenger vehicles, front seat outboard occupants Survey 

Number of seat belt citations issued during grant-funded 

enforcement activities

Grant activity 

reporting 

Number of impaired-driving arrests made during grant-funded 

enforcement activities

Grant activity 

reporting 

Number of speed citations issued during grant-funded activities Grant activity 

reporting 

National Highway 

Traffic Safety 

Administration 

(NHTSA). 2007. 

Performance 

Measures 

Discussion. 408 

Team Document 

#005, October 

29, 2007. 

National Highway 

Traffic Safety 

Administration.

2

Performance 

measure

A numerical 

metric used 

to monitor 

changes 

in system 

condition and 

performance 

against 

established 

visions, goals, 

and objectives.
4-4 UNIT 

4: SOLVING SAFETY PROBLEMS ROAD SAFETY FUNDAMENTALS

Components of 

safety management

The safety management process 

can be viewed in three general 

components. These components 

are carried out by the agency (or 

agencies) responsible for managing 

the safety of the road system: J Identifying safety problems

– The 

agency uses crash data and other 

safety data to identify road safety 

problems or problem locations.

J Developing potential safety 

strategies – The agency develops 

potential strategies to address 

the identified safety problems. 

These strategies might also be 

referred to as countermeasures 

or treatments.

J Selecting and implementing 

strategies – The agency weighs 

the potential strategies and 

decides which ones to implement.

Levels of safety management

Although all road safety 

management follows the same 

three general components listed 

above, the specific steps of the 

safety management process will be 

different depending on the scope. 

The process might be intended to 

address specific site-level issues, 

such as crash patterns at high 

priority intersections, curves, or 

corridors. On a larger scale, the 

process might be intended to 

address system-level issues, such as 

problems that can be addressed by 

policies, design standards, or broad 

ranging campaigns of education or 

enforcement. The following chapters 

will discuss safety management for 

these two levels: Chapter 11 presents 

site-level safety management; 

Chapter 12 presents system-level 

safety management.
ROAD SAFETY FUNDAMENTALS UNIT 4: SOLVING SAFETY PROBLEMS 4-5

Site-level safety management 

is the process of identifying and 

addressing safety issues at high 

priority sites. This contrasts with 

safety issues that are addressed for 

an entire transportation system (i.e., 

all roads in a city, county, or State). 

System-level safety management is 

covered in Chapter 12.

Agencies responsible for road 

safety often conduct some form 

of site-level safety management. 

They identify particular sites of 

concern and determine how best 

to address the safety problems at 

these priority sites. The methods 

of identifying priority sites and 

the safety strategies used to treat 

the sites differ according to the 

type of agency. A department of 

transportation (DOT) may install 

a sign or pavement marking; a law 

enforcement agency might increase 

enforcement in the area of the site. 

Regardless of the type of agency, it 

is important to conduct site-level 

safety management in a manner that 

uses good analysis methods driven 

by safety data.

Chapter 10 presented road safety 

management in terms of three 

general components: 

J Identifying safety problems

J Developing potential 

safety strategies

J Selecting and 

implementing strategies

When discussing site-level 

safety management, these three 

components can be further divided 

into six distinct steps. This sixstep process is common to the 

engineering discipline and is 

presented in Part B of the first 

edition of the Highway Safety 

Manual3

 (HSM). The process, shown 

in Figure 4-1, will be the framework 

for the discussion of site-level safety 

management in this chapter. The 

material presented in this chapter is 

based on the guidance presented in 

the HSM and material from a series 

of documents entitled “Reliability 

of Safety Management Methods” 

published by FHWA. These FHWA 

Site

A narrowly 

defined 

location of 

interest for 

safety analysis, 

such as an 

intersection, 

road section, 

interchange, 

or midblock 

crossing.

Highway Safety 

Manual, First 

edition, American 

Association of 

State Highway 

Transportation 

Officials, 2010.

3

Site-Level Safety Management

CHAPTER 11 UNIT 4: SOLVING SAFETY PROBLEMS

1. NETWORK SCREENING

2. DIAGNOSIS

3. COUNTERMEASURE 

 SELECTION

4. ECONOMIC APPRAISAL

5. PROJECT PRIORITIZATION

6. SAFETY EFFECTIVENESS 

 EVALUATION

FIGURE 4-1: Schematic Illustrating the 

Steps of Site-level Safety Management
4-6 UNIT 4: SOLVING SAFETY PROBLEMS ROAD SAFETY FUNDAMENTALS

documents provide in-depth 

guidance and examples on the 

following topics:

J Network screening – The network 

screening guide describes various 

methods and the latest tools to 

support network screening.4

J Diagnosis - The diagnosis 

information guide describes 

various methods and the latest 

tools to support diagnosis.5

J Countermeasure selection - 

The countermeasure selection 

information guide describes 

various methods and the 

latest tools to support 

countermeasure selection.6

J Safety effectiveness evaluation

- The safety effectiveness 

evaluation guide describes 

various methods and the 

latest tools to support safety 

effectiveness evaluation.7

J Systemic safety programs - The 

systemic safety programs guide 

describes the state-of-the-practice 

and the latest tools to support 

systemic safety analysis.8

The six steps of the site-level safety 

management process relate to the 

three general components of safety 

management as shown in Table 4-3. 

Each step is presented in more detail 

through the following sections 

in this chapter. 

SAFETY

MANAGEMEN

COMPONENTS STEPS OF SITE-LEVEL SAFETY MANAGEM

IDENTIFY 

SAFETY

PROBLEM

Step 1. Network screening: Identify locations that could benefit 

from treatments to reduce crash frequency and severity.

Step 2. Diagnosis: Identify crash trends and patterns based on 

reported crashes, assess the crash types and severity levels, 

and study other elements that characterize the crashes.

DEVELOP 

POTENTIAL

SAFETY

SOLUTIONS

Step 3. Countermeasure selection: Identify appropriate 

countermeasures to target crash contributing factors and 

reduce crash frequency and severity at identified locations. 

Step 4. Economic appraisal: Estimate the economic benefit and 

cost associated with implementing a particular countermeasure 

or set of countermeasures. 

SELECT AND

IMPLEMENT 

STRATEGIE

Step 5. Project prioritization: Develop a prioritized list of 

safety improvement projects, considering available resources.

Step 6. Safety effectiveness evaluation: Evaluate how a particular 

countermeasure (or group of countermeasures) has affected 

crash frequency and severity where it was installed. 

TABLE 4-3: Steps of the Site-level Safety Management Process

Srinivasan, R., F. Gross, 

G. Bahar (2016), 

Reliability of Safety 

Management Methods: 

Safety Effectiveness 

Evaluation, Report No. 

FHWA-SA-16-040, 

Federal Highway 

Administration, 

Washington, D.C.

Srinivasan, R., G. 

Bahar, F. Gross (2016), 

Reliability of Safety 

Management Methods: 

Diagnosis, Report No. 

FHWA-SA-16-038, 

Federal Highway 

Administration, 

Washington, D.C.

See next page.

Bahar, G. R. Srinivasan, 

F. Gross, (2016), 

Reliability of Safety 

Management Methods: 

Countermeasure 

Selection, Report No. 

FHWA-SA-16-039, 

Federal Highway 

Administration, 

Washington, D.C.

Srinivasan, R., F. Gross, 

B. Lan, G. Bahar 

(2016), Reliability of 

Safety Management 

Methods: Network 

Screening, Report No. 

FHWA-SA-16-037, 

Federal Highway 

Administration, 

Washington, D.C. 

7

5

8

6

4
ROAD SAFETY FUNDAMENTALS UNIT 4: SOLVING SAFETY PROBLEMS 4-7

Step 1. Network screening

Network screening refers to the 

process of selecting high priority 

sites that need safety treatment, 

often through an analysis of crash 

data. There are many ways in 

which an agency can use crash data 

to prioritize sites, ranging from 

simplistic methods, which are easy 

to understand and implement but 

can be inaccurate or ineffective, 

to more advanced methods, which 

require statistical expertise and 

more data but provide a better 

prioritization of sites.

For many years, the most prevalent 

methods for ranking specific sites 

for safety improvements were based 

on historical crash data alone. Many 

agencies still use these methods 

to allocate their road safety funds. 

Agencies that prioritize sites by 

historical crash frequency identify 

those sites that have the highest 

number of crashes in a certain 

time period (typically three to five 

years). This serves to assist agencies 

in addressing the magnitude of 

the problem, that is, attempting 

to address the highest number of 

crashes. By its nature, this method 

typically identifies sites that have 

high amounts of traffic (either 

vehicles, pedestrians, or other road 

users). However, this method may 

miss abnormally hazardous sites 

that do not present a relatively 

large number of crashes. Another 

variation of the crash frequency 

method uses crash severity, in 

which agencies weight the crash 

frequency by giving greater weight 

to higher severity crashes. This 

method counteracts some of the 

bias in the crash frequency method. 

For example, a general high crash 

frequency may prioritize a busy 

intersection that has many crashes, 

but a closer examination reveals 

that most crashes are low speed, low 

severity rear-end crashes. The crash 

severity method would lower the 

priority of this intersection in favor 

of other sites where more serious 

crashes occur. 

Some agencies prioritize sites 

by the historical crash rate. This 

method incorporates traffic volume 

to augment the crash data. The 

crash frequency at a site is divided 

by the traffic volume – either the 

annual average daily traffic (for road 

segments), total entering volume 

(for vehicle traffic at intersections), 

or other volumes, such as pedestrian 

crossing volume. The typical unit 

for this method is crashes per 

100 million vehicle miles traveled 

for road segments or crashes per 

100 million entering vehicles for 

intersections. Crash rate in these 

units is calculated as:

(from previous page)

Gross, F., T. Harmon, 

G. Bahar, K. Peach 

(2016), Reliability of 

Safety Management 

Methods: Systemic 

Safety Programs, 

Report No. 

FHWA-SA-16-041, 

Federal Highway 

Administration, 

Washington, D.C.

8

Crash 

frequency

The number 

of observed 

crashes 

per year.

Crash 

severity

The level of 

injury severity 

of the crash 

as an event, 

typically 

determined 

by the highest 

severity injury 

of any person 

involved in 

the crash.

Crash rate

The number 

of observed 

crashes 

per unit of 

traffic volume 

passing through 

the location.

Crash rate per 

100 million vehicle 

miles traveled

= (C×100,000,000)

(V×365×N×L)

C = Number of crashes in the study period

V = Traffic volumes using average annual 

daily traffic (AADT) volumes

N = Number of years of data

L = Length of the roadway segment in miles

This approach of prioritizing sites by 

crash rate serves to counteract the 

bias of crash frequency that overly 

prioritizes sites with high volume, 

since higher volume decreases 

the crash rate. However, it may 

inefficiently prioritize sites with 

very low volumes.
4-8 UNIT 4: SOLVING SAFETY PROBLEMS ROAD SAFETY FUNDAMENTALS

Agencies might use a combination 

of these two methods. They may set 

a minimum crash rate to generate 

an initial list of priority sites and 

then prioritize that group by crash 

frequency or severity. Regardless, 

these simplistic methods are known 

to have potential biases. One of 

the most prevalent biases is that 

the crash history used to prioritize 

sites with these methods usually 

reflects only the short-term trend 

of crashes. Given that the yearto-year occurrence of crashes at 

a location is random, it can be 

the case that a short-term crash 

history (one to three years) may 

be relatively high, but in the long 

run (ten years), the crashes would 

return to a lower amount, even if 

no safety improvements were done. 

This effect creates selection bias or 

regression-to-the-mean (RTM) bias in 

the safety analysis of this location.

As the years progressed, many 

transportation safety professionals 

recognized that while these 

simplistic methods did identify 

sites that benefited from safety 

improvement, they were not the 

locations where safety funds could 

be spent the most effectively. The 

selection of high crash sites was 

subject to RTM bias. Also, sites 

with high numbers of crashes were 

typically complex and required 

expensive reconstruction in order 

to reduce crashes appreciably. The 

question became, “How could road 

safety funds be spent in a way that 

provided the biggest bang for the 

buck?”

As the science of road safety 

advanced, researchers developed 

more advanced approaches 

for prioritizing sites for safety 

improvements. Dr. Ezra Hauer 

pushed forward a movement to 

identify “sites with promise.”9

 The 

main idea was to identify sites that 

experienced more crashes than 

would be expected from a site with 

that particular set of characteristics. 

In many cases, these abnormally 

performing sites could be addressed 

with low cost safety treatments, 

such as larger signs or pavement 

markings with greater visibility. This 

approach uses statistical regression 

models that predict crashes for a 

given set of characteristics. These 

models demonstrate the advantage 

of bringing together different types 

of safety data, which in this case 

could include crash data, roadway 

characteristics, and traffic volume.

Regressionto-the-mean

The fact that 

a short term 

examination of 

crash history 

at a location is 

likely inaccurate 

(e.g., lower or 

higher than 

its true safety 

performance). 

When a longer 

time period of 

crash history is 

examined, the 

crash frequency 

will “regress” 

to its “mean” 

and provide a 

better picture 

of the long term 

average crash 

frequency.

Comparing road segments by 

crash frequency and rate

Road Segment A: A three-mile section of 

road that has had four crashes over five 

years and has a traffic volume of 4,000

vehicles per day.

Road Segment B: A three-mile section 

of road that has had 10 crashes over five 

years and has a traffic volume of 12,000

vehicles per day.

If an agency is comparing these 

segments based on crash frequency, 

they would prioritize road segment B 

for having 10 crashes compared to road 

segment A which had four crashes.

If comparing these segments based on 

crash rate, the agency would calculate 

the crash rate of road segment A as 

(4 crashes x 100,000,000) / (4,000 

vehicles per day x 365 x 5 years x 3 miles) 

= 18.2 crashes per 100 million vehicle 

miles traveled. Following the same 

calculation, road segment B has a rate of 

15.2 crashes per 100 million vehicle miles 

traveled. According to crash rate, the 

agency would prioritize road segment A. 

The prioritization of these two segments 

changes when traffic volume is taken 

into account.

Hauer, E. (1997), 

Observational Before 

After Studies in Road 

Safety, Elsevier 

Science, New York.

9
ROAD SAFETY FUNDAMENTALS UNIT 4: SOLVING SAFETY PROBLEMS 4-9

The most basic of these regression 

methods calculates predicted 

crashes. This method requires 

information about certain geometric 

and operational characteristics, such 

as traffic volume, number of lanes, 

and type of road.

An SPF is developed or calibrated 

using data from an entire 

jurisdiction or State, so it is 

independent of the crash history 

of the specific site. This means 

that the predicted crash value is 

unaffected by the bias caused by 

RTM. Using SPFs, transportation 

agencies can predict crash values for 

many sites and prioritize the sites 

according to the highest predicted 

values. Another use of the predictive 

method is in systemic safety 

treatments, presented in Chapter 12 

under Risk Based Prioritization.

Predicted 

crashes

The frequency 

of crashes per 

year that would 

be predicted 

for a site based 

on the result 

of a crash 

prediction 

model, called 

a safety 

performance 

function (SPF).

TABLE 4-4: Performance Measures for Network Screening (Source: Highway Safety Manual, 1st ed.)

PERFORMANCE MEASU

ACCOUNTS

FOR TRAFFIC

VOLUME

ACCOUNTS

FOR 

RTM BI

ACCOUNTS

FOR CRASH

SEVERITY

1. Average crash frequency No No Not explicitly

2. Crash rate Yes No Not explicitly*

3. Equivalent property damage only 

(EPDO) average crash frequency No No Yes

4. Relative severity index No No Yes

5. Critical rate Yes No Not explicitly*

6. Excess predicted average crash 

frequency using method of moments No No Not explicitly*

7. Level of service of safety Yes No Not explicitly*

8. Excess predicted average crash 

frequency using SPFs Yes No Not explicitly*

9. Probability of specific crash types 

exceeding threshold proportion No Not affected 

by RTM bias** Not explicitly*

10. Excess proportion of 

specific crash types No Not affected 

by RTM bias** Not explicitly*

11. Expected average crash frequency 

with empirical Bayes adjustments Yes Yes Not explicitly

12. EPDO average crash frequency 

with EB adjustment Yes Yes Ye

13. Excess expected average crash 

frequency with EB adjustment Yes Yes Not explicitly

* While these measures do not explicitly 

mention severity, analysts can adapt any of the 

measures to consider any severity level.

** These two measures will not be affected by 

RTM only if they are based on data from a 

long time period.
4-10 UNIT 4: SOLVING SAFETY PROBLEMS ROAD SAFETY FUNDAMENTALS

The first edition of the HSM lists 

several benefits of the predictive 

method, including:

J RTM bias is addressed as the 

method concentrates on longterm expected average crash 

frequency rather than shortterm observed crash frequency.

J Reliance on availability of 

limited crash data for any one 

site is reduced by incorporating 

predictive relationships based on 

data from many similar sites.

J The method accounts for the 

fundamentally nonlinear 

relationship between crash 

frequency and traffic volume.

Agencies can also use the predicted 

crashes in combination with actual 

crash history at the site of interest to 

calculate expected crashes. A method 

called empirical Bayes (EB) brings 

these two values together to reflect 

a crash frequency that incorporates 

the general crash prediction from the 

SPF with the real world experience 

of crash history at the site to provide 

an accurate estimation of how many 

crashes should be expected at the 

site (see more detailed discussion 

of the EB method later in this step). 

Some agencies may also calculate 

excess crashes as a measure for site 

prioritization. This is the difference 

between the expected crashes and the 

observed crash frequency at the site.

Performance measures 

in network screening

The key to effective network screening 

is selecting an appropriate performance 

measure. Network screening 

methods should appropriately 

account for three major factors that 

can affect the screening outcome:

J Differences in traffic volumes

J Possible bias due to RTM

J Crash severity

Table 4-4 lists the thirteen 

performance measures discussed in 

the HSM with an indication of their 

ability to account for these major 

factors. While some measures directly 

account for crash severity (e.g., 

relative severity index), analysts 

can adapt any of the measures to 

account for crash severity.

SPFs can be obtained in two ways:

1) SPFs can be developed from scratch 

using crash, roadway, and traffic volume 

data from roads and intersections in the 

State. This requires significant data to be 

collected on hundreds of sites. A statistical 

expert must use these data to develop SPFs 

that are tailor made for that State.

2) SPFs can be obtained from national 

resources, such as the HSM; then 

calibrated for the particular State of 

interest. This requires data to be collected 

on a smaller number of sites than is 

required for developing a new SPF. 

The crashes predicted by the SPF are 

compared to the crashes observed on the 

State’s roads, and an analyst calculates 

a calibration factor to adjust the SPF 

prediction appropriately for the State.

SPF development or calibration is typically 

handled by the State DOT. FHWA provides 

guidance on deciding between developing 

a new SPF or calibrating an existing one.10 

States that decide to develop new SPFs 

can refer to guidance in a related FHWA 

publication.11 NCRHP provides guidance 

for those who decide to calibrate 

existing SPFs.12

Where can I get safety performance functions for my State?

Bahar, G (2014), 

User’s Guide to 

Develop Highway 

Safety Manual 

Safety Performance 

Function Calibration 

Factors, HR 20-

7(332), National 

Cooperative 

Highway Research 

Program, American 

Association of 

State Highway and 

Transportation 

Officials, Standing 

Committee on 

Traffic Safety, 

Washington, DC.

R. Srinivasan and 

K. Bauer (2013), 

Safety Performance 

Development 

Guide: Developing 

Jurisdiction-Specific 

SPFs, Report 

FHWA-SA-14-005, 

Federal Highway 

Administration, 

Washington, DC

Srinivasan, R., 

D. Carter, and 

K.Bauer (2013), 

Safety Performance 

Function Decision 

Guide: SPF 

Calibration vs SPF 

Development, 

Report No. 

FHWA-SA-14-004, 

Federal Highway 

Administration, 

Washington, DC.

12

11

10

Expected 

crashes, 

excess 

crashes

See next page.
ROAD SAFETY FUNDAMENTALS UNIT 4: SOLVING SAFETY PROBLEMS 4-11

Accounting for differences 

in traffic volumes

As discussed earlier, analysts have 

traditionally used crash rates to 

account for differences in traffic 

volume among sites. Crash rate 

is the ratio of crash frequency to 

exposure, which is typically the 

traffic volume. Crash rates implicitly 

assume a linear relationship 

between crash frequency and traffic 

volume; however, many studies 

have shown that the relationship 

between crashes and traffic volume 

is nonlinear, and the shape of this 

relationship depends on the type 

of facility. Nonlinear relationships, 

such as SPFs, are more appropriate 

than linear relationships, such as 

crash rates to account for differences 

in traffic volume among sites.

SPFs are a more reliable method to 

account for differences in traffic 

volume among sites because they 

reflect the nonlinear relationship 

between crash frequency and traffic 

volume. The SPF is an equation that 

represents a best-fit model that 

relates annual observed crashes to 

the site characteristics including 

annual traffic volume and other 

site characteristics. Typically, SPFs 

are estimated for a particular crash 

type for a type of facility (e.g., 

run-off-road crashes on rural two 

Predicted Crash Frequency

10

5

0 Traffic Volume (AADT) 100,000

Predicted Crash Frequency

40

30

20

10

0 Traffic Volume (AADT) 100,000

Excess 

crashes

The difference 

between the 

expected 

crashes and the 

observed crash 

frequency at 

the site.

Expected 

crashes

The frequency 

of crashes 

per year that 

represents the 

combination of 

the predicted 

crashes and 

the observed 

crashes that 

actually 

occurred at 

the site.

FIGURE 4-3: Example of SPF for single-vehicle crashes on rural, 4-lane freeways

FIGURE 4-2: Example of SPF for multi-vehicle crashes on rural, 4-lane freeways
4-12 UNIT 4: SOLVING SAFETY PROBLEMS ROAD SAFETY FUNDAMENTALS

lane roads) using data from an 

entire jurisdiction or State. Figure 

4-2 and Figure 4-3 show example 

SPFs where the points represent 

observed crashes at specific traffic 

volumes for individual sites, and 

the solid line represents the bestfit model (i.e., the SPF). If the 

relationship between exposure and 

crash frequency were linear, then 

the solid line would be a straight 

line instead of a curve. These two 

figures also demonstrate the nature 

of SPFs – each curve is different. For 

the rural, four lane freeways used in 

this example, multi-vehicle crashes 

rise exponentially with more traffic 

volume (Figure 4-2) but singlevehicle crashes behave differently; 

they level off with increasing levels 

of traffic volume (Figure 4-3). 

An SPF produces the average number 

of crashes that would be predicted 

for sites with a particular set of 

characteristics. By comparing a 

site’s observed number of crashes 

with the predicted number of 

crashes from an SPF, it may be 

possible to identify sites that 

experience more crashes than one 

would expect from a site with that 

particular set of characteristics. 

Sites where the observed number 

of crashes is larger than the 

predicted number of crashes from 

an SPF warrant further review and 

diagnosis. Two measures in Table 

4-4, level of service of safety (LOSS) 

and the excess predicted average 

crash frequency using SPFs, use 

the observed crash frequency and 

predicted frequency from an SPF to 

identify sites with promise. 

Ideally, SPFs should be estimated 

using data from the same 

jurisdiction as the site(s) being 

studied.13 However, that may 

not always be possible due to 

the availability of data or lack of 

statistical expertise. In that case, 

the SPFs developed from another 

jurisdiction could be calibrated using 

data from the jurisdiction with the 

study sites.15 

Avoiding bias due to 

regression-to-the-mean

As previously discussed, RTM 

describes the situation when 

periods with relatively high crash 

frequencies are followed by periods 

with relatively low crash frequencies 

simply due to the random nature of 

crashes. Figure 4-4 illustrates RTM, 

comparing the difference between 

short-term average and long-term 

average crash history.16 Due to RTM, 

the short-term average is not a 

reliable estimate of the long-term 

crash propensity of a particular 

site. If an agency selects sites based 

SPF Example 1

Some States use Safety Analyst, a 

software tool from AASHTO, to identify 

sites that may benefit from a safety 

treatment.14 The following is an SPF 

from Safety Analyst that predicts 

the total number of crashes on rural 

multilane divided roads:

P = L × e-5.05 × (AADT)0.66

P is the total number of crashes in one 

year on a segment of length L. 

This is a relatively simple SPF where the 

predicted number of crashes per mile 

is a function of just AADT. For example, 

if the AADT is 45,000, then the predicted 

number of crashes for a one mile segment 

based on the SPF will be the following:

P = 1 × e-5.05 × 450000.66

=7.55 crashes per year

R. Srinivasan and 

K. Bauer (2013), 

Safety Performance 

Development 

Guide: Developing 

Jurisdiction-Specific 

SPFs, Report 

FHWA-SA-14-005, 

Federal Highway 

Administration, 

Washington, DC.

G. Bahar and E. 

Hauer (2014), Users 

Guide to Develop 

HSM SPF Calibration 

Factors, NCHRP 

Project 20-7(332).

Susan Herbel, 

Lorrie Laing, 

Colleen McGovern 

(2010), Highway 

Safety Improvement 

Program (HSIP) 

Manual, FHWASA-09-029, 

Federal Highway 

Administration, 

Washington, DC.

http://www.

safetyanalyst.org/

13

15

16

14
ROAD SAFETY FUNDAMENTALS UNIT 4: SOLVING SAFETY PROBLEMS 4-13

on high short-term average crash 

history, crashes at those sites may 

be lower in the following years due 

to RTM, even if the agency does not 

install countermeasures at those 

sites. 

If RTM is not properly accounted for, 

sites with a randomly high count 

of crashes in the short term could 

be incorrectly identified as having 

a high potential for improvement, 

and vice versa. In this case, scarce 

resources may be inefficiently used 

on such sites while sites with a truly 

high potential for cost effective 

safety improvement remain 

unidentified.

One approach to address RTM bias 

is to use the EB method. The EB 

method is a statistical method 

that combines the observed crash 

frequency (obtained from crash 

reports) with the predicted crash 

frequency (derived from the 

appropriate SPF) to calculate the 

expected crash frequency for a site of 

interest. This method pulls the crash 

count towards the mean, accounting 

for the RTM bias.

