Manual for Selecting Safety Improvements on High Risk Rural Roads

 1

Manual for Selecting

Safety Improvements 

on High Risk Rural Roads

http://safety.fhwa.dot.gov
2

Federal Highway Administration | Office of Safety 

Notice

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

Transportation in the interest of information exchange. The U.S. Government assumes no 

liability for the use of the information contained in this document. This report does not 

constitute a standard, specification, or regulation.

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.
Manual for Selecting Safety Improvements on High Risk Rural Roads

TECHNICAL REPORT DOCUMENTATION PAGE

1. Report No. 2. Government Accession No. 3. Recipient's Catalog No.

FHWA-SA-14-075

4. Title and Subtitle 5. Report Date

Manual for Selecting Safety Improvements on High Risk Rural 

Roads

August 2014

6. Performing Organization Code

7. Author(s) 8. Performing Organization Report No.

Jennifer E. Atkinson, Brian E. Chandler, Vernon Betkey, Karen 

Weiss, Karen Dixon, Anna Giragosian, Kelly Donoughe, and Cara 

O'Donnell

9. Performing Organization Name and Address 10. Work Unit No. (TRAIS)

SAIC

11251 Roger Bacon Drive

Reston, VA 20190

Subconsultant: Texas A&M Transportation Institute

11. Contract or Grant No.

Contract No. DTFH61-10-D-00024, Task

Order No. T-12-006

12. Sponsoring Agency Name and Address 13. Type of Report and Period Covered

Federal Highway Administration

Office of Safety

1200 New Jersey Avenue SE 

Washington, DC 20590

Manual for Selecting Safety Improvements on 

High Risk Rural Roads

September 2012 through August 2014

14. Sponsoring Agency Code

FHWA HSA

15. Supplementary Notes

James Dahlem (james.dahlem@dot.gov), Office of Safety Technologies, served as the Technical Manager for the 

Federal Highway Administration (FHWA). The following FHWA staff members contributed as technical working 

group members, reviewers, and/or provided input or feedback to the project at various stages: Jeffrey Shaw, Erin 

Kenley, Beth Alicandri, Nick Artimovich, Joseph Cheung, Brian Fouch, Becky Crowe, Rosemarie Anderson, Karen 

Scurry, Rob Ritter, Cathy Satterfield, and Gabe Rousseau. Additionally, many individual safety partners 

representing Federal, State, Tribal, and local agencies and professional associations made significant contributions 

to this project; special thanks to Joseph Bonga (Bureau of Indian Affairs), Richie Beyer (Elmore County, Alabama), 

Matthew Enders (Washington DOT), Dave Brand (National Association of County Engineers; Madison County, 

Ohio), Marie Walsh (National Local Technical Assistance Program Association; Louisiana LTAP), Brian Roberts 

(National Association of Counties), Greg Parker (American Public Works Association), Ken Mammen (Utah DOT), 

and Joe Marek (Clackamas County, Oregon).

16. Abstract

This manual provides information on the costs and benefits of safety treatments on high-risk rural roads (HRRR). 

Agencies can use this manual to determine the following information on the treatments: Safety benefits; Costeffectiveness comparison of safety treatments; Applicability of treatment deployment with respect to identified 

need; and Initial and reoccurring maintenance costs associated with countermeasure installation. In addition, this 

manual provides information on the decision-making process necessary to identify treatments.

17. Key Words 18. Distribution Statement

High Risk Rural Roads, Safety Treatments, Safety 

Management, Safety Funding Sources

No restrictions

19. Security Classif. (of this report) 20. Security Classif. (of this page) 21. No of Pages 22. Price

Unclassified Unclassified 176 N/A

Form DOT F 1700.7 (8-72) Reproduction of completed page authorized.
4

ii

SI* (MODERN METRIC) CONVERSION FACTORS 

APPROXIMATE CONVERSIONS TO SI UNITS

Symbol When You Know Multiply By To Find Symbol 

LENGTH 

in inches 25.4 millimeters mm 

ft feet 0.305 meters m 

yd yards 0.914 meters m 

mi miles 1.61 kilometers km 

AREA 

in2 square inches 645.2 square millimeters mm2

ft2 square feet 0.093 square meters m2

yd2 square yard 0.836 square meters m2

ac acres 0.405 hectares ha 

mi2 square miles 2.59 square kilometers km2

VOLUME 

fl oz fluid ounces 29.57 milliliters mL 

gal gallons 3.785 liters L 

ft3 cubic feet 0.028 cubic meters m3 

yd3 cubic yards 0.765 cubic meters m3 

NOTE: volumes greater than 1000 L shall be shown in m3

MASS oz ounces 28.35 grams g

lb pounds 0.454 kilograms kg

T short tons (2000 lb) 0.907 megagrams (or "metric ton") Mg (or "t") 

TEMPERATURE (exact degrees) o

F Fahrenheit 5 (F-32)/9 Celsius oC 

or (F-32)/1.8 

ILLUMINATION 

fc foot-candles 10.76 lux lx 

fl foot-Lamberts 3.426 candela/m2 cd/m2

FORCE and PRESSURE or STRESS 

lbf poundforce 4.45 newtons N 

lbf/in2 poundforce per square inch 6.89 kilopascals kPa 

APPROXIMATE CONVERSIONS FROM SI UNITS 

Symbol When You Know Multiply By To Find Symbol 

LENGTH

mm millimeters 0.039 inches in 

m meters 3.28 feet ft 

m meters 1.09 yards yd 

km kilometers 0.621 miles mi 

AREA mm2

 square millimeters 0.0016 square inches in2 

m2 square meters 10.764 square feet ft2 

m2 square meters 1.195 square yards yd2 

ha hectares 2.47 acres ac 

km2 square kilometers 0.386 square miles mi2 

VOLUME 

mL milliliters 0.034 fluid ounces fl oz 

L liters 0.264 gallons gal 

m3 cubic meters 35.314 cubic feet ft3 

m3 cubic meters 1.307 cubic yards yd3 

MASS 

g grams 0.035 ounces oz

kg kilograms 2.202 pounds lb

Mg (or "t") megagrams (or "metric ton") 1.103 short tons (2000 lb) T 

TEMPERATURE (exact degrees) o

C Celsius 1.8C+32 Fahrenheit oF 

ILLUMINATION 

lx lux 0.0929 foot-candles fc 

cd/m2 candela/m2 0.2919 foot-Lamberts fl

FORCE and PRESSURE or STRESS 

N newtons 0.225 poundforce lbf 

kPa kilopascals 0.145 poundforce per square inch lbf/in2

*SI is the symbol for th International System of Units. Appropriate rounding should be made to comply with Section 4 of ASTM E e 380. 

(Revised March 2003)
v

List of Acronyms .........................................................................................................................xii

Executive Summary................................................................................................................... xiii

1. Introduction .............................................................................................................................1

1.1. Purpose ................................................................................................................................ 1

1.2. How to Use This Manual ................................................................................................... 1

2. High Risk Rural Roads Overview.............................................................................................3

2.1. High Risk Rural Road Safety............................................................................................... 3

2.2. Challenges of Applying Treatments to HRRR .................................................................. 4

3. Identifying Safety Treatments..................................................................................................5

3.1. Tools for Identifying HRRR Safety Issues.......................................................................... 5

Highway Safety Manual ................................................................................................................ 6

Safety Analyst................................................................................................................................. 6

Crash Modification Factor (CMF) Clearinghouse.................................................................... 6

Road Safety Audits......................................................................................................................... 7

Training .......................................................................................................................................... 7

3.2. Systemic Implementation and Spot Location Treatments................................................ 8

4. Selecting Safety Treatments......................................................................................................9

4.1. Horizontal Curves ............................................................................................................. 10

Install Curve Warning Signs ..................................................................................................... 11

Install/Upgrade Curve Warning Signs with Fluorescent Yellow Sheeting .......................... 12

Double Use of Advanced Warning Signs for Curves or Intersections ................................. 13

Use of Optical Speed Bars .......................................................................................................... 14

Install Chevron Signs ................................................................................................................. 15

Install Arrow Signs at Horizontal Curve Locations ............................................................... 16

Install Post-Mounted Delineators at Horizontal Curves ....................................................... 17

Install Targeted Longitudinal Rumble Strips on the Outside of Horizontal Curves .......... 18

Install Icy Curve Warning System ............................................................................................ 19

Improve Superelevation at Horizontal Curve Locations ....................................................... 20

Remove Compound Horizontal Curves .................................................................................. 21

Modify Horizontal/Vertical Geometry..................................................................................... 22

Table of Contents
Federal Highway Administration | Office of Safety 

vi

4.2. Intersections (Signalized) .................................................................................................. 23

Improve Traffic Signal Visibility (Larger Diameter Lens or Install Back Plate).................. 24

Provide Intersection Lighting .................................................................................................... 25

Install Pedestrian Signal Heads to Existing Signalized Intersections .................................. 26

Provide Flashing Beacons at Intersection Approaches........................................................... 27

Use Raised Median to Restrict Turning Movements ............................................................. 28

Install Priority Control Systems for Emergency Vehicles ..................................................... 29

Provide Advanced Dilemma Zone Detection for Rural High Speed Signalized 

 Approaches .............................................................................................................................. 30

Implement J-Turns Along a Signalized Corridor ................................................................... 31

Install Acceleration or Deceleration Lanes .............................................................................. 32

Install Right Turn Lane .............................................................................................................. 33

Install Left Turn Lane ................................................................................................................ 34

Install Offset (or Channelized) Left Turn Lane ...................................................................... 35

Convert a Traditional Signalized Intersection into a Roundabout ...................................... 36

Reconstruct At-Grade Intersection to Create an Interchange .............................................. 37

4.3. Intersections (Unsignalized).............................................................................................. 38

Relocate an Existing Stop Bar on Minor Approach ............................................................... 40

Install Stop Ahead Pavement Markings ................................................................................... 41

Install Advanced Intersection Warning Signs ......................................................................... 42

Provide a Stop Bar on Minor-Road Approaches .................................................................... 43

Improve Sight Distance within Sight Triangle ........................................................................ 44

Provide Upcoming Road Names on Advanced Warning Signs ............................................ 45

Install Retroreflective Strips on Sign Posts .............................................................................. 46

Upgrade to Larger Stop Signs .................................................................................................... 47

Double Use of Stop Signs ........................................................................................................... 48

Improve Sight Distance and Conspicuity at Railroad Grade Crossings .............................. 49

Install a Splitter Island ................................................................................................................ 50

Channelization of Major and Minor Roads (Physical or Painted) ....................................... 51

Provide Intersection Lighting .................................................................................................... 52

Install Dynamic Advanced Intersection Warning System .................................................... 53

Upgrade Existing Railroad Crossing Hardware and Warning Systems ............................... 54
Manual for Selecting Safety Improvements on High Risk Rural Roads

vii

Implement Lane Narrowing through Rumble Strips and Painted Median at Rural 

 Stop-Controlled Approaches.................................................................................................... 55

Provide Flashing Beacons at Intersection Approaches........................................................... 56

Convert Minor Road Stop Control to All-Way Stop Control ............................................... 57

Convert a Traditional Stop-Controlled Intersection into a J-Turn Intersection ............... 58

Use Raised Median to Restrict Turning Movements ............................................................. 59

Install Acceleration or Deceleration Lanes .............................................................................. 60

Install Railroad Crossing Hardware and Warning Systems Where They Currently 

 Do Not Exist ............................................................................................................................. 61

Convert a 4-Leg Intersection into Two 3-Leg Intersections (Offset T-Intersections)........ 62

Install Bypass Lane ..................................................................................................................... 63

Modify Horizontal and/or Vertical Geometry ........................................................................ 64

Improve Horizontal Intersection Alignment or Skew............................................................ 65

Install Traffic Signals................................................................................................................... 66

Install Right Turn Lane .............................................................................................................. 67

Install Left Turn Lane ................................................................................................................. 68

Install Offset (or Channelized) Left Turn Lane ...................................................................... 69

Install a Roundabout (From Stop-Controlled) ....................................................................... 70

Remove or Separate an Existing Railroad Grade Crossing ................................................... 71

4.4. Non-motorized User........................................................................................................... 72

Provide Crosswalks at Targeted Locations .............................................................................. 73

Install Pedestrian Signal Heads to Existing Signalized Intersections .................................. 74

Construct Wildlife Fencing ....................................................................................................... 75

Install Rectangular Rapid Flash Beacons ................................................................................. 76

Build Sidewalks ........................................................................................................................... 77

Construct Adjacent Shared-Use Paths ..................................................................................... 78

Construct Shared-Use Paved Shoulders for Horse & Buggy Road Users or Bicyclists ..... 79

Construct Exclusive Bicycle Lanes ........................................................................................... 80

Install Curb Extensions............................................................................................................... 81

Install or Modify Culverts to Accommodate Wildlife Crossing ........................................... 82

Install Pedestrian Hybrid Beacons or High Intensity Activated Crosswalk (HAWK) ....... 83

Construct Bicycle Trail Grade Separation Structures ............................................................ 84
Federal Highway Administration | Office of Safety 

viii

4.5. Pavement and Shoulder Resurfacing................................................................................ 85

Install a Safety Edge .................................................................................................................... 86

Install Center Line Rumble Strips ............................................................................................ 87

Install Edge Line or Shoulder Rumble Strips .......................................................................... 88

Install Transverse Rumble Strips .............................................................................................. 89

Regrade or Recondition Gravel Lanes...................................................................................... 90

Install Targeted Longitudinal Rumble Strips at Key Locations (Such as on the Outside 

 of Horizontal Curves Only) .................................................................................................... 91

Install or Maintain a Graded Shoulder .................................................................................... 92

Provide Turnout Areas ............................................................................................................... 93

Improve Pavement Friction/Increase Skid Resistance ........................................................... 94

Add Paved Shoulder ................................................................................................................... 95

Widen Existing Travel Lanes by Two Feet or Less per Lane ................................................. 96

Install Passing or Climbing Lanes ............................................................................................ 97

Increase Shoulder Width ........................................................................................................... 98

Improve Superelevation at Horizontal Curve Locations ....................................................... 99

4.6. Pavement Marking ........................................................................................................... 100

Provide a Stop Bar on Minor Road Approaches ................................................................... 101

Install Stop Ahead Pavement Markings ................................................................................. 102

Relocate an Existing Stop Bar on Minor Approach .............................................................. 103

Use of Optical Speed Bars ........................................................................................................ 104

Install Raised Pavement Markers ........................................................................................... 105

Install Edge Line Markings ...................................................................................................... 106

Install Center Line Markings .................................................................................................. 107

Install Wider Pavement Markings (With or Without Rumble Strips) ............................... 108

Implement Lane Narrowing Through Rumble Strips and Painted Median at 

Rural Stop-Controlled Approaches ........................................................................................ 109

Install Center Line and Edge Line Markings ........................................................................ 110

Convert a Four-Lane Two-Way Road into a Three-Lane Road With One Lane in 

 Each Direction of Travel Plus a Continuous Two-Way Left Turn Lane (Road Diet) ... 111

Convert a Four-Lane Two-Way Road into a Five-Lane Road with Two Lanes in 

 Each Direction of Travel Plus a Continuous Two-Way Left Turn Lane OR 

 Convert a Two-Lane Two-Way Road into a Three-Lane Road Plus a Continuous 

 Two-Way Left Turn Lane ...................................................................................................... 112
Manual for Selecting Safety Improvements on High Risk Rural Roads

ix

4.7. Roadside............................................................................................................................ 113

Install a Safety Edge .................................................................................................................. 114

Improve Sight Distance by Controlling Roadside Vegetation ............................................ 115

Convert Culvert Headwalls to Traversable End Treatments ............................................... 116

Remove Guardrail ..................................................................................................................... 117

Install or Maintain a Graded Shoulder .................................................................................. 118

Relocate Select Hazardous Utility Poles ................................................................................. 119

Install Median Guardrail ......................................................................................................... 120

Modify End Treatments of Existing Guardrail ..................................................................... 121

Install Impact Attenuation Devices at Select Roadside Hazard Locations (Such as 

 Exposed Bridge Columns) .................................................................................................... 122

Remove or Shield Obstacles in Clear Zone ........................................................................... 123

Increase Shoulder Width ......................................................................................................... 124

Widen Existing Median or Construct Median ...................................................................... 125

Install Median Cable Barrier ................................................................................................... 126

Flatten Road Sideslope ............................................................................................................. 127

Create or Increase Clear Zone ................................................................................................ 128

Add Paved Shoulder ................................................................................................................. 129

Install Concrete Median Barriers............................................................................................ 130

4.8. Signing .............................................................................................................................. 131

Install/Upgrade Curve Warning Signs with Fluorescent Yellow Sheeting ........................ 132

Install Curve Warning Signs ................................................................................................... 133

Install Retroreflective Strips on Sign Posts ............................................................................ 134

Double Use of Advanced Warning Signs for Curves or Intersections ............................... 135

Provide Upcoming Road Names on Advanced Warning Signs .......................................... 136

Install Advanced Intersection Warning Signs ....................................................................... 137

Upgrade to Larger Stop Signs .................................................................................................. 138

Double Use of Stop Signs ......................................................................................................... 139

Use of Supplemental Warning Signs ...................................................................................... 140

Install Chevron Signs................................................................................................................ 141

4.9. Vertical Curves................................................................................................................. 142

Install Advanced Intersection Warning Signs ....................................................................... 143

Install Dynamic Advanced Intersection Warning System .................................................. 144
Federal Highway Administration | Office of Safety 

x

Modify Horizontal/Vertical Geometry................................................................................... 145

Relocate Driveways, Entrances, and Intersections................................................................ 146

4.10. Other Treatments ........................................................................................................... 147

Mitigate Ground Water to Prevent Ponding and/or Icing .................................................. 148

Widen Functionally Obsolete Bridges ................................................................................... 149

5. Safety Management, the Funding Process, and 

Funding Sources........................................................................................................................150

5.1. Safety Management .......................................................................................................... 150

5.1.1.Safety Project Prioritization and Development ........................................................... 150

5.1.2.Initial and Ongoing Treatment Costs............................................................................ 150

5.2. The Funding Process ........................................................................................................ 151

5.3. Legislation and Funding Sources..................................................................................... 151

5.3.1. Legislation and Federal Funding Sources.................................................................... 151

5.3.2. Other Funding Sources................................................................................................... 154

5.4. Evaluation ......................................................................................................................... 154

6. Navigating the Safety Treatments ........................................................................................155

6.1. Identify Study Sites........................................................................................................... 155

6.2. Perform Safety Diagnosis................................................................................................. 155

6.3. Initiate Treatment Analysis.............................................................................................. 158

6.4. Perform Economic Analysis ............................................................................................ 159

6.5. Summarize Recommendations........................................................................................ 160

Glossary .....................................................................................................................................161

List of Tables

Table 1. Example Treatment Matrix........................................................................................................... 2

Table 2. 2010 Rural vs. Urban Collector and Local Road VMT and Fatality Rate 

 Comparison ................................................................................................................................................ 3

List of Figures

Figure 1. Flowchart A – HRRR Safety Enhancement Analysis ......................................................... 156

Figure 2. Flowchart B – Safety ............................................................................................................... 157

Figure 3. Flowchart C – Treatment Analysis ...................................................................................... 158

Figure 4. Flowchart D – Economic Analysis ...................................................................................... 160
Manual for Selecting Safety Improvements on High Risk Rural Roads

xi

List of Acronyms

AADT Average Annual Daily Traffic

ADHS Appalachian Development Highway 

System

ADT Average Daily Traffic

AASHTO American Association of State Highway 

and Transportation Officials

BCR Benefit-Cost Ratio

CMF Crash Modification Factor

COG Council of Governments

CRF Crash Reduction Factor

D-CS Detection-Control System

DOT Department of Transportation

FHWA Federal Highway Administration

FLMA Federal Land Management Agency

FLTP Federal Lands Transportation Program

FMCSA Federal Motor Carrier Safety 

Administration 

HAWK High Intensity Activated Crosswalk

HRRR High Risk Rural Roads

HRRRP High Risk Rural Roads Program

HSIP Highway Safety Improvement Program

HSM Highway Safety Manual

HSP Highway Safety Plan

ITS Intelligent Transportation Systems

km/h kilometers per hour

LED Light Emitting Diode

LTAP Local Technical Assistance Program 

MAP-21 Moving Ahead for Progress in the 21st 

Century Act

mph miles per hour

MPO Metropolitan Planning Organization

MUTCD Manual on Uniform Traffic Control 

Devices 

NACE National Association of County Engineers

NACO National Association of Counties 

NCHRP National Cooperative Highway Research 

Program

NHI National Highway Institute

NHPP National Highway Performance Program

NHS National Highway System

NHTSA National Highway Transportation Safety 

Administration

RPC Regional Planning Commission

RPO Regional Planning Organization

RRFB Rectangular Rapid Flash Beacon

RSA Roadway Safety Audit

SAFETEA-LU Safe, Accountable, Flexible Efficient 

Transportation Equity Act: A Legacy for 

Users

SHSP Strategic Highway Safety Plan

SLOSSS Suggested List of Surveillance Study Sites

SP&R State Planning & Research

STIP Statewide Transportation Improvement 

Program

STP Surface Transportation Program 

TAP Transportation Alternatives Program

TIP Transportation Improvement Program

TTAP Tribal Technical Assistance Program

TTP Tribal Transportation Program

TWLTL Two-Way Left Turn Lane

USC United States Code

USDOT United States Department of 

Transportation

VMT Vehicle Miles Traveled

vpd vehicles per day
Federal Highway Administration | Office of Safety 

xii

Executive Summary

Transportation agencies across the United States use many treatments to improve safety on high risk rural roads 

(HRRR). This manual provides information and criteria associated with those improvements including the following:

•	 Safety benefits;

•	 Cost-effectiveness comparison of safety treatments; 

•	 Applicability of treatment deployment with respect to identified need;

•	 Initial and reoccurring maintenance costs associated with treatment installation; and

•	 Decision-making process for treatment selection.

