UNIT 2: Human Behavior and Road Safety

Road Safety 

Fundamentals

Concepts, Strategies, and Practices that 

Reduce Fatalities and Injuries on the Road
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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

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University of North Carolina,

Highway Safety Research Center

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Federal Highway Administration Office of Safety

1200 New Jersey Ave., SE

Washington, DC 20590

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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

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188

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FREE

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November 2017

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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 i

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
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)

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/