The EB method is illustrated in 

Figure 4-5, which illustrates how 

the observed crash frequency is 

combined with the predicted crash 

frequency based on the SPF.18 The 

Bauer and Harwood17 provide a more 

complex SPF for fatal and injury crashes on 

rural two lane roads. This model provides 

a crash prediction that is more tailored to 

characteristics of the site, such as curve 

radius and vertical grade of the road:

NFI = fatal-and-injury crashes 

per mile per year

AADT = annual average daily traffic 

(vehicles/day)

G = absolute value of percent grade; 0% 

for level tangents; ≥ 1% otherwise

R = curve radius (ft); missing for tangents

I

HC = horizontal curve indicator: 

1 for horizontal curves; 0 otherwise

LC = horizontal curve length (mi); 

not applicable for tangents

ln = natural logarithm function

Bauer, K. and 

Harwood, D., Safety 

Effects of Horizontal 

Curve and Grade 

Combinations on 

Two-Lane Highways, 

Federal Highway 

Administration, 

Report No. FHWAHRT-13-077, January 

2014.

Susan Herbel, 

Lorrie Laing, 

Colleen McGovern 

(2010), Highway 

Safety Improvement 

Program (HSIP) 

Manual, FHWASA-09-029, 

Federal Highway 

Administration, 

Washington, DC.

17

18

SPF Example 2 Observed Crash Frequency

Years

Short Term 

average

Short Term 

average

Long Term

average

FIGURE 4-4: Chart to illustrate RTM phenomenon (Source: HSIP Manual, 2010)

NFI = exp [-8.76+1.00×ln(AADT)+0.044×G+0.19×ln(2×5730/R)×IHC

+4.52×(1/R)(1/Lc)×IHC ]
4-14 UNIT 4: SOLVING SAFETY PROBLEMS ROAD SAFETY FUNDAMENTALS

EB method is applied to calculate 

an expected crash frequency 

or corrected value, which lies 

somewhere between the observed 

value and the predicted value from 

the SPF.

Mathematically, the expected 

number of crashes can be written 

as a function of the predicted value 

from the SPF and the observed 

crashes in the following manner:

average crash frequency are provided 

in Part B of the HSM. For example, 

if the observed crash frequency in a 

particular site was nine crashes per 

year, the predicted crash frequency 

from the SPF was 6.4 crashes per 

year, and the w was 0.3, then Nexpected

will be as follows:

Crash Frequency

aaDT

Predicted number from SPF

Expected number using Eb

Observed number

SPF

Nexpected = expected average crash frequency 

for a certain study period

w = weighted adjustment to be placed 

on the SPF prediction (0 < w < 1)

Npredicted = predicted average crash frequency 

predicted using an SPF for the study 

period under the given conditions

Nobserved = observed crash frequency at the 

site over the study period

The weight w is a function of the 

predicted crash frequency (Npredicted) 

and a statistical parameter called the 

overdispersion parameter of the SPF. 

Procedures to estimate the expected 

=

=

w× Npredicted+(1 -w) × Nobserved

0.3 × 6.4+(1 - 0.3) × 9

Nexpected

Nexpected

Equation 1 We can prioritize sites by calculating 

the difference between the EB 

expected crashes at a particular 

site and the predicted crashes from 

an SPF. By comparing EB expected 

crashes at a particular site instead 

of observed crashes, we account for 

possible bias due to RTM.

The first eight measures presented 

in Table 4-4 do not account for 

possible bias due to RTM. Measure 9 

(probability of specific crash types 

exceeding threshold proportion) and 

measure 10 (excess proportion of 

specific crash types) are not affected 

by RTM unless they are based on 

short-term crash history. Measure 

11 (expected average crash frequency 

with EB adjustments), measure 

12 (EPDO average crash frequency 

= 8.22 crashes per year

FIGURE 4-5: Schematic to illustrate the empirical Bayes method (Source: HSIP Manual, 2010)
ROAD SAFETY FUNDAMENTALS UNIT 4: SOLVING SAFETY PROBLEMS 4-15

with EB adjustment), and measure 

13 (excess expected average crash 

frequency with EB adjustment) 

account for possible bias due to RTM 

using the EB adjustments.

Accounting for crash severity

The severity of crashes at a location 

can (and should) have a bearing on 

the priority of the site for safety 

treatment. Three of the measures in 

Table 4-4, measure 3 (EPDO average 

crash frequency), measure 4 (relative 

severity index), and measure 12 

(EPDO average crash frequency with 

EB adjustment), directly account for 

crash severity. Measures 3 and 12 use 

the EPDO method, which converts 

all crashes to a common unit, 

namely property damage only (PDO) 

crashes. Using these measures, the 

analyst assigns points to each crash 

based on its crash severity level. 

A PDO crash typically receives one 

point and the points increase as the 

severity of the crash increases. 

While other measures do not 

explicitly mention severity, analysts 

can adapt any of the measures to 

consider any severity level. For 

example, an analyst could use 

crash frequency and focus on the 

frequency of fatal and severe injury 

crashes to priority rank sites. It is 

important to note that the severity 

distribution of crashes may be a 

function of site characteristics 

including AADT. For example, 

sections with higher AADT values 

may be associated with lower speeds 

and consequently fewer severe 

crashes.

Step 2. Diagnosis

Diagnosis is the second step in 

the roadway safety management 

process, following network 

screening. Diagnosis is the process 

of further investigating the sites 

and issues identified from network 

screening. The intent of diagnosis 

is to identify crash patterns and the 

factors that contribute to crashes 

at the identified sites. Thorough 

diagnosis can also identify potential 

safety issues that have not yet 

manifested in crashes. Diagnosis 

often involves a review of the 

crash history, traffic operations, 

and general site conditions. While 

safety professionals could review 

these data from the office, a field 

visit provides the opportunity to 

observe road user behavior and 

site characteristics that are not 

available in the data. Sometimes, 

safety professionals may also 

conduct a field review at night or 

at other times that crash history 

has indicated to be of concern. It 

is important to diagnose the cause 

of the problem before developing 

potential countermeasures, just 

as a doctor examines symptoms 

to diagnose an underlying disease 

before formulating a prescription. 

Otherwise, resources may be 

misallocated if a countermeasure 

that does not target the underlying 

issues is selected and implemented. 

The Haddon Matrix is a framework to 

identify possible contributing factors 

(e.g., driver, vehicle, and roadway/

environment) which are crossreferenced against possible crash 

conditions before, during, and after 

a crash to identify possible reasons 

for events. This comprehensive 

understanding of crash contributing 

factors is important for the diagnosis 

of safety problems. An example of 

the Haddon Matrix is presented later 

under Countermeasure Selection on 

page 4-20. 
4-16 UNIT 4: SOLVING SAFETY PROBLEMS ROAD SAFETY FUNDAMENTALS

The HSM recommends that 

diagnosis include the following 

parts:

J A review of safety data

J An assessment of supporting 

documentation

J An assessment of field conditions

Safety data review

An analyst can conduct a detailed 

review of the crash data from police 

reports to identify patterns. This 

could involve reviewing the crash 

type, severity, sequence of events, 

and contributing circumstances. 

Different visualization tools, such 

pie charts, bar charts, or tabular 

summaries, can be used to display 

various crash statistics. In addition 

to reviewing descriptive statistics, 

analysts can use various methods 

to identify underlying safety issues 

based on the recognition of crash 

patterns. 

One method would be to identify 

locations that have a proportion of 

a specific collision type relative to 

the total collisions that is higher 

than some average or threshold 

proportion value for similar road 

types. Kononov found that looking 

at the percentage distribution of 

collisions by collision type can reveal 

the “existence of collision patterns 

susceptible to correction” that may 

or may not be accompanied by the 

overrepresentation in expected 

or expected excess collisions.19 

Heydecker and Wu originally 

proposed this method.20 The method 

is identical for different location 

types. However, only similar 

location types should be analyzed 

together because collision patterns 

will naturally differ. For example, 

the collision patterns are different 

for stop-controlled intersections, 

signalized intersections, and twolane roads, so the method would be 

applied separately to the three types 

of facilities and separately for urban 

and rural environments. Another 

method would be to investigate 

sites that experience a gradual or 

sudden increase in mean collision 

frequency.21

Following the detailed review of 

the crash data, the analyst can 

create collision diagrams, condition 

diagrams, and crash maps to 

summarize the crash information 

by location. A collision diagram 

is a tool to identify and display 

crash patterns. Many resources, 

including the HSM, provide guidance 

on developing collision diagrams. 

Examples of collision diagrams are 

shown in Figure 4-6 and Figure 4-7. 

Each crash at the site is displayed 

according to where it occurred, 

what type of crash it was, how 

severe it was, and various other 

characteristics. An analyst uses 

symbols to visually represent many 

of these characteristics.

Condition diagrams include a 

drawing with information about 

the site characteristics including 

information about the roadway 

(e.g., number of lanes, presence 

of medians, pedestrian and bicycle 

facilities, shoulder information), 

surrounding land uses, and 

pavement conditions. Condition 

diagrams can be overlaid on top of 

collisions diagrams to gain further 

insight to the crash patterns. 

Crash mapping involves the use of 

geographic information systems 

(GIS) to integrate information 

from the roadway network with 

information from geocoded crash 

data. If the geocoded crash data are 

Heydecker, B. J., and 

J. Wu (1991), Using 

the Information 

in Road Accident 

Records Proc., 19th 

PTRC Summer 

Annual Meeting, 

London.

Hauer, E. (1996), 

Detection of Safety 

Deterioration 

in a Series of 

Accident Counts. 

Transportation 

Research Record 

1542, 38-43. 

Hauer, E. (1996), 

Statistical Test 

of the Difference 

between Expected 

Accident 

Frequencies, 

Transportation 

Research Record 

1542, 24-29.

Kononov, J. 

(2002), Identifying 

Locations 

with Potential 

for Collision 

Reductions: 

Use of Direct 

Diagnostics and 

Pattern Recognition 

Methodologies, 

Transportation 

Research Record 

1784, pp. 153-158.

20

21

19
ROAD SAFETY FUNDAMENTALS UNIT 4: SOLVING SAFETY PROBLEMS 4-17

accurate, then crash mapping can 

provide valuable insights into crash 

locations and crash patterns. 

Assess supporting 

documentation

This step involves a review of 

documented information about 

the site along with interviews of 

local transportation professionals 

to obtain additional perspectives 

on the safety data review from 

the previous step. Examples of 

supporting documentation include 

traffic volumes, construction plans 

and design criteria, photos and 

maintenance logs, weather patterns, 

and recent traffic studies in the area.

Assess field conditions

Field observations are useful for 

supplementing crash data and can 

help the analyst understand the 

behavior of drivers, pedestrians, 

and bicyclists. The first stage of 

the field investigation should 

be an on-site examination of a 

road user’s experience. Those 

conducting the assessment should 

travel through the site at different 

times of the day using different 

modes of transportation (e.g., 

driving, walking, and bicycling). 

Assessors should observe the mix 

of vehicle traffic and other road 

users. They should also observe 

traffic movements, conflicts, and 

FIGURE 4-7: 

Example 

Collision 

Diagram at 

a Ramp

FIGURE 4-6: 

Example 

Collision 

Diagram at an 

Intersection
4-18 UNIT 4: SOLVING SAFETY PROBLEMS ROAD SAFETY FUNDAMENTALS

operating speeds. Those conducting 

the field review could determine 

whether the road and intersection 

characteristics are consistent 

with driver expectation and if 

roadside recovery zones are clear 

and traversable.

Road safety audits

One method to assess field 

conditions is a road safety audit 

(RSA). This is the formal safety 

performance examination of 

an existing or future road or 

intersection by an independent, 

multidisciplinary team. An RSA 

qualitatively estimates and reports 

on existing and potential road safety 

issues and identifies opportunities 

for safety improvements for all 

road users. FHWA encourages 

States, local jurisdictions and tribal 

governments to integrate RSAs into 

the project development process for 

new roads and intersections and to 

conduct RSAs on existing ones.

The purpose of an RSA is to answer 

the following questions: 

J What elements of the road may 

present a safety concern, and to 

what extent, to which road users, 

and under what circumstances? 

J What opportunities exist to 

eliminate or mitigate identified 

safety concerns?

The multidisciplinary audit team 

consists of people who represent 

different areas of expertise, such as 

engineering (e.g., design, traffic, 

and maintenance), law enforcement, 

safety educators, public officials, 

community traffic safety advocates, 

and others. Any phase of project 

development (planning, preliminary 

engineering, design, construction) 

and any sized project from minor 

intersection and roadway retrofits 

to mega-projects are eligible for 

an RSA.

Most State DOTs have established 

safety review processes. However, 

RSAs and a traditional safety reviews 

are different. Table 4-5 shows the 

difference between an RSA and a 

traditional safety review.22

“Road Safety Audits 

(RSA),” accessed 

August 7, 2013, 

http://safety.fhwa.

dot.gov/rsa/

22

TABLE 4-5: Differences between Road Safety Audit and Traditional Road Safety Review 

(Source: FHWA)

ROAD SAFETY AUDIT TRADITIONAL SAFETY 

Independent, multi-disciplinary team Safety review team within the project team 

with only safety and/or design experience

Considers all potential road users (pedestrians, 

bicyclists, motor vehicles, transit users) Often concentrates only on motor vehicles

Accounts for road user capabilities 

and limitations

Safety reviews do not normally 

consider human factor issues

Always generates a formal report Often does not generate a formal report

Always generates a formal response report Often does not generate a formal 

response report
ROAD SAFETY FUNDAMENTALS UNIT 4: SOLVING SAFETY PROBLEMS 4-19

Step 3. Countermeasure 

selection

After diagnosing the safety 

issues at the site, analysts select 

countermeasures to address 

the contributing factors for 

observed crashes. The first part 

of countermeasure selection is 

to identify countermeasures to 

target the underlying safety issues. 

Analysts can use tools like the 

Haddon Matrix and resources like 

the NCHRP Report 500 series to 

identify targeted countermeasures 

to address or mitigate underlying 

contributing factors. 

Identifying contributing factors

The Haddon Matrix is a tool 

originally developed for injury 

prevention, but it is directly 

applicable to highway safety in 

both diagnosis and countermeasure 

selection.24 The Haddon Matrix is 

useful to gain a comprehensive 

understanding of crash contributing 

factors. Analysts can use the Haddon 

Matrix to identify human, vehicle, 

and roadway factors contributing 

to the frequency and severity of 

crashes prior to, during, and after 

the crash event. Then, analysts 

can identify targeted reactive and 

proactive countermeasures to 

address or mitigate the underlying 

contributing factors for the given 

site. Chapter 6 of the 1st edition of 

the HSM provides further discussion 

of the Haddon Matrix.

The Haddon Matrix is comprised 

of nine cells to identify human, 

vehicle, and roadway factors 

contributing to the target crash 

type or severity outcome before, 

during, and after the crash. Precrash factors speak to the factors 

or actions prior to the crash that 

contributed to the occurrence of the 

crash. Crash factors speak to those 

factors or actions that occurred at 

the moment of the crash. Post-crash 

factors speak to factors that come 

into play after the crash that affect 

the severity of the injuries or speed 

of response. Examples of human 

factors include fatigue, inattention, 

age, and failure to wear a seat belt. 

Vehicle factors include bald tires, 

airbag operations, and worn brakes. 

Examples of roadway factors include 

pavement friction, weather, grade, 

and limited sight distance.

Table 4-6 is an example application 

of the Haddon Matrix from the 

Highway Safety Improvement 

Program (HSIP) Manual for crashes 

in an urban area.25 The top-left 

cell identifies driver behaviors or 

characteristics that may contribute 

to the likelihood or the severity of 

a collision, such as poor vision or 

reaction time, alcohol consumption, 

speeding, and risk taking. These 

http://www.irap.net/

http://toolkit.irap.

org/

Susan Herbel, 

Lorrie Laing, 

Colleen McGovern 

(2010), Highway 

Safety Improvement 

Program (HSIP) 

Manual, FHWASA-09-029, 

Federal Highway 

Administration, 

Washington, DC.

Haddon, W., Jr. 

(1972). A logical 

framework for 

categorizing 

highway safety 

phenomena and 

activity. Journal of 

Trauma 12: 193–207.

23

25

24

International Road 

Assessment Programme

The International Road Assessment 

Programme (iRAP) conducts safety 

inspections on high-risk roads in more 

than 70 countries. The iRAP inspectors 

perform a detailed road survey, focusing 

on road attributes that are known to be 

associated with crash risk. These include 

intersection design, number of lanes, 

roadside hazards, and provisions for 

pedestrian crossings. The inspectors 

use these data to develop a star rating, 

which reflects the level of safety of the 

road, and provide detailed feedback to 

the government agency in the form of an 

assessment report. iRAP also provides 

a Road Safety Toolkit, which helps 

engineers, planners, and policy makers 

develop safety plans for all road users.23
4-20 UNIT 4: SOLVING SAFETY PROBLEMS ROAD SAFETY FUNDAMENTALS

factors should be considered when 

selecting countermeasures. For 

example, based on these human 

factors, successful countermeasures 

may be those that improve visibility 

or reduce speeding. The matrix in its 

entirety provides a range of potential 

issues that can be addressed through 

a variety of countermeasures 

including education, enforcement, 

engineering, and emergency 

response solutions.

Countermeasure 

resources and tools

Diagnosing a roadway safety 

problem and identifying effective 

countermeasures is a skill 

developed through education, 

training, research, and experience. 

Many resources are available to 

help transportation professionals 

analyze and develop 

countermeasures. Since the 

transportation field continuously 

generates new knowledge and 

countermeasure approaches, it is 

important to stay informed of the 

available resources and tools.26

Some of the most useful resources 

and tools for countermeasure 

guidance and selection are listed 

below (alphabetically):

J Bicycle Safety Guide and 

Countermeasure Selection System 

(BIKESAFE, www.pedbikesafe.

org/bikesafe) – This resource 

provides practitioners with the 

latest information available 

for improving the safety and 

mobility of those who bike. 

The online tools provide the 

user with a list of possible 

engineering, education, or 

enforcement treatments to 

improve bicycle safety and/or 

mobility based on user input 

about a specific location.

J Countermeasures That Work: A 

Highway Safety Countermeasure 

Guide for State Highway Safety 

Offices – This document serves 

as a basic reference to help state 

Highway Safety 

Improvement 

Program Manual. 

Federal Highway 

Administration, 

Washington, D.C., 

2010, Chapter 3

26

TABLE 4-6: Haddon Matrix for crashes in an urban area (Source: HSIP Manual)

PERIOD HUMA

VEHICLE/

EQUIPMENT

PHYSICAL

ENVIRONMENT

SOCIOECONOMIC

PRECRASH Poor vision or

reaction time, 

alcohol, speeding, 

risk taking

Failed brakes, 

missing lights, 

lack of warning 

systems

Narrow 

shoulders, 

ill-timed signals

Cultural norms 

permitting 

speeding, red 

light running, DUI

CRASH Failure to

use occupant 

restraints

Malfunctioning 

safety belts, 

poorly engineered 

air bags

Poorly designed 

guardrails

Lack of 

vehicle design 

regulations

POSTCRASH High

susceptibility, 

alcohol

Poorly designed 

fuel tanks

Poor emergency 

communication 

systems

Lack of support 

for EMS and 

trauma systems
ROAD SAFETY FUNDAMENTALS UNIT 4: SOLVING SAFETY PROBLEMS 4-21

highway safety offices (SHSOs) 

select effective, evidence-based 

countermeasures for traffic 

safety problem areas related 

to user behaviors, such as 

alcohol-impaired and drugged 

driving, seat belts and child 

restraints, and aggressive 

driving and speeding.27

J Crash Modification Factors 

Clearinghouse (www.

cmfclearinghouse.org) – This 

website offers transportation 

professionals a central, online 

repository of crash modification 

factors (CMFs) that indicate the 

safety effect on crashes due to 

infrastructure improvements. 

The website also provides 

additional information and 

resources related to CMFs. 

This site is funded by FHWA.

J FHWA Proven Countermeasures 

(safety.fhwa.dot.gov/

provencountermeasures) – 

FHWA regularly compiles a list 

of countermeasures that have 

been shown to be effective in 

reducing crashes but have yet 

to be widely applied on a 

national basis.

J Handbook for Designing Roadways 

for the Aging Population (safety.

fhwa.dot.gov/older_users/

handbook) – This FHWA guide 

provides practitioners with a 

practical information source that 

links aging road user performance

 to highway design, operational, 

and traffic engineering features. 

This handbook supplements 

existing standards and guidelines 

in the areas of highway 

geometry, operations, and 

traffic control devices.28

J Highway Safety Manual (www.

highwaysafetymanual.org) – 

This document provides 

science-based knowledge 

and tools to conduct safety 

analyses, allowing for safety 

to be quantitatively evaluated 

alongside other transportation 

performance measures, such 

as traffic operations, 

environmental impacts, 

and construction costs. 

J National Cooperative Highway 

Research Program (NCHRP) 

Report 500 Series (safety.

transportation.org/guides.aspx)

– This resource is a collection 

of 23 reports in which relevant 

information is assembled into 

single concise volumes, each 

pertaining to specific types 

of highway crashes (e.g., 

run-off-the-road, head-on) 

or contributing factors (e.g., 

aggressive driving) related 

to behaviors, vehicles, and 

roadways. Countermeasures 

are categorized as proven, 

tried, and experimental.

J Pedestrian Safety Guide and 

Countermeasure Selection System 

(PEDSAFE, www.pedbikesafe.

org/pedsafe) – This resource 

provides practitioners with the 

latest information available 

for improving the safety and 

mobility of those who walk. 

The online tools provide the 

user with a list of possible 

engineering, education, or 

enforcement treatments to 

improve pedestrian safety and/

or mobility based on user input 

about a specific location.

Goodwin, A., 

Thomas, L., Kirley, 

B., Hall, W., O’Brien, 

N., & Hill, K. (2015). 

Countermeasures 

that work: A 

highway safety 

countermeasure 

guide for State 

highway safety 

offices, Eighth 

edition. (Report No. 

DOT HS 812 202). 

Washington, DC: 

National Highway 

Traffic Safety 

Administration. 

Accessed February 

2017 at www.nhtsa.

gov/staticfiles/

nti/pdf/812202-

Countermeasures

ThatWork8th.pdf

Brewer, M., D. 

Murillo, A. Pate 

(2014). Handbook 

for Designing 

Roadways for the 

Aging Population, 

Report No.

FHWA-SA-14-015, 

Federal Highway 

Administration, 

Washington, D.C. 

27

28
4-22 UNIT 4: SOLVING SAFETY PROBLEMS ROAD SAFETY FUNDAMENTALS

Identifying and selecting 

countermeasures

After identifying potential 

countermeasures to target 

the underlying issues, safety 

professionals must estimate the 

safety impact of countermeasures, 

individually and in combination. It 

is important to consider positive and 

negative safety impacts. Subsequent 

steps of the roadway safety 

management process (i.e., economic 

appraisal and project prioritization) 

include the consideration of other 

parameters, such as constructability, 

environmental impacts, and cost. 

The agency that will be making the 

final decision on countermeasure 

selection should make sure to 

coordinate with other safety 

partners to ensure that the 

countermeasure is appropriate for all 

parties. For example, a DOT should 

coordinate with law enforcement 

and emergency response to make 

sure that a proposed engineering 

installation will interfere with 

enforcement activities or impede 

emergency responders.

For infrastructure improvements, 

CMFs associated with different 

countermeasures provide a 

mechanism for determining 

the safety effect of different 

countermeasures. A CMF is a 

multiplicative factor used to 

compute the expected number of 

crashes after implementing a given 

countermeasure at a specific site. 

J If the CMF for a particular 

treatment is less than 1.0, then 

that countermeasure is expected 

to reduce crashes. 

J If the CMF for a particular 

treatment is greater than 1.0, 

then that countermeasure is 

expected to increase crashes. 

J A CMF of 1.0 implies that a 

countermeasure will not have 

any effect on safety. 

For example, if the expected number 

of crashes without a countermeasure 

is 5.6 crashes per year, and the CMF 

for the particular countermeasure 

is 0.8, then the expected number of 

crashes with the countermeasure is:

5.6 crashes per year x 0.8 = 

4.48 crashes per year

It is important to recognize that 

some countermeasures may decrease 

some types of crashes but increase 

other types. For example, installing 

a traffic signal would be expected to 

decrease severe collisions, such as 

right angle and left turn crashes, but 

it would be expected to increase less 

severe crashes, such as rear ends. 

The CMF Clearinghouse and the first 

edition of the HSM provide CMFs 

for a variety of countermeasures.29

Only those CMFs that passed a set 

of inclusion criteria based on quality 

and reliability were included in the 

HSM. The CMFs in the clearinghouse 

Guidance on CMF application

FHWA provides an extensive selection 

of guidance on selecting and applying 

CMFs through the CMF Clearinghouse 

(www.cmfclearinghouse.org). They 

present answers to frequently asked 

questions, such as “How can I apply 

multiple CMFs?” and “How do I choose 

between CMFs in my search results that 

have the same star rating but different 

CMF values?” The website also houses 

an archive of annual webinars in which 

experienced CMF users talk about 

issues related to applying CMFs in 

real world situations. 

www.

cmfclearinghouse.

org

29
ROAD SAFETY FUNDAMENTALS UNIT 4: SOLVING SAFETY PROBLEMS 4-23

are provided for any published 

study, regardless of quality, and 

are continuously updated based on 

the latest research. The CMFs in 

the clearinghouse are reviewed and 

given a star quality rating ranging 

from one to five stars, based on the 

quality of the study. Higher stars 

imply a better quality CMF.

CMFs should be applied to situations 

that closely match those from 

which the CMF was developed. 

Several variables can be used to 

match a CMF to a given scenario 

including roadway type, area type, 

segment or intersection geometry, 

intersection traffic control, and 

traffic volume. However, it is 

critical for practitioners to use 

engineering judgment when a CMF 

is not available for the situations 

encountered as there are some cases 

for which a CMF that was developed 

for different conditions might be the 

best available.

Step 4. Economic appraisal

An economic appraisal of alternative 

countermeasures should be 

conducted to ensure that safety 

funds are being used as efficiently 

as possible. This appraisal helps 

transportation agencies achieve 

their desired safety performance the 

fastest and at the lowest possible 

cost. An agency can compare 

Rodegerdts et al., 

“NCHRP Report 

572: Applying 

Roundabouts in 

the United States.” 

Washington, D.C., 

Transportation 

Research Board, 

National Research 

Council, (2007)

30

A city has a stop-controlled intersection 

with an expected crash frequency of 10 

crashes per year, consisting of one A-injury 

crash, one B-injury crash, two C-injury 

crashes, and six PDO crashes.

The city is considering installing a 

roundabout at the intersection. Based on 

a search of the FHWA CMF Clearinghouse, 

they decide that they will use a CMF of 0.19 

in the calculation of the crash reduction 

benefit.30 This CMF applies only to serious 

and minor injury crashes, so they do not 

use it to estimate any reduction to fatal or 

PDO crashes (see note).