With the large number of safety treatments available, it can be challenging for practitioners to select the most 

effective treatment to implement with limited funds. This manual is intended to assist an agency in understanding 

the effectiveness of safety improvements on HRRR to aid in the treatment selection process. 

Practitioners may use this manual to understand the potential use and applicable deployment locations for each 

treatment presented. The HRRR Treatment Matrix sorts through treatment selection and deployment criteria 

to identify potential improvements for a site. The manual includes overviews of safety program management, 

potential funding sources and funding processes, and provides decision-making tools for selecting appropriate 

safety treatments for given crash types and roadway characteristics. 
Manual for Selecting Safety Improvements on High Risk Rural Roads

1

1. Introduction

This manual provides information on the costs and benefits of safety treatments on high risk rural roads (HRRR). 

Agencies can use this manual to determine the following information related to the treatments:

•	 Safety benefits;

•	 Cost-effectiveness comparison of safety treatments; 

•	 Applicability of treatment deployment with respect to identified need; and

•	 Initial and reoccurring maintenance costs associated with countermeasure installation.

In addition, this manual provides information on the decision-making process necessary to identify treatments.

1.1. Purpose

With limited data specific to HRRR, it can be challenging for agencies to effectively use limited funds for 

treatments on HRRR. The purpose of this manual is to provide a comparison between the cost-effectiveness of 

safety treatments on HRRR, identify where the treatments may be more effectively used, and present initial and 

ongoing costs associated with installation. The objective is to assist agencies in finding effective ways to efficiently 

allocate safety improvement funds on HRRR to achieve a greater reduction in the number and severity of rural 

roadway crashes.

1.2. How to Use This Manual 

This manual is organized to assist in selection of safety treatments based on roadway feature type (e.g., horizontal 

curves). The treatments are organized into 10 categories such that treatments can be compared at like locations. 

The safety treatments are separated into the following sections according to the corresponding roadway feature 

type and correlate to a color coded tab at the bottom of the page:

Federal Highway Administration | Office of Safety 

10

4.1. Horizontal curves

Safety improvement treatments on horizontal curves range from low-cost improvements (such as signing) to 

high-cost improvements (such as modifying road geometry). This section covers safety improvement treatments 

that can be applied at horizontal curve locations. Some treatments in this section also appear in the sections on 

intersection improvements, signing, and roadside safety.1920

19 As discussed in Section 1.2, a BCR is only shown where data were available to calculate the ratio. Where data were unavailable, it has been left blank.

20 As stated in NCHRP Series 500 Reports (http://safety.transportation.org/guides.aspx). Proven: The safety effect for other similar applications has shown a proven benefit. 

Tried: The treatment has indications that it can be expected to reduce crashes, but has some conflicting reports as to its associated safety effects or has been deployed and 

observed to be effective. Experimental: New treatments that still need to be tested and for which the safety effect is unknown. Unknown: Not enough is known about an 

associated safety performance.

SAFETy TREATMENT For more information, 

visit page

COST

Frequency of 

Maintenance (years)

SAFETy 

BENEFIT

BENEFIT-COST

RATIO19

Initial 

Implementation

Ongoing 

Maintenance

NCHRP 500 

Performance Rating

Crash Modification 

Factor (CMF)

Lower Volume*, 

Optimal Width***

Higher Volume**, 

Optimal Conditions***

Lower Volume*, 

Narrower Conditions****

Higher Volume**, 

Narrower Conditions****

Install Curve Warning Signs 11 $ $ 5 P 0.70 33.8 270.1 43.5 428.4Install/Upgrade Curve Warning Signs with Fluorescent Yellow Sheeting 12 $ – 5 P 0.66 63.1 490.4 75.1 739.9Double Use of Advanced Warning Signs for Curves or Intersections 13 $ TUse of Optical Speed Bars 14 $Install Chevron Signs 15 $$ $ 5 P 0.75 10.6 84.7 13.0 127.7Install Arrow Signs at Horizontal Curve Locations 16 $$ – 10 P 27.9 222.8 34.1 336.1Install Post-mounted Delineators at Horizontal Curves 17 $$ – 10 P 5.3 42.4 6.5 63.9Install Targeted Longitudinal Rumble Strips on the Outside of Horizontal Curves 18 $$ T 0.85Install Icy Curve Warning System 19 $$ E 0.82

Improve Superelevation at Horizontal Curve Locations 20 $$$$ PRemove Compound Horizontal Curves 21 $$$$$ TModify Horizontal/Vertical Geometry 22 $$$$$ P

Horizontal Curves

Cost:$ = $0 to $5,000$$ = $5,001 to $20,000$$$ = $20,001 to $50,000$$$$ = $50,001 to $100,000$$$$$ = $100,001 and up

NCHRP 500 Performance Rating20

P – ProvenT – TriedE – ExperimentalU – Unknown

*Lower Volume ≤1000 vpd**Higher Volume = Between 1,001 and 8000 vpd***Optimal Conditions = 12-foot lanes, 6-foot paved shoulders****Narrower Conditions = 10-foot lanes and no shoulders

Color Coded 

Section Tab 

Identifier

Color Coded

Safety Treatment 

Matrix

Safety Treatment 

Section Title

Horizontal Curves

Intersections (Signalized)

Intersections (Unsignalized)

Non-Motorized User

Pavement and Shoulder Resurfacing

Pavement Marking

Roadside

Signing

Vertical Curves

Safety Treatment

Categories

Other Treatments

References to the 

treatment pages 

are hyperlinked
Federal Highway Administration | Office of Safety 

2

At the beginning of each treatment category section, a treatment matrix provides an overview of benefits and 

costs associated with each safety improvement in the section. The matrix may be used to help narrow the list 

of potential treatments by sorting through criteria specific to the practitioner’s needs and available resources. 

For example, if a practitioner would like to identify an intersection treatment with a maximum initial cost, the 

matrix can be used to narrow the treatments to only those falling within the maximum range. Figure 1 shows an 

abbreviated version of the Horizontal Curve Treatment Matrix.

Table 1. Example Treatment Matrix

Safety treatment

For more information, visit page

CoSt

Frequency of Maintenance (years)

Safety 

Benefit

Benefit-CoSt 

ratio19

Initial ImplementationOngoing MaintenanceNCHRP 500 Performance RatingCrash Modification Factor (CMF)Lower Volume*, Optimal Width***Higher Volume**, Optimal Conditions***Lower Volume*, Narrower Conditions****Higher Volume**, Narrower Conditions****

Install Curve Warning Signs 11 $ $ 5 P 0.70 33.8 270.1 43.5 428.4

Install/Upgrade Curve Warning Signs with 

Fluorescent Yellow Sheeting 12 $ – 5 P 0.66 63.1 490.4 75.1 739.9

Cost:

$ = $0 to $5,000

$$ = $5,001 to $20,000

$$$ = $20,001 to $50,000

$$$$ = $50,001 to $100,000

$$$$$ = $100,001 and up

nCHrP 500 Performance rating20

P – Proven

T – Tried

E – Experimental

U – Unknown

*Lower Volume ≤1000 vpd

**Higher Volume = Between 1,001 and 8000 vpd

***Optimal Conditions = 12-foot lanes, 6-foot paved shoulders

****Narrower Conditions = 10-foot lanes and no shoulders

The users of this manual can follow the decision flow charts in Chapter 6 to determine a range of treatment options 

based on the resources available to implement a treatment. This manual does not provide a full comprehensive list 

of every treatment available, and is only a guide to assist an agency in determining a potential range of treatments. 

An agency should always use an engineering study to determine if a specific treatment would be ideal at a location 

due to the site characteristics, agency standards, local driving laws, and other factors. In addition, the manual is 

focused on infrastructure safety improvements. It does not include enforcement, education, or emergency medical 

services treatments.

This manual only addresses treatments on HRRR, which are limited to rural collectors and rural local roads. 

While rural roads also include Interstate highways and arterials, those roadways are not addressed in this manual.

Treatment costs were identified through a survey of State, local, and Tribal agencies with experience applying safety 

treatments on HRRR. Resulting treatments costs were averaged and may not be representative of costs required to 

employ the treatments at each applicable location or costs incurred by each agency.

For each treatment where cost information was provided by agencies in the survey, a benefit cost ratio (BCR) is 

shown. A BCR value greater than 1.0 reflects a return on investment. For example, a BCR of 2.5 suggests that for 

every one dollar spent, a $2.50 benefit can be expected. Additional information related to how BCRs for safety 

treatments are calculated can be found in Section 6.4.

When responding to the survey, agencies did not always provide benefit or cost information for each safety 

treatment. In these cases, benefits, costs, or BCRs were not included in the HRRR Treatment Matrix. 
Manual for Selecting Safety Improvements on High Risk Rural Roads

3

2. High Risk Rural Roads Overview

High risk rural roads include rural collectors and rural local roads.1 The fatality rate on rural collectors and rural 

local roads is more than 1.5 times higher than the fatality rate on urban collectors and local roads, as shown in 

Table 1.2

 

Table 2. 2010 Rural vs. Urban Collector and Local Road VMT and Fatality Rate Comparison

Rural Urban

VMT* Fatalities Fatality Rate** VMT* Fatalities Fatality Rate**

357,351 5,169 1.45 451,285 4,056 0.90

VMT = vehicle miles traveled

* In Millions ** Per 100 Million VMT

Example: To obtain the rural fatality rate, 1.45=(5,169*100)/357,351

2.1. High Risk Rural Road Safety

The higher roadway fatality rate on 

rural roadways is the result of many 

factors, including the following:

The physical characteristics of the 

roadways. Many rural roadways 

on both the State and local systems 

lack shoulders and clear zones that 

provide an area of recovery for 

roadway departures, which is the 

most prevalent crash type on these 

roadways.

Behavioral issues such as higher 

speeds, reduced seat belt use, and 

higher rates of impaired driving.3

On rural routes, the ability to drive at 

a higher speed is not limited by the congestion found in urban areas. Motorists in rural areas are also more likely 

to drive while under the influence of alcohol and drugs. Rural areas also exhibit lower seat belt use than urban 

areas by nearly 20 percent.4

Increased Emergency Medical Services response time to incidents. When a severe crash occurs, the time it 

takes for victims to receive medical care is sometimes a determining factor of the severity of crash-caused injuries. 

In particular, the “golden hour” (one hour immediately following a roadway crash) is especially important when 

1 Per the Safe, Accountable, Flexible, Efficient Transportation Equity Act: A Legacy for Users (SAFETEA:LU) Title 23 Sec. 148 “Highway Safety Improvement Program” and 

Moving Ahead for Progress in the 21st Century (MAP-21) Title 23 Sec. 1112 “Highway Safety Improvement Program.”

2 U.S. Department of Transportation, National Highway Traffic Safety Administration, “Traffic Safety Facts 2010,” Rural and Urban Comparison 2010 Data. July 2012. Available 

at: http://www-nrd.nhtsa.dot.gov/Pubs/811637.pdf.

3 Chandler, B. and R. Anderson, “Implementing the High Risk Rural Roads Program,” March 2010. Available at: http://safety.fhwa.dot.gov/local_rural/training/fhwasa10012/

fhwasa10012.pdf.

4 Strine, T.W., L.F. Beck , J. Bolen, C. Okoro, S. Dhingra, and L. Balluz, “Geographic and Sociodemographic Variation in Self-reported Seat Belt Use in the United States,” 

Accident Analysis & Prevention, 2010 July; 42(4): 1066-71. Epub 2010 Jan 4.
Federal Highway Administration | Office of Safety 

4

a crash occurs. Due to the reduced likelihood of passers-by witnessing a crash or its effects in rural areas, the 

distance emergency medical responders often must travel, and the distance between a crash location and the 

location of a trauma center, the risk of severe injury and fatality outcomes due to crashes on rural roads is high. 

Challenges with limited data, safety expertise, and funding. The challenges of identifying safety improvements 

are due in part to the limited data available and varying levels of expertise of local agencies. Rural road issues 

compete for funding against the need for safety and expansion of urban road systems.

Each of these factors present challenges towards solving the fatal and severe crash problem on HRRR. 

2.2. Challenges of Applying Treatments to HRRR

Nearly 80 percent of HRRR are found on the locally owned road system.5 As of 2012, there were 89,004 local 

government units in the United States6

 that vary in the size of the engineering staff (including many jurisdictions 

with no engineering experience) and their expertise in making safety decisions. The financial responsibility for 

installing safety treatments in many locations is borne by the local agency, and competing community priorities 

may affect investment for upgrades in roadway safety.

Because local agencies maintain many of the HRRR, their challenges are important and include the following:

Insufficient Funding. Local transportation agencies often lack the funds needed to implement projects. Local 

agencies are often unfamiliar with the requirements of the State’s Federal-aid funding application process, 

procurement process, and Federal-aid requirements related to construction. In other cases a local agency may not 

be able to pay for the required matching funds or finance the upfront cost of the project prior to reimbursement. 

In addition, competition from the large number of local agencies for State or Federal funds can sometimes make it 

difficult to secure necessary safety funding. 

Potential solutions: It is important to establish effective means of communication and coordination between 

the local agencies and State DOTs so that local agencies can engage the State to best target available funds. 

Coordination between State and local agencies can include the State training local agencies about available 

funds for HRRR and educating them on how to apply.

Lack of Technical Expertise. Many local agencies have found it 

difficult to identify and select safety treatments, as local agencies are 

often structured differently than the State DOT and may not have a 

dedicated safety program with funding or dedicated staff. A single 

local agency staff member with responsibility for roadway safety 

may also play several roles within the local agency. When safety 

technical expertise is limited, local agencies may be unable to select 

the most appropriate solutions. 

Potential solutions: Local Technical Assistance Program (LTAP)- and Tribal Technical Assistance Program 

(TTAP)-led training and technical workshops covering low-cost safety improvements on HRRR and HSIP 

processes can support HRRR efforts by offering technical training to local and Tribal agencies related to safety 

data and safety management programs and by providing information on problem identification and safety 

improvement implementation.

5 FHWA, Developing Safety Plans: A Manual for Local Rural Road Owners, FHWA-SA-12-017 (Washington, DC: March 2012). Available at: http://safety.fhwa.dot.gov/local_

rural/training/fhwasa12017/.

6 U.S. Census Bureau. “2012 Census of Governments,” July 2012. Available at: http://www2.census.gov/govs/cog/2012/formatted_prelim_counts_23jul2012_2.pdf.
Manual for Selecting Safety Improvements on High Risk Rural Roads

5

In addition to the potential solutions listed previously, several State and local agencies have developed innovative 

contracting strategies to apply funding quickly and efficiently on high risk rural roads. These agencies have taken 

the following actions:

•	 Used public forces for labor and bulk materials purchases to more efficiently use funds on HRRR.

•	 Initiated on-call contracts that have decreased the amount of time that elapses between project selection and 

completion.

•	 Augmented DOT staffing with outside resources for data analysis, problem identification, project selection, 

and administration.7

•	 Used special safety program coordinators at the State DOT district and local levels.

•	 Maintained websites with helpful HRRR-related information for locals.

For additional information related to funding resources and process, see Sections 5.2 and 5.3. More discussion 

related to identifying HRRR safety issues, even with limited data, is found in Sections 3.1 and 3.2, while assistance 

in navigating the process for identifying appropriate safety treatments is in Section 6.

Lack of Data. In addition to a lack of funds and technical expertise can be a lack of 

understanding of which roadway and crash data are important to capture and how to 

go about the collection and evaluation process. 

Potential solutions: Agencies can use the limited data available, regardless of how small or incomplete the data 

set, to help determine a course of action. Data may include finite numerical values (quantitative data) or may 

come from conversations with law enforcement personnel and field staff to determine the types, contributing 

circumstances, and times of crashes that occur at specific locations (qualitative data). While specific volume 

data may not be available, agencies may be able to prioritize corridor-wide implementation by dividing 

roadways into low-, medium-, and high-volume categories. 

3. Identifying Safety Treatments

This chapter discusses several tools that can be used to identify and select safety treatments and presents the 

differences between the traditional methods of treating “spot” locations versus a systemic approach. 

3.1. Tools for Identifying HRRR Safety Issues

Technical expertise is cited as one of the most significant obstacles facing agencies when attempting to identify 

and implement safety treatments. Fortunately, many safety tools and opportunities for training exist for State and 

local transportation agencies. This section describes safety tools to assist with safety needs identification, use of 

available data—however limited—to make informed decisions with respect to selecting treatments, and additional 

resources and training opportunities.

7 FHWA, Implementing the High Risk Rural Roads Program, “Chapter 4. State Practices for Implementation,” FHWA-SA-10-012 (Washington, DC: March 2010). Available at: 

http://safety.fhwa.dot.gov/local_rural/training/fhwasa10012/chap_4.cfm.
Federal Highway Administration | Office of Safety 

6

Highway Safety Manual

The Highway Safety Manual (HSM) “Frequently Asked Questions” page describes the manual as providing: 

“... practitioners with information and tools to consider safety when making decisions related to design 

and operation of roadways. The HSM assists practitioners in selecting countermeasures and prioritizing 

projects, comparing alternatives, and quantifying and predicting the safety performance of roadway elements 

considered in planning, design, construction, maintenance, and operation.”8

 

The HSM uses data to estimate the safety impacts of incorporating safety features for existing roads or future 

projects by determining the impacts of design and other decisions on the expected safety performance of a facility. 

Safety Analyst

The Safety Analyst tool assists in making site-specific safety improvement recommendations that involve physical 

modifications to the roadway, either through systemic or spot location applications. As spot locations are being 

examined, the tool can help to identify crash patterns at specific locations and determine whether those crash 

types are overrepresented and the frequency at which crashes occur. The tool can help to identify opportunities for 

systemic solutions by identifying overrepresented crashes and clusters for highway segments or intersection types.9

 

Safety Analyst has the following capabilities to aid practitioners in each step of the safety management process, 

from needs identification to implementation and evaluation:

•	 A system-wide screening tool identifies potential sites for safety improvements. 

•	 A diagnostic tool detects the nature of safety problems at specific sites.

•	 A countermeasure selection tool assists users in selecting safety treatments to reduce crash frequency and 

severity at spot locations.

•	 An economic appraisal tool performs a financial assessment of a specific countermeasure or several 

alternative countermeasures for a specific site.

•	 A priority ranking tool provides a prioritized listing of sites and proposed improvements based on benefit and 

cost estimates determined by the economic appraisal tool.

•	 The evaluation tool assists practitioners in conducting before-and-after evaluations of implemented safety 

improvements.

Crash Modification Factor (CMF) Clearinghouse

The CMF Clearinghouse website10 provides a collection of calculated crash modification factors practitioners can 

apply to estimate the benefits of specific safety treatments. The website can be used by searching for a particular 

treatment name, which can be further refined by crash type or severity, roadway or intersection type, area 

type (e.g., urban, suburban, rural), and intersection geometry. Each safety improvement in the clearinghouse 

shows a CMF and Crash Reduction Factor (CRF), in addition to the quality or rating of the CMF. The quality 

rating indicates the quality or confidence in the results of the study producing the CMF.11 CMFs and CRFs are 

accompanied with details of the research conducted to develop the CMF.

8 AASHTO, “Highway Safety Manual-Related Frequently Asked Questions (FAQs),” last modified June 14, 2013, http://www.highwaysafetymanual.org/support.aspx.

9 Safety Analyst website, accessed October 9, 2013. http://www.safetyanalyst.org/.

10 CMF Clearinghouse website, accessed October 9, 2013. http://www.cmfclearinghouse.org.

11 CMF Clearinghouse website, “About the Star Quality Rating,” accessed October 9, 2013. http://www.cmfclearinghouse.org/sqr.cfm.
Manual for Selecting Safety Improvements on High Risk Rural Roads

7

Road Safety Audits

A Road Safety Audit (RSA) is the formal safety performance examination of an existing or future road or 

intersection by an independent, multidisciplinary team. It qualitatively estimates and reports on potential road 

safety issues and identifies opportunities for improvements in safety for all road users.12 RSAs can be integrated 

into the project development process for new roads and intersections, on existing roads and intersections, and for 

future or existing work zones. 

For HRRR, the multidisciplinary team’s expertise can 

include those familiar with rural issues, law 

enforcement officers, emergency service providers, 

human factors experts, and engineering fields including 

design, traffic safety, operations and maintenance, and 

others. The team assesses site-specific conditions and 

recommends improvements based on the team’s road 

safety expertise in each member’s respective fields.

RSAs can help to reduce crash severity and frequency 

while accounting for all road users. If performed 

during the design phase, RSAs serve as a proactive 

approach to improving safety before construction 

begins.