They multiply the CMF by the expected 

crashes before roundabout installation 

to determine the expected crashes after 

installation:

Thus, the benefit of a roundabout 

installation is expected to be a reduction of 

0.81 A-injury crashes, 0.81 B-injury crashes, 

and 1.62 C-injury crashes per year. 

NOTE: A roundabout would also likely bring 

a reduction to fatal and PDO crashes (i.e., 

additional CMFs could be incorporated), but 

the example has been simplified to a single 

CMF for illustration purposes.

Calculating benefits due to crash reduction

CRASH SEVERITY FA

A

INJURY

B

INJURY

CINJURY PDO

I Expected Crashes per Year 

before Roundabout 0 1 1 2 6

II CMF N/A 0.19 0.19 0.19 N/A

III Expected Crashes per Year 

after Roundabout (I x II) 0 0.19 0.19 0.38 6

IV Crash reduction benefit (I 

minus III) 0 0.81 0.81 1.62 0
4-24 UNIT 4: SOLVING SAFETY PROBLEMS ROAD SAFETY FUNDAMENTALS

the benefits expected from the 

countermeasure to the estimated 

costs of the countermeasure.

Some safety countermeasures have 

a higher-cost value than others. 

Geometric improvements to the 

road, such as straightening a tight 

curve to reduce run-off-road 

crashes, tend to be very expensive. 

Installing a curve warning sign 

and in curve delineation may 

address the same problem, but 

at a much lower cost. Although 

both countermeasures address the 

same problem, the actual safety 

benefit may not be the same. Safety 

professionals take the relative costs 

and benefits into consideration 

when prioritizing among 

countermeasures. Part of calculating 

the cost of a countermeasure 

is considering how those costs 

vary over time, while taking into 

consideration any maintenance 

costs and long term effectiveness. 

Estimating benefits

The primary benefit of a 

countermeasure is a reduction 

in crash frequency or severity. 

To estimate the safety benefits, 

a safety professional should use 

CMFs, such as those discussed 

in the countermeasure selection 

step. CMFs can be applied to the 

actual crashes or expected crashes 

based on the EB method. Expected 

crashes are preferred because they 

account for possible bias due to RTM. 

The estimated change in crashes 

represents the expected benefit from 

the countermeasure. 

For each proposed countermeasure, 

the change in crash frequency and/

or severity needs to be converted 

to monetary value, based on the 

monetary value of the type of 

crashes reduced. This monetary 

value is also called the crash cost. 

Crash costs are based on costs to 

society, such as lost productivity, 

medical costs, legal and court costs, 

emergency service costs, insurance 

administration costs, congestion 

costs, property damage, and 

workplace losses.31

The benefit from the 

countermeasure is the sum of the 

crash costs for crashes prevented by 

the countermeasure. Assigning costs 

to crashes is a topic that is under 

constant discussion and revision 

nationwide. States differ widely 

in the dollar amount that they 

assign to crashes, though all States 

apply higher values to more severe 

crashes. The CMF Clearinghouse 

provides a synthesis of crash costs 

that are used by various States.32

Additionally, the first edition of the 

HSM provided a list of crash costs by 

severity level (Table 4-7). However, 

since the publication of the first 

HSM in 2010, the USDOT has issued 

periodic recommendations that 

dramatically raised the values. For 

instance, the monetary value of a 

TABLE 4-7: Crash Costs by Severity Level 

in the Highway Safety Manual, 1st ed.

INJURY 

SEVERITY LEVEL

COMPREHENSIVE 

CRASH COS

Fatality (K) $4,008,900

Disabling Injury (A) $216,000

Evident Injury (B) $79,000

Fatal/Injury (K/A/B) $158,200

Possible Injury (C) $44,900

PDO (O) $7,400

Blincoe, L. J., Miller, 

T. R., Zaloshnja, E., 

and Lawrence, B. 

A. The economic 

and societal 

impact of motor 

vehicle crashes, 

2010. (Revised), 

National Highway 

Traffic Safety 

Administration, 

Report No. DOT HS 

812 013, Washington, 

DC, May 2015.

31

http://www.

cmfclearinghouse.

org/resources_

servlifecrash

costguide.cfm

32
ROAD SAFETY FUNDAMENTALS UNIT 4: SOLVING SAFETY PROBLEMS 4-25

fatal crash was listed as $4 million in 

the HSM, but recommended as over 

$9 million in a 2013 policy memo 

from USDOT.33

Although countermeasures are 

primarily expected to reduce 

crashes, there might be other 

benefits, including reduced travel 

times or lower fuel consumption. For 

example, a roundabout can decrease 

total delay at an intersection if 

applied and configured properly. 

An AASHTO publication provides 

guidance on estimating these other 

non-safety benefits.34

Estimating costs

The costs of the proposed 

countermeasure include the startup 

cost and the ongoing operational and 

maintenance costs. These costs can 

usually be estimated based on costs 

of materials, labor cost per personhour, cost of additional right-ofway, and past experience with 

similar countermeasures. Table 4-8 

illustrates the types of startup and 

ongoing costs that would be incurred 

for various countermeasures.

Service life

Another important consideration 

when calculating the benefits 

and costs of a countermeasure 

is the length of time that the 

countermeasure will last. This 

is referred to as the service life. 

Countermeasures, such as road 

edgelines or pavement reflectors, 

will have a much shorter service 

life (e.g., three to five years) than 

countermeasures, such as traffic 

signal installation or sidewalk 

construction (e.g., 20 years or 

more). Many States have a standard 

list of the service life values used 

for common countermeasures. 

The CMF Clearinghouse provides a 

survey of service life values used by 

various States for many different 

countermeasures.35

Trottenberg, 

Polly, and Robert 

Rivkin, “Revised 

Departmental 

Guidance 2013: 

Treatment of the 

Value of Preventing 

Fatalities and 

Injuries,” 

USDOT Office of 

the Secretary of 

Transportation, 2013.

User and Non-User 

Benefit Analysis for 

Highways, American 

Association of 

State Highway 

Transportation 

Officials, September 

2010

http://www.

cmfclearinghouse.

org/resources_

servlifecrash

costguide.cfm

33

34

35

The previous example showed that a city 

calculated a crash savings of 0.81 A-injury 

crashes, 0.81 B-injury crashes, and 1.62 

C-injury crashes per year by installing 

a roundabout. The city has examined 

guidance from the HSM, guidance from 

USDOT, and experiences of other cities 

and States and determined a standard set 

of crash costs they will use for all benefit/

cost calculations. They apply these costs 

to determine the monetary benefit of the 

expected crash reductions:

Thus, the city expects a total monetary benefit of $324,000+$81,000+$97,200 = 

$502,000 per year due to reduction in crashes.

Calculating monetary benefit of crash reduction

CRASH SEVERITY FA

A

INJURY

B

INJURY

CINJURY PDO

IV Crash Reduction Benefit 0 0.81 0.81 1.62 0

V This City’s Standard Crash Cost $5 mil $400,000 $100,000 $60,000 $10,000

VI Monetary benefit of crash 

reduction (IV x V) 0 $324,000 $81,000 $97,200 0
4-26 UNIT 4: SOLVING SAFETY PROBLEMS ROAD SAFETY FUNDAMENTALS

i×(1+i) y

The service life is used in the 

calculation of the present value 

of the benefits and costs of the 

proposed countermeasure. The 

calculation of present value includes 

a discount rate that reflects the time 

value of money (i.e., present dollars 

are worth more than future dollars). 

Present value of countermeasure 

benefits is calculated as follows:

costs, the final present value must 

also include the startup cost in the 

year of installation (see examples 

in Table 4-8).

Methods for 

economic appraisal

There are several methods for 

using the values of estimated 

benefits and costs to evaluate the 

economic effectiveness of safety 

improvement projects at a particular 

site. In particular, these methods 

TABLE 4-8: Examples of Countermeasure Costs

COUNTERMEASURE STARTUP CO

ONGOING COST 

DURING SERVICE LIFE

Install curve 

warning sign

Low – sign material, minimal 

labor for installation None

Install roundabout

High – Design plan, purchase 

of additional right-of-way, 

material, labor, traffic control 

during construction

Low – maintenance of 

grass and decorative 

vegetation

Install traffic signal

High – Timing plan, material, 

labor for installation, traffic 

control during construction

Moderate – electricity, 

bulb replacements, repairs, 

modifications to timing

PV = present value of benefits 

A = annual benefit (i.e., monetary value of 

crashes prevented)

i = discount rate

y = service life of countermeasure

Calculating present value in this way 

assumes a uniform annual benefit. 

The HSIP Manual demonstrates 

how to calculate present value if the 

benefits or costs each year are not 

the same.36

The present value of annual costs 

(i.e., operational and maintenance 

costs) can be calculated in the same 

manner as for benefits. However, for 

(1+i) y-1

PV = A ×

Herbel, Susan, 

Lorrie Laing, Colleen 

McGovern, Highway 

Safety Improvement 

Program 

(HSIP) Manual, 

Federal Highway 

Administration, 

FHWA-SA-09-029, 

January 2010

36

Calculating the present value 

of a crash reduction benefit

From the previous example, the city 

plans to install a roundabout and 

expects to see a benefit from crash 

reductions resulting in savings of 

$502,000 per year. They estimate that the 

roundabout will have a service life of 20 

years and they determine that a discount 

rate of 5% is appropriate. They calculate 

the present value of benefits as:

0.05×(1+0.05)

20

(1+0.05)

20-1

PV = $502,000 ×

= $6,256,030
ROAD SAFETY FUNDAMENTALS UNIT 4: SOLVING SAFETY PROBLEMS 4-27

are useful in situations where a 

safety professional is considering 

several alternatives and desires to 

choose the countermeasure with the 

greatest benefit for the cost. 

The HSIP Manual contains guidance 

on three methods - net present 

value, benefit/cost ratio, and cost 

effectiveness index.37 Net present 

value (NPV) is generally regarded 

as the most economically 

appropriate method, though the 

other two methods have certain 

advantages, as discussed below. 

The following sections provide 

quoted guidance from the HSIP 

Manual on economic appraisal.

Net Present Value

The NPV method, also called the 

net present worth (NPW) method, 

expresses the difference between the 

present values of benefits and costs 

of a safety improvement project. 

The NPV method has two basic 

functions: 1) determining which 

countermeasure(s) is/are most 

cost efficient based on the highest 

NPV and 2) determining whether 

a countermeasure’s benefits are 

greater than its costs (i.e., the 

project has a NPV greater than zero). 

The formula for NPV is: 

NPV = PVB − PVC

PVB = Present value of benefits

PVC = Present value of costs 

A countermeasure will result in a 

net benefit if the NPV is greater than 

zero. Table 4-9 summarizes the 

NPV calculations of four alternative 

countermeasures.

For Alternative A, the NPV can be 

calculated as follows: 

NPV = $1,800,268 − $500,000

= $1,300,268

The same calculation is performed 

for the other three countermeasure 

alternatives, and rank each 

countermeasure based on its NPV. 

As shown, all four alternatives 

are economically justified with a 

NPV greater than zero. However, 

Alternative B has the greatest NPV 

for this site based on this method. 

Benefit/Cost Ratio and Analysis

The benefit/cost ratio (BCR) is 

the ratio of the present value of a 

project’s benefits to the present 

value of a project’s costs.

Herbel, Susan, 

Lorrie Laing, Colleen 

McGovern, Highway 

Safety Improvement 

Program 

(HSIP) Manual, 

Federal Highway 

Administration, 

FHWA-SA-09-029, 

January 2010.

37

ALTERNATIV

COUNTERMEASUR

PRESENT 

VALUE OF

BENEFITS (I

PRESENT 

VALUE OF

COSTS (II)

NET 

PRESENT 

VALUE (I-II

ALTERNATIV

RAN

A $1,800,268 $500,000 $1,300,268 

B $3,255,892 $1,200,000 $2,055,892 

C $3,958,768 $2,100,000 $1,858,768 2

D $2,566,476 $1,270,000 $1,296,476 4

TABLE 4-9: Net Present Value (Source: HSIP Manual, Chapter 4)
4-28 UNIT 4: SOLVING SAFETY PROBLEMS ROAD SAFETY FUNDAMENTALS

The formula for BCR is: 

BCR = PVB / PVC

PVB = Present value of benefits

PVC = Present value of costs

Table 4-10 shows an example 

of using BCR to prioritize four 

alternatives.

A project with a BCR greater than 1.0 

indicates that the benefits outweigh 

the costs. However, the BCR is not 

applicable for comparing various 

countermeasures or multiple 

projects at various sites; this requires 

an incremental benefit/cost analysis.

An incremental benefit/cost analysis 

provides a basis of comparison of the 

benefits of a project for the dollars 

invested. It allows the analyst to 

compare the economic effectiveness 

of one project against another; 

however, it does not consider budget 

constraints. Optimization methods 

are best for prioritizing projects 

based on monetary constraints. 

An in-depth explanation of 

incremental benefit/cost analysis 

and an example is provided in 

Chapter 4 of the HSIP Manual. 

When conducting a benefit/

cost analysis, transportation 

professionals compare all of 

the benefits associated with 

a countermeasure (e.g., crash 

reduction), expressed in monetary 

terms, to the cost of implementing 

the countermeasure. A benefit/cost 

analysis provides a quantitative 

measure to help safety professionals 

prioritize countermeasures or 

projects and optimize the return 

on investment. 

Cost-Effectiveness Index

In situations where it is not 

possible or practical to monetize 

countermeasure benefits, 

transportation professionals can 

use the cost-effectiveness index 

method in lieu of the NPV or BCR. 

Cost-effectiveness is simply the 

amount of money invested divided 

by the crashes reduced. The result 

is a number that represents the 

cost of the avoided crashes of 

a certain countermeasure. The 

countermeasure with the lowest 

value is the most cost-effective and 

therefore ranked first. 

Cost-Effectiveness Index = PVC/CR 

PVC = Present value of project cost

ALTERNATIV

COUNTERMEASUR

PRESENT 

VALUE OF

BENEFITS (I

PRESENT 

VALUE OF

COSTS (II)

BENEFIT

COST 

RATIO (I/II

ALTERNATIV

RAN

A $1,800,268 $500,000 3.6 

B $3,255,892 $1,200,000 2.7 

C $3,958,768 $2,100,000 1.9 4

D $2,566,476 $1,270,000 2.0 3

TABLE 4-10: Example of Benefit/Cost Ratio Prioritization (Source: HSIP Manual, Chapter 4)
ROAD SAFETY FUNDAMENTALS UNIT 4: SOLVING SAFETY PROBLEMS 4-29

CR = Total crash reduction

The Cost-Effectiveness Index 

is a simple and quick method 

that provides an indication of a 

project’s value. Transportation 

professionals can use this formula 

and compare its results with other 

safety improvement projects. The 

Cost-Effectiveness Index method, 

however, does not account for value 

differences between reductions in 

fatal crashes compared to injury 

crashes, and whether a project is 

economically justified.38

Table 4-11 summarizes the 

calculations using the costeffectiveness index method to rank 

alternative countermeasures, given 

the present value of the costs and 

the total crash reduction.

For Alternative A, calculate the costeffectiveness index as follows: 

Cost-effectiveness index = 500,000/43 

= 11,628

Calculate the Cost-Effectiveness 

Index for the remaining alternatives 

and rank each countermeasure based 

on its Cost-Effectiveness Index 

value. With this method, the lowest 

index is the highest priority and 

therefore ranked first. Alternative 

A is ranked first, since it has the 

lowest cost associated with each 

crash reduction. 

The above example uses the number 

of crashes to determine the costeffectiveness index. Transportation 

professionals can use this same 

method using EPDO crash numbers, 

which has the advantage of 

considering severity.

Step 5. Project prioritization

If a transportation agency 

is considering installing 

countermeasures at one or more 

sites out of a group of potential 

sites, they will need to prioritize 

which projects they will implement. 

Ideally, the agency would implement 

all projects that bring a safety 

benefit (e.g., all those with a NPV 

greater than zero or a BCR greater 

than one). However, all agencies 

work within a limited budget and 

must prioritize where safety funds 

are spent.

The agency can use steps 1 through 

4 of this process to determine 

which countermeasure(s) would be 

used at each potential treatment 

ALTERNATIV

COUNTERMEASUR

PRESENT 

VALUE OF

COSTS

TOTAL

CRAS

REDUCTION

COSTEFFECTIVE- NESS INDEX

ALTERNATIV

RAN

A $500,000 43 $11,628 

B $1,200,000 63 $19,048 

C $2,100,000 70 $30,000 4

D $1,270,000 73 $17,397 2

TABLE 4-11: Cost-Effectiveness Index (Source: HSIP Manual, Chapter 4)

Highway Safety 

Improvement 

Program Manual.

Federal Highway 

Administration 

(Washington D.C., 

2010), Chapter 4

38
4-30 UNIT 4: SOLVING SAFETY PROBLEMS ROAD SAFETY FUNDAMENTALS

site and to conduct an economic 

appraisal of the expected effect of 

the countermeasure. The next step 

is to determine project priorities. 

The HSM discusses how projects 

can be prioritized by economic 

effectiveness, incremental 

benefit/cost analysis, or various 

optimization methods.

Prioritizing by 

economic effectiveness

Projects can be prioritized by ranking 

projects or project alternatives 

by the economic appraisal values 

produced in step 4. An agency 

might select those projects with the 

highest NPV, the highest BCR, or 

the highest cost effectiveness index. 

When using NPV the goal of a safety 

professional should be to implement 

all projects that have an NPV 

greater than zero, since each one 

brings a safety benefit. However, 

this is not possible since funds are 

limited, thus the goal should be to 

implement the group of projects 

that have the greatest combined 

NPV when added together (NPV is 

an additive property). Maximizing 

the NPV of a group of projects is 

different from prioritizing projects 

with high NPV. In other words, it 

may be best to implement numerous 

low cost projects with low NPV than 

one high cost project with a high 

NPV – but not higher than the NPV 

of all the low cost projects added up.

Prioritizing by incremental 

benefit/cost analysis

This method involves ranking all 

projects with benefit cost ratio 

greater than 1.0 in increasing order 

of their estimated cost. An analyst 

calculates an incremental BCR 

as such:

If the incremental BCR is greater 

than 1.0, the project with the 

higher cost is compared to the next 

project on this list; however, if the 

incremental BCR is less than 1.0, 

the project with the lower cost is 

compared to the next project on the 

list. This process is repeated and the 

project selected in the last pairing 

is the considered the best economic 

investment.

Prioritizing by 

optimization methods

Optimization methods take into 

account certain constraints when 

prioritizing projects. Linear 

programming, integer programming, 

and dynamic programming (refer 

to Chapter 8, Appendix A, HSM, 

2010) are optimization methods 

consistent with an incremental 

benefit/cost analysis, but they also 

account for budget constraints in 

the development of the project 

list. These optimization methods 

are more likely to be incorporated 

into a software package, rather 

than manually calculated. Multiobjective resource allocation is 

another optimization method. 

It incorporates nonmonetary 

elements (including decision factors 

not related to safety) into the 

prioritization process.

Safety professionals may use 

software applications to select 

and rank countermeasures. The 

SafetyAnalyst tool from AASHTO 

includes economic appraisal 

and priority ranking tools.39 The 

economic appraisal tool calculates 

(Cost of Project A − Cost of Project B) 

(Benefit of Project A − Benefit of Project B) 

Incremental BCR =

http://www.

safetyanalyst.org/

39
ROAD SAFETY FUNDAMENTALS UNIT 4: SOLVING SAFETY PROBLEMS 4-31

the BCR and other metrics for a set 

of countermeasures. The priorityranking tool ranks proposed 

improvement projects based on 

the benefit and cost estimates 

from the economic appraisal tool. 

The priority-ranking tool can also 

determine an optimal set of projects 

to maximize safety benefits.

Step 6. Safety 

effectiveness evaluation 

Once a countermeasure has been 

implemented at a site, or group of 

sites, it is important to determine 

whether it was effective in 

addressing the safety problem. For 

a safety professional to evaluate the 

countermeasure, he or she must 

determine how the countermeasure 

affected the frequency, type, and 

severity of crashes. For example, 

did the installation of a roundabout 

reduce the frequency of angle 

crashes? If so, by how much? Did 

it cause an increase to any other 

types of crashes? A countermeasure 

evaluation can result in a CMF 

for the countermeasure, which 

quantifies the effect on crashes (see 

CMF discussion in Step 4). 

Two documents entitled A Guide 

to Developing Quality Crash 

Modification Factors40 (from FHWA) 

and Recommended Protocols for 

Developing Crash Modification 

Factors41 (from NCHRP) provide 

guidance on the different methods 

for conducting evaluations. The 

following is an overview of study 

designs and methods for conducting 

evaluations. 

Categories of Study Designs

Study designs fall into two broad 

categories - experimental and 

observational. Experimental studies 

are conducted when sites are 

selected at random for treatment. 

There is general consensus that 

experimental studies are the most 

rigorous way to establish causality.42

In contrast, observational studies 

are conducted when sites are not 

selected as part of an experiment but 

selected for other reasons including 

Carter, D., R. 

Srinivasan, F. 

Gross, and F. 

Council (2012), 

Recommended 

Protocols for 

Developing Crash 

Modification 

Factors, Prepared 

as part of NCHRP 

Project 20-07 (Task 

314), Washington, 

D.C. Available 

at http://www.

cmfclearinghouse.

org/resources_

develop.cfm. 

Accessed July 2016.

Elvik, R. (2011a), 

Assessing Causality 

in Multivariate 

Accident Models, 

Accident Analysis 

and Prevention, Vol. 

43, pp. 253-264.

Gross, F., B. 

Persaud, and 

C. Lyon (2010), 

A Guide for 

Developing Quality 

Crash Modification 

Factors, Report 

FHWA-SA-10-032, 

Federal Highway 

Administration, 

Washington, 

D.C. Available 

at http://www.

cmfclearinghouse.

org/resources_

develop.cfm. 

Accessed July 2016.

41

42

40
4-32 UNIT 4: SOLVING SAFETY PROBLEMS ROAD SAFETY FUNDAMENTALS

safety. Truly experimental studies 

are not common in road safety 

partly because of potential liability 

considerations (i.e., a random 

selection may result in an agency 

being held liable for failing to treat 

some sites that have demonstrated 

high crash history). Observational 

studies are more common in 

countermeasure evaluations 

because most transportation 

agencies prioritize installation sites 

based on some kind of past safety 

performance (see Step 1, Network 

Screening). 

Observational studies of 

countermeasures can be broadly 

classified into cross-sectional 

studies and before-after studies. In 

cross-sectional studies, an analyst 

compares a group of sites with a 

certain feature to a group of sites 

without that feature. For example, 

an analyst might compare the 

safety performance of a group of 

stop-controlled intersections to 

that of a group of yield-controlled 

intersections to determine the effect 

of the type of traffic control on 

crashes. Cross-sectional studies can 

also be thought of as “with/without” 

studies. In before-after studies, an 

analyst takes a group of sites and 

compares the safety performance in 

the period before a countermeasure 

is implemented to the period after 

the countermeasure is implemented. 

For example, in a before-after study, 

an analyst could evaluate the effect 

of converting a stop-controlled 

intersection to a roundabout by 

comparing safety data before the 

roundabout conversion to the safety 

data afterwards. 

CMFs that result from crosssectional studies are not considered 

to be as robust as those resulting 

from a before-after study. In a 

typical before-after study, an 

analyst deals with same roadway 

unit located in a particular place, 

most likely used by the same road 

users during the before and after 

period. Since most of these factors 

can be assumed to be constant or 

almost constant in the before and 

after periods, they are less likely 

to cause significant biases. On 

the other hand, “cross-sectional 

studies compare different roads, 

used by different road users, located 

at different places and subject 

to different weather conditions. 

Besides, these roads will differ in 

very many other ways that are not 

measured.”43 However, there are 

issues in both types of studies that 

need to be addressed, and they are 

briefly discussed below.

Cross sectional studies

Analysts use cross-sectional studies 

to compare the safety of a group of 

sites with a feature with the safety of 

a group of sites without that feature. 

The resulting CMF can be derived by 

taking the ratio of the average crash 

frequency of sites with the feature 

to the average crash frequency of 

sites without the feature. For this 

method to work, the two groups 

of sites should be similar in their 

characteristics except for the 

feature. In practice, this is difficult 

to accomplish and multiple variable 

regression models are used. These 

cross-sectional models are also 

called SPFs. The coefficients of the 

variables from these equations are 

used to estimate the CMF associated 

with a treatment.

Guidance from FHWA on developing 

CMFs says that “the basic issue 

with the cross-sectional design is 

Elvik, R. (2011a), 

Assessing Causality 

in Multivariate 

Accident Models, 

Accident Analysis 

and Prevention, Vol. 

43, pp. 253-264.

43
ROAD SAFETY FUNDAMENTALS UNIT 4: SOLVING SAFETY PROBLEMS 4-33

that the comparison is between two 

distinct groups of sites. As such, 

the observed difference in crash 

experience can be due to known or 

unknown factors, other than the 

feature of interest. Known factors, 

such as traffic volume or geometric 

characteristics, can be controlled 

for in principle by estimating a 

multiple variable regression model 

and inferring the CMF for a feature 

from its coefficient. However, the 

issue is not completely resolved 

since it is difficult to properly 

account for unknown, or known 

but unmeasured, factors. For 

these reasons, caution needs to 

be exercised in making inferences 

about CMFs derived from crosssectional designs. Where there are 

sufficient applications of a specific 

countermeasure, the before-after 

design is clearly preferred.”45

Gross, F., B. 

Persaud, and 

C. Lyon (2010), 

A Guide for 

Developing Quality 

Crash Modification 

Factors, Report 

FHWA-SA-10-032, 

Federal Highway 

Administration, 

Washington, 

D.C. Available 

at http://www.

cmfclearinghouse.

org/resources_

develop.cfm. 

Accessed July 2016.

45

A CMF can be obtained from a cross 

sectional model. Suppose the intent is 

to estimate the CMF for shoulder width 

based on the following SPF, which was 

estimated to predict the number of crashes 

per mile per year on rural two-lane roads in 

mountainous roads with paved shoulders 

(Appendix B of Srinivasan and Carter, 201144):

Where, AADT is the annual average daily 

traffic and SW is the width of the paved 

shoulder in feet. If the intent is to estimate 

the CMF of changing the shoulder width 

from three to six feet, then the CMF can 

be estimated as the ratio of the predicted 

number of crashes when the shoulder 

width is six feet to the predicted number 

of crashes when the shoulder width is 

three feet:

This ratio simplifies to: 

CMF = exp [-0.0164 × (6-3) ] = 0.952

This CMF of 0.952 indicates that changing 

the shoulder width from three to six feet 

would be expected to reduce crashes (since 

the CMF is less than 1.0). Specifically, the 

expected change in crashes would be a 

4.8% reduction (1.0 – 0.952 x 100 = 4.8).

However, it is important to recognize that 

this CMF of 0.952 is the midpoint in a range 

of possible values (i.e., the confidence 

interval). This range can be calculated by 

using the standard deviation of the CMF. In 

order to estimate the standard deviation, 

the standard error of the coefficient of SW 

is needed, which was reported to be 0.0015 

in the original study. The high and low ends 

of the confidence interval are calculated 

using -0.0164+0.0015, and then using 

-0.0165-0.0015, and the difference between 

the two is divided by two. The equation is 

given below:

The approximate 95% confidence 

interval for the CMF is (0.952-1.96×0.004, 

0.952+1.96×0.004), which translates to a 

range of 0.944 to 0.960. Since the entire 95% 

confidence interval is below 1.0, the CMF is 

statistically significant, thereby indicating 

that widening the shoulder from three to six 

feet is very likely to reduce crashes. 

Srinivasan, R. and 

D. Carter (2011), 

Development of 

Safety Performance 

Functions for North 

Carolina, Report 

FHWA/NC/2010-

09, Submitted to 

NCDOT, December 

2011.

44

Using cross-sectional modeling to calculate a CMF for widening shoulders

Y = exp [ 0.8727 + 0.4414 × ln( ) + 0.4293 × ( ) -0.0164 × SW ]

StDev(CMF) = = 0.004

CMF = 

exp [ 0.8727 + 0.4414 × ln( ) + 0.4293 × ( ) -0.0164 × 6 ]

exp [ 0.8727 + 0.4414 × ln( ) + 0.4293 × ( ) -0.0164 × 3 ]

AADT

10000

AADT

10000

AADT

10000

AADT

10000

AADT

10000

AADT

10000

exp [-0.0164+0.0015 × (6-3) ] - exp [-0.0164-0.0015 × (6-3) ]

2
4-34 UNIT 4: SOLVING SAFETY PROBLEMS ROAD SAFETY FUNDAMENTALS

Holmes, W.M., (2013). 

Using Propensity Scores 

in Quasi-Experimental 

Designs. SAGE 

Publications.

Wood, J., Porter, R., 

(2013). Safety impacts 

of design exceptions 

on non-freeway 

segments. Transport. 

Res. Rec.: J. Transport.

Res. Board 2358, 29–37.

Gooch, J.P., Gayah, 

V.V., and Donnell, E.T. 

(2016), Quantifying 

the Safety Effects of 

Horizontal Curves 

on Two-Way, TwoLane Rural Roads, 

Accident Analysis 

and Prevention, Vol. 

92, pp. 71-81.

47

48

46

One way to account for some of 

the limitations of cross-sectional 

regression models is to use the 

propensity scores-potential 

outcome method. This method 

uses the “individual traits of a 

site to calculate its propensity 

score, defined as a measure of the 

likelihood of that site receiving a 

specific treatment. Sites with and 

without the treatment are then 

matched based on their propensity 

scores.”46 The matched data are 

then used to estimate a cross 

sectional regression model. The 

propensity score method has been 

shown to reduce selection bias by 

accounting for the non-random 

assignment of treatment sites.47

Recently, the propensity score 

method is starting to be used in 

place of traditional cross-sectional 

methods to conduct evaluations.48

Other types of cross-sectional 

methods include case control and 

cohort methods. “Case-control 

studies select sites based on outcome 

status (e.g., crash or no crash) and 

then determine the prior treatment 

(or risk factor) status within each 

outcome group.”49 Another critical 

component of many case-control 

studies is the matching of cases with 

controls in order to control for the 

effect of confounding factors. In 

cohort studies, sites are assigned to 

a particular cohort based on current 

treatment status and followed over 

time to observe exposure and event 

frequency. One cohort may include 

the treatment and the other may be 

a control group without the 

treatment. The time to a crash in 

these groups is used to determine a 

relative risk, which is the percentage 

change in the probability of a crash 

given the treatment.50

See next page.

Gross, F., B. Persaud,

and C. Lyon (2010), 

A Guide for 

Developing Quality 

Crash Modification 

Factors, Report 

FHWA-SA-10-032, 

Federal Highway 

Administration, 

Washington, D.C. 

Available at http://

www.cmfclearing 

house.org/

resources_ develop.

cfm. Accessed July 

2016.

50

49
ROAD SAFETY FUNDAMENTALS UNIT 4: SOLVING SAFETY PROBLEMS 4-35

Before after studies

An analyst can use a before-after 

study to evaluate a countermeasure 

by comparing the crashes before the 

countermeasure was installed to the 

crashes after installation. This study 

design is advantageous because 

the only change that has occurred 

at the site is the countermeasure 

installation (assuming the analyst 

has researched the site histories 

to discard any sites at which other 

significant changes occurred).

There are issues for consideration 

with this study design as well. 

The analyst must know when the 

countermeasure was installed and 

must have data, such as crash and 

traffic volume, available in the before 

and after periods. For high-cost, 

high-profile countermeasures, such 

as road widening or traffic signal 

installation, the installation records 

will be readily available. However, for 

low-cost countermeasures, such as 

sign installations, there may be little 

to no documentation on when they 

were installed.

The analyst might simply compare 

the number of crashes per year 

before the countermeasure to the 

number of crashes per year after the 

countermeasure, known as a simple 

or naïve before-after evaluation. 

Although a simple before-after 

evaluation can be done easily 

using only crash data, it is prone to 

significant bias. One of the most 

influential biases for this method 

is the possible bias due to RTM. As 

discussed earlier, RTM describes a 

situation in which crash rates are 

artificially high during the before 

period and would have been reduced 

even without an improvement to 

the site. Programs focused on highhazard locations are vulnerable to 

the RTM bias. This potential bias 

is greatest when sites are chosen 

because of their extreme value (e.g., 

high number of crashes or crash 

rate) in a given time period. A simple 

before-after evaluation has a high 

likelihood of showing a much greater 

benefit from the safety treatment 

than actually occurred.

As discussed earlier under the 

network screening section, the EB 

method is one of the methods that 

has been found to be effective in 

dealing with the possible bias due to 

RTM. The following steps are needed 

to conduct an EB before-after 

evaluation:

1. IDENTIFY a reference group of 

sites without the treatment, but 

similar to the treatment sites 

in terms of the major factors 

that affect crash risk including 

traffic volume and other site 

characteristics. One way to 

identify a reference group that 

is similar to the treatment is to 

use the propensity score method 

discussed earlier under crosssectional studies.

2. Using data from the reference 

site, ESTIMATE SPFs using data 

from the reference sites relating 

crashes to independent variables, 

such as traffic volume and other 

site characteristics. As discussed 

in the following steps, SPFs 

are used in the EB method to 

predict the average number of 

crashes based on AADT and site 

characteristics. By selecting 

the reference group to be 

similar to the treatment group 

in terms of the major risk 

factors, we can reduce the 

possible bias due to confounding 

on these predictions. 

Carter, D., R. 

Srinivasan, F. 

Gross, and F. 

Council (2012), 

Recommended 

Protocols for 

Developing Crash 

Modification 

Factors, Prepared 

as part of NCHRP 

Project 20-07 (Task 

314), Washington, 

D.C. Available 

at http://www.

cmfclearinghouse.

org/resources_

develop.cfm. 

Accessed July 2016.

50
4-36 UNIT 4: SOLVING SAFETY PROBLEMS ROAD SAFETY FUNDAMENTALS

This example is an illustration of an EB 

before-after evaluation that was conducted 

as part of NCHRP Project 17-35.51 The 

countermeasure was a change from 

permissive to protected-permissive left turn 

phasing at signalized intersections in North 

Carolina. Data from twelve locations were 

used in this evaluation. A reference group 

of 49 signalized intersections was identified 

for the development of SPFs. The analysis 

looked at total intersection crashes, injury 

and fatal crashes, rear end crashes, and left 

turn opposing through (LTOT) crashes. In 

this example, only the data for LTOT crashes 

will be used.

The SPF for LTOT crashes based on the data 

from the reference group was:

LTOT crashes/intersection/year = 

e-0.3696 (MajAADT/10000)

0.5564

e0.6585×(MinAADT / 10000)

Where, MajAADT is the major road AADT 

and the MinAADT is the minor road AADT. 

The overdispersion parameter (k) for this 

SPF was 0.5641.

In the first site of this study, there were 10 

observed crashes in the before period (Xb

), 

and the predicted number of crashes from 

the SPF in the before period was 5.535 (Pb

). 

The formula for obtaining the EB estimate 

of the expected crashes in the before period 

(EBb

) is as follows:

EBb = w × Pb + ( 1 - w ) × Xb

Where, Xb is the observed crashes in the 

before period, and w is the EB weight that is 

calculated as follows:

Where, k is the overdispersion parameter 

for the estimated SPF.

In this example: 

The EB estimate of the crashes in the before 

period (EBb

) = 5.535*0.243 + 10*(1-0.243) = 

8.917 crashes.

The predicted number of crashes from the 

SPF in the after period was 11.391 (Pa

). 

The formula for the EB expected number 

of crashes that would have occurred 

in the after period had there been no 

countermeasure is given by: 

π = EBb × ( Pa / Pb )

In this example, the EB expected number 

of crashes in the after period had the 

countermeasure not been implemented 

(π) is equal to:

8.917 × ( 11.391 / 5.535 )

= 18.350 crashes

The variance of this expected number of 

crashes is also estimated in this step:

Var( π ) = π × ( Pa / Pb ) × ( 1 - w )

Where, Pa is the SPF predictions in the after 

period. In this example, the variance of ππ 

is estimated as follows:

Var( π ) = 18.350 × ( 11.391 / 5.535 ) 

× ( 1 - 0.243 ) = 28.603

This process was repeated for all 12 sites. 

Based on the data for all the 12 sites that 

were used in the evaluation, the actual 

crashes in the after period were 115, the EB 

expected crashes had the countermeasure 

not been implemented was 131.933 with a 

variance of 140.080. 

(continued on next page)

Srinivasan, R. et 

al., Evaluation of 

Safety Strategies 

at Signalized 

Intersections, 

NCHRP Report 705, 

Washington, DC.

51

Using an EB before-after evaluation to develop a CMF for signal phasing changes

1

( 1 + k × Pb

 )

w =

1

( 1 + 0.5641 × 5.535 )

w = = 0.243
ROAD SAFETY FUNDAMENTALS UNIT 4: SOLVING SAFETY PROBLEMS 4-37

The formula for the CMF and its standard 

deviation (StDev) are as follows:

Where, λsum is the total number of crashes 

that occurred in the after period, for all 

the treated sites in the sample, πsum is the 

total number of expected crashes in the 

after period had the countermeasure not 

been implemented, and Var represents the 

variance. Since crashes are assumed to 

be Poisson distributed, Var(λsum) is usually 

assumed to be equal to λsum. So, (Var(λsum))/

(λsum

2

 ) will be equal to 1/λsum.

In this example, the overall CMF was 

calculated as:

This CMF of 0.865 indicates that the 

countermeasure (changing from permissive 

to protected-permissive left turn phasing) 

would decrease crashes, since the CMF 

is less than 1.0. It would be expected 

to decrease crashes by 13.5% 

(1.0 – 0.865 x 100 = 13.5).

Again, it is important to recognize that the 

CMF is the midpoint of a range of possible 

values (i.e., the confidence interval). The 

standard deviation of the CMF can be 

estimated as follows:

Based on this standard deviation 

of the CMF, the approximate 95% 

confidence interval is (0.865-1.96×0.111, 

0.865+1.96×0.111), which translates 

to a range of 0.647 to 1.083. Since this 

confidence interval includes values greater 

than 1.0, the CMF is not statistically 

different from 1.0 at the 95% confidence 

level. This indicates that there is less 

confidence that this countermeasure 

will reduce crashes compared to a 

countermeasure whose CMF is significantly 

different from 1.0.

λsum

πsum

 Var ( πsum ) 2

π2

sum

CMF =

1 +

 115

131.933

 140.080

131.9332

CMF = = 0.865

= 0.111

1 +

StDev( CMF ) =

StDev( CMF ) =

 Var ( λsum )

λ2

sum

 Var ( πsum )

π2

sum

 Var ( πsum )

π2

sum

CMF2 +

( 1 + ) 2

 1

115

 140.080

131.9332

 140.080

131.9332

0.8652 +

( 1 +

( 

) 2

)
4-38 UNIT 4: SOLVING SAFETY PROBLEMS ROAD SAFETY FUNDAMENTALS

3. In estimating SPFs, CALIBRATE

annual SPF multipliers to 

account for the temporal effects 

(e.g., variation in weather, 

demography, and crash 

reporting) on safety. The annual 

SPF multiplier is the ratio of the 

observed crashes to the predicted 

crashes from the SPF. In using 

the annual SPF multipliers from 

the SPFs to account for temporal 

effects, it is assumed that the 

trends in the crash counts are 

similar in the treatment and 

reference groups.

4. USE the SPFs, annual SPF 

multipliers, and data on traffic 

volumes for each year in the 

before period for each treatment 

site to estimate the number of 

crashes that would be predicted 

for the before period in each site.

5. CALCULATE the EB estimate 

of the expected crashes in the 

before period at each treatment 

site as the weighted sum of the 

actual crashes in the before 

period and predicted crashes 

from Step 4. 

6. For each treatment site, 

ESTIMATE the product of the EB 

estimate of the expected crashes 

in the before period and the SPF 

predictions for the after period 

divided by these predictions for 

the before period. This is the EB 

expected number of crashes that 

would have occurred had there 

been no treatment. The variance 

of this expected number of 

crashes is also estimated in 

this step.

The expected number of crashes 

without the treatment along with 

the variance of this parameter and 

the number of reported crashes after 

the treatment is used to calculate 

the CMF and the standard deviation 

of the CMF. This procedure is 

repeated for each treated site. Once 

CMFs have been calculated for each 

individual site in a group of treated 

sites, the CMFs can be combined to 

calculate the overall effectiveness 

of the countermeasure. More details 

on this procedure are provided in 

the previously mentioned guidance 

documents.52,53

In some cases, treatments may 

be installed system-wide for a 

particular type of facility. For 

example, a jurisdiction may decide 

to increase the retroreflectivity 

of all their stop signs. Since sites 

are not specifically selected based 

on their crash history, the bias 

due to RTM is minimal. However, 

it is still necessary to account for 

changes in traffic volume and other 

trends. To evaluate the safety of 

such installations, an EB method 

could still be used, and while a 

reference group is not necessary, 

a comparison group is necessary 

in order to account for trends. 

SPFs can be estimated using the 

before-data from the treatment 

sites and these SPFs can be used 

to account for changes in traffic 

volumes. In addition, SPFs could be 

estimated for a group of comparison 

sites and the annual factors from 

these SPFs can be used to account 

for trends. Further details about 

such evaluations can be found 

elsewhere.54

Carter, D., R. 

Srinivasan, F. 

Gross, and F. 

Council (2012), 

Recommended 

Protocols for 

Developing Crash 

Modification 

Factors, Prepared 

as part of NCHRP 

Project 20-07 (Task 

314), Washington, 

D.C. Available 

at http://www.

cmfclearinghouse.

org/resources_

develop.cfm. 

Accessed July 2016.

B. Persaud and 

C. Lyon (2007), 

Empirical Bayes 

Before After 

Studies: Lessons 

Learned from 

Two Decades of 

Experience and 

Future Directions, 

Accident Analysis 

and Prevention, 

39(3):546-55.

Gross, F., B. 

Persaud, and 

C. Lyon (2010), 

A Guide for 

Developing Quality 

Crash Modification 

Factors, Report 

FHWA-SA-10-032, 

Federal Highway 

Administration, 

Washington, 

D.C. Available 

at http://www.

cmfclearinghouse.

org/resources_

develop.cfm. 

Accessed July 2016.

53

54

52
ROAD SAFETY FUNDAMENTALS UNIT 4: SOLVING SAFETY PROBLEMS 4-39

System-level safety management 

involves addressing road safety 

issues that affect the broad 

transportation system, as opposed 

to treating specific high priority 

sites. The size and scope of the 

transportation system depends 

on the agency or jurisdiction. For 

a State DOT, the transportation 

system would consist of all Stateowned roads, signals, bridges, and 

other features across the entire 

State, whereas the transportation 

system for a town would consist of 

a much smaller area and roadway 

network. Road safety at a systemlevel often has to do with policies, 

whether design policies for the 

construction and operation of roads 

and intersections, driver policies for 

licensing, or vehicle policies that 

require certain safety technologies. 

Other system-level efforts would 

include broad media or enforcement 

campaigns.

Recall that Chapter 10 presented 

road safety management in terms of 

three general components: 

J Identifying safety problems

J Developing potential 

safety strategies

J Selecting and 

implementing strategies

This chapter will discuss how each of 

these components can be addressed 

at a system-level.

Identifying safety problems

To identify safety problems on a 

system-level, safety professionals 

analyze safety data that apply 

to the entire jurisdiction. They 

examine crash data and link crashes 

to other safety data to determine 

the nature and locations of safety 

problems. Problem identification on 

a system-level involves identifying 

crash trends and using risk-based 

methods to prioritize safety efforts.

Identifying crash type trends

Safety professionals can examine 

crash types and contributing factors 

to determine the nature of crashes 

within their agency’s jurisdiction. 

This type of examination may reveal 

crash trends, such as those related 

to alcohol involvement, seat belt 

use, driver age, or vulnerable road 

users. For example, crash data 

might show that crashes involving 

unbelted occupants have been 

increasing over the past several 

System-Level Safety Management

CHAPTER 12 UNIT 4: SOLVING SAFETY PROBLEMS

System-wide vs. systemic?

System-wide is a general term that refers 

to treating safety issues across an entire 

transportation system using policies or 

campaigns. Systemic is a more specific 

term that refers to identifying a subset 

of a transportation system based on 

risk factors and implementing safety 

efforts that address the particular 

characteristics of that subset. 

See page 4-41 for more discussion 

on the systemic approach.
4-40 UNIT 4: SOLVING SAFETY PROBLEMS ROAD SAFETY FUNDAMENTALS

years, or it might show that the 

number of crashes involving 

unbelted occupants is significantly 

higher than other nearby agencies, 

such as adjacent counties or 

States. This would lead an agency 

to consider how to increase seat 

belt use, perhaps through media 

campaigns, increased enforcement, 

or educational campaigns in schools. 

This type of agency-wide analysis 

of crash data can demonstrate 

broad scale trends that need to 

be addressed through broad scale 

efforts. 

It is important that safety 

professionals are specific when 

identifying safety problems in 

crash trends. For example, “crashes 

involving teen drivers” is not 

defined well enough, because the 

causes of crashes for 16 year-olds 

is markedly different from those 

of older, more experienced teens. 

Crashes in which teens are victims 

of other drivers’ errors require 

different solutions from those where 

the teen was at fault. Similarly, the 

cause of crashes depends greatly on 

the specific time, place and driving 

environment. A better target crash 

type would be “crashes occurring 

between 7-9 a.m. involving 16-year 

old drivers.” 

Example of safety 

problem identification in 

State Highway Safety Plans

A good example of identifying 

safety problems from crash type 

trends can be seen in how States 

develop strategic highway safety plans 

(SHSPs). The development of a SHSP 

involves the identification of safety 

problems on the State and local 

roads. A State analyzes safety data 

to determine the priorities, referred 

to as emphasis areas. The analysis 

can involve an examination of crash 

proportions between categories of 

crashes, crash trends, crash severity 

(e.g., fatal and serious injury), or 

more advanced crash modeling 

techniques. As presented in the 

call-out boxes, Ohio and Florida 

conducted analyses of their crash 

data and identified areas of concern.

Strategic 

highway 

safety plan

A statewidecoordinated 

safety plan 

that provides a 

comprehensive 

framework 

for reducing 

highway 

fatalities and 

serious injuries 

on all public 

roads.

Florida’s emphasis on 

motorcyclist safety

The State of Florida examined its crash 

data to identify emphasis areas in the 

development of their SHSP in 2012. One 

area that continued to be a focus was 

motorcyclist safety. The data indicated 

that crashes involving motorcycles 

had decreased somewhat during the 

time period analyzed (2006 to 1010) 

but remained a significant portion of 

the crashes on Florida roads. Florida’s 

safety professionals recognized that 

since Florida hosts numerous national 

motorcycle events, the state’s SHSP 

should have motorcycle safety as an 

emphasis area.

2006 2007 2008 2009 2010

2,324

2,548

Serious Injuries

Fatalities

2,813 2,758

2,850

383 402

550 550 532

FIGURE 4-8. Florida motorcycle crash 

trend 2006-2010
ROAD SAFETY FUNDAMENTALS UNIT 4: SOLVING SAFETY PROBLEMS 4-41

Risk based prioritization – 

the systemic approach

Chapter 11 presented various 

methods of selecting high priority 

sites through a process of network 

screening based on crash data. Many 

safety professionals recognize that 

this process of identifying specific 

locations using past crash data does 

not adequately address the fact that 

there may be locations that pose 

a safety threat but have not yet 

experienced many (or any) crashes. 

This recognition led to an increased 

use of risk-based prioritization, also 

called the systemic approach.55

In this approach, a transportation 

agency identifies priority locations 

based on the presence of risk factors 

rather than crashes. In the medical 

field, doctors pay attention to factors 

that may elevate a person’s risk for 

disease. A history of smoking, poor 

eating habits, and a lack of exercise 

may indicate a higher-than-average 

risk for heart disease, even if the 

person has not yet experienced heart 

problems. Similarly, a section of 

road with certain characteristics, 

such as sharp curvature, old 

pavement, or lack of visibility, may 

be at risk for run-off-road crashes, 

even if none have occurred yet. 

Agencies can be proactive in their 

approach to safety management 

by identifying and treating these 

sites before crashes occur. These 

treatments are often low cost, such 

as signs and markings, so many 

systemic-identified locations can be 

treated within an agency’s limited 

budget. 

An agency using the systemic 

approach selects the focus crash 

type(s) and identifies risk factors 

associated with the focus crashes. 

Risk factors are site characteristics 

(e.g., design and operational 

features) that are common across 

Systemic

The process of 

identifying road 

or intersection 

characteristics 

that increase 

the risk of 

crashes and 

selecting 

locations 

for safety 

treatment 

based on the 

presence of 

these risk 

factors.

Ohio’s emphasis on 

older driver safety

Ohio developed a SHSP in 2014 in which 

they identified fifteen emphasis areas. One 

of the emphasis areas was the safety of 

older drivers (65 and older). The crash data 

showed that older driver-related crashes 

accounted for 18% of highway deaths and 

16% of serious injuries. They recognized 

that these numbers would likely increase 

with an aging population. The crash trends 

over the time period examined (2003 to 

2013) showed a slight upward trend to 

older driver serious injuries and a slight 

downward trend to older driver fatalities. 

This contrasted to other types of crashes 

that experienced significant declines. 

These reasons motivated Ohio to make 

older driver safety an emphasis area in their 

2014 SHSP. 

http://safety.fhwa.

dot.gov/systemic/

55
4-42 UNIT 4: SOLVING SAFETY PROBLEMS ROAD SAFETY FUNDAMENTALS

locations with the focus crash 

type(s). The agency can identify risk 

factors by analyzing crash data from 

their jurisdiction or by reviewing 

previous research studies. Using 

the list of risk factors as a guide, the 

agency identifies a list of sites with 

those specific characteristics, and 

then develops targeted treatments 

to address or mitigate the specific 

risk factors. The agency can apply 

crash history and other thresholds 

to reduce the list of sites based on 

available resources and program 

objectives. 

The systemic approach has two 

attractive features. First, an agency 

can employ the systemic approach 

even for roads or intersections where 

crash data are not fully available 

(e.g., where location accuracy is 

questionable or underreporting is 

a problem). For instance, locating 

crashes accurately and precisely in 

rural areas or on non-State owned 

urban roads can be difficult. Second, 

the systemic approach is useful 

for treating safety issues where 

crashes are highly dispersed, such 

as on rural or low volume roads. 

Specifically, agencies can use the 

systemic approach to address 

existing and potential safety issues 

across a large portion of the network 

(e.g., shoulder rumble strips on all 

rural, two-lane roads with a certain 

shoulder width and traffic volume 

level). 

Developing potential 

safety strategies

After safety professionals analyze 

data and identify safety problems, 

they must develop potential 

strategies to address the problems. 

It is important to engage safety 

stakeholders and other partners 

when selecting potential strategies 

as they may provide unique 

perspectives. Safety professionals 

should seek to involve local officials, 

citizens, and safety partners to 

produce effective multidisciplinary 

strategies. For example, addressing 

a particular safety problem with 

law enforcement and education 

can be far more economical than 

implementing a multimilliondollar engineering fix. On the other 

hand, law enforcement tends to 

be effective only during the time 

in which it is active, so a more 

permanent engineering measure 

may be needed in some cases. It is 

often the case that a combination 

of strategies is necessary to 

effectively address the multitude of 

contributing factors.

On a system level, agencies must 

think broadly across the many 

disciplines represented by those 

who have a stake in road safety. 

Potential strategies might address 

infrastructure policies and practices 

(e.g., design standards, speed limits, 

etc.) or they may be directed at 

specific population focused efforts 

(e.g., seat belt laws, helmet laws, 

young driver restrictions, etc.).

Just as the identification of problems 

was based on safety data, so too 

must the development and selection 

of strategies be driven by the data. 

If an agency identified concerning 

trends in certain types of crashes, 

then they should further examine 

the crash data to determine how 

best to address the safety problem. 

For example, Figure 4-9 shows an 

example of alcohol-related crashes 

where an agency identified a spike in 

frequency (or high pole) of crashes 

occurring near 2:00 AM. Further 

examination revealed that bars in 
ROAD SAFETY FUNDAMENTALS UNIT 4: SOLVING SAFETY PROBLEMS 4-43

The Thurston County Public Works 

Department in Washington conducted 

a systemic safety analysis for their road 

network. Based on a review of severe 

crashes, Thurston County decided to focus 

on roadway departure crashes in horizontal 

curves on arterial and collector roadways 

when it found that:

1. Most of the severe crashes occurred 

due to roadway departures, and that

2. 81% of the severe curve /roadway 

departure crashes occurred on arterial 

and collector roads. Because this 

effort coincided with ongoing efforts 

to identify and upgrade warning 

signs for horizontal curves on their 

County road system, Thurston County 

chose to focus on currently signed 

horizontal curves.