Training

Opportunities for and depth of training vary based on the agency’s need. Practitioners can inquire about training 

based on their own specific needs beginning with the following resources: 

•	 Local Technical Assistance Programs (LTAP) and Tribal Technical Assistance Programs (TTAP). LTAPs 

and TTAPs are a great technical resource and regularly provide training opportunities on many program 

areas. For more information, a visit to the national LTAP website can direct practitioners toward the LTAP or 

TTAP in their area.13

•	 Highway Safety Manual. The HSM website Training Page has information on HSM courses currently 

available.14 The National Highway Institute (NHI) offers courses related to the HSM.15 For more information 

State and local departments of transportation can contact their FHWA Division Office for training assistance. 

•	 Road Safety Audits. FHWA provides technical assistance and trainings for RSAs. For more information, see 

FHWA’s RSA website.16

•	 National Association of County Engineers (NACE) and National Association of Counties (NACO). 

NACE and NACO convene regularly, on both regional and national levels. The association is a forum 

for county engineers and staff to discuss safety and other issues related to the local road system. More 

information can be found on the NACE and NACO websites.17,18 

12 FHWA Road Safety Audit website. Accessed October 9, 2013. http://safety.fhwa.dot.gov/rsa/.

13 Local and Tribal Technical Assistance Program website, accessed December 3, 2013. http://www.ltap.org/.

14 Highway Safety Manual Training website, accessed December 3, 2013. http://www.highwaysafetymanual.org/Pages/Training.aspx.

15 National Highway Institute website, accessed December 3, 2013. https://www.nhi.fhwa.dot.gov/default.aspx.

16 FHWA Road Safety Audit website, accessed December 3, 2013. http://safety.fhwa.dot.gov/rsa.

17 National Association of County Engineers website, accessed December 3, 2013. http://www.countyengineers.org.

18 National Association of Counties website, accessed December 3, 2013. http://www.naco.org.
Federal Highway Administration | Office of Safety 

8

3.2. Systemic Implementation and Spot Location Treatments

A challenge in addressing safety in rural areas is that crashes tend to be widely dispersed geographically. The 

high number of lane miles and the dispersed nature of crashes make it difficult to target specific locations for 

assessment and improvement. Therefore, applying a systemic approach to addressing safety issues is a beneficial 

method for proactively addressing widespread safety concerns and cost-effectively minimizing crash potential. 

Rather than focus on specific crash locations, a systemic approach targets common risk factors in crashes 

throughout the roadway network. A systemic improvement is widely implemented based on high-risk roadway 

features that are correlated with particular crash types rather than location-based crash frequency. The systemic 

problem identification entails a system-wide crash analysis targeting specific crash characteristics at the system 

level. 

Systemic solutions can reduce overall severe crashes of certain types in a jurisdiction more effectively than 

choosing a small number of spot locations. This approach allows an agency to compensate for incomplete 

and lower quality crash history or roadway data, as it is less vital for that information to be perfect when many 

locations or segments are addressed with low-cost treatments. 

With the systemic approach, implementation must be widespread enough to make a region-wide impact. 

Additionally, it can sometimes be difficult to convince stakeholders to apply safety treatments (even if low-cost) at 

locations that do not have a history of crashes.

Traditionally, a common approach has been to identify “black spots,” or locations with the highest crash frequency. 

While specific implementation sites are easily identified using roadway and crash data, this approach does not 

adequately deal with the randomness of the location of fatal and severe injury crashes. The traditional approach 

does not directly account for the most prevalent risk types associated with system-wide crashes.

This manual presents safety treatments that can be applied systemically, specifically at spot locations, or using both 

implementation methods.

For additional information on spot location and systemic safety treatment installations, please visit the following 

resources:

•	 A Systemic Approach to Safety: Using Risk to Drive Action. 

Available at: http://safety.fhwa.dot.gov/systemic/index.htm

•	 Roadway Safety Information Analysis: A Manual for Local Rural Road Owners. 

Available at: http://safety.fhwa.dot.gov/local_rural/training/fhwasaxx1210/index.cfm
Manual for Selecting Safety Improvements on High Risk Rural Roads

4. Selecting Safety Treatments

This chapter features safety improvements used on HRRR that were identified by a survey of State, local, and Tribal 

agencies. The treatments are separated by section under the following categories. Each category has a color coded 

tab on the bottom of the page to assist with locating specific sections:

 9

Applicability of “Urban” Treatments to HRRR

Several agencies identified treatments used on high risk rural roads even though the treatments are 

typically viewed as treatments used in urban areas. In these cases, the functional classification of a 

HRRR did not change when the road passed through a small city or town and was still classified as rural. 

These treatments include, but are not limited to:

•	 Shared-used paths adjacent to the roadway;

•	 Shoulders for non-motorized users;

•	 Exclusive bicycle lanes;

•	 Bicycle trail grade separation structures;

•	 Sidewalks;

•	 Crosswalks at targeted locations;

•	 Pedestrian hybrid beacons (or high intensity activated crosswalk, known as HAWK)

•	 Rectangular rapid flash beacons;

•	 Staggered and raised median islands;

•	 Curb extensions; and

•	 Pedestrian signal heads added to existing signalized intersections.

Horizontal Curves

Intersections (Signalized)

Intersections (Unsignalized)

Non-Motorized User

Pavement and Shoulder Resurfacing

Pavement Marking 

Roadside

Signing

Vertical Curves

Other Treatments
Federal Highway Administration | Office of Safety 

10

4.1. Horizontal Curves

Safety improvement treatments on horizontal curves range from low-cost improvements (such as signing) to 

high-cost improvements (such as modifying road geometry). This section covers safety improvement treatments 

that can be applied at horizontal curve locations. Some treatments in this section also appear in the sections on 

intersection improvements, signing, and roadside safety.1920

19 As discussed in Section 1.2, a BCR is only shown where data were available to calculate the ratio. Where data were unavailable, it has been left blank.

20 As stated in NCHRP Series 500 Reports (http://safety.transportation.org/guides.aspx). Proven: The safety effect for other similar applications has shown a proven benefit. 

Tried: The treatment has indications that it can be expected to reduce crashes, but has some conflicting reports as to its associated safety effects or has been deployed and 

observed to be effective. Experimental: New treatments that still need to be tested and for which the safety effect is unknown. Unknown: Not enough is known about an 

associated safety performance.

Safet

y Treatment

For more information, 

visit page

C

ost

Frequency of 

Maintenance (years)

Safet

y

Benefit

Benefit-Cost

Ratio 19

Initial 

Implementation

Ongoing 

Maintenance

NCHRP 500 

Performance Rating

Crash Modification 

Factor (CMF)

Lower Volume*, 

Optimal Conditions***

Higher Volume**, 

Optimal Conditions***

Lower Volume*, 

Narrower Conditions****

Higher Volume**, 

Narrower Conditions****

Install Curve Warning Signs 11 $ $ 5 P 0.70 33.8 270.1 43.5 428.4Install/Upgrade Curve Warning Signs with Fluorescent Yellow Sheeting 12 $ – 5 P 0.66 63.1 490.4 75.1 739.9Double Use of Advanced Warning Signs for Curves or Intersections 13 $

T

Use of Optical Speed Bars 14 $Install Chevron Signs 15 $$ $ 5 P 0.75 10.6 84.7 13.0 127.7Install Arrow Signs at Horizontal Curve Locations 16 $$ – 10 P 27.9 222.8 34.1 336.1Install Post-Mounted Delineators at Horizontal Curves 17 $$ – 10 P 5.3 42.4 6.5 63.9Install Targeted Longitudinal Rumble Strips on the Outside of Horizontal Curves 18 $$ T 0.85Install Icy Curve Warning System 19 $$ E 0.82

Improve Superelevation at Horizontal Curve Locations 20 $$$$ PRemove Compound Horizontal Curves 21 $$$$$

T

Modify Horizontal/Vertical Geometry 22 $$$$$ P

Horizontal Curves

Cost:$ = $0 to $5,000$$ = $5,001 to $20,000$$$ = $20,001 to $50,000$$$$ = $50,001 to $100,000$$$$$ = $100,001 and up

NCHRP 500 Performance Rating20

P – ProvenT – TriedE – ExperimentalU – Unknown

*Lower Volume ≤1000 vpd**Higher Volume = Between 1,001 and 8000 vpd***Optimal Conditions = 12-foot lanes, 6-foot paved shoulders****Narrower Conditions = 10-foot lanes and no shoulders
Manual for Selecting Safety Improvements on High Risk Rural Roads

Install Curve Warning Signs 11

Install Curve Warning Signs 

Some of the most serious crashes on rural roads occur 

at horizontal curves. Horizontal alignment signs, 

informally called curve warning signs, can improve safety 

by alerting drivers to changes in roadway geometry that 

may not be apparent or expected. These signs provide 

visual information for the driver about the nature of the 

curve they are approaching, letting them know whether 

it’s a gradual curve, a sharp turn, a hairpin turn, or some 

combination. Different types of curve warning signs are 

identified in the MUTCD. 

Where to Use: Curve warning signs should be applied 

to any curve or turn with a history of roadway departure 

crashes and curves or turns with similar geometry or 

traffic volumes yet to experience crashes. According to 

the 2009 MUTCD, warning signs are required on curves 

or turns where the advisory speed is 10 mph less than the 

posted speed.

Studies have shown that reductions in crashes due to the 

installation of curve warning signs are more prominent at 

locations with higher traffic volumes, sharper curves, or 

hazardous roadsides.

Top Recommended Resources:

1. University of California, Berkley, Institute of Transportation Studies, Technology Transfer Program, Tech 

Transfer Newsletter, “Signs for Curves and Turns.” Available at: 

http://www.techtransfer.berkeley.edu/newsletter/08-2/signs-for-curves-and-turns.php.

2. FHWA, Roadway Departure Safety: A Manual for Local Rural Road Owners, January 2011. Available at: 

http://safety.fhwa.dot.gov/local_rural/training/fhwasa1109/fhwasa1109.pdf.

Install Curve Warning Signs

- Initial Investment: $2,400

- Cost of Maintenance: $1,280

- Frequency of Maintenance: 5 years

Benefit-Cost 

Ratio

NCHRP 500 

Performance 

Rating

Crash 

Modification 

Factor (CMF)

Lower Volume Optimal Conditions 33.8 Proven 0.70

Higher Volume Optimal Conditions 207.1 Proven 0.70

Lower Volume Narrower Conditions 43.5 Proven 0.70

Higher Volume Narrower Conditions 428.4 Proven 0.70
Federal Highway Administration | Office of Safety 

12

Install/Upgrade Curve Warning Signs with Fluorescent Yellow Sheeting 

Fluorescent yellow sheeting can improve the effectiveness 

of curve warning and delineation signs by increasing the 

conspicuity, or prominent visibility, of the sign, especially 

during dark conditions.

Where to Use: Connecticut DOT used fluorescent 

yellow sheeting to improve signing at horizontal curves 

between 2002 and 2006. These curves were selected 

through a regular program called the Suggested List of 

Surveillance Study Sites (SLOSSS), which uses crash data, 

traffic volumes, and roadway characteristics to identify 

intersections and road segments with higher than 

expected crash rates.

Top Recommended Resource:

1. FHWA, Safety Evaluation of Improved Curve Delineation, September 2009. Available at: 

http://www.fhwa.dot.gov/publications/research/safety/09045/09045.pdf

Install/Upgrade Curve Warning Signs with 

Fluorescent Yellow Sheeting 

- Initial Investment: $1,280

- Cost of Maintenance: n/a

- Frequency of Maintenance: 5 years (2 applications)

Benefit-Cost 

Ratio

NCHRP 500 

Performance 

Rating

Crash 

Modification 

Factor (CMF)

Lower Volume Optimal Conditions 63.1 Proven 0.66

Higher Volume Optimal Conditions 490.4 Proven 0.66

Lower Volume Narrower Conditions 75.1 Proven 0.66

Higher Volume Narrower Conditions 739.9 Proven 0.66

Install/Upgrade Curve Warning Signs with Fluorescent Yellow Sheeting 
Manual for Selecting Safety Improvements on High Risk Rural Roads

 13

Double Use of Advanced Warning Signs for Curves or Intersections 

Doubling the use of either Intersection Ahead warning signs or Curve Ahead warning signs (i.e., on the left and 

right) is recommended for locations where the crash rates have not been reduced after installation of a single 

advanced warning sign.

Where to Use: This treatment may be used at locations where crashes indicate that motorists do not heed existing 

advanced warning signs and additional conspicuity is needed.

Top Recommended Resource:

1. FHWA, Low Cost Treatments for Horizontal Curve Safety, December 2006. Available at: 

http://safety.fhwa.dot.gov/roadway_dept/horicurves/fhwasa07002/.

Safety Treatment

Initial 

Implementation 

Cost

NCHRP 500 

Performance 

Rating

Double Use of Advanced Warning Signs $0 to $5,000 Tried

Double Use of Advanced Warning Signs for Curves or Intersections
Federal Highway Administration | Office of Safety 

14

Use of Optical Speed Bars 

Optical speed bars are transverse stripes spaced at gradually 

decreasing distances. The rationale for using them is to increase 

drivers’ perception of speed and cause them to reduce speed, 

which can be helpful near intersections or horizontal curves. The 

Optical speed bar name comes from this intended visual effect 

on drivers’ speed as they react to the spacing of the painted lines. 

These white transverse stripes are 18 inches long and 12 inches 

wide. The preferred material is thermoplastic because of the 

exposure to traffic volume over time. 

Where to Use: This treatment may be used at locations where speed reductions are needed, such as near 

intersections and horizontal curves. 

Top Recommended Resource:

1. FHWA, Low Cost Treatments for Horizontal Curve Safety, December 2006. Available at: 

http://safety.fhwa.dot.gov/roadway_dept/horicurves/fhwasa07002/.

Safety Treatment

Initial 

Implementation 

Cost

Use of Optical Speed Bars $0 to $5,000

Use of Optical Speed Bars
Manual for Selecting Safety Improvements on High Risk Rural Roads

 15

Install Chevron Signs 

Chevron signs (or curve delineation signs) indicate to 

drivers the alignment of the roadway when they are 

within the actual horizontal alignment of a curve. The 

signs show the shape and degree of curvature, and they 

guide drivers through the entire curve or turn.

Where to Use: Chevrons should be installed at any 

curve or turn with a history of roadway departure 

crashes and at curves or turns with similar geometry 

or traffic volume yet to experience crashes. According 

to the 2009 MUTCD, alignment delineation (or a 

single-directional large arrow) is required on curves 

or turns where the advisory speed is 15 mph less than 

the posted speed limit. They can be installed at locations where no chevrons currently exist, or to supplement 

chevrons that are already in place.

Top Recommended Resource:

1. FHWA, Roadway Departure Safety: A Manual for Local Rural Road Owners, January 2011. Available at: 

http://safety.fhwa.dot.gov/local_rural/training/fhwasa1109/fhwasa1109.pdf.

Install Chevron Signs

- Initial Investment: $7,200

- Cost of Maintenance: $3,600

- Frequency of Maintenance: 5 years

Benefit-Cost 

Ratio

NCHRP 500 

Performance 

Rating

Crash 

Modification 

Factor (CMF)

Lower Volume Optimal Conditions 10.6 Proven 0.75

Higher Volume Optimal Conditions 84.7 Proven 0.75

Lower Volume Narrower Conditions 13.0 Proven 0.75

Higher Volume Narrower Conditions 127.7 Proven 0.75

Install Chevron Signs
Federal Highway Administration | Office of Safety 

16

Install Arrow Signs at Horizontal Curve Locations 

The One-Direction Large Arrow sign is used to 

define a change in horizontal alignment. It can be 

used alone or to supplement other curve warning 

signs, such as chevrons. 

Where to Use: The sign is typically placed on 

the outside of the curve directly in line with 

the approaching tangent section. The MUTCD 

guidance regarding the application of this sign is 

to install either the One-Direction Large Arrow 

sign or the Chevron Alignment sign when the Hairpin Curve sign or the Loop sign is installed. Based on standard 

practice, this sign is limited to sharper curves (turns). It should not be used when there is no advisory speed 

plaque.

Top Recommended Resource:

1. FHWA, Low Cost Treatments for Horizontal Curve Safety, December 2006. Available at: 

http://safety.fhwa.dot.gov/roadway_dept/horicurves/fhwasa07002/.

Install Arrow Signs at Horizontal Curve Locations

- Initial Investment: $5,600

- Cost of Maintenance: n/a

- Frequency of Maintenance: 10 years

Benefit-Cost 

Ratio

NCHRP 500 

Performance 

Rating

Lower Volume Optimal Conditions 27.9 Proven

Higher Volume Optimal Conditions 222.8 Proven

Lower Volume Narrower Conditions 34.1 Proven

Higher Volume Narrower Conditions 336.1 Proven

Install Arrow Signs at Horizontal Curve Locations
Manual for Selecting Safety Improvements on High Risk Rural Roads

 17

Install Post-Mounted Delineators at Horizontal Curves 

When used within horizontal curves, 

post-mounted delineators with 

retroreflective sheeting the full length of the 

post improves driver lane position both at 

the entry to the curve and at its midpoint. 

Where to Use: For best results, 

post-mounted delineators are to be installed 

on each chevron support post and coupled 

with edge line and center line pavement 

markings.

Top Recommended Resource:

1. FHWA, Low Cost Treatments for Horizontal Curve Safety, December 2006. Available at: 

http://safety.fhwa.dot.gov/roadway_dept/horicurves/fhwasa07002/.

Install Post-Mounted Delineators at Horizontal Curves

- Initial Investment: $5,600

- Cost of Maintenance: n/a

- Frequency of Maintenance: 10 years

Benefit-Cost 

Ratio

NCHRP 500 

Performance 

Rating

Lower Volume Optimal Conditions 5.3 Proven

Higher Volume Optimal Conditions 42.4 Proven

Lower Volume Narrower Conditions 6.5 Proven

Higher Volume Narrower Conditions 63.9 Proven

Install Post-Mounted Delineators at Horizontal Curves
Federal Highway Administration | Office of Safety 

18

Install Targeted Longitudinal Rumble Strips on the Outside of Horizontal Curves

Shoulder or edge line milled rumble strips can be used 

on roads with a history of roadway departure crashes. 

While it is recommended that rumble strips be applied 

systematically along an entire route instead of only at 

spot locations, where appropriate, they can be used on 

the outside of horizontal curves and the tangent leading 

to the curves.

Where to Use: This treatment may be used at 

horizontal curve locations with a high frequency of 

roadway departure crashes.

Top Recommended Resource:

1. FHWA, Low Cost Treatments for Horizontal Curve Safety, December 2006. Available at: 

http://safety.fhwa.dot.gov/roadway_dept/horicurves/fhwasa07002/.

Safety Treatment

Initial 

Implementation 

Cost

NCHRP 500 

Performance 

Rating

Crash 

Modification 

Factor (CMF)

Install Targeted Longitudinal Rumble Strips on the 

Outside of Horizontal Curves $5,001 to $20,000 Tried 0.85

Install Targeted Longitudinal Rumble Strips on the Outside of Horizontal Curves
Manual for Selecting Safety Improvements on High Risk Rural Roads

 19

Install Icy Curve Warning System 

Icy curve warning systems may be installed at problematic areas where ice 

formation frequently recurs. Using in-pavement weather sensors, icy curve 

warning signs are activated to alert motorists of upcoming icy conditions. 

Where to Use: This treatment may be useful in locations that experience 

recurring icy conditions, such as horizontal curves located in mountain passes.

Top Recommended Resource:

1. Ye, Z., D. Veneziano, and I. Turnbull, Safety Effects of Icy Curve Warning Systems, 2012. Available at: 

http://www.westernstates.org/projects/coats/Documents/TRB2012/Fredonyer%20ICWS_TRB%20Safety%20

Paper_2012-1-23_FINAL.pdf.

Safety Treatment

Initial 

Implementation 

Cost

NCHRP 500 

Performance 

Rating

Crash 

Modification 

Factor (CMF)

Install Icy Curve Warning System $5,001 to $20,000 Experimental 0.82

Install Icy Curve Warning System 
Federal Highway Administration | Office of Safety 

20

Improve Superelevation at Horizontal Curve Locations 

Superelevation is the rotation of the 

pavement on the approach to and through 

a horizontal curve and is intended to 

assist the driver in negotiating the curve 

by counteracting the lateral acceleration 

produced by tracking. In other words, 

the road is designed so that the pavement 

rises as it curves, offsetting the horizontal 

sideways momentum of the approaching 

vehicle.

Where to Use: Superelevation is expressed as a decimal representing the ratio of the pavement slope to width, 

ranging from 0 to 0.12 feet. The adopted criteria allow for the use of maximum superelevation rates from 0.04 to 

0.12. Maximum superelevation rates for design are established by policy by each State. Selection of a maximum 

superelevation rate is based on several variables, such as climate, terrain, highway location (urban vs. rural), 

and frequency of very slow-moving vehicles. Specific guidance on superelevation rates can be found in A Policy 

on Geometric Design of Highways and Streets, AASHTO, 2011 and Guidelines for Geometric Design of Very 

Low‐Volume Local Roads (ADT ≤ 400), AASHTO, 2001.

Top Recommended Resources:

1. FHWA, Mitigating Strategies for Design Exceptions, July 2007. Available at: 

http://safety.fhwa.dot.gov/geometric/pubs/mitigationstrategies/.