Thurston County accessed an inventory 

of their roads and intersections through 

a database maintained by the Statewide 

County Road Advisory Board. In addition, 

Thurston County assembled crash data 

for the 2006-to-2010 timeframe from the 

Washington State DOT crash database. 

They linked the road, intersection, and 

curve data with crash data and used these 

data to identify risk factors. Thurston 

County assembled a list of 19 potential risk 

factors and then performed a descriptive 

statistics analysis to identify 9 risk factors 

for use in screening and prioritizing 

candidate locations. The identified risk 

factors were:

J Roadway class of major rural collector

J Presence of an intersection

J Traffic volume of 3,000 to 7,500 

annual average daily traffic

J Edge clearance rating of 3

J Paved shoulders equal to or 

greater than 4 feet in width

J Presence of a vertical curve

J Consecutive horizontal curves 

(windy roads)

J Speed differential between posted 

approach speed and curve advisory 

speed of 0, 5, and 10 miles per hour

J Presence of a visual trap (a minor road 

on the tangent extended)

Thurston County decided that a risk factor 

could be worth one point or a one-half 

point. Those factors present in at least 30% 

of the severe (fatal and injury) crashes and 

overrepresented by at least 10% (when 

comparing the proportion of all locations 

with the proportion of severe crash 

locations) were used as a guideline to have 

a high confidence and assigned one point 

in the risk assessment process. The risk 

factors that had a lower confidence in their 

relative data were assigned one-half point. 

Thurston County then tallied the number 

of risk factors present for each of the 

curves. The risk factor totals for the ten 

curves with the highest scores ranged 

from 4.5 to 6.0. All 270 signed curves 

were prioritized for potential low cost 

safety investments. They identified the 

following low-cost, low-maintenance 

countermeasures with documented 

crash reductions to implement at the 

selected locations: 

J Traffic signs – enhanced curve 

delineation with the addition of 

chevrons and larger advance 

warning signs

J Pavement markings – dotted extension 

lines at intersections and recessed 

raised pavement markers

J Shoulder rumble strips

J Roadside improvements – object 

removal, guardrail, and slope flattening

Systemic analysis provided Thurston 

County a proactive, data-driven, and 

defensible approach to identifying curves 

for improvement prior to a severe crash 

occurring, rather than reacting after an 

incident has occurred.56

“Thurston County, 

Washington, Public 

Works Department 

Applies Systemic 

Safety Project 

Selection Tool” 

FHWA-SA-13-026, 

June 2013. http://

safety.fhwa.dot.gov/

systemic/

56

Case Study: Systemic Analysis in Thurston County, Washington
4-44 UNIT 4: SOLVING SAFETY PROBLEMS ROAD SAFETY FUNDAMENTALS

that jurisdiction closed at 2:00 AM. 

This could lead to potential strategies, 

such as increased enforcement of 

impaired driving at that time of night 

and in the vicinity of bars. 

It is also important to use the data 

to determine the necessary scope of 

the intervention. If the data show 

that the problem exists year-round, 

then the solution needs to match 

that. For example, a “safe ride 

program” for drinkers to get home 

on New Year’s Eve is not going to 

significantly impact the problem of 

impaired driving overall.

Critical thinking is needed to 

develop effective solutions to the 

safety problems at hand. Analysts 

should look for characteristics of 

crash trends that could be addressed 

by practical strategies. An NCHRP 

report on an integrated safety 

management process states that 

safety professionals should use 

safety data to perform “further 

analyses of those characteristics 

that are found to be significantly

or practically over-represented on 

a percentage or rate basis.”57 The 

report gives a set of guidelines to be 

considered in analyzing crash data to 

identify trends and develop potential 

safety strategies:

1. ASK the questions, “Is this 

information sufficient for action 

item development? If not, what 

further information is needed to 

act on this finding?”

2. CONSIDER cross tabulations of 

two variables within the subset 

of data that pertains to the 

activities under consideration 

if one or more of the following 

types of conditions hold: 

J If the activities are time 

critical (e.g., all selective 

0

5

10

15

20

0:00 2:00 4:00 6:00 8:00 10:00 12:00 14:00 16:00 18:00 20:00 22:00

Example of a high pole in a jurisdiction 

where bars close at 2:00 a.m.

NUMBER OF COLLISIONS

TIME OF DAY

FIGURE 4-9. Example of “high pole” in crash data (Source: NCHRP Report 501)

Consider How Specific Behaviors 

Influence the Safety Problem

Safety professionals must identify 

and target road user behaviors that 

contribute to the identified safety 

problem. The target behavior should 

be specific. For example, “safe driving” 

is not a specific behavior that can be 

changed because it involves a number of 

different behaviors. However, “speeding 

on Main Street” is a specific behavior 

that can be targeted. It is also important 

to consider the factors influencing this 

behavior. Why are people speeding on 

Main Street? Which social, cultural, or 

environmental factors are influencing 

this behavior? Does it vary by time of day 

or week, perhaps reflecting the kind of 

drivers who are speeding?

Bahar, G., M. 

Masliah, C. Mollett, 

and B. Persaud, 

Integrated Safety 

Management 

Process, National 

Cooperative 

Highway Research 

Program, Report 

501, Transportation 

Research Board 

of the National 

Academies, 

Washington, D.C., 

2003

57
ROAD SAFETY FUNDAMENTALS UNIT 4: SOLVING SAFETY PROBLEMS 4-45

enforcement strategies), 

perform a time-of-day by 

day-of-the-week analysis. 

As an example, alcoholrelated crashes will likely be 

over-represented in the early 

morning and on weekend 

days. A logical approach is to 

perform a cross tabulation of 

time-of day by day-of-theweek to determine the best 

times and days for driving 

under the influence (DUI)

selective enforcement. The 

goal of the procedure at 

this point is to determine 

additional details (who, what, 

where, when, and how) for 

those crash types identified

by the analyses performed to 

this point. 

J If the over-represented 

variable is not constant 

over all crash severities, 

cross tabulate the variable 

by severity (e.g., nighttime, 

rural, and older-driver 

crashes tend to be more 

severe). 

J If the activities can be 

targeted to geographic 

location, age group, 

gender, race, or any other 

demographic factor within 

the crash records, consider 

these variables for cross 

tabulation with other overrepresented variables.

3. CONSIDER creating subsets 

of the data for additional 

comparisons where activities 

are to be targeted to a particular 

subgroup of the population. For 

example, insight into a graduated 

driver’s license strategy can be 

obtained by comparing 16-yearold causal driver crashes against 

17- to 20-year-old causal 

driver crashes. As another 

example, insight into youth 

alcohol enforcement activities 

can be attained by comparing 

alcohol-related crashes of 16- 

to 20-year-old causal drivers 

against alcohol-related crashes 

of their 21-year-old and older 

counterparts. Each of these 

types of comparisons can 

show differences between the 

respective subpopulations. 

4. USE the results of each analysis 

to determine what further 

information is needed before 

the best decision can be made, 

and repeat the analysis with the 

additional information. 

5. PERSIST and maintain a thread 

of evidence until the information 

available has been exhausted. 

If the information generated 

indicates a significant factor,

create further subsets of the data 

(e.g., youth-pedestrian crashes), 

and repeat the entire analysis. 

6. REJECT any strategies and 

activities at this point that 

the data clearly show to be 

counterproductive (i.e., activities 

that will consume resources 

that could be better applied 

elsewhere). Maintain a list of 

all potential strategies and 

corresponding activities that will 

be subjected to further analysis 

in the optimization procedure.58

Many system-level safety strategies 

focus on behaviors of drivers 

and other road users. Resources 

like Countermeasures That Work 

provide a useful listing of potential 

safety strategies for system-level 

safety management.59 The excerpt 

from Countermeasures That Work in 

Goodwin, A., 

Thomas, L., 

Kirley, B., Hall, W., 

O’Brien, N., & Hill, 

K. Countermeasures 

That Work: A 

Highway Safety 

Countermeasure 

Guide for State 

Highway Safety 

Offices, Eighth 

edition, National 

Highway 

Traffic Safety 

Administration, 

Report No. DOT 

HS 812 202, 

Washington, DC, 

2015.

Bahar, G., M. 

Masliah, C. Mollett, 

and B. Persaud, 

Integrated Safety 

Management 

Process, National 

Cooperative 

Highway Research 

Program, Report 

501, Transportation 

Research Board 

of the National 

Academies, 

Washington, D.C., 

2003

59

58
4-46 UNIT 4: SOLVING SAFETY PROBLEMS ROAD SAFETY FUNDAMENTALS

1. Laws

† When enforced and obeyed

2. Enforcement

† Can be covered by income from citations

†† For aggressive driving, but use of short-term, high-visibility enforcement campaigns for 

speeding is more widespread

3. Penalties and Adjudication

4. Communications and Outreach

Effectiveness:

 Demonstrated to be effective by several 

high-quality evaluations with consistent results

 Demonstrated to be effective in certain situations

 Likely to be effective based on balance of evidence 

from high-quality evaluations or other sources

 Effectiveness still undetermined; different methods of 

implementing this countermeasure produce different results

 Limited or no high-quality evaluation evidence

COUNTERMEASURE EFFECTIVENESS COST USE TIM

1.1 Speed limits  $ High Short

1.2 Aggressive driving laws  $ Low Shor

COUNTERMEASURE EFFECTIVENESS COST USE TIM

3.1 Penalty types and levels  Varies High Low

3.2 Diversion and plea agreements  Varies Unknown Varies

COUNTERMEASURE EFFECTIVENESS COST USE TIM

4.1 Public Information 

 supporting enforcement  Varies Medium Medium

COUNTERMEASURE EFFECTIVENESS COST USE TIM

2.1 Automated enforcement  $$$ Medium Mediu

2.2 High-visibility enforcement  $$$ Low Medium

2.3 Other enforcement methods  Varies Unknown Varies

†

†

††

FIGURE 4-10. Potential Safety Strategies to Address Speeding and Aggressive Driving
ROAD SAFETY FUNDAMENTALS UNIT 4: SOLVING SAFETY PROBLEMS 4-47

Figure 4-10 gives a list of potential 

strategies for addressing speedingrelated crashes, from either 

laws, enforcement, penalties and 

adjudication, or communications 

and outreach. The list also includes 

an indication of the effectiveness, 

cost, current usage, and time of each 

strategy, which are all important 

considerations when selecting safety 

strategies to implement.

If the agency identifies safety 

problems from a systemic analysis, 

the potential safety strategies 

should address the types of crashes 

that were related to the roadway 

characteristic risk factors. These 

strategies may often be engineering 

improvements related to the 

risk factors. For example, if an 

examination of crash trends may 

highlight run-off-road crashes, 

and a systemic analysis would 

identify the type(s) of road on which 

run-off-road crashes are likely to 

occur. Table 4-12 shows a list of 

potential safety strategies that could 

be implemented for engineering 

treatments for a run-off-road crash 

problem. In a systemic approach, 

these engineering treatments would 

be implemented across some or all 

roads meeting the risk factors that 

increase the likelihood of run-offroad crashes.

Example of system-level 

safety strategies in 

state highway safety plans

SHSPs provide many good examples 

of system-level strategies that 

address safety problems identified 

through analysis of crash and other 

safety data. The previous section 

showed how Ohio and Florida 

had identified safety priorities on 

older drivers and motorcyclists, 

respectively. The SHSPs from these 

States also demonstrated the types 

of safety strategies each State 

intended to pursue to combat the 

safety problems in these areas.

Selecting and 

implementing strategies

A transportation agency must 

determine which of the potential 

strategies they will implement 

to address the identified safety 

problems. Since system-level safety 

solutions can involve broad changes 

to policies, design practices, or 

jurisdiction-wide road user behavior, 

there are different issues to consider 

compared to implementing a 

safety countermeasure at a specific 

Florida’s strategies for 

motorcyclist safety

After identifying motorcyclist safety as 

an emphasis area in their 2012 SHSP, 

Florida identified a list of strategies to 

address motorcyclist safety. Example 

strategies include:

J Promote personal protective 

gear and its value in reducing 

motorcyclist injury levels and 

increasing rider conspicuity

J Promote adequate rider training 

and preparation to new and 

experienced motorcycle riders 

by qualified instructors at Stateapproved training centers

J Incorporate motorcycle-friendly 

policies and practices into roadway 

design, traffic control, construction, 

operation, and maintenance

J Develop and implement 

communications strategies that 

target high-risk populations and 

improve public awareness of 

motorcycle crash problems and 

programs.
4-48 UNIT 4: SOLVING SAFETY PROBLEMS ROAD SAFETY FUNDAMENTALS

OBJECTIVES COUNTERMEASUR

RELATIVE

COST TO 

IMPLEMENT 

AND OPERA

EFFECTIVE- NESS

15.1 A: KEEP

VEHICLES 

FROM 

ENCROACHING

ON THE 

ROADSID

15.1A1: Install shoulder 

rumble strips Low Tried

15.1 A2: Install edgelines 

“profile marking”, edgeline 

rumble strips or modified 

shoulder rumble strips on 

section with narrow or no 

paved shoulders

Low Experimental

15.1 A5: Provide improved 

highway geometry for 

horizontal curves

High Proven

15.1 A6: Provide enhanced 

pavement markings Low Tried

15.1 A7: Provide skidresistance pavement surfaces Moderate Proven

15.1 B:

MINIMIZE THE 

LIKELIHOOD 

OF CRASHIN

INTO AN

OBJECT OR

OVERTURNING 

IF THE VEHICLE 

TRAVELS OFF

THE SHOULDER

15.1 B1: Design safer slopes 

and ditches to prevent 

rollovers

Moderate Proven

15.1 B2: Remove/relocate 

objects in hazardous locations

Moderate 

to High Proven

15.1 C: REDUCE 

THE SEVERITY 

OF THE CRAS

15.1 C1: Improve design of 

roadside hardware

Moderate 

to High Tried

15.1 C2: Improve design and 

application of barrier and 

attenuation systems

Moderate 

to High Tried

TABLE 4-12. Potential Safety Strategies for Run-Off-Road Crashes (Source: NCHRP 500, Volume 6)
ROAD SAFETY FUNDAMENTALS UNIT 

4: SOLVING SAFETY PROBLEMS

4-49

location. Many more people will 

be affected by the system-level 

changes. This carries great promise 

in that safety might be improved 

across an entire system, but it also 

carries unique challenges.

Agencies will need to consider the 

following questions when selecting 

strategies to implement: J Safety effectiveness – How 

likely will it address the safety 

problem?

J Public acceptance – How will 

the strategy be accepted by the 

public? What kind of marketing 

will be needed to communicate 

the intent and benefit of the 

strategy?

J Stakeholders and partners – 

Which parties will need to be 

involved in implementing the 

strategy?

J Cost efficiency – What kind of 

return on the dollar would be 

expected?

J Time – How long will it take to 

implement the strategy?

Communication is critically 

important for system-level safety 

strategies. Both the general public 

and road users affected by the 

strategy must understand the 

benefits. Other public agencies 

may need to integrate their efforts 

with the proposed safety strategy. 

Administrators, lawmakers, 

and other key decision-making 

personnel must understand how 

the strategy will improve road 

safety for their constituency and 

bring an overall financial benefit. 

Unit 5 provides more discussion on 

communication, marketing, and 

outreach for agencies who seek to 

implement system-level safety 

strategies.

Evaluating a system-level strategy 

(e.g., program or intervention) to 

determine its effectiveness is a 

critical but often overlooked step. 

The transportation agency in charge 

should evaluate the effect of the 

safety strategy using good quality 

data; ideally the same type of data 

that was used to identify the safety 

problem initially. If a program or 

intervention is not effective, the 

overseeing agency should consider 

why this might be the case. Can the 

program be improved, or should 

other approaches be considered 

instead? If successful, how can the 

intervention be institutionalized 

to ensure long term support (and 

therefore lasting change)? Finally, 

it is important to remember that 

success or failure in one location 

does not guarantee the same results 

at a different location.

Ohio’s strategies for 

older driver safety

Ohio identified three strategies to 

address the older driver emphasis area 

in their 2014 SHSP: J Coordinate older driver messages 

developed by multi-agency 

communication committee.

J Create a comprehensive and 

coordinated outreach effort that 

educates older drivers and their 

caregivers on driving risks and 

remedies.

J Encourage roadway design and 

engineering measures that reduce 

the risks of traffic crashes for older 

drivers.
4-50 UNIT 4: SOLVING SAFETY PROBLEMS ROAD SAFETY FUNDAMENTALS

Example of System-Level 

Safety Management

The following provides an 

example of using system-level 

safety management to address a 

specific problem. This example 

demonstrates the three general 

components of safety management 

presented in this unit.

1. Identify the safety problem.

County A noticed a large number 

of crashes involving 16-17 year old 

drivers occurring weekdays between 

11:00am and 1:00pm. Neighboring 

counties have not experienced this 

problem. County officials coordinate 

with school district staff to tackle 

this issue.

In exploring the problem, the 

officials discover that County A is 

the only jurisdiction that has an 

open campus lunch policy allowing 

students to leave school during 

their lunch period. Allowing teens 

to leave campus during lunch 

means there are many young, 

inexperienced drivers on the roads at 

the same time. They may be carrying 

additional passengers which 

research has established leads to 

an increased risk of a fatal crash.60,61 

The brief lunch period also results in 

pressure to get back in time for the 

next class. Combined, these factors 

lead to a risky driving situation and 

an increased risk of crashing.

2. Develop potential safety strategies.

In this situation, an informational 

approach that simply tells teenagers 

about the problem would likely 

not make a difference. Teens are 

not crashing because they lack 

information about the importance of 

safe driving or the consequences of 

unsafe driving. Teens are crashing 

largely because they lack the driving 

experience that equips most drivers 

to intuitively/near instantaneously 

do the things necessary to avoid 

crashing. Because of this, changing 

the environment is more likely 

to be effective. 

The officials recognize that 

eliminating the policy that allows 

students to leave campus during 

lunch would lead to a reduction in 

crashes during this time. This policy 

would eliminate exposure to the 

risky driving situation and reduce 

the potential for crashes.

3. Select and implement strategies.

The school districts accordingly 

eliminate the policy allowing 

students to leave campus during 

lunch. They recognize that this 

policy change should be evaluated 

to determine its safety effect. Crash 

data would be needed to examine 

whether the closed school lunch 

policy has an effect on weekday 

crashes between 11:00am and 

1:00pm. However, it will take many 

years to accumulate enough data 

for this evaluation. In this example, 

there is a proxy measure that can 

be used in the interim. A before and 

after observational survey with an 

appropriate control could quantify 

the number of students leaving 

campus during lunch before and 

after the change. In this case the 

officials know that the proxy measure 

(reduced driving from 11:00am to 1:00 

pm) is a guaranteed indicator of crash 

reduction for this specific problem. 

However, it is not often the case that 

proxy measures are so closely aligned 

to the outcome of interest.

Chen, L., Baker, S.P., 

Braver, E.R., & Li, 

G. (2000). Carrying 

Passengers as a Risk 

Factor for Crashes 

Fatal to 16- and 

17-Year-Old Drivers. 

Journal of the 

American Medical 

Association, 283, 

1578-1582.

61

Tefft B.C., Williams 

A.F., & Grabowski 

J.G. (2013). Teen 

driver risk in relation 

to age and number 

of passengers, 

United States, 

2007-2010. Traffic 

Injury Prevention, 

14, 283-292.

60
ROAD SAFETY FUNDAMENTALS UNIT 

4: SOLVING SAFETY PROBLEMS

4-51

Unit Summary

Solving road safety problems 

requires a comprehensive process 

to identify safety problems, 

develop potential safety strategies, 

and select and implement those 

strategies. To get the most effective 

results, this process must be based 

on solid safety data, particularly 

good quality crash data. The 

methods of undertaking the safety 

management process will depend on 

the scope of the effort. 

Safety management of individual 

sites involves a six-step process of 

screening the network for highpriority sites, diagnosing the safety 

issues at those sites, selecting 

appropriate countermeasures, 

conducting an economic appraisal 

for all options, prioritizing the 

countermeasure projects based on 

estimated costs and benefits, and 

evaluating the countermeasure 

performance afterwards. Safety 

management at a system-level 

involves identifying safety problems 

by examining crash trends or using 

a systemic approach to identifying 

high-risk road characteristics. 

State agencies who are developing 

system-wide safety strategies 

must examine the data trends 

and the road users involved. They 

must consider factors, such as how 

system-wide policies and programs 

will be accepted by the public and 

who will be the partners to involve 

in implementing the safety strategy.
4-52 UNIT 4: SOLVING SAFETY PROBLEMS ROAD SAFETY FUNDAMENTALS

J PRESENT an example road safety 

problem and compare and contrast the 

ways in which the problem could be 

addressed at a system-level vs. site-level.

J Your state has a small, rural, 

mountainous county where a large 

number of motorcycle crashes are 

happening. The crash rate per registered 

motorcycle in this county is nearly 10 

times the state average. Upon further 

investigation you learn that this county 

is a popular motorcycling tourist 

destination. People come from all over 

the country to ride the curvy mountain 

roads. In fact, the majority of people 

involved in crashes are not from that 

area at all. Clusters of crashes occur 

on certain curves. What are some 

approaches that could be used to reduce 

crashes in this county? How could these 

approaches be evaluated? In particular, 

DETAIL how you would apply the three 

major components described in this 

unit:

J Identify the safety problem

J Develop potential safety strategies

J Selecting and implement strategies

When you work through this process, 

recall the discussion of human behavior 

from Unit 2. What are possible behaviors 

leading to the safety problem? What 

other factors could be influencing this 

behavior? How does this affect your 

identification and selection of potential 

safety strategies?

J If possible, OBTAIN three to five years of 

crash data for an intersection or section 

of road in your area. You will likely need 

to contact the controlling agency – the 

State DOT, county, or city. Describe how 

you would apply the steps in Chapter 

11 on site-level safety management to 

this location (the network screening 

step would not apply since this location 

is already identified). Consider safety 

strategies across a range of disciplines 

(e.g., engineering, law enforcement, 

public communication and education, 

etc.).

J This exercise should be conducting 

using the Excel spreadsheet that 

accompanies this book. The goal of this 

exercise is to USE selected performance 

metrics to create a ranked list of sites 

for further investigation as part of a 

network screening effort. The Excel 

spreadsheet includes nearly 1,400 

intersections, or sites. Each site has a 

unique ID number, traffic volume data, 

and other information about its location 

and characteristics. Three performance 

metrics have been calculated for each 

site. These have been calculated using 

five years of data (2010-2014) and one 

year of data (2014), resulting in a total of 

six performance metrics per site. Your 

assignment is to rank the sites using 

these various performance metrics and 

document the results. Document the 

twenty highest priority sites based on 

each method. Use the results to answer 

the following questions:

J What were some of the sites 

that routinely ranked in the top 

twenty? What were some of their 

characteristics (volumes, number of 

lanes, stop/signal control)?

J Were there any sites that were 

only occasionally present in the 

top twenty? What were some 

characteristics of these sites?

EXERCISES
ROAD SAFETY FUNDAMENTALS UNIT 4: SOLVING SAFETY PROBLEMS 4-53

THIS PAGE INTENTIONALLY LEFT BLANK
5-b UNIT 5: IMPLEMENTING ROAD SAFETY EFFORTS ROAD SAFETY FUNDAMENTALS

After reading the chapters and completing 

exercises in Unit 5, the reader will be able to:

J IDENTIFY the current road safety 

partner agencies and define their role 

in addressing safety problems

J DEFINE three areas of 

road safety research

J DEFINE the characteristics of 

strategic communications

J RECOGNIZE potential avenues for 

advancing road safety efforts

LEARNING OBJECTIVES

Implementing 

Road Safety 

Efforts

UNIT 5
ROAD SAFETY FUNDAMENTALS UNIT 5: IMPLEMENTING ROAD SAFETY EFFORTS 5-1

Who Does What

The greatest gains in road safety 

occur when transportation agencies 

work together rather than tackling 

problems alone. This can be 

challenging given the fragmented 

nature of transportation governance 

in the U.S. There are numerous 

agencies operating in different focus 

areas and at different levels. This 

chapter presents an overview of the 

various agencies and organizations 

that have a direct hand in advancing 

road safety and the initiatives that 

they undertake.

U.S. transportation agencies are 

typically structured around particular 

focus areas, such as roadway, 

vehicles, or road users. This 

approach is also seen on the 

international scale – the United 

Nations (U.N.) used a generalization 

called the “Five Pillar” structure as 

part of the Decade of Action for Road 

Safety. 1

 The U.N. recognized that 

efforts to improve road safety must 

address various pillars including 

road safety 

management, safer roads and mobility, 

safer vehicles, safer road users, and 

better post-crash response. 2

Likewise, U.S. transportation 

agencies are organized to address 

focus areas that are similar in theme 

to the U.N. five pillars, though not 

the same. Table 5-1 shows how 

agencies at all levels (Federal, State, 

and local) address five focus areas in 

road safety.

CHAPTER 13 IMPLEMENTING ROAD SAFETY EFFORTS

United Nations, 

A/RES/64/255, 

Geneva, 2010

Global Status 

Report on Road 

Safety 2013: 

Supporting a 

Decade of Action, 

World Health 

Organization, ISBN 

978 92 4 156456 4, 

2013.

1

2

TABLE 5-1: Transportation Agencies by Focus Area

FOCUS AREA FEDERAL STATE 

Road Design / 

Environment

Federal Highway 

Administration

Departments of 

transportation

City public works

Metropolitan/rural 

planning organizations

Road User 

Behavio

National Highway 

Traffic Safety 

Administration

Federal Motor 

Carrier Safety 

Administration

Highway safety offices

Departments of 

motor vehicles

Health departments

No specific agency

Vehicle Design /

Technology

Departments of 

motor vehicles No specific agency

Law Enforcement No specific agency State police / 

highway patrol Police departments

Transit Safety Federal Transit 

Administration No specific agency

Metropolitan planning 

organizations

Municipal transit agencies
5-2 UNIT 5: IMPLEMENTING ROAD SAFETY EFFORTS ROAD SAFETY FUNDAMENTALS

Federal Agencies

The Federal role in implementing 

road safety initiative is carried out 

largely through the U.S. Department 

of Transportation (USDOT) and the 

many agencies under that department. 

These agencies are each tasked with 

a specific focus area as the Federal 

Government seeks to address safety 

issues for various modes of travel. 

These agencies include:

J Federal Highway Administration

J National Highway Traffic Safety 

Administration

J Federal Motor Carrier Safety 

Administration

J Federal Transit Administration

J Federal Railroad Administration

Federal Highway 

Administration 

www.fhwa.dot.gov

Focus Area: Road Design 

and Environment

The Federal Highway Administration 

(FHWA) works to reduce highway 

fatalities through partnerships with 

State and local agencies, community 

groups, and private industry. The 

FHWA Office of Safety advocates 

designs and technologies that improve 

road safety and administers safety 

programs, such as the Highway 

Safety Improvement Program (HSIP). 

FHWA’s Resource Center also provides 

technical assistance, technology 

deployment, and training. FHWA has 

a significant role in safety research 

through the Office of Safety Research 

and Development, which develops 

and implements safety innovations 

through teams of research engineers, 

scientists, and psychologists. 

In addition, FHWA oversees 

the Local and Tribal Technical 

Assistance Program (LTAP/TTAP), 

which provides information and 

training programs to local agencies 

and Native American Indian tribes 

to improve road safety.3

 Further, 

FHWA maintains division offices in 

each state to deliver assistance to 

partners and customers in highway 

transportation and safety services at 

the State level.

National Highway Traffic 

Safety Administration 

www.nhtsa.gov

Focus Areas: Road User Behavior 

and Vehicle Design and Technology

The National Highway Traffic 

Safety Administration (NHTSA) 

focuses on the safety of the vehicle, 

driver, and road user. NHTSA 

investigates safety defects in motor 

vehicles, establishes and enforces 

safety performance standards for 

motor vehicles and motor vehicle 

equipment, sets and enforces fuel 

economy standards, collects data, 

and conducts research on driver 

behavior and traffic safety, and 

helps states and local communities 

reduce the threat of impaired 

driving and other dangerous 

road user behaviors. 

NHTSA carries out research and 

demonstration programs in many 

behavioral areas including impaired 

driving, occupant protection, speed 

management (shared with FHWA), 

pedestrian, motorcycle and bicycle 

safety, older and younger road users, 

drowsy, and distracted driving. 

NHTSA is also the lead Federal 

agency for emergency medical 

services (EMS) and 9-1-1 systems.

“About the National 

Program,” last 

updated June 20, 

2013, accessed June 

20, 2013, http://

www.ltap.org/about/.

“Who We Are and 

What We Do,” 

accessed June 20, 

2013, https://www.

nhtsa.gov/aboutnhtsa. 

3

4
ROAD SAFETY FUNDAMENTALS UNIT 5: IMPLEMENTING ROAD SAFETY EFFORTS 5-3

Federal Motor Carrier 

Safety Administration 

www.fmcsa.dot.gov

Focus Areas: Road User Behavior 

and Vehicle Design and Technology

The Federal Motor Carrier Safety 

Administration (FMCSA) focuses 

on reducing crashes, injuries, and 

fatalities involving commercial use 

of large trucks and buses. FMCSA 

develops and enforces researchbased regulations that balance 

safety and efficiency. The agency 

manages safety information systems 

to enforce safety regulations with 

regards to drivers who have high 

risk in factors, such as health, age, 

experience, and education. 

FMCSA also targets educational 

messages to carriers, commercial 

drivers, and the public.5

 Some key 

programs administered by the 

agency include:

J Commercial Driver’s License 

Program: FMCSA develops, 

monitors, and ensures 

compliance with the commercial 

driving licensing standards for 

drivers, carriers, and States.

J Motor Carrier Safety Identification 

and Information Systems: FMCSA 

provides safety data, State 

and national crash statistics, 

current analysis results, and 

detailed motor carrier safety 

performance data to industry 

and the public. This data allows 

Federal and State enforcement 

officials to target inspections 

and investigations on higher risk 

carriers, vehicles, and drivers.

J Safety education and outreach:

FMCSA implements educational 

strategies to increase motor 

carrier compliance with the 

safety regulations and reduce 

the likelihood of a commercial 

vehicle crash. Messages are 

aimed at all highway users 

including passenger car drivers, 

truck drivers, pedestrians, 

and bicyclists.6

The Federal Motor Carrier Safety Administration develops, monitors, and ensures 

compliance with commercial driving licensing standards.

“About FMCSA,” 

accessed June 20, 

2013, https://www.

fmcsa.dot.gov/

mission/about-us.

“Key FMCSA 

Programs,” 

accessed October 

15, 2013, https://

www.fmcsa.dot.gov/

mission/we-arefmcsa-brochure.

5

6
5-4 UNIT 5: IMPLEMENTING ROAD SAFETY EFFORTS ROAD SAFETY FUNDAMENTALS

Federal Transit Administration 

www.transit.dot.gov

Focus Area: Transit Safety

The Federal Transit Administration 

(FTA) seeks to improve public 

transportation by assisting State and 

local governments with planning, 

implementation, and financing of 

public transportation projects.7

 FTA 

manages many transit-oriented 

safety programs including:

J Bus and Bus Facilities: This 

program provides capital funding 

to replace, rehabilitate, and 

purchase buses and related 

equipment and to construct busrelated facilities.

J Public Transportation Emergency 

Relief Program: This program 

helps States and public 

transportation systems pay 

for protecting, repairing, and/

or replacing equipment and 

facilities that may suffer or have 

suffered serious damage because 

of an emergency including 

natural disasters.

J Research, Development, 

Demonstration, and Deployment 

Projects: This program supports 

research activities that improve 

the safety, reliability, efficiency, 

and sustainability of public 

transportation.

J Transit Safety and Oversight: FTA 

has the authority to establish and 

enforce a new comprehensive 

framework to oversee the 

safety of public transportation 

throughout the United States 

as it pertains to heavy rail, 

light rail, buses, ferries, and 

streetcars.8

The Federal Transit Administration seeks to improve public transportation, such as buses.

“Federal Transit 

Administration,” 

last updated 

September 6, 

2013, https://

www.usa.gov/

federal-agencies/

federal-transitadministration.

“MAP-21 Programs,” 

accessed October 

16, 2013, https://

www.transit.dot.

gov/regulationsand-guidance/

legislation/map-21/

map-21-programfact-sheets.

7

8
ROAD SAFETY FUNDAMENTALS UNIT 5: IMPLEMENTING ROAD SAFETY EFFORTS 5-5

Federal Safety Programs

Federal agencies advance road 

safety through numerous programs 

and initiatives. Federal programs 

can be very influential due to large 

funding sources provided by Federal 

legislation. These funds are often 

distributed to State and local levels 

to implement various improvements 

to roads and intersections. 

Specific funding programs can 

change with each new piece of 

transportation legislation. However, 

it may be useful to look at an 

overview of some of the types of 

current and past funding programs. 

Below are listed a few programs 

that have been widely used through 

the years to develop and implement 

improvements to road safety:

J Highway Safety Improvement 

Program (FHWA)

J Traffic Records Improvement 

Grants (NHTSA)

J Safety Data Improvement Program 

Grant (FMCSA)

Highway Safety Improvement 

Program (FHWA)

HSIP is a Federal program focused 

on infrastructure improvements that 

will lead to significant reduction in 

traffic fatalities and serious injuries 

on all public roads. HSIP is Federally 

funded and administered by FHWA, 

but it is implemented by the State 

departments of transportation 

per the strategies laid out in the 

State’s Strategic Highway Safety 

Plan (SHSP). Funding is provided 

for safety-related infrastructure 

improvements, such as sidewalks, 

traffic calming, or signing upgrades. 

The States are required to develop 

a data-driven, strategic approach 

for improving highway safety 

through the implementation of 

such infrastructure improvements.9

States are also required to report to 

the U.S. Secretary of Transportation 

on progress made implementing 

highway safety improvements and 

the extent to which fatalities and 

serious injuries on all public roads 

have been reduced. 

Traffic Records Improvement 

Grants (NHTSA)

NHTSA administers Federal funding 

to encourage States to implement 

programs that will improve the 

timeliness, accuracy, completeness, 

uniformity, integration, and 

accessibility of State data used in 

traffic safety programs. The Federal 

SAFETEA-LU legislation established 

this program of incentive grants, 

and the funding continued under 

subsequent legislation. The funds 

were to be used to evaluate the 

effectiveness of efforts to make 

safety data improvements, to link 

safety data systems within the State, 

and to improve the compatibility 

of the State data system with 

national data systems and data 

systems of other States. A State 

may use these grant funds only to 

implement such data improvement 

programs. To qualify, a State must 

meet certain requirements including 

a functioning Traffic Records 

Coordinating Committee (TRCC), 

a strategic plan to address data 

deficiencies, and a regular traffic 

records assessment.10

Safety Data Improvement 

Program Grant (FMCSA)

The Safety Data Improvement 

Program (SaDIP), administered 

by FMCSA, provides financial and 

Data-driven

An approach 

of which the 

priorities are 

determined by 

examination of 

crash data or 

other objective 

and reliable 

safety data, 

rather than 

priorities set by 

preferences of 

a few parties, 

current “hot” 

topics, or high 

profile rare 

events.

Source: “Highway 

Safety Improvement 

Program (HSIP),” 

accessed August 12, 

2013, http://safety.

fhwa.dot.gov/hsip/ 

and “HSIP History,” 

accessed August 

12, 2013, http://

safety.fhwa.dot.

gov/hsip/gen_info/

hsip_history.cfm.

NHTSA, Section 

408 SAFETEA-LU 

Fact Sheet, 

https://one.

nhtsa.gov/Laws-

&-Regulations/

Section-408-

SAFETEA%

E2%80%93

LU-Fact-Sheet

9

10
5-6 UNIT 5: IMPLEMENTING ROAD SAFETY EFFORTS ROAD SAFETY FUNDAMENTALS

technical assistance to States to 

improve data collected on truck 

and bus crashes that result in 

injuries or fatalities. The assistance 

is provided to State departments 

of public safety, departments 

of transportation, or State law 

enforcement agencies. SaDIP funds 

have been used to hire staff to code 

safety performance data, purchase 

software for field data collection, 

and revise outdated crash forms.

FMCSA maintains the Motor Carrier 

Management Information System 

(MCMIS) and supplies access to the 

system for designated employees in 

each State through SAFETYNET, an 

online network of safety data. States 

use MCMIS and SAFETYNET to enter 

data on motor carriers, drivers, 

compliance reviews, inspections, 

and crashes. At the national level, 

FMCSA uses the data to characterize 

the safety experience of commercial 

motor vehicles, and to help States 

with the task of identifying high 

risk carriers and drivers. The data 

are also used by motor carrier 

companies, safety researchers, 

advocacy groups, insurance 

companies, the public, and a variety 

of other entities.

State Agencies

All fifty States, the District 

of Columbia, and Puerto Rico 

administer road safety programs. 

State agencies administer roadway 

systems, driver licensing, injury 

prevention programs, traffic law 

enforcement, and other road safety 

activities. However, assignment of 

these responsibilities varies widely 

from State to State. In many cases, 

two or three government agencies 

are responsible for most or all 

of these activities. Other States 

distribute these responsibilities 

to numerous agencies and 

offices. Regardless of how these 

responsibilities are distributed, 

States share a vital role in improving 

road safety for all citizens.

In general, State agencies that 

address road safety issues include:

J State departments 

of transportation

J State highway safety offices

J State departments 

of motor vehicles

J State highway patrols

J State health departments

State 

departments of 

transportation 

oversee design, 

construction, 

maintenance, 

and operation 

of roads.
ROAD SAFETY FUNDAMENTALS UNIT 5: IMPLEMENTING ROAD SAFETY EFFORTS 5-7

State Departments 

of Transportation

Focus Area: Road Design 

and Environment

Each State has a department of 

transportation (DOT), which 

oversees the design, construction, 

maintenance, and operation of the 

State’s roads. This agency may 

also be called the State Highway 

Administration or Department 

of Roads. State DOTs have many 

official responsibilities. For highway 

safety issues, State DOTs have 

official transportation planning, 

programming, and project 

implementation responsibility. 

These agencies typically oversee 

all Interstate highways and most 

primary highways (State highways). 

State DOTs focus on roadway 

safety, and thus work in direct 

partnership with FHWA. They serve 

as liaisons between the Federal and 

local transportation agencies and 

provide resources and technical 

assistance to local agencies. State 

DOTs coordinate the use of Federal 

HSIP funds to improve roads and 

intersections on the local level.

In some States, the DOT 

administers, maintains, and 

operates county and city streets or 

secondary roads. State DOTs also 

work cooperatively with tolling 

authorities, ports, local agencies, 

and special districts that own, 

operate, or maintain portions of the 

transportation network.

The State DOT typically leads 

the development of the SHSP, a 

statewide-coordinated safety plan 

that provides a comprehensive 

framework for reducing highway 

fatalities and serious injuries on 

all public roads. The State DOT 

also develops long-range (20 to 

30 year) transportation plans 

and short range (five to 10 year) 

plans that outline the vision of the 

transportation network and which 

projects will be constructed to fulfill 

that vision. 

State Highway Safety Offices

Focus Area: Road User Behavior

State Highway Safety Offices 

(SHSOs) administer a variety of 

national highway safety grant 

programs authorized and funded 

through Federal legislation.11 The 

governor of each State appoints a 

highway safety representative to 

administer the Federal Highway 

Safety Grant Program and numerous 

other highway safety programs 

designated by Congress. The 

governor’s representative promotes 

safety initiatives in the State, such 

as high visibility enforcement 

campaigns like Click It or Ticket. 

The State Highway Safety Office 

focuses on behavioral aspects of 

roadway users, and thus works in 

direct partnership with NHTSA. 

Safety programs implemented by 

the SHSO include:

J Encouraging safety belt, child car 

seat, and helmet use

J Discouraging impaired driving

J Promoting motorcycle safety

J Improving the skills of younger 

and older drivers

State Departments 

of Motor Vehicles

Focus Area: Vehicle Design 

and Technology

State Departments of Motor Vehicles 

“SHSO Programs & 

Funding,” accessed 

June 20, 2013, 

http://www.ghsa.

org/about/federalgrant-programs.

11
5-8 UNIT 5: IMPLEMENTING ROAD SAFETY EFFORTS ROAD SAFETY FUNDAMENTALS

(DMVs) administer State programs 

for driver licensing, and automobile 

inspection and registration. 

Generally, DMVs reside either within 

the State DOT or a department of 

public safety. A few States have a 

cabinet-level DMV. 

The DMV is responsible for 

identifying at-risk drivers and 

maintaining driver records. The 

agency also implements driver 

license standards, monitors 

graduated licensing programs, and 

establishes requirements for driver 

education. Some State DMVs also 

serve as the primary owners of the 

statewide crash data.

State Highway Patrols

Focus Area: Law Enforcement

State highway patrols (also known 

as State police and State patrols) 

operate in every State except Hawaii. 

State police patrol highways and 

enforce motor vehicle laws 

and regulations. 

State law enforcement agencies play 

an important role in reducing the 

frequency and severity of crashes. 

At the scene of crashes, State police 

direct traffic, administer first aid, 

call for emergency equipment, 

write traffic citations, and 

complete crash reports. 

State highway patrols also 

investigate motor vehicle crashes, 

which are important sources of 

State and Federal crash data. They 

work closely with State highway 

safety representatives to identify 

enforcement needs. They play a 

vital role in implementing impaired 

driving laws, safety belt use, and 

other safety programs. Certain 

troopers in the State highway 

patrol are tasked with inspecting 

large trucks to ensure the driver 

and the vehicle comply with safety 

regulations, such as vehicle size and 

weight, driver hours of service, and 

medical fitness.

State Health Departments

Focus Area: Road User Behavior

State health departments also 

play an important role in reducing 

crash severity. These agencies 

are typically responsible for 

statewide trauma center planning. 

State health departments provide 

training, certification, and technical 

assistance for EMS providers, 

administer injury prevention 

programs, and maintain trauma and 

injury databases. Some State health 

departments coordinate with other 

public agencies and community 

groups to promote young driver 

safety, older driver safety, child 

passenger safety, and pedestrian 

and bicycle safety.

State highway 

patrols enforce 

motor vehicle laws 

and regulations, 

investigate 

crashes, and 

work to identify 

enforcement 

needs.

Comprehensive

Using all types 

of strategies to 

improve road 

safety, such as 

infrastructure 

improvements, 

law enforcement,

and campaigns 

to change 

driver behavior. 

This is seen in 

the types of 

crashes which 

serve as the 

focus areas of 

an SHSP, such 

as speeding 

related crashes, 

which are most 

effectively 

addressed 

through a 

combination 

of speed 

enforcement, 

engineering 

modifications, 

and behavioral 

campaigns.

Coordinated

People from 

many agencies 

come together 

to develop an 

SHSP, including 

those from the 

department of 

transportation, 

department 

of motor 

vehicles, state 

highway patrol, 

public health, 

universities, 

and others.
ROAD SAFETY FUNDAMENTALS UNIT 5: IMPLEMENTING ROAD SAFETY EFFORTS 5-9

State Safety Plans 

and Programs

State agencies use numerous 

approaches to improve road safety 

within their State. Often, they seek 

to identify State-specific safety 

issues and direct Federal or State 

funding to solve those issues. State 

agencies take the lead in developing 

statewide safety plans or programs, 

many of which are encouraged or 

required by the Federal Government. 

Although States differ in their 

specific safety improvement efforts, 

the following plans or programs are 

developed in every State:

J Strategic Highway Safety Plan

J Long Range Transportation Plan

J Statewide Transportation 

Improvement Program

J Railway-Highway 

Crossing Program

J Highway Safety Program

Although the HSIP was previously 

covered under Federal safety 

programs, it should be noted that 

the State plays the major role 

in selecting locations that need 

safety improvement, designing, 

and implementing the safety 

improvement, and reporting annually 

on all the HSIP funded projects that 

were constructed that year. 

Strategic Highway Safety Plan

A State’s SHSP is a statewidecoordinated safety plan that provides 

a comprehensive framework for 

reducing highway fatalities and 

serious injuries on all public roads. 

An SHSP identifies a State’s key 

safety needs and guides investment 

decisions toward strategies with the 

highest potential to save lives and 

prevent injuries. Since 2005, Federal 

legislation has required States to 

develop, implement,evaluate, and 

update their SHSP.12,13

The State DOT develops an SHSP 

in a cooperative process with local, 

State, Federal, tribal, and private 

sector safety stakeholders. It is 

a data-driven, multi-year plan 

that establishes statewide goals, 

objectives, and key emphasis 

areas. The development of an SHSP 

provides a venue for highway safety 

partners in the State to align goals, 

leverage resources (i.e., combine 

Federal and State resources), and 

collectively address the State’s 

safety challenges.14

An ideal SHSP meets several criteria:

J It addresses engineering, 

management, operation, 

education, enforcement, and 

emergency service elements of 

highway safety as key factors in 

evaluating highway projects.

J It considers safety needs of, and 

high-fatality segments of, all 

public roads.

J It considers the results of 

State, regional, or local 

transportation and highway 

safety planning processes.

J It describes strategies to reduce 

or eliminate safety hazards.

J It gains approval of the governor 

of the State or a responsible 

State agency.15

As mentioned on page 5-5, in order 

to spend HSIP funds, a State must 

have a current SHSP, produce a 

program of projects or strategies to 

reduce safety problems, and evaluate 

the SHSP on a regular basis.16 

Coordinated, 

Comprehensive

See previous 

page.

“Strategic Highway 

Safety Plans: 

A Champion’s 

Guidebook to Saving 

Lives 2nd ed.,” 

Federal Highway 

Administration 

(Washington, 

D.C., October 

2012), History and 

Background, http://

safety.fhwa.dot.

gov/hsip/shsp/

guidebook/ovrvw.

cfm

“Map-21,” Title 

23 U.S.C. (2012), 

accessed August 19, 

2013, http://www.

gpo.gov/fdsys/pkg/

PLAW-112publ141/

pdf/PLAW112publ141.pdf

“Highway Safety 

Improvement Plan 

(HSIP),” accessed 

August 14, 2013, 

http://www.fhwa.

dot.gov/map21/hsip.

cfm.

“Strategic Highway 

Safety Plan (SHSP),” 

accessed August 13, 

2013, http://safety.

fhwa.dot.gov/hsip/

shsp/.

12

15

16

13 14
5-10 UNIT 5: IMPLEMENTING ROAD SAFETY EFFORTS ROAD SAFETY FUNDAMENTALS

Long-Range 

Transportation Plans

Long-range transportation plans 

(LRTPs) identify transportation 

goals, objectives, needs, and 

performance measures over a 20- to 

25-year horizon and provide policy 

and strategy recommendations 

for accommodating those needs. 

LRTPs are prepared at both the 

State and MPO level. LRTPs are 

fiscally-unconstrained and typically 

present a systems-level approach 

that considers roadways, transit, 

pedestrian, and bicycle facilities. 

LRTP’s have wide scopes; the 

components of the plan may be 

policy-oriented and strategic or 

focused on specific projects. The 

types of improvements range 

widely, as well. Safety-focused 

improvements in a LRTP may be 

directed at infrastructure, such 

as building new interchanges 

or bringing certain highways 

up to current design standards, 

or behavioral efforts, such as 

addressing seat belt use or 

aggressive driving.

Statewide Transportation 

Improvement Programs

The Statewide Transportation 

Improvement Program (STIP) 

identifies the funding and 

scheduling of transportation 

projects throughout the State that 

support the goals identified in 

the LRTP. STIPs are short-range 

(typically an outlook of five to ten 

years) and fiscally constrained, 

meaning that the projects must have 

designated funding. While many 

STIP projects are constructed for 

capacity or mobility reasons (i.e., 

build a bypass or widen a road), 

there are also STIP projects that are 

focused on improving safety, such 

as widening shoulders or installing 

rumble strips. Projects included in 

STIPs must have identified funding 

sources (e.g., HSIP, State, or local 

funding). The State DOT identifies 

projects in areas outside MPOs, 

such as rural areas and smaller 

urban jurisdictions, for inclusion 

in the STIP.17

Railway-Highway 

Crossings Program

The Railway-Highway Crossings 

Program funds safety improvements 

to reduce the number of fatalities, 

injuries, and crashes at public grade 

crossings.18 A grade crossing is a 

location where a public highway, 

road, street, or private roadway 

(including associated sidewalks and 

pathways) crosses a railroad track at 

the same level as the street. These 

locations are high-risk spots for 

road users. The United States has 

more than 200,000 grade crossings.19 

Types of crossing improvements 

that the Railway-Highway Crossings 

Program implements include:

J Crossing approach improvements:

projects such as channelization, 

new or upgraded signals on the 

approach, guardrail, pedestrian/

bicycle path improvements near 

the crossing, and illumination

J Crossing warning sign and 

pavement marking Improvements:

projects such as signs, 

pavement markings, and/or 

delineation where these project 

activities are the predominant 

safety improvements

J Active grade crossing equipment 

installation/upgrade: projects 

such as new or upgraded flashing 

lights and gates, track circuitry, 

“Railway-Highway 

Crossings Program,” 

accessed August 

9, 2013, http://

www.fhwa.dot.gov/

map21/rhc.cfm.

Title 49, United 

States Code, § 5304

Railroad-Highway 

Grade Crossing 

Handbook 2nd ed. 

Federal Highway 

Administration 

(Washington D.C., 

August 2007)

18

17

19
ROAD SAFETY FUNDAMENTALS UNIT 5: IMPLEMENTING ROAD SAFETY EFFORTS 5-11

wayside horns, and signal 

improvements such as railwayhighway signal interconnection 

and pre-emption.20

Highway Safety Program

Each State administers a Highway 

Safety Program, approved by the 

U.S. Secretary of Transportation. 

The program is designed to reduce 

deaths and injuries on the road by 

targeting user behavior through 

education and enforcement 

campaigns.21 The State conducts 

this program through the State 

highway safety office. A State is 

eligible for SHSP grants by having 

and implementing an approved 

Highway Safety Plan (HSP). The 

HSP establishes goals, performance 

measures, targets, strategies, and 

projects to improve highway safety 

in the State. It also documents the 

State’s efforts to coordinate with 

the goals and strategies in the 

SHSP. However, the Highway Safety 

Program is distinct from an SHSP. 

SHSPs target improvements to 

infrastructure and road users, and 

are broad in content and context, 

while highway safety programs 

focus more on road user behavior.22

An HSP might address issues such 

as excess speeds, proper use of 

occupant protection devices, driving 

while impaired, and quality of traffic 

records data.23

The Railway-Highway Crossings Program funds safety improvements at crossings.

“MAP-21,” Title 

23, U.S.C. (2012), 

accessed August 

16, 2013, http://

www.fhwa.dot.

gov/map21/docs/

title23usc.pdf, Sec. 

148.

“MAP-21,” Title 

23, U.S.C. (2012), 

accessed August 

16, 2013, http://

www.fhwa.dot.

gov/map21/docs/

title23usc.pdf, Sec. 

402.

“Railway-Highway 

Crossings Program 

Reporting 

Guidance,” 

accessed August 

9, 2013, http://

www.fhwa.dot.gov/

map21/guidance/

guiderhcp.cfm.

22

21 23

20
5-12 UNIT 5: IMPLEMENTING ROAD SAFETY EFFORTS ROAD SAFETY FUNDAMENTALS

Local Agencies

Local agencies, such as city and 

county governments, play an 

important role in improving road 

safety and identifying and selecting 

transportation projects. These agencies 

that administer roads at the local level 

may be called by various names: public 

road agency, department of public 

works, departments of transportation, 

or road commissions. Due to their 

smaller size, many local agencies 

may not have a staff member who is 

specifically focused on road safety. 

The urban nature of their jurisdiction 

naturally causes their efforts to be 

focused on different types of road 

safety topics than a State DOT. 

For example, a city transportation 

department would typically focus on 

urban elements such as sidewalks, 

transit accommodations, and high 

density access management, where 

as a State DOT would typically be 

focused on more rural elements, such 

as high speed curves and isolated 

intersections.

Most safety issues for local streets, 

intersections, or corridors are the 

responsibility of the city or county 

government. These agencies 

supplement State laws, establish 

traffic laws in their jurisdictions, 

and determine penalties for 

noncompliance. Local law enforcement 

agencies investigate crashes and 

submit crash data to State and Federal 

agencies. City and county planning and 

engineering staff help plan and design 

roads, bike lanes, and sidewalks. Many 

local police departments partner with 

State police to implement impaired 

driving, work zone safety, motorcycle 

safety, heavy truck, and safety belt 

education and enforcement programs. 

In some States, the State DOT owns 

many of the major roads in the city 

and may coordinate with the local 

agency to identify potential safety 

improvements and get them installed. 