2. NCHRP Project 17-18(3), Strategy 15.2 A12: Improve or Restore Superelevation (P). Available at: 

http://safety.transportation.org/htmlguides/horz_crvs/default.htm.

3. AASHTO, Guidelines for Geometric Design of Very Low-volume Local Roads (ADT 400), January 2001.

4. AASHTO, A Policy on Geometric Design of Highways and Streets, November 2011.

Safety Treatment

Initial 

Implementation 

Cost

NCHRP 500 

Performance 

Rating

Improve Superelevation at Horizontal Curve Locations $50,001 to 

$100,000 Proven

Improve Superelevation at Horizontal Curve Locations
Manual for Selecting Safety Improvements on High Risk Rural Roads

 21

Remove Compound Horizontal Curves 

Drivers typically expect a single steering setting while negotiating a 

horizontal curve. Replacing compound curves with a single radius 

curve better adheres to driver expectations.

Where to Use: This treatment may be used on HRRR with locations 

of compound horizontal curves that experience a high frequency of 

roadway departure crashes. This treatment is especially applicable 

where other treatments have been applied at the curve location and 

have not been successful in reducing crashes.

Safety Treatment

Initial 

Implementation 

Cost

NCHRP 500 

Performance 

Rating

Remove Compound Horizontal Curves $100,001 and up Tried

Remove Compound Horizontal Curves 

Top Recommended Resource:

1. NCHRP Project 17-18(3), Strategy 15.2 A13: Modify Horizontal Alignment (P). Available at: 

http://safety.transportation.org/htmlguides/horz_crvs/default.htm.
Federal Highway Administration | Office of Safety 

22

Modify Horizontal/Vertical Geometry

Horizontal and vertical geometry may be reconstructed 

in a variety of ways. For example, horizontal and vertical 

curves may benefit from increased radii, thereby increasing 

sight distance. Modifying road geometry may also include 

eliminating horizontal or vertical curves and providing a 

more direct alignment. 

Where to Use: This treatment may be used at locations 

where improved sight distance is needed and at locations that 

experience head-on collisions and run-off-road crashes.

Top Recommended Resource:

1. NCHRP Project 17-18(3), Strategy 15.2 A13: Modify Horizontal Alignment (P). Available at: 

http://safety.transportation.org/htmlguides/horz_crvs/default.htm.

Safety Treatment

Initial 

Implementation 

Cost

NCHRP 500 

Performance 

Rating

Modify Horizontal/Vertical Geometry $100,001 and up Proven

Modify Horizontal/Vertical Geometry
Manual for Selecting Safety Improvements on High Risk Rural Roads

 23

4.2. Intersections (Signalized)

Signalized intersection-specific safety treatments assist drivers in recognizing they are at or approaching 

signal-controlled intersecting routes, provide storage for turning traffic,21 and give positive guidance to motorists 

through the intersection.2

 3

21 Turn lane storage is the length of turn lane provided based on anticipated traffic needs.

22 As discussed in Section 1.2, a BCR is only shown where data were available to calculate the ratio. Where data were unavailable, the BCR has been left blank.

23 As stated in NCHRP Series 500 Reports (http://safety.transportation.org/guides.aspx). Proven: The safety effect for other similar applications has shown a proven benefit. 

Tried: The treatment has indications that it can be expected to reduce crashes, but has some conflicting reports as to its associated safety effects or has been deployed and 

observed to be effective. Experimental: New treatments that still need to be tested and for which the safety effect is unknown. Unknown: Not enough is known about an 

associated safety performance.

Safet

y Treatment

For more information, 

visit page

C

ost

Frequency of 

Maintenance (years)

Safet

y

Benefit

Benefit- Cost

Ratio 22

Initial 

Implementation

Ongoing 

Maintenance

NCHRP 500 

Performance Rating

Crash Modification 

Factor (CMF)

Lower Volume*

Higher Volume**

Improve Traffic Signal Visibility (Larger Diameter Lens or Install Back Plate) 24 $ P 0.85

Provide Intersection Lighting 25 $$ $ 1 P 0.41-0.88 26.9 93.8Install Pedestrian Signal Heads to Existing Signalized Intersections 26 $$ PProvide Flashing Beacons at Intersection Approaches 27 $$$ $ 2 P 11.0 38.2Use Raised Median to Restrict Turning Movements 28 $$$-$$$$ P 0.61-1.09

Install Priority Control Systems for Emergency Vehicles 29 $$$-$$$$

T

Provide Advanced Dilemma Zone Detection for Rural High Speed Signalized Approaches 30 $$$-$$$$ P 0.61

Implement J-Turns Along a Signalized Corridor 31 $$$$ $ 10 P 45.4 159.1

Install Acceleration or Deceleration Lanes 32 $$$$ PInstall Right Turn Lane 33 $$$$$ $$ 10 P 0.77-0.96 4.9 16.9

Install Left Turn Lane 34 $$$$$ $$ 10 P 0.50-0.80 4.1 14.1Install Offset (or Channelized) Left Turn Lane 35 $$$$$ $$ 10 P 0.80 4.1 14.1

Convert a Traditional Signalized Intersection into a Roundabout 36 $$$$$ $$$ 10 P 0.26-0.82 4.8 16.6

Reconstruct At-Grade Intersection to Create an Interchange 37 $$$$$ $$$ 10 P 0.43-0.64 0.1 0.4

Cost:$ = $0 to $5,000$$ = $5,001 to $20,000$$$ = $20,001 to $50,000$$$$ = $50,001 to $100,000$$$$$ = $100,001 and up

NCHRP 500 Performance Rating23 

P – ProvenT – TriedE – ExperimentalU – Unknown

*Lower Volume ≤1000 vpd**Higher Volume = Between 1,001 and  8000 vpd

Intersections (Signalized)
Federal Highway Administration | Office of Safety 

24

Improve Traffic Signal Visibility (Larger Diameter Lens or Install Back Plate)

Enhancing the visibility of traffic signals can help to 

eliminate red-light running and associated crashes. 

Enhancements may include installing signal lenses with a 

larger diameter and using reflective back plates. 

Where to Use: This treatment may be used when crash 

types such as red-light running indicate that visibility of 

traffic signal is an issue. 

Top Recommended Resource:

1. FHWA, Signalized Intersections Informational Guide, July 2013. Available at: 

http://safety.fhwa.dot.gov/intersection/signalized/13027/index.cfm.

Safety Treatment

Initial 

Implementation 

Cost

NCHRP 500 

Performance 

Rating

Crash 

Modification 

Factor (CMF)

Improve Traffic Signal Visibility $2,000 Proven 0.85

Improve Traffic Signal Visibility (Larger Diameter Lens or Install Back Plate)
Manual for Selecting Safety Improvements on High Risk Rural Roads

 25

Provide Intersection Lighting

Many intersection crashes during late-night and 

early-morning hours occur due to poor visibility, 

which results in drivers being unable to see conflicting 

traffic, other road users, or—specifically in the case 

of unsignalized intersections—the presence of the 

intersection itself. At night in rural areas, the only 

source of lighting for roadways is often provided 

by vehicle headlights. Roadway lighting allows for 

greater visibility of the intersection, which makes 

the intersection more conspicuous to motorists and 

provides aid in helping drivers determine their paths 

through the intersection by making signs and markings 

more visible.

Where to Use: Lighting should be provided at signalized or unsignalized intersections, particularly those with 

a high instance of dark crashes. Rear-end, right-angle, or turning crashes on the major road approaches to an 

unsignalized intersection may indicate that approaching drivers are unaware of the presence of the intersection. 

Top Recommended Resource:

1. FHWA, Signalized Intersections Informational Guide, July 2013. Available at: 

http://safety.fhwa.dot.gov/intersection/signalized/13027/index.cfm.

Provide Intersection Lighting

- Initial Investment: $20,000

- Cost of Maintenance: $500

- Frequency of Maintenance: 1 year

Benefit-Cost 

Ratio

NCHRP 500 

Performance 

Rating

Crash 

Modification 

Factor (CMF)

Lower Volume Signalized Intersections 26.9 Proven 0.41–0.88

Higher Volume Signalized Intersections 93.8 Proven 0.41–0.88

Provide Intersection Lighting
Federal Highway Administration | Office of Safety 

26

Install Pedestrian Signal Heads to Existing Signalized Intersections 

Pedestrian signal heads provide special types of traffic signal indications exclusively intended for controlling 

pedestrian traffic. These signal indications consist of the illuminated symbols of a walking person (symbolizing 

Walk) and an upraised hand (symbolizing Don’t Walk).

Where to Use: This treatment is applicable where pedestrian traffic exists at signalized intersections.

Top Recommended Resources:

1. FHWA, Manual on Uniform Traffic Control Devices, “Chapter 4E. Pedestrian Control Features,” December 

2009. Available at: http://mutcd.fhwa.dot.gov/pdfs/2009r1r2/mutcd2009r1r2edition.pdf. 

2. FHWA, Signalized Intersections Informational Guide, July 2013. Available at: 

http://safety.fhwa.dot.gov/intersection/signalized/13027/index.cfm.

Safety Treatment

Initial 

Implementation 

Cost

NCHRP 500 

Performance 

Rating

Install Pedestrian Signal Heads to Existing Signalized 

Intersections $5,001 to $20,000 Proven

Install Pedestrian Signal Heads to Existing Signalized Intersections 
Manual for Selecting Safety Improvements on High Risk Rural Roads

 27

Provide Flashing Beacons at Intersection Approaches

Flashing beacons provide a visible signal to the 

presence of an intersection and can be very effective 

in rural areas where there may be long stretches 

between intersections as well as in locations where 

nighttime intersection visibility is an issue. 

Where to Use: Flashing beacons can be installed 

prior to signalized intersections with patterns of 

right-angle crashes related to lack of driver awareness 

of the upcoming signalized intersection. The beacons 

can be installed atop Advance Signal Ahead signs.

Top Recommended Resource:

1. FHWA, Intersection Safety: A Manual for Local Rural Road Owners, “Chapter 4. Countermeasures,” January 

2011. Available at: http://safety.fhwa.dot.gov/local_rural/training/fhwasa1108/ch4.cfm.

Provide Flashing Beacons at Intersection Approaches

- Initial Investment: $25,000

- Cost of Maintenance: $1,000

- Frequency of Maintenance: 2 years

Benefit-Cost 

Ratio

NCHRP 500 

Performance 

Rating

Lower Volume Signalized Intersections 11.0 Proven

Higher Volume Signalized Intersections 38.2 Proven

Provide Flashing Beacons at Intersection Approaches
Federal Highway Administration | Office of Safety 

28

Use Raised Median to Restrict Turning Movements 

Raised medians can be helpful in limiting access and restricting 

turning movements within the functional limits of intersections, 

thereby reducing conflicts between through traffic and turning 

vehicles.

Where to Use: This treatment may be used at locations where 

access to streets, businesses, homes, and other properties falls within 

the intersection functional area.

Top Recommended Resource:

1. FHWA, Signalized Intersections Informational Guide, July 2013. Available at: 

http://safety.fhwa.dot.gov/intersection/signalized/13027/index.cfm.

Safety Treatment

Initial 

Implementation 

Cost

NCHRP 500 

Performance 

Rating

Crash 

Modification 

Factor (CMF)

Use Raised Median to Restrict Turning Movements $20,001 to 

$100,000 Proven 0.61–1.09

Use Raised Median to Restrict Turning Movements 
Manual for Selecting Safety Improvements on High Risk Rural Roads

 29

Install Priority Control Systems for Emergency Vehicles 

Emergency priority control systems are 

designed to give emergency response 

vehicles a green indication on their 

approach to a signalized intersection 

while providing a red light to conflicting 

approaches.

Where to Use: This system may be most 

beneficial where vehicles approaching 

a green signal cannot see emergency 

vehicles approaching on the intersecting 

roadway because of line-of-sight problems 

with nearby buildings, vegetation, or hills.

Top Recommended Resources:

1. FHWA, Traffic Signal Preemption for Emergency Vehicles: A Cross-Cutting Study, January 2006. Available at: 

http://www.gtt.com/wp-content/uploads/Traffic-signal-preemption-for-emergency-vehicles-A-cross-cutting-study.pdf.

2. FHWA, Traffic Signal Timing Manual, “Chapter 9,” June 2008. Available at: 

http://ops.fhwa.dot.gov/publications/fhwahop08024/chapter9.htm

Safety Treatment

Initial 

Implementation 

Cost

NCHRP 500 

Performance 

Rating

Install Priority Control Systems for Emergency Vehicles $20,001 to 

$100,000 Tried

Install Priority Control Systems for Emergency Vehicles 
Federal Highway Administration | Office of Safety 

30

Provide Advanced Dilemma Zone Detection for Rural High Speed Signalized 

Approaches 

Advanced dilemma zone detection systems enhance safety at 

signalized intersections by modifying traffic control signal timing 

to reduce the number of drivers that may have difficulty deciding 

whether to stop or proceed during a yellow phase. This may 

reduce rear-end crashes associated with unsafe stopping and angle 

crashes due to illegally continuing into the intersection during the 

red phase.

Where to Use: This treatment may be used at locations with a high 

frequency of crashes associated with the traffic signal phase change 

(e.g., rear-end and angle crashes) and high frequencies of red-light 

violations. Additional benefits of this treatment include reducing 

delay and stop frequency on the major road and maintaining or 

reducing overall intersection delay.

Top Recommended Resource:

1. FHWA, Advanced Dilemma-Zone Detection System, May 2009. Available at: 

http://safety.fhwa.dot.gov/intersection/resources/techsum/fhwasa09008/.

Safety Treatment

Initial 

Implementation 

Cost

NCHRP 500 

Performance 

Rating

Crash 

Modification 

Factor (CMF)

Provide Advanced Dilemma Zone Detection for Rural 

High Speed Signalized Approaches

$20,001 to 

$100,000 Proven 0.61

Provide Advanced Dilemma Zone Detection for Rural High Speed Signalized Approaches

Note: The sign shown may not be consistent 

with the latest version of the MUTCD.
Manual for Selecting Safety Improvements on High Risk Rural Roads

 31

Top Recommended Resource:

1. FHWA, Restricted Crossing U-Turn Intersection, October 2009. Available at: 

http://www.fhwa.dot.gov/publications/research/safety/09059/09059.pdf.

Implement J-Turns Along a Signalized Corridor

- Initial Investment: $100,000

- Cost of Maintenance: $5,000

- Frequency of Maintenance: 10 years

Benefit-Cost 

Ratio

NCHRP 500 

Performance 

Rating

Lower Volume Signalized Intersections 45.4 Proven

Higher Volume Signalized Intersections 159.1 Proven

Implement J-Turns Along a Signalized Corridor 

The J-turn intersection is characterized 

by the prohibition of left turn and 

through movements from side street 

approaches as permitted in conventional 

designs. The J-turn intersection 

accommodates these movements by 

requiring drivers to turn right onto the 

main road and then make a U-turn 

maneuver at a one-way median opening 

400 to 1,000 feet after the intersection. 

Left turns from the main road 

approaches are executed in a manner 

similar to left turns at conventional intersections and are unchanged in this design. Left turn movements from the 

major road could also be removed at primarily rural unsignalized J-turn designs.

Where to Use: J-turn intersections are typically implemented as part of a corridor treatment; however, they can 

be used at isolated intersections. Unsignalized J-turn intersections preserve corridor capacity and can be installed 

without the adverse effects of signal control. Scenarios where J-turn intersections are most applicable include the 

following:

•	 Relatively low to medium side-street through volumes and heavy left turn volumes from the major road.

•	 The minor road total volume to total intersection volume ratio is typically less than or equal to 0.20.

•	 Areas where median widths are greater than 40 feet. For narrower medians, loons or bulb-outs on the 

shoulders need to be constructed.

For intersections with very high left turn and through volumes from the side road approaches, the J-turn 

intersection design is not the optimal choice. 

Implement J-Turns Along a Signalized Corridor 
Federal Highway Administration | Office of Safety 

32

Install Acceleration or Deceleration Lanes

Drivers turning onto an uncongested highway 

generally accelerate until they approach the 

desired open-road speed. When acceleration 

by entering traffic takes place directly on the 

traveled way, it may disrupt the flow of through 

traffic. To minimize this operational problem 

due to right- or left turning traffic at highway 

intersections, acceleration lanes may be used. 

An acceleration lane is an auxiliary or 

speed-change lane that allows vehicles to 

accelerate to highway speeds before entering 

the through traffic lanes of a highway. 

Acceleration lanes should be of sufficient 

length to permit adjustments in speeds of both 

through and entering vehicles so that the driver 

of the entering vehicle can accelerate and maneuver into that gap before reaching the end of the acceleration lane.

Additionally, the purpose of a parallel deceleration lane is to provide drivers exiting or turning from the road with 

an opportunity to slow down to a more reasonable speed prior to turning.

Where to Use: This treatment may be used at unsignalized intersections on highways that experience a high 

proportion of rear-end crashes related to the speed differential caused by vehicles turning left or right onto or 

from the highway. They may also be used where intersection sight distance is inadequate or where there are high 

volumes of trucks or recreational vehicles entering or exiting the highway.

Acceleration or deceleration lanes can be added as median acceleration/deceleration lanes, as installed at several 

locations in Missouri, or as lanes next to the shoulder for vehicles entering or exiting the roadway on the right 

side, as installed in Kentucky. 

Safety Treatment

Initial 

Implementation 

Cost

NCHRP 500 

Performance 

Rating

Install Acceleration or Deceleration Lanes $100,000 Proven

Top Recommended Resources:

1. FHWA. NCHRP Report 500 / Volume 5: A Guide for Addressing Unsignalized Intersection Collisions, “Strategy 

B9. Provide Right-Turn Acceleration Lanes at Intersections,” July 2003. Available at: 

http://safety.fhwa.dot.gov/intersection/resources/intsafestratbro/ub9.cfm. 

2. FHWA. NCHRP Report 500 / Volume 5: A Guide for Addressing Unsignalized Intersection Collisions, “Strategy 

B5. Provide Left-Turn Acceleration Lanes at Intersections,” July 2003. Available at: 

http://safety.fhwa.dot.gov/intersection/resources/intsafestratbro/ub5.cfm.

Install Acceleration or Deceleration Lanes
Manual for Selecting Safety Improvements on High Risk Rural Roads

 33

Install Right Turn Lane 

Providing a right turn lane at an intersection can 

reduce rear-end crashes by allowing vehicles to 

proceed through the intersection without having 

to stop or slow down for vehicles making a right 

turn. Assuming turn lanes are of adequate length, 

vehicles will not be stopped in the travel lanes; 

this allows for through traffic to continue without 

stopping for vehicles turning at an intersection. 

Where to Use: Right turn lanes should be 

constructed at intersections with a high frequency 

of rear-end crashes resulting from conflicts 

between (1) vehicles turning right and following 

vehicles, and (2) vehicles turning right and 

through vehicles coming from the left on the cross 

street. 

Top Recommended Resources:

1. FHWA, Techbrief: Safety Effectiveness of Intersection Left- and Right-Turn Lanes, 2002. Available at: 

http://www.fhwa.dot.gov/publications/research/safety/02103/02103techbrief.pdf

2. FHWA, Signalized Intersections Informational Guide, July 2013. Available at: 

http://safety.fhwa.dot.gov/intersection/signalized/13027/index.cfm.

Install Right Turn Lane

- Initial Investment: $400,000

- Cost of Maintenance: $20,000

- Frequency of Maintenance: 10 years

Benefit-Cost 

Ratio

NCHRP 500 

Performance 

Rating

Crash 

Modification 

Factor (CMF)

Lower Volume Signalized Intersections 4.9 Proven 0.77–0.96

Higher Volume Signalized Intersections 16.9 Proven 0.77–0.96

Install Right Turn Lane 
Federal Highway Administration | Office of Safety 

34

Install Left Turn Lane 

Left turn lanes are used as auxiliary lanes 

for storage or to accommodate left turning 

vehicles with decreasing speed as they 

approach the intersection. Installing left 

turn lanes can reduce rear-end crashes by 

allowing vehicles to proceed through the 

intersection without having to stop or slow 

down for vehicles waiting to make a left turn.

Where to Use: The AASHTO Green Book 

recommends that left turning traffic be 

removed from the through lanes whenever 

practical, and that left turn lanes should be 

provided at street intersections along major 

arterials and collector roads wherever left 

turns are permitted. Consideration of 

left turn lanes has traditionally been based on such factors as the number of through lanes, speeds, left turn 

volumes, opposing through volumes, and/or left turning crashes.

Intersections with a high frequency of crashes resulting from the conflicts between (1) vehicles turning left 

and following vehicles, and (2) vehicles turning left and opposing through vehicles are also candidates for the 

installation of left turn lanes. 

Practitioners should consider installing left turn lanes for the major road approaches to improve safety at 3- and 

4-leg intersections with two-way stop control on the minor road at locations where significant turning volumes 

exist or where there is a history of turn-related crashes. 

Top Recommended Resources:

1. FHWA, Signalized Intersections Informational Guide, July 2013. Available at: 

http://safety.fhwa.dot.gov/intersection/signalized/13027/index.cfm.

2. FHWA, Intersection Safety: A Manual for Local Rural Road Owners, January 2011. Available at: 

http://safety.fhwa.dot.gov/local_rural/training/fhwasa1108/fhwasa1108.pdf.

Install Left Turn Lane

- Initial Investment: $400,000

- Cost of Maintenance: $20,000

- Frequency of Maintenance: 10 years

Benefit-Cost 

Ratio

NCHRP 500 

Performance 

Rating

Crash 

Modification 

Factor (CMF)

Lower Volume Signalized Intersections 4.1 Proven 0.50–0.80

Higher Volume Signalized Intersections 14.1 Proven 0.50–0.80

Install Left Turn Lane 
Manual for Selecting Safety Improvements on High Risk Rural Roads

 35

Install Offset (or Channelized) Left Turn Lane 

Offset left turn lanes provide the left turning motorist a line of 

sight to opposing through vehicles. Instead of attempting to look 

around opposing left turning vehicles, the motorist can clearly see 

oncoming traffic. 

Where to Use: Offset left turn lanes should be used at 

unsignalized 4-leg intersections with a high frequency of crashes 

between vehicles turning left and opposing through vehicles. This 

treatment can be applied at intersections on divided highways 

with medians wide enough to provide the appropriate positive offset, and also on approaches without medians if 

sufficient width exists.

Top Recommended Resource:

1. FHWA, Signalized Intersections Informational Guide, July 2013. Available at: 

http://safety.fhwa.dot.gov/intersection/signalized/13027/index.cfm.

Install Offset (or Channelized) Left Turn Lane

- Initial Investment: $250,000

- Cost of Maintenance: $1,000

- Frequency of Maintenance: 10 years

Benefit-Cost 

Ratio

NCHRP 500 

Performance 

Rating

Crash 

Modification 

Factor (CMF)

Lower Volume Signalized Intersections 4.1 Proven 0.80

Higher Volume Signalized Intersections 14.1 Proven 0.80

Install Offset (or Channelized) Left Turn Lane 
Federal Highway Administration | Office of Safety 

36

Convert a Traditional Signalized Intersection into a Roundabout 

The modern roundabout is a type of circular 

intersection defined by the basic operational 

principle that entering traffic yields to 

vehicles on the circulatory roadway. Key 

design principles achieve deflection of 

entering traffic by channelization at the 

entrance and deflection around a center 

island. Roundabout intersections eliminate 

a number of vehicle conflict points typically 

associated with traditional intersections. 

A 4-leg, single-lane roundabout has 

75 percent fewer vehicle conflict points than 

a traditional stop-controlled intersection. 

Roundabouts also enhance safety by 

reducing vehicle speeds both in and through 

the intersection and by changing the 

crash type from angle to sideswipe, which 

typically results in less severe crashes.

Where to Use: Roundabouts are the preferred safety alternative for a wide range of intersections. Although 

they may not be appropriate in all circumstances, they may be considered as an alternative for all proposed new 

intersections on federally-funded highway projects. Roundabouts should also be considered for all existing 

intersections that have been identified as needing major safety or operational improvements. This would include 

freeway interchange ramp terminals and rural intersections.

Top Recommended Resources:

1. FHWA, “Guidance Memorandum on Consideration and Implementation of Proven Safety Countermeasures,” 

2010. Available at: http://safety.fhwa.dot.gov/policy/memo071008/.

2. FHWA, Intersection Safety Case Study: Minnesota Roundabout—A Scott County Success Story, February 2010. 

Available at: http://safety.fhwa.dot.gov/intersection/resources/casestudies/fhwasa09013/.

Convert a Traditional Signalized Intersection into a 

Roundabout

- Initial Investment: $400,000

- Cost of Maintenance: $40,000

- Frequency of Maintenance: 10 years

Benefit-Cost 

Ratio

NCHRP 500 

Performance 

Rating

Crash 

Modification 

Factor (CMF)

Lower Volume Signalized Intersections 4.8 Proven 0.26–0.82

Higher Volume Signalized Intersections 16.6 Proven 0.26–0.82

Convert a Traditional Signalized Intersection into a Roundabout 
Manual for Selecting Safety Improvements on High Risk Rural Roads

 37

Reconstruct At-Grade Intersection to Create an Interchange 

In removing an existing at-grade intersection 

and navigating traffic through an interchange, 

the through movements on the major street 

are physically separated from the other turning 

movements, which are typically served by 

one or two intersections (ramp terminals) on 

the minor street. The interchange may take 

several forms: a diamond interchange, a single 

point urban interchange, and a compressed 

diamond interchange. Each interchange type has 

independent safety implications. 

Where to Use: This improvement may be 

applicable to 4-leg intersections with high volumes 

on the through street and a high number of angle 

crashes. 

Top Recommended Resources:

1. FHWA, Signalized Intersections Informational Guide, July 2013. Available at: 

http://safety.fhwa.dot.gov/intersection/signalized/13027/index.cfm.

2. FHWA, Rural Public Transportation Technologies: User Needs and Applications FR1-798, July 1997. Available 

at: http://www.fhwa.dot.gov/publications/research/safety/97106/ch01/ch01.cfm.

Reconstruct At-Grade Intersection to Create an 

Interchange

- Initial Investment: $10,000,00

- Cost of Maintenance: $40,000

- Frequency of Maintenance: 10 years

*Calculations include a salvage value of $1,000,000

Benefit-Cost 

Ratio

NCHRP 500 

Performance 

Rating

Crash 

Modification 

Factor (CMF)

Low Volume Signalized Intersections 0.1 Proven 0.43–0.64

Higher Volume Signalized Intersections 0.4 Proven 0.43–0.64

Reconstruct At-Grade Intersection to Create an Interchange 
Federal Highway Administration | Office of Safety 

38

4.3. Intersections (Unsignalized)

Intersection-specific safety treatments assist drivers in recognizing they are at or approaching an unsignalized 

intersection, provide storage for turning traffic,24 and give positive guidance to motorists through the intersection. 

Among others, improvements cited in this section include Railway-Highway Grade Crossing treatments.1 2

24 Turn lane storage is the length of turn lane provided based on anticipated traffic needs.

25 As discussed in Section 1.2, a BCR is only shown where data were available to calculate the ratio. Where data were unavailable, the BCR has been left blank.

Safet

y Treatment

For more information, 

visit page

C

ost

Frequency of 

Maintenance (years)

SAFET

Y

bENEFIT

Benefit-Cost

Ratio 25

Initial 

Implementation

Ongoing 

Maintenance

NCHRP 500 

Performance Rating

Crash Modification Factor 

(CMF)

4-

lEG 

iNTERSECTIONS

3-

lEG 

iNTERSECTIONS

Lower Volume*

Higher Volume**

Lower Volume*

Higher Volume**

Relocate an Existing Stop Bar on Minor Approach 40 $

T

Install Stop Ahead Pavement Markings 41 $ P 0.44- 0.69Install Advanced Intersection Warning Signs 42 $ P

Provide a Stop Bar on Minor-Road Approaches 43 $ – 5 P 337.7 1175.8 287.1 1484.1

Improve Sight Distance within Sight Triangle 44 $ $ 5 P 0.44- 0.89 157.3 547.8 66.9 345.7

Provide Upcoming Road Names on Advanced Warning Signs 45 $

T 0.90- 0.99

Install Retroreflective Strips on Sign Posts 46 $

T

Upgrade to Larger Stop Signs 47 $ P

Double Use of Stop Signs 48 $

T

Improve Sight Distance and Conspicuity at Railroad Grade Crossings 49 $ T

Install a Splitter Island 50 $$

T

Channelization of Major and Minor Roads (Physical or Painted) 51 $$ P

Provide Intersection Lighting 52 $$ $ 1 P 23.1 80.6 10.5 54.2Install Dynamic Advanced Intersection Warning System 53 $$ P 0.10- 0.76

Upgrade Existing Railroad Crossing Hardware and Warning Systems 54 $$-$$$ P 0.55

Implement Lane Narrowing through Rumble Strips and Painted Median at Rural Stop-Controlled Approaches

55 $$-$$$

T 0.60- 0.80

Intersections (Unsignalized)
Manual for Selecting Safety Improvements on High Risk Rural Roads

 39

1

26 As stated in NCHRP Series 500 Reports (http://safety.transportation.org/guides.aspx). Proven: The safety effect for other similar applications has shown a proven benefit. 

Tried: The treatment has indications that it can be expected to reduce crashes, but has some conflicting reports as to its associated safety effects or has been deployed and 

observed to be effective. Experimental: New treatments that still need to be tested and for which the safety effect is unknown. Unknown: Not enough is known about an 

associated safety performance.

Safet

y Treatment

For more information, 

visit page

C

ost

Frequency of 

Maintenance (years)

SAFET

Y

bENEFIT

Benefit-Cost

Ratio 25

Initial 

Implementation

Ongoing 

Maintenance

NCHRP 500 

Performance Rating

Crash Modification Factor 

(CMF)

4-

lEG 

iNTERSECTIONS

3-

lEG 

iNTERSECTIONS

Lower Volume*

Higher Volume**

Lower Volume*

Higher Volume**

Provide Flashing Beacons at Intersection Approaches 56 $$$ $ 2 P 0.85 16.3 56.8 6.8 35.8

Convert Minor-Road Stop Control to All-Way Stop Control 57 $$$ $ 10 P 0.30 77.2 268.8 32.8 169.7

Convert a Traditional Stop-Controlled Intersection into a J-Turn Intersection 58 $$$- $$$$ $ 10 P 0.0- 0.91 46.4 161.4 n/a n/a

Use Raised Median to Restrict Turning Movements 59 $$$- $$$$ P

Install Acceleration or Deceleration Lanes 60 $$$- $$$$ P

Install Railroad Crossing Hardware and Warning Systems Where They Currently Do Not Exist 61 $$$- $$$$ P 0.75

Convert a 4-Leg Intersection into Two 3-Leg Intersections (Offset T-Intersections) 62 $$$$ P 0.70

Install Bypass Lane 63 $$$$ $$ 10 P 11.6 40.6 5.0 25.6Modify Horizontal and/or Vertical Geometry 64 $$$$$ P

Improve Horizontal Intersection Alignment or Skew 65 $$$$$ – – P 1.0 7.9 1.0 7.9Install Traffic Signals 66 $$$$$ $$ 1 P 0.23- 1.58 15.4 53.8 6.9 35.5Install Right Turn Lane 67 $$$$$ $$ 10 P 16.0 55.9 6.8 35.3Install Left Turn Lane 68 $$$$$ $$ 10 P 6.0 20.8 3.7 18.9Install Offset (or Channelized) Left Turn Lane 69 $$$$$ $$ 10 P 6.0 20.8 3.7 18.9Install a Roundabout (From Stop-Controlled) 70 $$$$$ $$$ 10 P 0.54- 1.11 4.8 16.8

Remove or Separate an Existing Railroad Grade Crossing 71 $$$$$ P

Cost:$ = $0 to $5,000$$ = $5,001 to $20,000$$$ = $20,001 to $50,000$$$$ = $50,001 to $100,000$$$$$ = $100,001 and up

NCHRP 500 Performance Rating26

P – ProvenT – TriedE – ExperimentalU – Unknown

*Lower Volume ≤1000 vpd**Higher Volume = Between 1,001 and 8000 vpd

Intersections (Unsignalized)
Federal Highway Administration | Office of Safety 

40

Relocate an Existing Stop Bar on Minor Approach 

A minor approach may have an existing 

stop bar that is located where vehicles 

stopping at the bar have limited sight 

distance at the intersection. The stop 

bar may be relocated closer to the 

intersection at a point where the stopped 

vehicle would have better sight distance 

for approaching traffic. 

Where to Use: This treatment may be 

used at locations where existing sight 

distance may be obstructed or where 

sight distance may be significantly 

improved by moving the stop bar.

Top Recommended Resource:

1. FHWA. NCHRP Report 500 / Volume 5: A Guide for Addressing Unsignalized Intersection Collisions, “Strategy 

E4. Provide a Stop Bar (or Provide a Wider Stop Bar) on Minor Road Approaches,” July 2003. Available at: 

http://safety.fhwa.dot.gov/intersection/resources/intsafestratbro/ue4.cfm.

Safety Treatment

Initial 

Implementation 

Cost

NCHRP 500 

Performance 

Rating

Relocate an Existing Stop Bar on Minor Approach $0 to $5,000 Tried

Relocate an Existing Stop Bar on Minor Approach 
Manual for Selecting Safety Improvements on High Risk Rural Roads

 41

Install Stop Ahead Pavement Markings 

Providing pavement markings with 

supplementary messages (such as Stop Ahead) 

can help alert drivers on the stop-controlled 

approach to the presence of an intersection. 

Where to Use: It is likely that Stop Ahead 

pavement markings will be most effective 

at locations with a high frequency of target 

collisions (i.e., right-angle and rear-end), 

particularly where driver awareness may be an 

issue.

Top Recommended Resource:

1. FHWA, Techbrief: Safety Evaluation of STOP AHEAD Pavement Markings, March 2008. Available at: 

http://www.fhwa.dot.gov/publications/research/safety/08045/index.cfm.

Safety Treatment

Initial 

Implementation 

Cost

NCHRP 500 

Performance 

Rating

Crash 

Modification 

Factor (CMF)

Install Stop Ahead Pavement Markings $0 to $5,000 Proven 0.44–0.69

Install Stop Ahead Pavement Markings 
Federal Highway Administration | Office of Safety 

42

Install Advanced Intersection Warning Signs 

Advanced intersection warning signs 

can help alert drivers to the presence 

of an intersection ahead. Signs can be 

placed with sufficient distance prior to the 

intersection to allow drivers to perceive 

and react. They can also be installed on 

both sides of the roadway to solicit greater 

awareness.

Where to Use: Advanced intersection 

warning signs are to be applied 

predominantly on single through 

lane, high-crash, stop-controlled State 

intersections in both rural and urban 

areas. They may also be applied on dual 

through lane, high-crash, stop-controlled 

intersections with lower traffic volumes 

(less than about 25,000 average annual 

daily traffic (AADT)) where the use of 

J-treatments is not appropriate and the 

frequency of acceptable gaps for entering 

traffic is such that long waiting and higher 

risk taking are present at the intersection.

Top Recommended Resources:

1. FHWA, Example Intersection Safety Implementation Plan, 2009.

2. FHWA, Stop-Controlled Intersection Safety: Through Route Activated Warning Systems, February 2011. 

Available at: http://safety.fhwa.dot.gov/intersection/resources/fhwasa11015/traws.pdf.

Safety Treatment

Initial 

Implementation 

Cost

NCHRP 500 

Performance 

Rating

Install Advanced Intersection Warning Signs $0 to $5,000 Proven

Install Advanced Intersection Warning Signs 
Manual for Selecting Safety Improvements on High Risk Rural Roads

 43

Provide a Stop Bar on Minor-Road Approaches 

Providing visible stop bars on the minor road 

approach to an unsignalized intersection 

can help direct the attention of drivers to the 

presence of the intersection.

Where to Use: Minor road approaches where 

conditions allow the stop bar to be seen by an 

approaching driver at a significant distance from 

the intersection. Locations should be identified 

by patterns of crashes related to lack of driver 

recognition of the intersection.

Top Recommended Resource:

1. FHWA, Intersection Safety: A Manual for Local Rural Road Owners, January 2011. Available at: 

http://safety.fhwa.dot.gov/local_rural/training/fhwasa1108/fhwasa1108.pdf.

Provide a Stop Bar on Minor-Road Approaches

- Initial Investment: $1,000 (4ST), $500 (3ST)

- Cost of Maintenance: $0

- Frequency of Maintenance: 5 years (4 applications)

Benefit-Cost 

Ratio

NCHRP 500 

Performance 

Rating

Lower Volume 4-Way Intersections 337.7 Proven

Higher Volume 4-Way Intersections 1175.8 Proven

Lower Volume 3-Leg Intersections 287.1 Proven

Higher Volume 3-Leg Intersections 1484.1 Proven

Provide a Stop Bar on Minor-Road Approaches 
Federal Highway Administration | Office of Safety 

44

Improve Sight Distance within Sight Triangle 

By removing sight distance restrictions (e.g., 

vegetation, parked vehicles, signs, buildings) 

from the sight triangles at stop or yield-controlled 

intersection approaches, drivers will be able see 

approaching vehicles on the main line without 

obstruction and therefore make better decisions 

about entering the intersection safely.

Where to Use: This treatment may be used at 

unsignalized intersections with restricted sight 

distance and patterns of crashes related to lack 

of sight distance where sight distance can be 

improved by clearing roadside obstructions 

without major construction.

Top Recommended Resource:

1. FHWA, Intersection Safety: A Manual for Local Rural Road Owners, January 2011. Available at: 

http://safety.fhwa.dot.gov/local_rural/training/fhwasa1108/fhwasa1108.pdf.

Improve Sight Distance within Sight Triangle

- Initial Investment: $4,500

- Cost of Maintenance: $1,000

- Frequency of Maintenance: 5 years

Benefit-Cost 

Ratio

NCHRP 500 

Performance 

Rating

Crash 

Modification 

Factor (CMF)

Lower Volume 4-Way Intersections 157.3 Proven 0.44–0.89

Higher Volume 4-Way Intersections 547.8 Proven 0.44–0.89

Lower Volume 3-Leg Intersections 66.9 Proven 0.44–0.89

Higher Volume 3-Leg Intersections 345.7 Proven 0.44–0.89

Improve Sight Distance within Sight Triangle 
Manual for Selecting Safety Improvements on High Risk Rural Roads

 45

Provide Upcoming Road Names on Advanced Warning Signs 

At locations where Intersection Ahead warning signs are used, it is 

recommended that street name plaques be placed underneath the 

upcoming street sign. These street name plaques provide the driver 

with additional information about the street so he or she can make an 

early decision regarding potential turning movements.

Where to Use: This treatment may be used at locations where crashes 

could potentially be reduced by providing advanced turn information.

Top Recommended Resource:

1. FHWA, Intersection Safety: A Manual for Local Rural Road Owners, January 2011. Available at: 

http://safety.fhwa.dot.gov/local_rural/training/fhwasa1108/fhwasa1108.pdf.

Safety Treatment

Initial 

Implementation 

Cost

NCHRP 500 

Performance 

Rating

Crash 

Modification 

Factor (CMF)

Provide Upcoming Road Names on Advanced Warning 

Signs $0 to $5,000 Tried 0.90–0.99

Provide Upcoming Road Names on Advanced Warning Signs 
Federal Highway Administration | Office of Safety 

46

Install Retroreflective Strips on Sign Posts 

The use of retroreflective strips on sign posts may be beneficial when 

there is a need to draw additional attention to the signs, especially at 

night. Reflective strips may be added to Stop signs, curve or intersection 

warning signs, regulatory or guidance signs, etc. 

Where to Use: The MUTCD provides the following guidance for the use 

of reflective strips on sign posts: “The material must be at least 2 inches 

wide and must be placed the full length of the post, from the sign to 

within 2 feet above the horizontal surface into which the sign is fixed. 

In addition, the color of the material must match the background color 

of the sign except that the color of the strip for Yield and Do Not Enter 

signs must be red.”

Top Recommended Resource:

1. FHWA, “Intersection Safety Implementation Plan Workshop,” presentation, July 2009. Available at: 

http://safety.fhwa.dot.gov/intersection/resources/ex_wksp_pres0109/.

Safety Treatment

Initial 

Implementation 

Cost

NCHRP 500 

Performance 

Rating

Install Retroreflective Strips on Sign Posts $0 to $5,000 Tried

Install Retroreflective Strips on Sign Posts 
Manual for Selecting Safety Improvements on High Risk Rural Roads

 47

Upgrade to Larger Stop Signs 

A high number of crashes relate to the driver’s inability 

or failure to see the Stop sign at stop-controlled 

intersections. To improve recognition of the signs, 

larger Stop signs can be installed. Sizes can range 

from 30 inches, to 36 inches, to 48 inches and larger, if 

needed.

 

Where to Use: While roadway classification and 

speed can help determine proper Stop sign size, larger 

sizes may be used when crash types indicate that Stop 

sign visibility may be an issue.

Top Recommended Resource:

1. FHWA, Stop Sign-Controlled Intersections: Enhanced Signs and Markings—A Winston-Salem Success Story, 

November 2009. Available at: http://safety.fhwa.dot.gov/intersection/resources/casestudies/fhwasa09010/.

Safety Treatment

Initial 

Implementation 

Cost

NCHRP 500 

Performance 

Rating

Upgrade to Larger Stop Signs $0 to $5,000 Proven

Upgrade to Larger Stop Signs 
Federal Highway Administration | Office of Safety 

48

Double Use of Stop Signs 

Two Stop signs (mounted left and right) can be used 

to call greater attention to the need for motorists to 

stop at an intersection. The first Stop sign is installed 

at the traditional right side location; a second is 

recommended in the median (if available) of the 

approach. To accommodate this left-mounted Stop 

sign, a small mountable curb is suggested. This 

curb and associated pavement markings provide the 

motorist with additional information that he or she is 

entering an intersection. 

Where to Use: This treatment may be used at 

locations where crashes indicate that motorists 

do not obey existing Stop signs and additional 

intersection conspicuity is needed.

Top Recommended Resources:

1. FHWA, Intersection Safety: A Manual for Local Rural Road Owners, January 2011. Available at: 

http://safety.fhwa.dot.gov/local_rural/training/fhwasa1108/fhwasa1108.pdf.