Many local agencies also collaborate 

with the State DOT to develop a Local 

Road Safety Plan.

At the regional level, metropolitan 

planning organizations (MPOs) plan, 

program, and coordinate Federal 

highway and transit investments. 

When an urban area meets certain 

minimum characteristics (e.g., 

population), Federal law requires the 

creation of an MPO for the region 

to qualify for Federal highway or 

transit funds in urbanized areas. 

MPOs do not typically own or operate 

the transportation systems in their 

jurisdiction. MPOs play a coordination 

and consensus-building role in 

planning and programming funds for 

capital improvements, maintenance, 

and operations. MPOs involve local 

transportation providers in the 

planning process by coordinating 

with transit agencies, State and 

local highway departments, airport 

authorities, maritime operators, 

rail-freight operators, Amtrak, port 

operators, private providers of public 

transportation, and others within the 

MPO region.26

Charlotte Pedestrian Safety

The City of Charlotte developed its 

Transportation Action Plan (TAP) in 

2011 to describe how to reach its safety 

and mobility transportation goals. The 

plan emphasized the safety of all road 

users and included objectives such as 

constructing 375 miles of new sidewalk by 

2035.24 To support the goal of pedestrian 

safety, Charlotte developed Charlotte 

WALKS, the city’s first comprehensive 

Pedestrian Plan. This plan identified new 

strategies to meet the pedestrian safety 

and walkability goals in Charlotte’s TAP.25

The City of 

Charlotte 

Transportation 

Action Plan Policy 

Document, 5 Year 

Update, August 22, 

2011. 

http://charlottenc.

gov/Transportation/

Programs/Pages/

default.aspx

The Transportation 

Planning Process 

Briefing Book, 

Federal Highway 

Administration 

and Federal Transit 

Administration, 

2015 Update, 

http://www.fhwa.

dot.gov/planning/

publications/

briefing_book/

fhwahep15048.pdf

24

25

26
ROAD SAFETY FUNDAMENTALS UNIT 5: IMPLEMENTING ROAD SAFETY EFFORTS 5-13

Other Safety Partners

Although government agencies have 

the support of large budgets and 

institutional authority to 

implement improvements to road 

safety, they are not the only entities 

working to improve road safety. 

Government agencies work with 

partners from a variety of fields 

to improve the nation’s roadways 

including those in private industry, 

special interest groups, and 

professional organizations.

Private industry

Automobile Manufacturers

Auto manufacturers have a critical 

effect on road safety by designing 

vehicles that assist the driver in 

avoiding crashes and that absorb 

energy in crashes that do occur. 

Federal standards stipulate that 

vehicles must have certain safety 

improvements, such as seat belts, 

air bags, and electronic 

stability control.27 However, 

auto manufacturers have also 

implemented various non-required 

safety improvements. These 

improvements typically make use of 

emerging technologies or materials. 

For instance, in the early 2000’s, 

auto manufacturers began 

manufacturing vehicles that 

had “smart” technologies to 

improve safety, such as collision 

warnings and assisted braking. 

These technologies, which were 

not required by the government, 

addressed some of the most 

common crash types, such as rear 

end crashes. These improvements 

also set the stage for more 

advanced automated vehicle 

designs and technologies.

Insurance Companies

Insurance companies often assist 

in identifying ways to improve 

safety on the nation’s roads. The 

most notable organization in this 

respect is the Insurance Institute 

for Highway Safety (IIHS) and its 

sister organization, the Highway 

Loss Data Institute (HLDI). These 

are organizations that study road 

safety issues and use insurance data 

to provide data-based evidence of 

safety by vehicle make and model. 

These organizations are funded 

by a pooled group of insurance 

companies and associations. IIHS 

runs the Vehicle Research Center, 

which conducts crash tests of many 

vehicle types to encourage auto 

manufacturers to produce safer 

vehicles and inform the consumer 

on vehicle safety ratings.

Title 49 of the 

United States Code, 

Chapter 301, Motor 

Vehicle Safety; 

and Federal Motor 

Vehicle Safety 

Standard (FMVSS) 

No. 218

27
5-14 UNIT 5: IMPLEMENTING ROAD SAFETY EFFORTS ROAD SAFETY FUNDAMENTALS

Special interest groups

Special interest groups are 

associations of individuals or 

organizations that promote their 

common interests by influencing the 

legislative process at the local, State, 

and/or Federal levels of government. 

Many interest groups also serve 

other functions, such as providing 

services and information to their 

members. Interest groups fill a 

vital role in advancing the cause of 

safety-related legislation.

A few examples of road safetyfocused interest groups include the 

AAA Foundation for Traffic Safety, 

National Safety Council, Mothers 

Against Drunk Driving (MADD), 

the American Council of the Blind, 

and the National Federation of the 

Blind. There are many other interest 

groups involved in influencing 

transportation and safety legislation. 

These groups engage 

in a variety of activities, 

such as sponsoring independent 

research and evaluation, 

mobilizing citizens to contact their 

legislators in support of or against 

certain pieces of legislation, and 

disseminating policy reports in 

support of or against legislation 

affecting the safety of the road users 

they represent. 

Professional organizations

Professional organizations bring 

together road safety professionals 

from common backgrounds or 

spheres of influence to foster 

discussion and advancement of 

safety issues. Members of these 

organizations who recognize 

emerging road safety issues can 

use the power of the group to 

advocate legislation or sponsor 

research to address these issues. 

These organizations often hold 

regular conferences that allow 

safety professionals to network, 

share ideas, and gain knowledge 

from others in their field. The 

organizations also provide training 

opportunities that help advance and 

disseminate road safety knowledge.

There are many professional 

organizations covering many 

disciplines that relate to road safety. 

While this textbook is not intended 

to provide an encyclopedic listing, a 

few examples are listed below.

American Association of 

State Highway Transportation 

Officials (AASHTO)

AASHTO members consist of 

representatives from highway 

American Council of the Blind 

(ACB) and National Federation of 

the Blind (NFB)

The ACB and NFB represent the 

interests of people who are blind or 

visually impaired. These organizations 

work to inform legislators, city and 

State agencies, and the public about 

road safety issues that are unique to 

individuals with visual impairment. 

They promote policies and practices 

that assist visually impaired individuals 

in traveling safety and independently. 

These include enhancements, such as 

auditory stop announcements on buses 

and accessible pushbuttons that provide 

information about street crossing 

signals.
ROAD SAFETY FUNDAMENTALS UNIT 5: IMPLEMENTING ROAD SAFETY EFFORTS 5-15

and transportation departments 

in the 50 States, the District of 

Columbia, and Puerto Rico. AASHTO 

provides tools such as Safety 

Analyst, an analytical software 

package, and publishes the Highway 

Safety Manual, which provides 

an analytical and quantitative 

framework for analyzing a road’s 

safety performance. AASHTO focuses 

on emerging safety issues through 

its Standing Committee on Highway 

Traffic Safety. AASHTO inspired the 

development of a national safety 

plan called Toward Zero Deaths, 

committed to reducing the number 

of highway fatalities to zero.

Institute of Transportation 

Engineers (ITE)

ITE is an association of 

transportation professionals 

who are responsible for meeting 

mobility and safety needs. ITE 

promotes professional development 

of its members and facilitates 

the application of technology and 

scientific principles to the safety 

of ground transportation. ITE’s 

Transportation Safety Council covers 

issues, such as roadside safety, 

pedestrian and bicyclist safety, and 

work zone safety.

Association of Transportation Safety 

Information Professionals (ATSIP)

ATSIP focuses on data and is the 

leading advocate for improving the 

quality and use of transportation 

safety information. ATSIP furthers 

the development and sharing of 

traffic records system procedures, 

tools, and professionalism. Its goal 

is to improve the quality of safety 

data and encourage their use in 

safety programs and policies.

Governors Highway Safety 

Association (GHSA)

GHSA represents the State and 

territorial highway safety offices 

that implement programs to 

address behavioral highway 

safety issues including occupant 

protection, impaired driving, and 

speeding. GHSA provides leadership 

and advocacy for the States and 

territories to improve traffic safety, 

influence national policy, enhance 

program management, and promote 

best practices.

International Organizations

As of 2017, there is no U.S. 

organization that combines the 

narrow focus of improving road 

safety and a broad multidisciplinary 

approach. The current inventory 

of U.S. professional organizations 

is usually specific to a type of 

discipline, such as engineering or 

behavioral science. Looking beyond 

the U.S. borders shows that other 

countries have formed organizations 

that bring together many different 

disciplines to address road safety 

including the following:

J World Road Association (PIARC, 

after its former name Permanent 

International Association of Road 

Congresses), www.piarc.org/en/

J La Prévention Routière 

Internationale (PRI), www.lapri.org 

J United Nations Road 

Safety Collaboration, 

www.who.int/roadsafety/en/ 

J Global Road Safety Partnership, 

www.grsproadsafety.org

J International Road Federation, 

www.irf.global
5-16 UNIT 

5: IMPLEMENTING ROAD SAFETY EFFORTS ROAD SAFETY FUNDAMENTALS

J RESEARCH a recent road safety project 

in your city, county, State, or region. 

Identify the roles and responsibilities 

of the Federal, State, and/or local 

governmental agencies in the project. 

Prepare a brief report for a 

class presentation.

J USE your local, State, or regional 

highway department’s website to 

determine its most pressing road safety 

concerns. Prepare a brief report that 

explains the concerns, how the agency 

identified them, the proposed remedies, 

and the agency’s next steps.

J PREPARE a brief presentation that 

summarizes how your local government 

administers roadway programs. Identify 

the form of government (city, county, 

municipality, parish, etc.), the local 

agencies, and their responsibilities to 

roadway safety programs.

J RESEARCH a private or nonprofit 

interest group that works to improve 

road safety. Prepare a class presentation 

that includes a brief history of the interest 

group, a synopsis of important and 

successful campaigns, and a summary 

of its current work. Some examples of 

private or nonprofit interest groups 

include the Automobile Association 

of America (AAA), Mothers against 

Drunk Driving (MADD), the Insurance 

Institute for Highway Safety (IIHS), and 

the American Bikers Aimed Toward 

Education (ABATE), and many others.

J RESEARCH your local, State, or regional 

transportation safety planning group. 

Prepare a brief report that identifies the 

group’s current safety goal(s), explains 

how the group plans to alleviate the 

safety challenge(s), and describes the 

group’s strategic communications plan. 

J RESEARCH a private sector or industry 

association that works to improve road 

safety. Prepare a class presentation that 

includes a brief history of the interest 

group, a synopsis of important and 

successful campaigns, and a summary 

of its current work. Some examples of 

private sector or industry associations 

include the American Insurance 

Association (AIA), the American Traffic 

Safety Services Association (ATSSA), 

the American Road and Transportation 

Builders Association (ARTBA), the 

National Association of County Engineers

 (NACE), the American Public Works 

Association (APWA), and many others.

J FIND OUT how professional associations 

like the National League of Cities, the 

American Association of State Highway 

Transportation Officials (AASHTO), the 

Governor’s Highway Safety Association 

(GHSA), and the Standing Committee 

on Highway Traffic Safety (SCOHTS) 

influence road safety policy. 

What are some examples of past 

successful campaigns?

J Using the State DOT website, 

RESEARCH your home State’s Highway 

Safety Program. Prepare a brief 

presentation that identifies the State and 

describes how it is working to improve 

roadway safety. You may want to focus on 

the State’s efforts with a particular road 

user or road safety provider. Be sure 

to include details about how the State 

identified the safety challenge(s), how 

the State chose its countermeasure(s), 

and how its efforts measure against 

national performance criteria.

EXERCISES
ROAD SAFETY FUNDAMENTALS UNIT 5: IMPLEMENTING ROAD SAFETY EFFORTS 5-17

Road safety practitioners are 

constantly seeking the most 

effective means for preventing 

injuries and fatalities on the 

road. To accomplish this, they 

need to understand the nature 

of the road safety problems and 

which behavioral or infrastructure 

countermeasures are the best at 

addressing these problems. When 

weighing two possible safety 

treatments, they need to know 

which one is more effective (would 

prevent more crashes) and more 

efficient (preventing crashes at a 

lower cost). Additionally, safety 

practitioners work with a limited 

budget, so they need to know which 

safety treatment is more cost 

effective, that is, how many crashes 

can be prevented for the same dollar 

spent. These goals lead to many 

questions, such as:

J What age range should be 

targeted in a young driver 

safety program?

J What is an effective strategy 

for preventing 

run-off-road crashes?

J How many crashes would be 

expected on one type of road 

versus another type?

J How many serious injuries 

could be prevented by installing 

additional safety measures at a 

signalized intersection?

Research is the key to answering 

these questions and providing 

quality information to the safety 

practitioner. Unit 3 of this textbook 

provides a look at the various types 

of safety data and how they can 

be used together. Good research 

analyzes one or more kinds of safety 

data to gain knowledge on ways to 

prevent crashes or decrease injuries 

when crashes do occur. 

General Types of 

Road Safety Research

The intention of this chapter is not 

to summarize the entire field of 

road safety research, but rather to 

provide an overview that will show 

what types of research have been 

conducted within the topic of 

road safety. 

Road Safety Research

CHAPTER 14 IMPLEMENTING ROAD SAFETY EFFORTS
5-18 UNIT 5: IMPLEMENTING ROAD SAFETY EFFORTS ROAD SAFETY FUNDAMENTALS

One way that these road safety 

research projects can be generally 

categorized is by grouping them by 

the safety factor they address: the 

person, the vehicle, or the roadway. 

For each of these categories, safety 

research typically focuses either 

on identifying safety problems or 

on evaluating solutions to safety 

problems. Table 5-2 demonstrates 

this classification of safety research 

areas and provides example 

questions that would drive research 

studies in each area.

While this chapter presents 

road safety research in terms of 

identifying problems or evaluating 

solutions, researchers also play key 

roles in developing new solutions 

to road safety problems. For 

example, the Florida Department 

of Transportation (FDOT) was 

experiencing thousands of crashes, 

including many fatalities, in 

construction work zones and sought 

an alternative to the traditional 

work-zone barrier. University of 

Florida civil engineering researchers 

hired by FDOT developed a new 

type of portable temporary lowprofile barrier that can redirect 

cars and small trucks, preventing 

them from crashing into the work 

zone and protecting the passengers 

in the vehicle. The barrier was 

advantageous in that it could be 

broken down into small inexpensive 

segments that are easy to install 

and move around.26 Additional 

research was carried out to evaluate 

this new type of barrier in terms of 

criteria like crash performance 

and durability.

TABLE 5-2: Safety Research Categorization

RESEARCH QUESTION EXAMPL

PROBLEM IDENTIFICATION EVALUA

PERSON

What are characteristics of crashes 

involving teen drivers?

What type of driver is overrepresented 

in alcohol-related crashes? 

What is the safety effect of instituting 

a graduated driver license law? 

Has the arrival of ride-sharing apps in 

cities reduced alcohol-related crashes?

VEHICLE

What models of vehicle are more 

prone to run-off-road crashes? 

What factors are associated with 

large truck-related crashes?

What is the effect of an antilock 

braking system on run-off-road crashes?

What is the effect of airbags on 

injury severity?

RO

AD

ENVIRONMENT

What road features are associated 

with run-off-road crashes? 

How does lane width influence 

driver speed?

Are some land development patterns 

riskier from a safety standpoint?

What is the safety effect of installing 

rumble strips?

What is the safety effect of narrowing 

lanes on urban roads?

What is the safety effect of controlling 

road access in dense urban areas?

University of 

Florida, Office 

of Technology 

Licensing, “Portable 

Temporary LowProfile Barrier 

(PTB) for Roadside 

Safety”, UF #11052, 

US Patent 6,767,158

26
ROAD SAFETY FUNDAMENTALS UNIT 5: IMPLEMENTING ROAD SAFETY EFFORTS 5-19

Examples of 

Road Safety Research

The following sections provide 

descriptions and examples of 

research studies. These examples 

will give the reader a look at the 

types of studies that are conducted 

within each of the six categories 

shown in Table 5-2.

Research on the Person

Problem Identification

The IIHS sponsored a study to 

examine the characteristics of 

crashes involving 16-year old 

drivers. The researchers used 

crash data from NHTSA’s General 

Estimates System (a national crash 

database built on sampling from 

police agencies around the U.S.). 

They compared crash involvement 

of sixteen-year-olds to that of 

other age categories of drivers 

and found that sixteen-year-olds 

were more likely to be involved in 

single-vehicle crashes and night 

time crashes (6:00pm to 11:59pm). 

Sixteen-year-olds were also more 

likely to have received a moving 

violation and been at fault for a 

crash. They were also more likely 

to be accompanied by other teenage 

passengers. Researchers also found 

some indications that drivers 

with less on-the-road experience 

(females in this study) were 

proportionately more involved 

in crashes.28

Evaluation of Solutions

In 1997, Michigan instituted its 

Graduated Driver Licensing (GDL) 

program to address the high rate of 

fatal crashes involving teen drivers. 

This program required teen drivers 

to gain driving experience under 

relatively low risk conditions before 

obtaining full driving privileges. 

A new driver would progress 

through Level 1 (a learner’s stage 

requiring extensive supervised 

practice), Level 2 (an intermediate 

stage which prohibited teenage 

passengers and driving at night), 

and Level 3 (full licensure with 

no restrictions). NHTSA funded a 

group of researchers to evaluate the 

effect of the GDL program on the 

crash risk of 16-year-old drivers. 

The researchers examined Michigan 

statewide crash data from 1996 

(pre-GDL) and 1998 and 1999 (postGDL). They analyzed the pre-GDL 

and post-GDL rates of 16-yearold drivers involved in crashes by 

unit of the statewide population. 

Researchers also compared to crash 

rates of drivers over age 25 to 

control for any other trends. They 

found that the overall crash risk 

for 16-year-old drivers decreased 

25% by the year 1999 (two years 

after GDL was implemented). They 

also found significant reductions 

in many specific crash types, such 

as night crashes and single vehicle 

crashes. These findings showed 

a significant benefit to the GDL 

program and served to support GDL 

implementation in other States.29

Research on the Vehicle

Problem Identification

The design of a vehicle, particularly 

how well it protects the occupants 

in the event of a crash, can have 

a significant effect on injuries 

sustained in the crash. A group 

of researchers from the IIHS 

investigated the relation of vehicle 

roof strength to occupant injury 

during crashes. They examined 

crash data from fourteen States 

Shope, J., L. Molnar, 

M. Elliott, P. 

Waller. Graduated 

Driver Licensing 

in Michigan: Early 

Impact on Motor 

Vehicle Crashes 

Among 16-YearOld Drivers. 

Journal of the 

American Medical 

Association, Vol. 

286, No. 13, October, 

2001. http://jama.

jamanetwork.

com/article.aspx? 

articleid=194251

Ulmer, Robert G., 

Allan F. Williams, 

and David F. 

Preusser, Crash 

Involvements of 

16-Year-Old Drivers, 

Journal of Safety 

Research, Vol. 28, 

No. 2, pp 97-103, 

1997. http://www.

sciencedirect.com/

science/article/pii/

S0022437596000412

29

28
5-20 UNIT 5: IMPLEMENTING ROAD SAFETY EFFORTS ROAD SAFETY FUNDAMENTALS

for single-vehicle rollover crashes 

involving midsize SUVs. They also 

used a rating of roof strength for 

each vehicle type in the crash data. 

Their findings showed that the 

crush resistance of a vehicle’s roof 

was strongly related to the risk of 

fatal or incapacitating injury to the 

occupants. This research identified 

one statistically significant factor 

(roof strength) in the severity of 

rollover crashes. The researchers 

also recommended the study of 

other vehicle factors to determine 

their effect on the severity of 

rollover crashes.30

Evaluation of Solutions

Anti lock braking system (ABS) is 

a technology that was developed 

to combat the problem of drivers 

losing control of their vehicle during 

hard braking due to locked wheels. 

ABS modulates braking power to 

prevent a vehicle’s wheels from 

locking up. Since this technology 

requires drivers to employ it 

correctly (i.e., step and hold on the 

brake rather than pumping), the 

Federal Government conducted a 

public information campaign in 

1995 to inform drivers how to use 

ABS correctly. The NHTSA sponsored 

a study that took a long term look at 

the effect of ABS from 1995 to 2007. 

The researchers used crash data 

from two Federal databases (the 

Fatality Analysis Reporting System 

and the General Estimates System of 

the National Automotive Sampling 

System) to estimate the long-term 

effectiveness of ABS for passenger 

cars, light trucks, and vans. They 

found that ABS reduced fatal crashes 

with pedestrians but increased fatal 

run-off-road crashes. ABS proved to 

be quite effective in reducing nonfatal 

crashes in all types of vehicles. 

This result is for the ABS alone; the 

authors recognized that electronic 

stability control (a technology which 

automatically applies brakes to 

individual wheels to keep the driver 

on the road) would soon be paired 

with ABS for potentially greater 

crash reductions.31

Research on the Road 

Environment

Problem Identification

Curves on the road, both horizontal 

and vertical, are known to be 

problem spots for road safety. 

They are particularly concerning 

when they occur together, such 

as a horizontal curve at the peak 

of a hill. FHWA sponsored a study 

to identify and quantify the road 

and curve characteristics that are 

associated with higher instances 

of crashes. The researchers 

examined curves in Washington 

State using crash data and roadway 

characteristics contained in the 

Highway Safety Information System 

(HSIS). They analyzed locations 

where horizontal and vertical curves 

occurred independently, as well as 

locations where both occurred in 

the same place. The researchers 

developed equations that predicted 

the effect on crash frequency for 

each type of curve combination. 

These predictive equations included 

road and curve characteristics found 

to affect the frequency of crashes. 

These characteristics included the 

sharpness of the vertical curve and 

the radius of the horizontal curve.32

Evaluation of Solutions

Rumble strips are expected to 

decrease crashes by generating 

noise to alert sleepy or inattentive 

drivers that they are about to leave 

Kahane, C., and J. 

Dang. The LongTerm Effect of 

ABS in Passenger 

Cars and LTVs. 

National Highway 

Traffic Safety 

Administration, 

Report DOT HS 811 

182, August 2009.

Bauer, K.M. and 

Harwood, D.W. 

Safety Effects 

of Horizontal 

Curve and Grade 

Combinations on 

Rural Two-Lane 

Highways, Report 

No. FHWAHRT-13-077, 

Federal Highway 

Administration, 

Washington, DC, 

2013.

Brumbelow, M., E. 

Teoh, D. Zuby, and 

A. McCartt. Roof 

Strength and Injury 

Risk in Rollover 

Crashes. Traffic 

Injury Prevention, 

10:252-265, 2009. 

DOI: 10.1080/ 

15389580902781343

31

32

30
ROAD SAFETY FUNDAMENTALS UNIT 5: IMPLEMENTING ROAD SAFETY EFFORTS 5-21

the travel lane. Rumble strips on 

both the centerline and shoulder 

ensure that drivers are alerted no 

matter which side of the lane they 

depart. FHWA, through a pooled 

fund from 38 States, conducted 

a study to determine the safety 

effect of installing centerline and 

shoulder rumble strips on rural 

two-lane roads. The researchers 

gathered data on roads in three 

States and compared crash 

performance for roads where the 

rumble strips were installed versus 

roads without rumble strips. The 

analysis showed that the combined 

rumble strip strategy was effective 

at reducing crashes. As expected, 

the greatest crash reductions were 

for crash types that were related 

to lane departure including headon crashes (37% decrease), runoff-road crashes (26% decrease), 

and sideswipe-opposite-direction 

crashes (24% decrease).35

Major Road Safety 

Research Sponsors and 

Research Programs

Most road safety research is funded 

by the government, through state 

or federal agencies. However, some 

research is also funded by privately 

run companies or foundations. The 

organizations that sponsor research 

projects are often focused on one 

category of research. The list below 

presents a look at some of the major 

research sponsors and their area of 

focus in road safety research.

Federal Research Sponsors

Federal Highway Administration

FHWA sponsors research studies 

on a variety of road safety topics, 

and their primary focus is on the 

roadway or the built environment. 

This research investigates the 

impact of road characteristics on 

Lyon, Craig; 

Bhagwant Persaud; 

and Kimberly Eccles. 

“Safety Evaluation 

of Centerline 

Plus Shoulder 

Rumble Strips.” 

Federal Highway 

Administration, 

Report FHWAHRT-15-048, 2015.

Maartens, N., A. 

Wills, and C. Adams. 

Lawrence of Arabia, 

Sir Hugh Cairns, 

and the Origin of 

Motorcycle Helmets. 

Neurosurgery, 

Vol. 50, No. 1, 

January 2002.

Liu, B., R. Ivers, R. 

Norton, S. Blows, 

S.K. Lo. Helmets 

for preventing 

injury in motorcycle 

riders (review). 

The Cochrane 

Collaboration, John 

Wiley and Sons, Ltd. 

January 2008. DOI: 

10.1002/14651858.

CD004333.pub3

35

33

34

Motorcycle helmets are now a common 

road safety element to reduce serious head 

injuries, but they were not always so. The 

original interest in motorcycle helmets 

began when Colonel T.E. Lawrence (better 

known as Lawrence of Arabia) died after 

suffering a head injury in a motorcycle 

crash. One of the physicians who attended 

him, Hugh Cairns, was moved by the 

incident and began studying the prevalence 

of head injuries among motorcyclists in 

the British Army. His work ultimately led to 

helmets becoming mandatory in the British 

Army and the U.K. 

Early motorcycle helmets were leather caps 

that did little to protect riders. Then in the 

1950s, Roth and Lombard came up with the 

idea of using a crushable, energy absorbing 

material (Styrofoam) inside the helmet. A 

study in 1957 by a physician named George 

Snively helped this new type of helmet take 

hold through unusual means – testing six 

popular motorcycle helmets on human 

cadavers. The Roth and Lombard helmet 

with the protective lining was by far the 

most effective in preventing head injuries. 

Many more studies have documented the 

effectiveness of motorcycle helmets. This 

eventually led to standards for motorcycle 

helmets and universal helmet laws.33,34

How Research Affects 

Implementation: 

Motorcycle Helmets
5-22 UNIT 5: IMPLEMENTING ROAD SAFETY EFFORTS ROAD SAFETY FUNDAMENTALS

road safety and seeks solutions to 

known safety problems. The FHWA 

Offices of Safety and Safety Research

and Development conduct research 

to address issues including driver 

interaction with the roadway, 

intersection safety, pedestrian and 

bicycle safety, and keeping vehicles 

on the roadway.36 The FHWA TurnerFairbank Research Center houses 

more than 20 laboratories, data 

centers, and support facilities, and 

conducts applied and exploratory 

advanced research in road safety, 

among other topics. Additionally, 

FHWA staff participates and 

provides input to many other venues 

of research around the nation.