2. FHWA, Stop Sign-Controlled Intersections: Enhanced Signs and Markings—A Winston-Salem Success Story, 

November 2009. Available at: http://safety.fhwa.dot.gov/intersection/resources/casestudies/fhwasa09010/.

Safety Treatment

Initial 

Implementation 

Cost

NCHRP 500 

Performance 

Rating

Double Use of Stop Signs $0 to $5,000 Tried

Double Use of Stop Signs
Manual for Selecting Safety Improvements on High Risk Rural Roads

 49

Improve Sight Distance and Conspicuity at Railroad Grade Crossings 

Where passive warning devices are used at 

railroad crossings, improvements in vertical 

alignment or through removing vegetation 

and other obstructions can help to provide 

increased sight distance. Conspicuity of the 

intersection may be helped by providing 

brighter sign sheeting or upgrading to larger 

signs.

Where to Use: This treatment is appropriate 

for use at all railroad grade crossings.

Top Recommended Resource:

1. FHWA, Railroad-Highway Grade Crossing Handbook, Revised Second Edition, August 2007. Available at: 

http://safety.fhwa.dot.gov/xings/com_roaduser/07010/.

Safety Treatment

Initial 

Implementation 

Cost

NCHRP 500 

Performance 

Rating

Improve Sight Distance and Conspicuity at Railroad 

Grade Crossings $0 to $5,000 Tried

Improve Sight Distance and Conspicuity at Railroad Grade Crossings 
Federal Highway Administration | Office of Safety 

50

Install a Splitter Island 

A splitter island separates traffic moving in opposite directions of 

travel. A splitter island that is installed on the minor approach 

creates a physical separation between other vehicles that are turning 

onto the minor road. In addition, the installation of a splitter island 

allows for a second Stop sign to be mounted in the median to make 

the intersection more conspicuous.

Where to Use: Splitter islands should be applied to minor road approaches of unsignalized intersections where 

the presence of the intersection or the Stop sign is not readily visible to approaching motorists. The strategy is 

particularly appropriate for intersections where the speeds on the minor road are high.

Top Recommended Resource:

1. FHWA, Intersection Safety: A Manual for Local Rural Road Owners, January 2011. Available at: 

http://safety.fhwa.dot.gov/local_rural/training/fhwasa1108/fhwasa1108.pdf.

Safety Treatment

Initial 

Implementation 

Cost

NCHRP 500 

Performance 

Rating

Install a Splitter Island $5,001 to $20,000 Tried

Install a Splitter Island 
Manual for Selecting Safety Improvements on High Risk Rural Roads

 51

Channelization of Major and Minor Roads (Physical or Painted) 

The installation of channelizing separator islands at stop-controlled intersection approaches can accommodate 

redundancy of the Stop sign and increase driver compliance with the Stop sign.

Where to Use: This practice has greater potential for effectiveness on intersections of high-speed roadways; 

however, they can also be applied to intersections with lower posted speed limits.

Top Recommended Resource:

1. FHWA, Summary Report: Two Low-Cost Safety Concepts for Two-Way STOP-Controlled, Rural Intersections 

on High-Speed Two-Lane, Two-Way Roadways, December 2008. Available at: 

http://www.fhwa.dot.gov/publications/research/safety/08063/.

Safety Treatment

Initial 

Implementation 

Cost

NCHRP 500 

Performance 

Rating

Channelization of Major and Minor Roads 

(Physical or Painted) $5,001 to $20,000 Proven

Channelization of Major and Minor Roads (Physical or Painted) 
Federal Highway Administration | Office of Safety 

52

Provide Intersection Lighting

Many intersection crashes during late-night 

and early-morning hours occur due to drivers 

being unable to see conflicting traffic, other 

road users, or—specifically in the case of 

unsignalized intersections—the presence of 

the intersection itself. At night in rural areas, 

the only source of lighting for roadways is 

often provided by vehicle headlights. Roadway 

lighting allows for greater visibility of the 

intersection, making signs and markings more 

visible and helping drivers determine a safe 

path through the intersection.

Where to Use: Lighting should be provided at signalized or unsignalized intersections, particularly those with 

a high instance of dark crashes. Rear-end, right-angle, or turning crashes on the major road approaches to an 

unsignalized intersection may indicate that approaching drivers are unaware of the presence of the intersection. 

Top Recommended Resources:

1. FHWA. NCHRP Report 500 / Volume 5: A Guide for Addressing Unsignalized Intersection Collisions, “Strategy 

E2. Improve Visibility of the Intersection by Providing Lighting,” July 2003. Available at: 

http://safety.fhwa.dot.gov/intersection/resources/intsafestratbro/ue2.cfm.

2. Minnesota DOT, Safety Impacts of Street Lighting at Isolated Rural Intersections—Part II, September 2006. 

Available at: http://www.intrans.iastate.edu/reports/rural_lighting_FINAL.pdf.

Provide Intersection Lighting

- Initial Investment: $20,000

- Cost of Maintenance: $500

- Frequency of Maintenance: 1 year

Benefit-Cost 

Ratio

NCHRP 500 

Performance 

Rating

Lower Volume 4-Way Intersections 23.1 Proven

Higher Volume 4-Way Intersections 80.6 Proven

Lower Volume 3-Leg Intersections 10.5 Proven

Higher Volume 3-Leg Intersections 54.2 Proven

Provide Intersection Lighting
Manual for Selecting Safety Improvements on High Risk Rural Roads

 53

Install Dynamic Advanced Intersection Warning System 

Infrastructure-based Intelligent Transportation System (ITS) 

technologies can be used to significantly improve the safety at 

stop-controlled intersections. These systems provide enhanced 

safety warning information for approaching drivers compared 

to passive warning systems. A dynamic advanced intersection 

warning system can provide:

•	 Enhanced warning to the through driver that there is a 

vehicle on a cross road stop approach that may enter the 

intersection.

•	 Enhanced warning to drivers on a stop approach that their 

trajectory speed is high and that they may run the Stop sign.

•	 Enhanced warning to through drivers that they are traveling 

at too high an intersection entry speed and advising them to 

slow down.

•	 Enhanced warning to drivers on the stop approach of 

entering vehicles on the through approach, inferring 

potential unsafe gaps.

Where to Use: This treatment may be provided at intersections that experience severe intersection-related crashes 

due to speed, low visibility, or insufficient gaps.

Top Recommended Resource:

1. FHWA, Stop-Controlled Intersection Safety: Through Route Activated Warning Systems, February 2011. 

Available at: http://safety.fhwa.dot.gov/intersection/resources/fhwasa11015/traws.pdf.

Safety Treatment

Initial 

Implementation 

Cost

NCHRP 500 

Performance 

Rating

Crash 

Modification 

Factor (CMF)

Install Dynamic Advanced Intersection 

Warning System $5,001 to $20,000 Proven 0.10–0.76

Install Dynamic Advanced Intersection Warning System 
Federal Highway Administration | Office of Safety 

54

Upgrade Existing Railroad Crossing Hardware and Warning Systems 

The installation of enhanced railroad crossing hardware and warning systems not only 

notifies motorists as to the presence of an approaching train but can limit their ability to 

proceed through the intersection through the use of gates and other devices.

Where to Use: This treatment is applicable where additional notification and/or the ability 

to limit drivers from proceeding through the crossing is needed.

Top Recommended Resource:

1. FHWA, Railroad-Highway Grade Crossing Handbook, Revised Second Edition, August 2007. Available at: 

http://safety.fhwa.dot.gov/xings/com_roaduser/07010/.

Safety Treatment

Initial 

Implementation 

Cost

NCHRP 500 

Performance 

Rating

Crash 

Modification 

Factor (CMF)

Upgrade Existing Railroad Crossing Hardware and 

Warning Systems $5,001 to $50,000 Proven 0.55

Upgrade Existing Railroad Crossing Hardware and Warning Systems 
Manual for Selecting Safety Improvements on High Risk Rural Roads

 55

Implement Lane Narrowing through Rumble Strips and Painted Median at Rural 

Stop-Controlled Approaches

Lane narrowing features the 

introduction of rumble strips on the 

outside shoulders and in a painted 

yellow median island on the major 

road approaches. The objective of 

lane narrowing is to induce drivers on 

major roads to reduce approach speeds 

at intersections by effectively reducing 

the lane width.

 Where to Use: This practice has greater potential for effectiveness for intersections on high-speed roadways. 

However, the treatment can also be applied to intersections with lower posted speed limits.

Top Recommended Resource:

1. FHWA, Railroad-Highway Grade Crossing Handbook, Revised Second Edition, August 2007. Available at: 

http://safety.fhwa.dot.gov/xings/com_roaduser/07010/.

Safety Treatment

Initial 

Implementation 

Cost

NCHRP 500 

Performance 

Rating

Crash 

Modification 

Factor (CMF)

Implement Lane Narrowing through Rumble Strips and 

Painted Median at Rural Stop-Controlled Approaches $5,001 to $50,000 Tried 0.60–0.80

Implement Lane Narrowing through Rumble Strips and Painted Median at Rural Stop-Controlled Approaches
Federal Highway Administration | Office of Safety 

56

Provide Flashing Beacons at Intersection Approaches

Flashing beacons provide a visible signal indicating the presence of an 

intersection and can be very effective in rural areas where there may be 

long stretches between intersections. They may also improve safety at 

locations where nighttime visibility of intersections is an issue. 

Where to Use: Flashing beacons can be installed at unsignalized 

intersections with patterns of right-angle crashes related to lack of driver 

awareness of the intersection on an uncontrolled approach and lack of 

driver awareness of the Stop sign on a stop-controlled approach. The 

beacons can be installed either atop Stop signs or Advance Intersection 

Warning Signs, where applicable.

Top Recommended Resource:

1. FHWA, Intersection Safety: A Manual for Local Rural Road Owners, “Chapter 4. Countermeasures,” January 

2011. Available at: http://safety.fhwa.dot.gov/local_rural/training/fhwasa1108/ch4.cfm.

Provide Flashing Beacons at Intersection 

Approaches

- Initial Investment: $25,000

- Cost of Maintenance: $1,000

- Frequency of Maintenance: 2 years

Benefit-Cost 

Ratio

NCHRP 500 

Performance 

Rating

Crash 

Modification 

Factor (CMF)

Lower Volume 4-Way Intersections 16.3 Proven 0.85

Higher Volume 4-Way Intersections 56.8 Proven 0.85

Lower Volume 3-Leg Intersections 6.8 Proven 0.85

Higher Volume 3-Leg Intersections 35.8 Proven 0.85

Provide Flashing Beacons at Intersection Approaches
Manual for Selecting Safety Improvements on High Risk Rural Roads

 57

Convert Minor Road Stop Control to All-Way Stop Control 

At locations where there is a pattern of 

high-severity frontal impact crashes, 

all‐way stop control can be implemented 

quickly by installing Stop signs on the 

unrestricted approach. It is important to 

ensure adequate sight distance for all stop 

conditions and to consult the MUTCD 

for proper installation guidelines.

Where to Use: This treatment can be 

installed at locations where there is a 

pattern of high severity frontal impact 

crashes.

Top Recommended Resource:

1. FHWA. NCHRP Report 500 / Volume 5: A Guide for Addressing Unsignalized Intersection Collisions, “Strategy 

F2. Provide All-Way Stop Control at Appropriate Intersections,” July 2003. Available at: 

http://safety.fhwa.dot.gov/intersection/resources/intsafestratbro/uf2.cfm.

Convert Minor Road Stop Control to All-Way Stop 

Control

- Initial Investment: $30,000

- Cost of Maintenance: $5,000

- Frequency of Maintenance: 10 years

Benefit-Cost 

Ratio

NCHRP 500 

Performance 

Rating

Crash 

Modification 

Factor (CMF)

Lower Volume 4-Way Intersections 77.2 Proven 0.30

Higher Volume 4-Way Intersections 268.8 Proven 0.30

Lower Volume 3-Leg Intersections 32.8 Proven 0.30

Higher Volume 3-Leg Intersections 169.7 Proven 0.30

Convert Minor Road Stop Control to All-Way Stop Control 
Federal Highway Administration | Office of Safety 

58

Convert a Traditional Stop-Controlled Intersection into a J-Turn Intersection 

The J-turn intersection is characterized by 

the prohibition of left turn and through 

movements from side street approaches as 

permitted in conventional designs. The J-turn 

intersection accommodates these movements 

by requiring drivers to turn right onto the 

main road and then make a U-turn maneuver 

at a one-way median opening 400 to 1,000 feet 

after the intersection. Left turns from the main 

road approaches are executed in a manner 

similar to left turns at conventional intersections and are unchanged in this design. Left turn movements from the 

major road could also be removed at primarily rural unsignalized J-turn designs.

Where to Use: J-turn intersections are typically implemented as part of a corridor treatment; however, they can 

be used at isolated intersections. Unsignalized J-turn intersections preserve corridor capacity and can be installed 

without the adverse effects of signal control. Scenarios where J-turn intersections are most applicable include the 

following:

•	 Relatively low to medium side-street through volumes and heavy left turn volumes from the major road.

•	 The minor road total volume to total intersection volume ratio is typically less than or equal to 0.20.

•	 Areas where median widths are greater than 40 feet. For narrower medians, loons or bulb-outs on the 

shoulders need to be constructed.

For intersections with very high left turn and through volumes from the side road approaches, the J-turn 

intersection design is not the optimum choice. 

Top Recommended Resource:

1. FHWA, Restricted Crossing U-Turn Intersection, October 2009. Available at: 

http://www.fhwa.dot.gov/publications/research/safety/09059/09059.pdf.

Convert a Traditional Stop-Controlled Intersection 

into a J-Turn Intersection 

- Initial Investment: $50,000-$100,000

- Cost of Maintenance: $5,000

- Frequency of Maintenance: 10 years

Benefit-Cost 

Ratio

NCHRP 500 

Performance 

Rating

Crash 

Modification 

Factor (CMF)

Lower Volume 4-Way Intersections 46.1 Proven 0.0–0.91

Higher Volume 4-Way Intersections 161.4 Proven 0.0–0.91

Lower Volume 3-Leg Intersections n/a Proven 0.0–0.91

Higher Volume 3-Leg Intersections n/a Proven 0.0–0.91

Convert a Traditional Stop-Controlled Intersection into a J-Turn Intersection 
Manual for Selecting Safety Improvements on High Risk Rural Roads

 59

Use Raised Median to Restrict Turning Movements 

Raised medians can be helpful in limiting access and restricting 

turning movements within the functional limits of intersections, 

thereby reducing conflicts between through traffic and turning 

vehicles.

Where to Use: This treatment may be used at locations where 

access to streets, businesses, homes, and other properties falls 

within the intersection functional area. 

Top Recommended Resource:

1. FHWA, Signalized Intersections Informational Guide, July 2013. Available at: 

http://safety.fhwa.dot.gov/intersection/signalized/13027/index.cfm.

Safety Treatment

Initial 

Implementation 

Cost

NCHRP 500 

Performance 

Rating

Use Raised Median to Restrict Turning Movements $20,001 to 

$100,000 Proven

Use Raised Median to Restrict Turning Movements 
Federal Highway Administration | Office of Safety 

60

Install Acceleration or Deceleration Lanes

Drivers turning onto an uncongested highway 

generally accelerate until they approach the 

desired open-road speed. When the entering 

traffic accelerates within the traveled way, 

it has the potential to disrupt the flow of 

through traffic. To minimize this operational 

problem due to right or left turning traffic at 

divided highway intersections, acceleration 

lanes may be used. 

An acceleration lane is an auxiliary or 

speed-change lane that allows vehicles to 

accelerate to highway speeds before entering 

the through traffic lanes of a highway. Acceleration lanes should be of sufficient length to permit adjustments 

in speeds of both through and entering vehicles so that the driver of the entering vehicle can maneuver into that 

gap before reaching the end of the acceleration lane. Additionally, the purpose of a parallel deceleration lane is 

to provide drivers exiting or turning from the road with an opportunity to slow down to a more reasonable speed 

prior to turning.

Where to Use: This treatment may be used at unsignalized intersections on divided highways that experience a 

high proportion of rear-end crashes related to the speed differential caused by vehicles turning left or right onto or 

from the highway. They may also be used where intersection sight distance is inadequate or where there are high 

volumes of trucks or recreational vehicles entering or exiting the divided highway.

Acceleration or deceleration lanes can be added as median acceleration or deceleration lanes—as installed at 

several locations in Missouri—or as lanes next to the shoulder for vehicles entering or exiting the roadway on the 

right side—as installed in Kentucky. 

Top Recommended Resources:

1. FHWA, NCHRP Report 500 / Volume 5: A Guide for Addressing Unsignalized Intersection Collisions, “Strategy 

B9. Provide Right-Turn Acceleration Lanes at Intersections,” 2003. Available at: 

http://safety.fhwa.dot.gov/intersection/resources/intsafestratbro/ub9.cfm

2. FHWA, NCHRP Report 500 / Volume 5: A Guide for Addressing Unsignalized Intersection Collisions, “Strategy 

B5. Provide Left-Turn Acceleration Lanes at Intersections,” 2003. Available at: 

http://safety.fhwa.dot.gov/intersection/resources/intsafestratbro/ub9.cfm

Safety Treatment

Initial 

Implementation 

Cost

NCHRP 500 

Performance 

Rating

Install Acceleration or Deceleration Lanes $20,001 to 

$100,000 Proven

Install Acceleration or Deceleration Lanes 
Manual for Selecting Safety Improvements on High Risk Rural Roads

 61

Install Railroad Crossing Hardware and Warning Systems Where They Currently 

Do Not Exist 

By installing railroad crossing hardware and warning devices, 

motorists are notified as to the presence of an approaching 

train and can make an informed decision whether to cross.

Where to Use: This treatment may be applied where railroad 

crossings exist with no form of warning device.

Top Recommended Resource:

1. FHWA, Railroad-Highway Grade Crossing Handbook, Revised Second Edition, August 2007. Available at: 

http://safety.fhwa.dot.gov/xings/com_roaduser/07010/.

Safety Treatment

Initial 

Implementation 

Cost

NCHRP 500 

Performance 

Rating

Crash 

Modification 

Factor (CMF)

Install Railroad Crossing Hardware and Warning 

Systems Where They Currently Do Not Exist

$20,001 to 

$100,000 Proven 0.75

Install Railroad Crossing Hardware and Warning Systems Where They Currently Do Not Exist 
Federal Highway Administration | Office of Safety 

62

Convert a 4-Leg Intersection into Two 3-Leg Intersections (Offset T-Intersections)

For some 4-leg intersections with very low through volumes on the cross street, one method of improving safety 

may be to convert the intersection to two T-intersections. This conversion can be accomplished by realigning the 

two cross-street approaches an appreciable distance along the major road, thus creating separate intersections that 

operate relatively independently of one another. 

Where to Use: This improvement may be applicable to 4-leg intersections with very low through volumes on the 

cross street, yet with a relatively high number of unusually severe collisions.

Top Recommended Resource:

1. FHWA, Signalized Intersections Informational Guide, July 2013. Available at: 

http://safety.fhwa.dot.gov/intersection/signalized/13027/index.cfm.

Safety Treatment

Initial 

Implementation 

Cost

NCHRP 500 

Performance 

Rating

Crash 

Modification 

Factor (CMF)

Convert a 4-Leg Intersection into Two 3-Leg 

Intersections (Offset T-Intersections)

$50,001 to 

$100,000 Proven 0.70

Convert a 4-Leg Intersection into Two 3-Leg Intersections (Offset T-Intersections)
Manual for Selecting Safety Improvements on High Risk Rural Roads

 63

Install Bypass Lane 

Installation of this treatment is accomplished by adding bypass 

lanes using the shoulder at intersections. The bypass lanes 

are intended for vehicles to continue through the intersection 

without having to stop for traffic making left turns.

Where to Use: Bypass lanes should be used at 3-leg 

intersections on two-lane highways with moderate through 

and turning volumes, especially intersections that have 

rear-end collisions involving vehicles waiting to turn left from 

the mainline. 

Top Recommended Resource:

1. FHWA, Intersection Safety: A Manual for Local Rural Road Owners, January 2011. Available at: 

http://safety.fhwa.dot.gov/local_rural/training/fhwasa1108/fhwasa1108.pdf.

Install Bypass Lane

- Initial Investment: $75,000

- Cost of Maintenance: $20,000

- Frequency of Maintenance: 10 years

Benefit-Cost 

Ratio

NCHRP 500 

Performance 

Rating

Lower Volume 4-Way Intersections 11.6 Proven

Higher Volume 4-Way Intersections 40.6 Proven

Lower Volume 3-Leg Intersections 5.0 Proven

Higher Volume 3-Leg Intersections 25.6 Proven

Install Bypass Lane 
Federal Highway Administration | Office of Safety 

64

Modify Horizontal and/or Vertical Geometry 

Although changing alignment is a high-cost treatment, in some cases sight distance is restricted by horizontal 

and vertical curvature. Straightening a roadway will increase sight distance and allow for better visibility of other 

vehicles and the intersection itself.

Where to Use: This treatment may be used at unsignalized intersections with restricted sight distance due to 

horizontal and/or vertical geometry and with patterns of crashes related to that lack of sight distance that cannot 

be ameliorated by less expensive methods.