National Highway Traffic Safety 

Administration

NHTSA studies behaviors and 

attitudes in road safety, focusing 

on drivers, passengers, 

pedestrians, and motorcyclists. 

Research sponsored by NHTSA 

identifies and measures behaviors 

involved in crashes or associated 

with injuries, and develops and 

refines countermeasures to

 deter unsafe behaviors and 

promote safe alternatives. The 

research topics include occupant 

protection, distracted driving, 

motorcycle safety, speeding, 

and young drivers.37

Transportation Research Board

The Transportation Research 

Board (TRB) is part of the National 

Academies of Sciences and provides 

advice to the nation and informs 

public policy decisions. TRB plays a 

major role in road safety research. 

It hosts an annual meeting where 

transportation professionals 

https://www.fhwa.

dot.gov/research/

tfhrc/programs/

safety/index.cfm

https://www.nhtsa.

gov/research-data

Graham, J.L., 

Richard, K.R. , 

O’Laughlin, M.K., 

Harwood, D.W., 

“Safety Evaluation 

of the Safety 

Edge Treatment” 

Report No. 

FHWA-HRT-11-024, 

Federal Highway 

Administration, 

Washington, DC. 

(2011) http://www.

fhwa.dot.gov/

publications/

research/

safety/11024/11024.

pdf

36

37

38

The ultimate intent of safety research is 

to provide solid data to affect the way that 

safety measures are carried out in the real 

world. The development of Safety EdgeSM is 

a good example of this.

Drivers who run off the road and then 

try to regain control often go too far and 

over-steer, leading to veering into the 

opposite lane or running off the road 

on the other side. This problem is made 

worse when the soil is eroded away from 

the pavement edge, creating a drop off. 

This safety concern was recognized in the 

1980s, and the 1989 AASHTO Roadside 

Design Guide included a recommendation 

for adding a sloped edge to the pavement 

to assist drivers in regaining control onto 

the roadway. A few States attempted 

this treatment, but it was not widely 

implemented. Through the following 

years, other research showed a correlation 

between drop off crashes and fatalities.

In the early 2000s, several States (Georgia, 

New York, Colorado, and Indiana) decided 

to install several miles of the sloped edge 

as demonstration project. The FHWA 

sponsored a research study to evaluate the 

effect of the sloped edge, now called Safety 

EdgeSM, on run-off-road crashes. The results 

showed a positive effect, and this finding 

swayed many safety offices in favor of the 

treatment. Those now in favor of Safety 

EdgeSM worked to get other offices, such as 

pavement offices, on board with the idea. 

Eventually it became a widespread practice, 

and by 2015, forty States required Safety 

EdgeSM to some degree in their 

design policies.38

How Research Affects 

Implementation: Safety EdgeSM
ROAD SAFETY FUNDAMENTALS UNIT 5: IMPLEMENTING ROAD SAFETY EFFORTS 5-23

from around the world present 

new research on many different 

transportation topics. The papers 

presented at the annual meeting 

are peer-reviewed, and a portion 

of them are published in the 

Transportation Research Record.

TRB also maintains standing 

committees that provide direction 

to the research field and assist in 

disseminating research findings. 

Committees such as Transportation 

Safety Management, Highway 

Safety Performance, Pedestrians, 

Occupant Protection, and many 

others specifically address topics 

related to road safety. TRB manages 

the National Cooperative Highway 

Research Program (NCHRP), 

described below. 

State Research Sponsors

American Association of State 

Highway Transportation Officials 

(AASHTO)

AASHTO is the organization behind 

NCHRP. The NCHRP funds many 

road safety research projects each 

year on a variety of topics that are 

integral to the State departments 

of transportation (DOTs) and 

transportation professionals at 

all levels of government and the 

private sector. The NCHRP is 

administered by the Transportation 

Research Board (TRB) and 

sponsored by individual State 

departments of transportation. The 

research projects are conducted in 

cooperation with FHWA (FHWA). 

Individual projects are conducted by 

contractors with oversight provided 

by volunteer panels of expert 

stakeholders. NCHRP projects cover 

a wide range of highway topics, but 

there is a specific focus area for 

safety.39 AASHTO also maintains 

several committees that oversee 

road safety topics including the 

Standing Committee on Highway 

Traffic Safety and the Subcommittee 

on Safety Management. These 

groups decide which research topics 

should be prioritized for funding 

under NCHRP.

State Research Programs

In addition to participating in 

large scale research efforts, such 

as NCHRP, State departments of 

transportation often fund road 

safety research projects on topics 

that are of particular interest to 

their State. They use portions from 

Federal funds that are specially 

designated for research projects. 

Every State has a different process 

for how the research projects are 

conceived and conducted, but 

a common arrangement is that 

the State DOT contracts with 

universities in the State to conduct 

the research. The research topics 

typically pertain to current road 

safety issues that are high priority 

within the State or issues related to 

geography, terrain, weather, driver 

population, or other such factors 

that may be particular to that State. 

For example, a State in a snowy 

climate may sponsor a research 

project on how snowplowing affects 

the visibility and durability of inpavement reflective markers. 

http://www.trb.org/

NCHRP/NCHRP.

aspx

39

Other Research Sponsors

Although the majority of road safety 

research is funded by government 

sources, private companies and 

organizations also participate in 

funding road safety research. Prominent 

examples of these are the IIHS and 

the American Automobile Association 

Foundation for Traffic Safety.
5-24 UNIT 5: IMPLEMENTING ROAD SAFETY EFFORTS ROAD SAFETY FUNDAMENTALS

A key part of many efforts to 

improve road safety is sharing 

safety messages through strategic 

communications. This chapter 

provides an outline of the most 

basic elements of strategic 

communications that transportation 

safety professionals should 

use when working with their 

communications teams to craft and 

disseminate messages that seek 

to improve traffic safety culture. 

As mentioned in Unit 1, strategic 

communications programs like 

public education campaigns are 

commonly used to improve road user 

attitudes and awareness. 

A strategic communications 

program involves elements of 

communications, marketing, and 

public outreach. These components 

often overlap and are not easily 

separated into distinct categories 

with unique functions. Strategic 

communications is more than the 

sum of its parts. Rather, it is a 

structured methodology that fuses 

messaging with marketing while 

garnering public support.

Several examples demonstrate that 

strategic communications can result 

in behavioral changes. An effort 

in the late 1980s to stop impaired 

driving resulted in substantial 

decreases in Driving Under the 

Influence (DUI) citations. NHTSA 

saw successful results from the 

implementation of the “Buckle Up 

America Campaign” and the National 

Safety Council’s “Airbag and Seat 

Belt Safety Campaign” and the highvisibility public information program 

“Click It or Ticket” safety belt 

enforcement campaign. Strategic 

communications was a key element 

of all of these efforts.

Other examples of communications 

efforts include:

J Campaigns with careful pre-testing 

and delineation of a target group 

that receives the messages. 

J Longer-term programs that 

deliver a message in sufficient 

intensity over time.

Strategic Communications

CHAPTER 15 IMPLEMENTING ROAD SAFETY EFFORTS

Public education campaigns like this 

one are commonly used to improve road 

user attitudes and awareness. 

(Source: NHTSA)
ROAD SAFETY FUNDAMENTALS UNIT 5: IMPLEMENTING ROAD SAFETY EFFORTS 5-25

J Education programs built around 

behavioral change models, using 

interactive methods to teach 

skills to resist social influences 

through role playing.

J Public information campaigns 

that accompany other ongoing 

prevention activities. 

J Programs conducted as part of a 

broader community effort or in 

support of law enforcement.

An effective strategic 

communications program, like any 

effective endeavor, needs a plan. The 

following are key steps in developing 

a strategic communications plan that 

every road safety professional should 

know:

1. Develop objectives

2. Identify target audience

3. Design messaging

4. Select communications channels 

5. Determine budget and resources

6. Measure results

Each step of this communications 

plan outline is discussed in the 

sections below.

1. Develop Objectives 

The first phase in creating a 

strategic communications plan is 

to determine objectives. A welldesigned communications strategy 

may achieve multiple goals, such 

as informing the public about 

transportation safety issues, 

educating key political leaders 

on their roles in saving lives, and 

encouraging active participation 

from safety partners. 

To develop objectives, safety 

professionals must start by defining 

what “success” should look like. 

Important questions include: 

J What are we trying to achieve?

J Do we want people to take a new 

action, or do we want people to 

modify an old behavior? 

J How do we know when we have 

achieved our goal (i.e., what are 

our target metrics)?

Establishing measurable goals is 

an important piece that should be 

not be overlooked. Having a target 

or measurable goal (metric) makes 

it simpler to gauge the success of a 

campaign. 

2. Identify Target Audience

After developing communications 

objectives, the next step is deciding 

what populations to target. For 

example, safety professionals must 

decide if the program should be 

aimed at the general public or a 

specific sub-set of the population, 

such as young drivers, pedestrians, 

or people who drive aggressively. A 

message could also be aimed at road 

safety professionals and government 

officials. In addition to a target 

audience or audiences, secondary 

audiences may be included. For 

instance, if the program targets young 

drivers, a secondary audience may 

include the parents of these novice 

drivers. 

3. Design Messaging

Once safety professionals identify the 

target audience, they must determine 

what the message will be. A key 

step is to define the problem that 

needs to be solved in order to craft 

the message. Messaging should be 

designed so that it encourages specific 

actions, and draws upon established 
5-26 UNIT 5: IMPLEMENTING ROAD SAFETY EFFORTS ROAD SAFETY FUNDAMENTALS

objectives to determine what those 

actions should be. Designing the 

message will bring about questions 

like these: “Is the intended action 

a change in safety funding or 

policies? Or is the goal a change in 

user behavior?” Focusing efforts 

on strategies that connect with 

the target audience is particularly 

important in today’s environment of 

tight budgets and scarce resources.

After message development, safety 

professionals should consider pretesting the message with the target 

audience. A pre-test can identify 

points of view of the target audience, 

provide unexpected insights or 

reactions that can help further refine 

messaging, and help determine if the 

communications plan will improve 

the chance of accomplishing the 

stated objectives. 

4. Select Communications 

Channels 

Carefully crafted messages need to 

be conveyed through appropriate 

channels in order to be effective. 

Communications channels include 

the personal and the non-personal. 

Personal channels include the 

advocate channel (advocates 

championing the objectives of 

a campaign), expert channel 

(independent experts making 

statements to the target audience), 

and social channel (word of mouth 

communications). Non-personal 

channels include media, events, 

and public outreach – examples 

of common non-personal 

dissemination techniques include, 

but are not limited to, the following:

J Brochures

Watch for Me NC is a comprehensive 

program run by the North Carolina 

Department of Transportation (NCDOT) 

in partnership with local communities. 

It is aimed at reducing the number of 

pedestrians and bicyclists crashes.

The Watch for Me NC program involves 

two key elements: 1) safety and 

educational messages directed toward 

drivers, pedestrians, and bicyclists, and 

2) enforcement efforts by area police to 

crack down on some of the violations of 

traffic safety laws. Local programs are 

typically led by municipal, county, or regional 

government staff with the involvement 

of many others including pedestrian 

and bicycle advocates, city planners, law 

enforcement agencies, engineers, public 

health professionals, elected officials, 

school administrators and others.

All North Carolina communities are 

encouraged to use Watch for Me NC 

campaign materials to improve pedestrian 

and bicyclist safety in their communities.

Watch for Me NC

WatchForMeNC.org

Make room for bikes.

1,400 copies of this public document were printed at a cost of $410.20, or $0.293 per copy. (07/13) 

WatchForMeNC.org

Yield to people in crosswalks.

It’s the law.

2,000 copies of this public document were printed at a cost of $586, or $0.293 per copy. (07/13) 

(Source: Watch for Me NC)
ROAD SAFETY FUNDAMENTALS UNIT 5: IMPLEMENTING ROAD SAFETY EFFORTS 5-27

J Conferences/workshops 

J Dynamic message signs 

J Media advisories

J New media (e.g., blogs, podcasts, 

Facebook pages)

J News media events 

J Newsletters and press releases

J Public service announcements 

J Print, radio, and television 

advertising

J Social media

J Websites

Safety professionals must work 

with the communications team 

to determine the right media 

mix, which is the combination of 

communication channels needed to 

meet communications objectives. 

Together they must figure out 

which channels -- personal and/

or non-personnel – and which 

tactics will help meet the stated 

road safety goals. For example, 

personal channels may work well 

with government officials, while 

non-personnel channels may 

work best with reaching out to the 

public. Also, a detailed timeline of 

channels and tactics to employ, is 

crucial for implementing a strategic 

communications plan.

5. Determine Budget 

and Resources

Implementing a comprehensive 

communications program requires 

resources like money, staff, and 

time. Therefore, developing a budget 

for the program is an integral part 

of carrying out the plan. Safety 

professionals should consider every 

element of the proposed plan, and 

make sure there are resources to 

cover them all. For instance, it may be 

necessary to hire an outside firm to 

help develop and refine messages and 

tactics, and that should be factored 

into the budget. All program expenses 

should be tracked to determine how 

well the budget has been met when 

measuring results.

6. Measure Results

Evaluation of a strategic 

communications program is 

essential. Without evaluation, current 

programs may waste resources and 

fail to contribute to a road safety 

program’s goals. Evaluations help 

safety professionals learn from 

outcomes and help them allocate 

funds in the most efficient manner. 

If a program does not meet expected 

metrics, they should re-examine the 

program and/or move the resources to 

other efforts.

To measure the results of the 

program, safety professionals must 

go back to the objectives and predetermined measurable goals and 

targets. The original questions in 

Step 1 will guide the evaluation of 

the success of the program. Surveys, 

focus groups, and/or one-on-one 

interviews are often good ways of 

measuring the performance of a 

strategic communications program. 

As far as data allow, safety professionals 

should also attempt to compare the 

effectiveness of communication 

campaigns in the same way that 

they compare the performance 

of traditional infrastructure 

countermeasures. The comparison 

will help identify campaigns that are 

both effective and efficient.
5-28 UNIT 5: IMPLEMENTING ROAD SAFETY EFFORTS ROAD SAFETY FUNDAMENTALS

This chapter covers the crucial role 

that safety leaders, champions, 

and coalitions play in road safety 

management. While the various 

agencies and organizations involved 

in road safety bring unique and 

valuable perspectives to the 

problem of road safety, they also 

bring competing philosophies 

and problem-solving approaches. 

Bringing these various entities 

together to develop and implement 

an effective road safety program 

is a challenge. 

The major topics include:

J Leaders

J Champions

J Coalitions

Leaders

Leadership is essential in any field, 

but it is particularly important in 

road safety for three major reasons:

J The safety field is diverse. 

It draws on the skills of 

educators, politicians, advocates, 

bureaucrats, public servants, 

and others. These groups 

sometimes work in harmony, 

but too often, they work in 

isolation. Leaders are necessary 

for cohesion in a complex, 

multi-stakeholder environment.

J A great deal of technical 

knowledge is available in the 

safety field regarding the most 

effective means of addressing the 

contributing factors to crashes. 

However, technical knowledge 

is not sufficient for change to 

occur. Leadership is necessary 

to ensure technical knowledge 

is used.

J Road safety programs and 

projects compete with other 

public sector priorities. Without 

strong leaders to support the 

safety cause, public sector 

decision makers might not 

consider or prioritize safety.

Leadership Activities

Leaders are an instrumental part 

of any planning process, and road 

safety programs are no exception. 

Leaders bring people together, 

provide essential direction, and 

motivate people to participate in and 

implement the program. Leaders 

should be engaged and actively 

involved in the process. 

Consider a few examples of 

leadership in safety:

J State DOT leaders decide that 

reducing fatal and serious 

crashes should be the first 

priority of the department. They 

garner staff support to make 

funding and structural changes 

to the organization to support 

the shift in priorities.

J Law enforcement officers 

develop new incentive programs 

to encourage officers to identify 

and arrest impaired drivers. They 

successfully sell the program to 

their managers.

Advancing Road Safety

CHAPTER 16 IMPLEMENTING ROAD SAFETY EFFORTS
ROAD SAFETY FUNDAMENTALS UNIT 5: IMPLEMENTING ROAD SAFETY EFFORTS 5-29

J A trauma nurse initiates a 

“teachable moments” campaign 

in which nurses teach patients 

about the risks associated with 

drinking and driving.

J A mayor recognizes that many 

streets in her city are not suitable 

for safe travel by pedestrians 

and garners support and funding 

from the city council to build 

sidewalks and improve the safety 

of transit stops. 

In each of these examples, the 

leaders recognized a need for 

change, acted on the need, and 

inspired others to follow. Anyone 

with drive, dedication, and a good 

idea can lead.

Leadership Traits and Skills

Good leaders influence policy 

direction, set priorities, and 

define performance expectations. 

They energize the road safety 

process and see to it that a plan is 

developed, and once developed, is 

implemented. They are risk takers, 

problems solvers, and creative 

thinkers committed to doing what 

is necessary to advance the cause, 

which sometimes means breaking 

traditional institutional barriers 

and balancing competing 

agency priorities.

Leaders are often known as program 

managers, and their activities keep 

the implementation process on 

track. They manage the process 

and attend to the day-to-day tasks 

of arranging, facilitating, and 

documenting meetings, tracking 

progress, and moving discrete 

activities through to completion.

Leaders are needed throughout all 

stages of road safety development, 

implementation, and evaluation. 

They communicate the safety 

vision and support a collaborative 

framework that enables safety 

stakeholders to participate actively 

in implementation.

Leaders bring people together, provide essential direction, and motivate people.
5-30 UNIT 5: IMPLEMENTING ROAD SAFETY EFFORTS ROAD SAFETY FUNDAMENTALS

Leadership Development

To expand leadership support, begin 

with the safety partners already 

committed to the safety concept and 

process. Encourage the leadership 

of those partners to contact their 

peers, explain the significance of 

their efforts, and marshal support. 

Their endorsement of the safety 

vision should include encouraging 

staff to stay engaged and building 

relationships across organizational 

boundaries and traditional areas 

of responsibility. 

Leadership support affects agencies 

or organizations internally by 

granting permission to dedicate time 

and resources to the safety effort. 

It also holds those responsible for 

safety accountable. Leadership 

should recognize that this is an 

ongoing process and institutionalize 

the change in the safety decisionmaking culture.

The safety program manager may 

perform either as a part- or fulltime permanent role; experience 

demonstrates a dedicated role 

is preferable.

Champions

Successful road safety programs 

call for at least one champion to 

assist in gathering all critical safety 

partners into a collaborative group. 

Champions provide enthusiasm and 

support for the safety programs. 
ROAD SAFETY FUNDAMENTALS UNIT 5: IMPLEMENTING ROAD SAFETY EFFORTS 5-31

http://safety.fhwa.

dot.gov/hsip/shsp/

39

Like leaders, champions must 

be credible and accountable, 

have excellent interpersonal and 

organizational skills, and be 

skilled expediters. 

Champion Activities

Safety champions help secure the 

necessary leadership, resources, 

visibility, support, and commitment 

of all partners. Sometimes the DOT 

leadership, or the leadership of 

the primary sponsoring agency, 

appoints the champion. A safety 

champion can reside at any level 

within the organizational structure 

and can perform various functions. 

For example, a safety champion 

may lead the executive committee 

that meets periodically to solve 

problems, remove barriers, track 

progress, and recommend further 

action. The role of the executive 

committee is to decide which 

projects or strategies are funded 

based on input from the emphasis 

area teams, and to prioritize them 

based on benefit/cost analysis, 

expected fatality reductions, and 

the extent to which they address the 

project’s goals and objectives. 

Where relationships are not fully 

developed, the champion may 

have to put in additional effort to 

keep the full range of safety 

partners committed and 

actively participating.

Champion Traits and Skills

FHWA published the “Strategic 

Highway Safety Plan 

Implementation Process Model” 

that identifies two types of 

transportation safety champions.39 

The first have access to resources 

and the ability to implement 

change. In other words, they may 

not be involved in the day-today management responsibility 

for program development and 

implementation, but they are able 

to “move mountains” in terms 

of resource allocation and policy 

support. The second are leaders 

who inspire others to follow their 

direction. These champions are 

people who provide enthusiasm and 

support to transportation project 

implementation. They tend to be 

subject matter experts and highly 

respected within their own agencies 

and in the safety community.

Succession Planning

All agencies and organizations 

undergo staff changes, and it is 

essential to train the leaders of 

tomorrow to ensure that the focus 

on safety continues into the future. 

This can be accomplished by 

assigning leadership responsibilities 

for program implementation to 

newer staff and by ensuring that all 

staff have opportunities to engage 

and lead during meetings and 

other activities.

To ensure continuity when an 

individual champion or leader 

retires, takes a position in another 

organization, or moves out of State, 

a systematic approach to identifying 

their replacement is necessary. The 

selection process should be based 

on individual skills, leadership 

traits, and the position held within 

a stakeholder organization. One 

way to institutionalize the selection 

of safety committee members is to 

link their selection to the position 

they hold within the stakeholder 

organization. For example, whoever 

assumes the previous safety 

champion or committee member’s 

position should also become the new 

committee member. 
5-32 UNIT 5: IMPLEMENTING ROAD SAFETY EFFORTS ROAD SAFETY FUNDAMENTALS

Coalitions

Safety partners and organizations 

bring unique and valuable perspectives 

to bear on the transportation 

safety problem. However, differing 

philosophies, competing priorities, 

and varying business cultures may 

make collaboration a challenge. 

Coalitions are an opportunity for road 

safety leaders and champions to bring 

together the various disciplines and 

agencies and focus on the shared 

goal of reducing crashes. Whether 

coalitions are short-term, longterm, or permanent, they offer road 

safety collaborators the prospect 

of solving complex issues through 

partnerships.

Safety Partners

The organizational structure of 

agencies and interagency working 

relationships are important factors 

to consider when bringing safety 

partners together. Rather than 

create entirely new committees, 

a champion should build upon 

existing relationships, interagency 

working groups, and committees. 

Many States have functioning 

transportation safety committees, 

such as a TRCC, an Executive Committee 

for Highway Safety, or a Towards 

Zero Deaths (TZD) coalition. 

Regardless of how safety partners 

are brought together and organized 

to contribute to the safety process, 

champions should look for ways to 

expand membership to include a 

broad range of partners, such as 

insurance, trucking and motor coach 

companies, fire and rescue, local 

businesses, and others. 

When States implement the 

Federally required SHSPs, their 

safety partners typically include 

those that are Federally required, 

such as EMS providers, health and 

education departments, Motor 

Carrier Safety Assistance Program 

(MCSAP) managers, local agencies, 

tribal governments, special interest 

groups (e.g., MADD), and others.

With an emphasis on wide-ranging 

collaboration that includes many 

external partners, it can be easy to 

overlook the importance of broad 

DOT involvement, as well. Early 

involvement of planning, design, 

operations, and maintenance will 

enhance the implementation of 

safety strategies, especially if they 

are new or experimental.

Some champions bring partners 

together by convening a safety 

summit or meeting. This could be 

a large initial kickoff meeting or a 

meeting of the safety working group 

or steering committee. It provides 

an opportunity to learn about each 

of the safety partner priorities and 

understand what they contribute. 

Coalitions should give participants 

the opportunity to describe their 

safety concerns and current 

programs. This may advance the 

discussion of critical safety issues, 

identify opportunities, and forge an 

agreement on how to proceed.

Benefits of Collaboration

Engineering, planning, emergency 

response, and behavioral approaches 

all have roles to play in addressing 

road safety. Professionals in these 

various disciplines have different 

skill sets, and they approach 

solutions using different methods. 

Dramatic improvements in 

roadway safety are more likely to 

result through a combination of 

techniques than from techniques 

from a single discipline. This need 
ROAD SAFETY FUNDAMENTALS UNIT 5: IMPLEMENTING ROAD SAFETY EFFORTS 5-33

for multidisciplinary solutions 

necessitates collaboration.

Unit Summary

Improving road safety is a complex 

endeavor requiring the knowledge 

and expertise of a wide range 

of professionals. Road safety 

improvement is a joint effort 

across many Federal, State, and 

local agencies, each with their own 

particular focus area. 

Federal agencies often play a 

role in providing funding and 

national cooperation for focused 

road safety efforts. State and local 

agencies implement road safety 

improvements, either for roads and 

intersections in their jurisdiction, or 

on the road users themselves. The 

efforts of these government agencies 

is supported by a broad base of 

road safety research, which provides 

knowledge on identifying safety 

problems or evaluating potential 

solutions. Strategic communications 

allow all road safety partners to be 

effective in their efforts to improve 

road safety, either in communicating 

to the public or to transportation 

professionals.

Leadership is essential in the road 

safety field. The diversity of the 

field, the importance of coordination 

among disciplines, and the need 

to defend safety programs among 

a host of competing public sector 

priorities all contribute to the need 

for strong leadership. Successfully 

implementing road safety efforts 

relies on safety champions and 

coalitions that bring together 

safety partners from all agencies 

and disciplines.

J IDENTIFY a road safety leader in your 

community, State, or region. Determine 

the leader’s area(s) of concern, observe 

how the leader engages with the 

transportation safety community, and 

assess the leader’s success. Write a 

brief report summarizing your research. 

Include an explanation for why or why 

not the leader was successful.

J FHWA has explicitly stated that a 

“safety champion” should lead safety 

efforts, specifically development of 

State SHSPs. Using your home State’s 

DOT website, RESEARCH past or 

present safety champions. Prepare a 

brief class presentation that identifies 

the champion, explains why he or 

she was chosen for the role, what the 

requirements of the position were, and 

what projects the State implemented 

under the champion’s guidance. Be 

sure to include an assessment of the 

champion’s tenure.

J Coalition building requires a thoughtful, 

reasoned approach. CHOOSE an 

important road safety issue that the 

transportation community is still 

studying. Propose a list of coalition 

members that could best approach 

the issue from all available disciplines 

and interests. Be sure to keep the list 

reasonable. In a report, summarize 

the safety issue and introduce the 

coalition members. Explain why each 

member is critical to the coalition 

and the expectations for each 

member’s contributions. 

EXERCISES
THIS PAGE INTENTIONALLY LEFT BLANK

FHWA, Office of Safety

Felix H. Delgado, P.E.

Felix.Delgado@dot.gov

FHWA-SA-18-003

Road Safety Fundamentals is available for free at: 

https://rspcb.safety.fhwa.dot.gov/rsf/