Top Recommended Resource:

1. FHWA, Intersection Safety: A Manual for Local Rural Road Owners, January 2011. Available at: 

http://safety.fhwa.dot.gov/local_rural/training/fhwasa1108/fhwasa1108.pdf.

Safety Treatment

Initial 

Implementation 

Cost

NCHRP 500 

Performance 

Rating

Modify Horizontal and/or Vertical Geometry $100,001 and up Proven

Modify Horizontal and/or Vertical Geometry 
Manual for Selecting Safety Improvements on High Risk Rural Roads

 65

Improve Horizontal Intersection Alignment or Skew

Reducing or eliminating the skew at 

intersection approaches helps address 

problems like vehicle alignment, long 

exposure in the intersection, and potential 

driver confusion. Intersection skew 

treatments include pavement markings, 

channelizing islands, and realignment. 

Where to Use: This treatment may be 

used at unsignalized intersections with a 

high frequency of crashes resulting from 

insufficient intersection sight distance 

and awkward sight lines at a skewed 

intersection.

Top Recommended Resource:

1. FHWA, Intersection Safety: A Manual for Local Rural Road Owners, January 2011. Available at: 

http://safety.fhwa.dot.gov/local_rural/training/fhwasa1108/fhwasa1108.pdf.

Improve Horizontal Intersection Alignment or Skew

- Initial Investment: $300,000

- Cost of Maintenance: n/a

- Frequency of Maintenance: n/a

Benefit-Cost 

Ratio

NCHRP 500 

Performance 

Rating

Lower Volume Optimal Conditions 1.0 Proven

Higher Volume Optimal Conditions 7.9 Proven

Improve Horizontal Intersection Alignment or Skew
Federal Highway Administration | Office of Safety 

66

Install Traffic Signals

Traffic signals help to assign right-of-way to traffic movements and 

have been shown to reduce the severity of total collisions experienced 

at intersections. The MUTCD lists eight warrants for the placement of 

traffic signals, which should be reviewed as installation of this treatment is 

considered. The safety benefit of signalizing an unsignalized intersection 

is a function of the crash history by crash type, the traffic entering the 

intersection on the major and minor approaches, and whether the 

intersection is a 3-leg T-intersection or a conventional 4-leg intersection.

Where to Use: Traffic signals can be installed at intersections that experience a high frequency of right-angle 

collisions with adequate sight distance to that intersection from all approaches. Signalization may be particularly 

effective where the ratio of right-angle to rear-end crashes is high.

Top Recommended Resource:

1. AASHTO, NCHRP Report 617: Accident Modification Factors for Traffic Engineering and ITS Improvements, 

July 2008. Available at: http://onlinepubs.trb.org/onlinepubs/nchrp/nchrp_rpt_617.pdf.

Install Traffic Signals

- Initial Investment: $150,000

- Cost of Maintenance: $8,000

- Frequency of Maintenance: 1 year

Benefit-Cost 

Ratio

NCHRP 500 

Performance 

Rating

Crash 

Modification 

Factor (CMF)

Lower Volume 4-Way Intersections 15.4 Proven 0.23–1.58

Higher Volume 4-Way Intersections 53.8 Proven 0.23–1.58

Lower Volume 3-Leg Intersections 6.9 Proven 0.23–1.58

Higher Volume 3-Leg Intersections 35.5 Proven 0.23–1.58

Install Traffic Signals
Manual for Selecting Safety Improvements on High Risk Rural Roads

 67

Install Right Turn Lane 

Providing a right turn lane at an intersection 

can reduce rear-end crashes by allowing 

vehicles to proceed through the intersection 

without having to stop or slow down for 

vehicles making a right turn. Assuming turn 

lanes are of adequate length, vehicles will not 

be stopped in the travel lanes; this allows for 

through traffic to continue without stopping 

for vehicles turning at an intersection. 

Where to Use: Right turn lanes should be constructed at unsignalized intersections with a high frequency of 

rear-end crashes resulting from conflicts between (1) vehicles turning right and following vehicles, and (2) vehicles 

turning right and through vehicles coming from the left on the cross street. 

Top Recommended Resources:

1. FHWA, Techbrief: Safety Effectiveness of Intersection Left- and Right-Turn Lanes, 2002. Available at: 

http://www.fhwa.dot.gov/publications/research/safety/02103/02103techbrief.pdf

2. FHWA, Safety Effectiveness of Intersection Left- and Right-Turn Lanes, July 2002. Available at: 

http://www.fhwa.dot.gov/publications/research/safety/02089/02089.pdf.

Install Right Turn Lane

- Initial Investment: $400,000

- Cost of Maintenance: $20,000

- Frequency of Maintenance: 10 years

Benefit-Cost 

Ratio

NCHRP 500 

Performance 

Rating

Lower Volume 4-Way Intersections 16.0 Proven

Higher Volume 4-Way Intersections 55.9 Proven

Lower Volume 3-Leg Intersections 6.8 Proven

Higher Volume 3-Leg Intersections 35.3 Proven

Install Right Turn Lane 
Federal Highway Administration | Office of Safety 

68

Install Left Turn Lane 

Left turn lanes are auxiliary lanes for storage or to accommodate 

the decreasing speed of left turning vehicles as they approach 

the intersection speed change of left turning vehicles. Installing 

left turn lanes at an intersection can reduce rear-end crashes by 

allowing vehicles to proceed through the intersection without 

having to stop or slow down for vehicles waiting to make a left 

turn.

Where to Use: The AASHTO Green Book recommends that 

left turning traffic be removed from the through lanes whenever 

practical, and that left turn lanes should be provided at street intersections along major arterials and collector 

roads wherever left turns are permitted. Consideration of left turn lanes has traditionally been based on such 

factors as the number of through lanes, speeds, left turn volumes, opposing through volumes, and/or left turning 

crashes.

Intersections with a high frequency of crashes resulting from the conflicts between (1) vehicles turning left 

and following vehicles, and (2) vehicles turning left and opposing through vehicles are also candidates for the 

installation of left turn lanes. 

Practitioners should consider installing left turn lanes for the major road approaches to improve safety at 3- and 

4-leg intersections with two-way stop control on the minor road at locations where significant turning volumes 

exist or where there is a history of turn-related crashes.

Top Recommended Resource:

1. AASHTO, NCHRP Report 617: Accident Modification Factors for Traffic Engineering and ITS Improvements, 

July 2008. Available at: http://onlinepubs.trb.org/onlinepubs/nchrp/nchrp_rpt_617.pdf.

Install Left Turn Lane

- Initial Investment: $400,000

- Cost of Maintenance: $20,000

- Frequency of Maintenance: 10 years

Benefit-Cost 

Ratio

NCHRP 500 

Performance 

Rating

Lower Volume 4-Way Intersections 6.0 Proven

Higher Volume 4-Way Intersections 20.8 Proven

Lower Volume 3-Leg Intersections 3.7 Proven

Higher Volume 3-Leg Intersections 18.9 Proven

Install Left Turn Lane 
Manual for Selecting Safety Improvements on High Risk Rural Roads

 69

Install Offset (or Channelized) Left Turn Lane 

Offset left turn lanes provide the left turning motorist 

a line of sight to opposing through vehicles. Instead of 

attempting to look around opposing left turning vehicles, 

the motorist can clearly see oncoming traffic. 

Where to Use: Offset left turn lanes should be used at 

unsignalized 4-leg intersections with a high frequency 

of crashes between vehicles turning left and opposing 

through vehicles. This treatment can be applied at 

intersections on divided highways with medians wide 

enough to provide the appropriate positive offset, and 

also on approaches without medians if sufficient width 

exists.

Top Recommended Resource:

1. FHWA, Signalized Intersections Informational Guide, July 2013. Available at: 

http://safety.fhwa.dot.gov/intersection/signalized/13027/index.cfm.

Install Offset (or Channelized) Left Turn Lane

- Initial Investment: $400,000

- Cost of Maintenance: $20,000

- Frequency of Maintenance: 10 years

Benefit-Cost 

Ratio

NCHRP 500 

Performance 

Rating

Lower Volume 4-Way Intersections 6.0 Proven

Higher Volume 4-Way Intersections 20.8 Proven

Lower Volume 3-Leg Intersections 3.7 Proven

Higher Volume 3-Leg Intersections 18.9 Proven

Install Offset (or Channelized) Left Turn Lane 
Federal Highway Administration | Office of Safety 

70

Install a Roundabout (From Stop-Controlled) 

The modern roundabout is a type of circular 

intersection defined by the basic operational 

principle that entering traffic yields to vehicles 

on the circulatory roadway. Key design 

principles achieve deflection of entering traffic 

by channelization at the entrance and deflection 

around a center island. Roundabout intersections 

eliminate a number of vehicle conflict points 

typically associated with traditional intersections. 

A 4-leg, single-lane roundabout has 75 percent 

fewer vehicle conflict points than a traditional 

stop-controlled intersection. Roundabouts also 

enhance safety by reducing vehicle speeds both 

in and through the intersection and by changing 

the crash type from angle to sideswipe, which 

typically results in less severe crashes.

Where to Use: Roundabouts are the preferred safety alternative for a wide range of intersections. Although 

they may not be appropriate in all circumstances, they may be considered as an alternative for all proposed new 

intersections on federally funded highway projects. Roundabouts should also be considered for all existing 

intersections that have been identified as needing major safety or operational improvements. This would include 

freeway interchange ramp terminals and rural intersections.

Top Recommended Resources:

1. FHWA, “Guidance Memorandum on Consideration and Implementation of Proven Safety Countermeasures,” 

July 2010. Available at: http://safety.fhwa.dot.gov/policy/memo071008/.

2. FHWA, Intersection Safety Case Study: Minnesota Roundabout—A Scott County Success Story, February 2010. 

Available at: http://safety.fhwa.dot.gov/intersection/resources/casestudies/fhwasa09013/.

Install a Roundabout (From Stop-Controlled)

- Initial Investment: $400,000

- Cost of Maintenance: $40,000

- Frequency of Maintenance: 10 years

Benefit-Cost 

Ratio

NCHRP 500 

Performance 

Rating

Crash 

Modification 

Factor (CMF)

Lower Volume 4-Way Intersections 4.8 Proven 0.54–1.11

Higher Volume 4-Way Intersections 16.8 Proven 0.54–1.11

Lower Volume 3-Leg Intersections n/a Proven 0.54–1.11

Higher Volume 3-Leg Intersections n/a Proven 0.54–1.11

Install a Roundabout (From Stop-Controlled) 
Manual for Selecting Safety Improvements on High Risk Rural Roads

 71

Remove or Separate an Existing Railroad Grade Crossing 

Conflicts between road users and 

trains can be reduced by completely 

eliminating a crossing or separating it 

from vehicular traffic. This will likely 

divert traffic to another grade crossing, 

whether it is a grade-separated 

structure or another at-grade 

intersection.

Where to Use: This treatment may 

be applicable where a high frequency 

of severe vehicle-rail crashes occur 

and at locations where more suitable 

alternative crossings are available.

Top Recommended Resource:

1. FHWA, Railroad-Highway Grade Crossing Handbook - Revised Second Edition, 2007. Available at: 

http://safety.fhwa.dot.gov/xings/com_roaduser/07010/

Remove or Separate an Existing Railroad Grade Crossing 

Safety Treatment

Initial 

Implementation 

Cost

NCHRP 500 

Performance 

Rating

Remove or Separate an Existing Railroad Grade 

Crossing $100,001 and up Proven
Federal Highway Administration | Office of Safety 

72

4.4. Non-motorized User

Non-motorized users generally consist of cyclists and pedestrians but also include equestrian, horse-drawn 

buggies, in-line skaters, and other methods. Their needs must be addressed due to increased risks they encounter 

on rural roads. Rural pedestrian crashes are nearly twice as likely to result in a fatality and rural bicycle crashes 

are three times as likely to result in a fatality compared to urban crashes.27 Risky riding and walking behaviors 

may indicate that the transportation infrastructure does not adequately address the safety and mobility needs of 

non-motorized users.123

27 UNC Highway Safety Research Center, Factors Contributing to Pedestrian and Bicycle Crashes on Rural Highways – Final Report, 

http://www.hsisinfo.org/pdf/HSIS-Rural-PedBike-Final-Report.pdf

28 As discussed in Section 1.2, a BCR is only shown where data were available to calculate the ratio. Where data were unavailable, the BCR has been left blank.

29 As stated in NCHRP Series 500 Reports (http://safety.transportation.org/guides.aspx). Proven: The safety effect for other similar applications has shown a proven benefit. 

Tried: The treatment has indications that it can be expected to reduce crashes, but has some conflicting reports as to its associated safety effects or has been deployed and 

observed to be effective. Experimental: New treatments that still need to be tested and for which the safety effect is unknown. Unknown: Not enough is known about an 

associated safety performance.

Safet

y Treatment

For more information, 

visit page

C

ost

Frequency of 

Maintenance (years)

SAFET

Y

bENEFIT

Benefit-Cost

Ratio 28

Initial 

Implementation

Ongoing 

Maintenance

NCHRP 500 

Performance Rating

Crash Modification 

Factor (CMF)

Lower Volume*, 

Optimal Conditions***

Higher Volume**, 

Optimal Conditions***

Lower Volume*, 

Narrow Conditions****

Higher Volume**, 

Narrow Conditions****

Provide Crosswalks at Targeted Locations 73 $ P & T

Install Pedestrian Signal Heads to Existing Signalized Intersections 74 $$ P

Construct Wildlife Fencing 75 $$

T

Install Rectangular Rapid Flash Beacons (RRFBs) 76 $$ P

Build Sidewalks 77 $$-$$$ P

Construct Adjacent Shared-Use Paths 78 $$-$$$ P

Construct Shared-Use Paved Shoulders for Horse & Buggy Road Users or Bicyclists

79 $$-$$$

T

Construct Exclusive Bicycle Lanes 80 $$-$$$

T

Install Curb Extensions 81 $$$

T

Install or Modify Culverts to Accommodate Wildlife Crossing 82 $$$- $$$$

T

Install Pedestrian Hybrid Beacons or High intensity Activated Crosswalks (HAWK) 

83 $$$- $$$$ P 0.712

Construct Bicycle Trail Grade Separation Structures 84 $$$$$ P

Cost:$ = $0 to $5,000$$ = $5,001 to $20,000$$$ = $20,001 to $50,000$$$$ = $50,001 to $100,000$$$$$ = $100,001 and up

NCHRP 500 Performance Rating29 

P – ProvenT – TriedE – ExperimentalU – Unknown

*Lower Volume ≤1000 vpd**Higher Volume = Between 1,001 and 8000 vpd***Optimal Conditions = 12-foot lanes, 6-foot paved shoulders****Narrower Conditions = 10-foot lanes and no shoulders

Non-Motorized User
Manual for Selecting Safety Improvements on High Risk Rural Roads

 73

Provide Crosswalks at Targeted Locations 

Crosswalks help call attention to pedestrians crossing a road 

and provide a defined location in which to do so. 

Where to use: Marked pedestrian crosswalks may be used to 

delineate preferred pedestrian paths across roadways under the 

following conditions:

•	 At locations with stop signs or traffic signals to direct 

pedestrians to those crossing locations and to prevent 

vehicular traffic from blocking the pedestrian path when 

stopping for a stop sign or red light.

•	 At nonsignalized street crossing locations in designated school zones. Use of adult crossing guards, school 

signs and markings, and/or traffic signals with pedestrian signals (when warranted) should be considered in 

conjunction with the marked crosswalk, as needed.

•	 At nonsignalized locations where engineering judgment dictates that the number of motor vehicle lanes, 

pedestrian exposure, average daily traffic (ADT), posted speed limit, and geometry of the location would 

make the use of specially designated crosswalks desirable for traffic/pedestrian safety and mobility.

Marked crosswalks alone (i.e., without traffic-calming treatments, traffic signals and pedestrian signals when 

warranted, or other substantial crossing improvement) are insufficient and should not be used under the 

following conditions:

•	 Where the speed limit exceeds 64.4 km/h (40 mi/h).

•	 On a roadway with four or more lanes without a raised median or crossing island that has (or will soon have) 

an ADT of 12,000 or greater.

•	 On a roadway with four or more lanes with a raised median or crossing island that has (or soon will have) an 

ADT of 15,000 or greater. 

Top Recommended Resource:

1. FHWA, Safety Effects of Marked Versus Unmarked Crosswalks at Uncontrolled Locations: Final Report and 

Recommended Guidelines, September 2005. Available at: 

http://www.fhwa.dot.gov/publications/research/safety/04100/04.cfm.

Safety Treatment

Initial 

Implementation 

Cost

NCHRP 500 

Performance 

Rating

Provide Crosswalks at Targeted Locations $0 to $5,000 Proven & Tried

Provide Crosswalks at Targeted Locations 
Federal Highway Administration | Office of Safety 

74

Install Pedestrian Signal Heads to Existing Signalized Intersections 

Pedestrian signal heads provide special types of 

traffic signal indications exclusively intended for 

controlling pedestrian traffic. These signal indications 

consist of the illuminated symbols of a walking 

person (symbolizing Walk) and an upraised hand 

(symbolizing Don’t Walk).

Where to Use: This treatment is applicable where pedestrian traffic exists at signalized intersections.

Top Recommended Resources:

1. FHWA, Manual on Uniform Traffic Control Devices, “Chapter 4E. Pedestrian Control Features,” 

December 2009. Available at: http://mutcd.fhwa.dot.gov/pdfs/2009r1r2/mutcd2009r1r2edition.pdf. 

2. FHWA, Signalized Intersections Informational Guide, July 2013. Available at: 

http://safety.fhwa.dot.gov/intersection/signalized/13027/index.cfm.

Safety Treatment

Initial 

Implementation 

Cost

NCHRP 500 

Performance 

Rating

Install Pedestrian Signal Heads to Existing 

Signalized Intersections $5,001 to $20,000 Proven

Install Pedestrian Signal Heads to Existing Signalized Intersections 
Manual for Selecting Safety Improvements on High Risk Rural Roads

 75

Construct Wildlife Fencing 

Wildlife fences help to prevent livestock and wildlife from 

straying onto highways.

Where to Use: Wildlife fence may be constructed along the 

right-of-way at locations with expansive open plains, paths that 

are known to be a crossing area, or locations that experience a 

moderately high frequency of crashes involving wildlife. Several 

States give guidance on how and where to properly construct 

wildlife fencing.

Safety Treatment

Initial 

Implementation 

Cost

NCHRP 500 

Performance 

Rating

Construct Wildlife Fencing $5,001 to $20,000 Tried

Construct Wildlife Fencing 
Federal Highway Administration | Office of Safety 

76

Install Rectangular Rapid Flash Beacons 

Rectangular Rapid Flash Beacons (RRFBs) are user-actuated amber Light 

Emitting Diodes (LEDs) that supplement warning signs at unsignalized 

intersections or mid-block crosswalks. They can be activated by pedestrians 

manually by a push button or passively by a pedestrian detection system. 

RRFBs can enhance safety by reducing crashes between vehicles and 

pedestrians at unsignalized intersections and mid-block pedestrian crossings 

by increasing driver awareness of potential pedestrian conflicts. RRFBs are 

also referred to as LED Rapid-Flash System, Stutter Flash or LED Beacons.

Where to use: RRFBs may be installed on either two-lane or multi-lane roadways at unsignlized intersections and 

mid-block pedestrian crossings. 

Top Recommended Resource:

1. FHWA, “Rectangular Rapid Flash Beacons (RRFB),” May 2009. Available at: 

http://safety.fhwa.dot.gov/intersection/resources/techsum/fhwasa09009/fhwasa09009.pdf.

Safety Treatment

Initial 

Implementation 

Cost

NCHRP 500 

Performance 

Rating

Install Rectangular Rapid Flash Beacons $5,001 to $20,000 Proven

Install Rectangular Rapid Flash Beacons 
Manual for Selecting Safety Improvements on High Risk Rural Roads

 77

Build Sidewalks 

Providing sidewalks and associated accommodations for 

pedestrians along heavily traveled corridors gives refuge 

for pedestrians and helps to enhance roadway operations, 

mobility, and safety. This treatment is especially useful at 

locations with heavy pedestrian volumes, such as business 

districts, schools, and community centers.

Where to Use: This treatment should be considered when 

heavy pedestrian volumes exist along a corridor or specific 

location, impacting the safety of all road users.

Safety Treatment

Initial 

Implementation 

Cost

NCHRP 500 

Performance 

Rating

Build Sidewalks $5,001 to $50,000 Proven

Build Sidewalks 
Federal Highway Administration | Office of Safety 

78

Construct Adjacent Shared-Use Paths 

A shared-use path serves as part of a transportation circulation 

system and supports multiple recreation opportunities, such as 

walking, bicycling, and in-line skating. A shared-use path typically 

has a surface that is asphalt, concrete, or firmly packed crushed 

aggregate. The 2012 AASHTO Guide for the Development of 

Bicycle Facilities defines a shared-use path as being physically 

separated from motor vehicular traffic with an open space or barrier. 

Shared-use paths should always be designed to include pedestrians 

even if the primary anticipated users are bicyclists.

Where to Use: This treatment can be used when a high volume of non-motorized traffic exists along a corridor, 

such as along designated hiking trails or known bicycle routes.

Top Recommended Resources:

1. FHWA, Designing Sidewalks and Trails for Access, Part I of II: Review of Existing Guidelines and Practices, 

July 1999. Available at: http://www.fhwa.dot.gov/environment/bicycle_pedestrian/publications/sidewalks/.

2. FHWA, Designing Sidewalks and Trails for Access, Part II of II: Best Practices Design Guide, September 2001. 

Available at: http://www.fhwa.dot.gov/environment/bicycle_pedestrian/publications/sidewalk2/pdf.cfm.

3. AASHTO, Guide for the Development of Bicycle Facilities, 4th Edition, June 2012.

Safety Treatment

Initial 

Implementation 

Cost

NCHRP 500 

Performance 

Rating

Construct Adjacent Shared-Use Paths $5,001 to $50,000 Proven

Construct Adjacent Shared-Use Paths 
Manual for Selecting Safety Improvements on High Risk Rural Roads

 79

Construct Shared-Use Paved Shoulders for Horse & Buggy Road Users or Bicyclists 

HRRR located near communities where horse and buggies are used 

in conjunction with motorized transportation may experience abrupt 

disruptions in traffic flow as faster moving vehicles overtake slower traffic; 

the same is true for HRRR that are known bicycle routes. Providing a paved 

shoulder adjacent to the travel way with sufficient width to accommodate 

alternate modes of transportation can help separate slower moving traffic 

from the travel lane.

Where to Use: This treatment may be used at locations where slower moving traffic is known to exist frequently, 

such as bicycle routes and locations with horse and buggy users, and that experience a high frequency of crashes 

associated with the alternate modes of traffic coming in contact with motorized traffic.

Top Recommended Resources:

1. FHWA, Non-Motorized User Safety: A Manual for Local Rural Road Owners, November 2012. Available at: 

http://safety.fhwa.dot.gov/local_rural/training/fhwasa010413/nonmotorize.pdf.

2. AASHTO, Guide for the Development of Bicycle Facilities, 4th Edition, June 2012.

Safety Treatment

Initial 

Implementation 

Cost

NCHRP 500 

Performance 

Rating

Construct Shared-Use Paved Shoulders for Horse & 

Buggy Road Users or Bicyclists $5,001 to $50,000 Tried

Construct Shared-Use Paved Shoulders for Horse & Buggy Road Users or Bicyclists 
Federal Highway Administration | Office of Safety 

80

Construct Exclusive Bicycle Lanes 

Bike lanes are defined as a portion of the roadway that has been 

designated by striping, signing, and pavement marking for the 

preferential or exclusive use by bicyclists. Bicycle lanes make the 

movements of both motorists and bicyclists more predictable and, 

as with other bicycle facilities, there are advantages to all road users 

in striping them on the roadway.

Where to Use: This treatment can be used when a high volume 

of bicycle traffic exists along a corridor, such as known State- or 

nation-wide bicycle routes.

Top Recommended Resources:

1. FHWA, Pedestrian and Bicycle Information Center, “Bike Lanes.” Available at: 

http://www.bicyclinginfo.org/engineering/facilities-bikelanes.cfm. 

2. FHWA, Bicycle Facilities and the Manual on Uniform Traffic Control Devices, February 28, 2014. Available at: 

http://www.fhwa.dot.gov/environment/bicycle_pedestrian/guidance/design_guidance/mutcd_bike.cfm. 

Safety Treatment

Initial 

Implementation 

Cost

NCHRP 500 

Performance 

Rating

Construct Exclusive Bicycle Lanes $5,001 to $50,000 Tried

Construct Exclusive Bicycle Lanes 
Manual for Selecting Safety Improvements on High Risk Rural Roads

 81

Install Curb Extensions

Curb extensions extend the sidewalk or curb line out into the 

parking lane, which reduces the effective street width. Curb 

extensions significantly improve pedestrian crossings by reducing 

the pedestrian crossing distance, improving the ability of 

pedestrians and motorists to see each other, and reducing the time 

that pedestrians are in the street.

Where to Use: Curb extensions should typically be used where 

there is a parking lane and where transit and cyclists will be 

traveling outside the curb edge for the length of the street. 

Safety Treatment

Initial 

Implementation 

Cost

NCHRP 500 

Performance 

Rating

Install Curb Extensions $20,001 to 

$50,000 Tried

Install Curb Extensions
Federal Highway Administration | Office of Safety 

82

Install or Modify Culverts to Accommodate Wildlife Crossing 

A mix of underpasses, bridge extensions, culvert 

installations, and culvert modifications can be 

used to facilitate wildlife movement and reduce 

collisions on HRRR associated with wildlife.

Where to Use: Culverts may be used to 

accommodate wildlife crossings at locations with 

expansive open plains, paths that are known to 

be a crossing area, or locations that experience a 

moderately high frequency of crashes involving 

wildlife. Several States provide guidance on how 

and where to properly construct wildlife fencing.

Safety Treatment

Initial 

Implementation 

Cost

NCHRP 500 

Performance 

Rating

Install or Modify Culverts to Accommodate Wildlife 

Crossing

$20,001 to 

$100,000 Tried

Install or Modify Culverts to Accommodate Wildlife Crossing 
Manual for Selecting Safety Improvements on High Risk Rural Roads

 83

Install Pedestrian Hybrid Beacons or High Intensity Activated Crosswalk (HAWK)

The HAWK is a pedestrian activated beacon 

located on the roadside and on mast arms 

over major approaches to an intersection. The 

HAWK signal head consists of two red lenses 

over a single yellow lens. It displays a red 

indication to drivers when activated, which 

creates a gap for pedestrians to cross a major 

roadway. The HAWK is not illuminated until 

it is activated by a pedestrian, triggering the 

warning flashing yellow lens on the major 

street. After a set amount of time, the indication 

changes to a solid yellow light to inform drivers 

to prepare to stop. The beacon then displays a 

dual solid red light to drivers on the major street 

and a walking person symbol to pedestrians. At 

the conclusion of the walk phase, the beacon displays an alternating flashing red light to drivers, and pedestrians 

are shown an upraised hand symbol with a countdown display informing them of the time left to cross.

Where to use: This treatment may be used at locations with a high number of pedestrian crashes where additional 

visibility of pedestrian crossings is needed. 

Top Recommended Resource:

1. FHWA, Safety Effectiveness of the HAWK Pedestrian Crossing Treatment, July 2010. Available at: 

http://www.fhwa.dot.gov/publications/research/safety/10042/index.cfm.

Install Pedestrian Hybrid Beacons or High Intensity Activated Crosswalk (HAWK)

Safety Treatment

Initial 

Implementation 

Cost

NCHRP 500 

Performance 

Rating

Crash 

Modification 

Factor (CMF)

Install Pedestrian Hybrid Beacons or High Intensity 

Activated Crosswalk (HAWK)

$20,001 to 

$100,000 Proven 0.712
Federal Highway Administration | Office of Safety 

84

Construct Bicycle Trail Grade Separation Structures 

This treatment can be an elevated or subterranean 

structure that minimizes or eliminates conflicts with 

motorized vehicles. Bicycle trail grade-separated 

structures allow for passage over otherwise 

un-navigable or difficultly-traversed locations such 

as waterways, rail, limited access freeways, or highvolume intersections.

Where to Use: This treatment can be used at locations 

where safe passage of bicycles is difficult due to terrain, 

traffic volume, or geographic obstacles. 

Safety Treatment

Initial 

Implementation 

Cost

NCHRP 500 

Performance 

Rating

Construct Bicycle Trail Grade Separation Structures $100,001 and up Proven

Construct Bicycle Trail Grade Separation Structures 
Manual for Selecting Safety Improvements on High Risk Rural Roads

 85

4.5. Pavement and Shoulder Resurfacing

Pavement and shoulder resurfacing and widening infrastructure safety treatments may improve a vehicle’s ability 

to remain on the roadway. This occurs by increasing the paved area for use by a vehicle, providing warning when a 

vehicle is leaving the driving lane, or improving the friction to reduce hydroplaning and loss of vehicle control.1 2

30 As discussed in Section 1.2, a BCR is only shown where data were available to calculate the ratio. Where data were unavailable, the BCR has been left blank.

31 As stated in NCHRP Series 500 Reports (http://safety.transportation.org/guides.aspx). Proven: The safety effect for other similar applications has shown a proven benefit. 

Tried: The treatment has indications that it can be expected to reduce crashes, but has some conflicting reports as to its associated safety effects or has been deployed and 

observed to be effective. Experimental: New treatments that still need to be tested and for which the safety effect is unknown. Unknown: Not enough is known about an 

associated safety performance.

Safet

y Treatment

For more information, 

visit page

C

ost

Frequency of 

Maintenance (years)

Safet

y

Benefit

Benefit-Cost

Ratio 30

Initial 

Implementation

Ongoing 

Maintenance

NCHRP 500 

Performance Rating

Crash Modification 

Factor (CMF)

Lower Volume*, 

Optimal Conditions***

Higher Volume**, 

Optimal Conditions***

Lower Volume*, 

Narrower Conditions****

Higher Volume**, 

Narrower Conditions****

Install a Safety Edge 86 $ – 20 P 0.85-0.92 33.4 267.2 40.9 403.2

Install Center Line Rumble Strips 87 $ – 10 P 0.75-0.85 21.3 170.6 26.1 257.5

Install Edge Line or Shoulder Rumble Strips 88 $ – 10 P 0.78-0.90 58.6 469.0 71.8 707.7

Install Transverse Rumble Strips 89 $ P 0.76-0.91Regrade or Recondition Gravel Lanes 90 $-$$

T

Install Targeted Longitudinal Rumble Strips at Key Locations (Such as on the Outside of Horizontal Curves Only)

91 $$-$$$ T 0.85

Install or Maintain a Graded Shoulder 92 $$-$$$ P 0.52Provide Turnout Areas 93 $$-$$$

T

Improve Pavement Friction/Increase Skid Resistance 94 $$$$ – 10 P 0.25-0.60 3.3 26.7 4.1 40.3

Add Paved Shoulder 95 $$$$$ $$ 2 P 0.86 n/a n/a 0.5 4.5

Widen Existing Travel Lanes by Two Feet or Less per Lane 96 $$$$$ $$$ 10 P 0.95 n/a n/a 0.3 2.8

Install Passing or Climbing Lanes 97 $$$$$ $$$ 10 P 0.3 2.3 0.4 3.5

Increase Shoulder Width 98 $$$$$ P 0.90-0.97Improve Superelevation at Horizontal Curve Locations 99 $$$$$ P

Cost:$ = $0 to $5,000$$ = $5,001 to $20,000$$$ = $20,001 to $50,000$$$$ = $50,001 to $100,000$$$$$ = $100,001 and up

NCHRP 500 Performance Rating 31P – ProvenT – TriedE – ExperimentalU – Unknown

*Lower Volume ≤1000 vpd**Higher Volume = Between 1,001 and 8000 vpd***Optimal Conditions = 12-foot lanes, 6-foot paved shoulders****Narrower Conditions = 10-foot lanes and no shoulders

Pavement and Shoulder Resurfacing
Federal Highway Administration | Office of Safety 

86

Install a Safety Edge 

When a vehicle leaves the traveled way and encounters a pavement-shoulder 

drop-off, it can be difficult for the driver to return safely to the roadway. A 

safety edge is a treatment intended to minimize drop-off-related crashes. 

With this treatment, the pavement edge is sloped at an angle (30-35 degrees) 

to make it easier for a driver to safely reenter the roadway after inadvertently 

driving onto the shoulder. This treatment is designed to be a standard policy 

for any overlay project. 

Where to Use: Each State should implement policies and procedures to 

incorporate the Safety Edge where pavement and non-pavement surfaces 

interface on all paving and resurfacing projects with surface differentials of 2.5 inches or more. The differentials 

should be measured from the pavement surface to the adjacent non-pavement surface, accounting for grading 

along the pavement edge during construction and including existing drop-offs. The Safety Edge is appropriately 

used at locations where pavement edge drop-offs occur through everyday use, particularly on rural roads with 

unpaved shoulders. 

Note: In general, the Safety Edge is used the entire length of a project, rather than only in locations where a drop-off 

exists for a short distance.

Top Recommended Resources:

1. FHWA, Summary Report: Safety Evaluation of the Safety Edge Treatment, February 2011. Available at: 

http://www.fhwa.dot.gov/publications/research/safety/hsis/11025/11025.pdf.

2. FHWA, “Proven Safety Countermeasures: Safety Edge,” January 2012. Available at: 

http://safety.fhwa.dot.gov/provencountermeasures/fhwa_sa_12_010.htm.

3. FHWA, Roadway Departure Safety: A Manual for Local Rural Road Owners, January 2011. Available at: 

http://safety.fhwa.dot.gov/local_rural/training/fhwasa1109/fhwasa1109.pdf.

Install a Safety Edge 

- Initial Investment: $2,145

- Cost of Maintenance: n/a

- Frequency of Maintenance: 20 years

Benefit-Cost 

Ratio

NCHRP 500 

Performance 

Rating

Crash 

Modification 

Factor (CMF)

Lower Volume Optimal Conditions 33.4 Proven 0.85–0.92

Higher Volume Optimal Conditions 267.2 Proven 0.85–0.92

Lower Volume Narrower Conditions 40.9 Proven 0.85–0.92

Higher Volume Narrower Conditions 403.2 Proven 0.85–0.92

Install a Safety Edge 
Manual for Selecting Safety Improvements on High Risk Rural Roads

 87

Install Center Line Rumble Strips 

Rumble strips are raised or grooved patterns on the roadway that provide both an 

audible warning (rumbling sound) and a physical vibration to alert drivers that 

they are leaving the driving lane. Rumble strips may be installed on the center 

line of undivided highways, on the roadway shoulder, or on the roadway surface 

(transverse rumble strips). 

Where to Use: Center line rumble strips can be used on virtually any roadway—especially those with a history 

of head-on crashes. It is recommended that rumble strips be applied systematically along an entire route instead 

of only at spot locations. For all rumble strips, pavement condition should be sufficient to accept milled rumble 

strips.

Rumble strips should be provided on all new rural freeways and on all new rural two-lane highways with travel 

speeds of 50 mph or greater. In addition, State 3R and 4R policies should consider installation of center line 

rumble strips on rural two-lane road projects where the lane plus shoulder width beyond the rumble strip will be 

at least 13 feet wide; particularly roadways with higher traffic volumes, poor geometrics, or a history of head-on 

and opposite-direction sideswipe crashes.

Top Recommended Resources:

1. FHWA, “Proven Safety Countermeasures: Longitudinal Rumble Strips and Stripes on 2-Lane Roads,” 

April 2012. Available at: http://safety.fhwa.dot.gov/provencountermeasures/fhwa_sa_12_008.htm.

2. FHWA, “Promoting the Implementation of Proven Safety Countermeasures,” memorandum. January 12, 

2012. Available at: http://safety.fhwa.dot.gov/provencountermeasures/pc_memo.htm.

3. FHWA, Roadway Departure Safety: A Manual for Local Rural Road Owners, January 2011. Available at: 

http://safety.fhwa.dot.gov/local_rural/training/fhwasa1109/fhwasa1109.pdf.

Install Center Line Rumble Strips 

- Initial Investment: $5,000

- Cost of Maintenance: n/a

- Frequency of Maintenance: 10 years (2 applications)

Benefit-Cost 

Ratio

NCHRP 500 

Performance 

Rating

Crash 

Modification 

Factor (CMF)

Lower Volume Optimal Conditions 21.3 Proven 0.75–0.85

Higher Volume Optimal Conditions 170.6 Proven 0.75–0.85

Lower Volume Narrower Conditions 26.1 Proven 0.75–0.85

Higher Volume Narrower Conditions 257.5 Proven 0.75–0.85

Install Center Line Rumble Strips 
Federal Highway Administration | Office of Safety 

88

Install Edge Line or Shoulder Rumble Strips 

Rumble strips are raised or grooved patterns on the roadway that 

provide both an audible warning (rumbling sound) and a physical 

vibration to alert drivers that they are leaving the driving lane. 

Rumble strips may be installed on the center line of undivided 

highways, on the roadway shoulder, or on the roadway surface 

(transverse rumble strips). 

Where to Use: Shoulder milled rumble strips should be used 

on roads with a history of roadway departure crashes. It is 

recommended that rumble strips be applied systematically along 

an entire route instead of only at spot locations. For all rumble 

strips, pavement condition should be sufficient to accept milled 

rumble strips.

Rumble strips should be provided on all new rural freeways and 

on all new rural two-lane highways with travel speeds of 50 mph 

or greater. In addition, State 3R and 4R policies should consider 

installation of continuous shoulder rumble strips on all rural 

freeways and on all rural two-lane highways with travel speeds of 50 mph or above (or as agreed to by the Division 

and the State) and/or a history of roadway departure crashes, where the remaining shoulder width beyond the 

rumble strip will be 4 feet or greater, paved or unpaved. 

Top Recommended Resources:

1. FHWA, “Proven Safety Countermeasures: Longitudinal Rumble Strips and Stripes on 2-Lane Roads,” 

April 2012. Available at: http://safety.fhwa.dot.gov/provencountermeasures/fhwa_sa_12_008.htm.

2. FHWA, “Promoting the Implementation of Proven Safety Countermeasures,” memorandum. January 12, 

2012. Available at: http://safety.fhwa.dot.gov/provencountermeasures/pc_memo.htm.

3. FHWA, Roadway Departure Safety: A Manual for Local Rural Road Owners, January 2011. Available at: 

http://safety.fhwa.dot.gov/local_rural/training/fhwasa1109/fhwasa1109.pdf.

Install Edge Line or Shoulder Rumble Strips 

- Initial Investment: $3,000

- Cost of Maintenance: n/a

- Frequency of Maintenance: 10 years (2 applications)

Benefit-Cost 

Ratio

NCHRP 500 

Performance 

Rating

Crash 

Modification 

Factor (CMF)

Lower Volume Optimal Conditions 58.6 Proven 0.78–0.90

Higher Volume Optimal Conditions 469.0 Proven 0.78–0.90

Lower Volume Narrower Conditions 71.8 Proven 0.78–0.90

Higher Volume Narrower Conditions 707.7 Proven 0.78–0.90

Install Edge Line or Shoulder Rumble Strips 
Manual for Selecting Safety Improvements on High Risk Rural Roads

 89

Install Transverse Rumble Strips 

Rumble strips are raised or grooved patterns on the roadway 

that provide both an audible warning (rumbling sound) 

and physical vibration to alert drivers of an upcoming 

intersection, curve, or other geometry change. Rumble 

strips may be installed on the center line of undivided 

highways, on the roadway shoulder, or on the roadway 

surface (transverse rumble strips). 

Where to Use: Transverse rumble strips have been used by 

some agencies to warn drivers in rural areas that they are 

approaching an intersection, a horizontal curve, or reduced 

speeds. 

Top Recommended Resources:

1. FHWA, Low Cost Treatments for Horizontal Curve Safety, December 2006. Available at: 

http://safety.fhwa.dot.gov/roadway_dept/horicurves/fhwasa07002/.

2. FHWA, “Proven Safety Countermeasures: Longitudinal Rumble Strips and Stripes on 2-Lane Roads,” 

April 2012. Available at: http://safety.fhwa.dot.gov/provencountermeasures/fhwa_sa_12_008.htm.

3. FHWA, “Promoting the Implementation of Proven Safety Countermeasures,” memorandum. January 12, 

2012. Available at: http://safety.fhwa.dot.gov/provencountermeasures/pc_memo.htm.

4. FHWA, Roadway Departure Safety: A Manual for Local Rural Road Owners, January 2011. Available at: 

http://safety.fhwa.dot.gov/local_rural/training/fhwasa1109/fhwasa1109.pdf.

Safety Treatment

Initial 

Implementation 

Cost

NCHRP 500 

Performance 

Rating

Crash 

Modification 

Factor (CMF)

Install Transverse Rumble Strips $0 to $5,000 Proven 0.76–0.91

Install Transverse Rumble Strips 
Federal Highway Administration | Office of Safety 

90

Regrade or Recondition Gravel Lanes

Maintaining a proper grade on gravel roads helps to remove rutting, 

shape the road to allow for proper drainage, smooth the driving surface, 

and bring the road surface up to bridge approaches or low water 

crossing approaches. Each of these considerations helps improve safety 

for those traveling along the route.

Where to Use: This treatment should be considered as routine 

maintenance on all unpaved roadways.

Top Recommended Resource:

1. Huntington, G., “Road Geometry, Surface Materials Are Key to Safety on Gravel Roads,” Safety Compass 6, 

No. 2 (2012), 4-5.

Safety Treatment

Initial 

Implementation 

Cost

NCHRP 500 

Performance 

Rating

Regrade or Recondition Gravel Lanes $0 to $20,000 Tried

Regrade or Recondition Gravel Lanes
Manual for Selecting Safety Improvements on High Risk Rural Roads

 91

Install Targeted Longitudinal Rumble Strips at Key Locations (Such as on the 

Outside of Horizontal Curves Only) 

Shoulder or edge line milled rumble strips can 

be used on roads with a history of roadway 

departure crashes. While it is recommended 

that rumble strips be applied systematically 

along an entire route instead of only at spot 

locations, where appropriate, they can be used 

on the outside of horizontal curves and the 

tangents leading to the curves.

Where to Use: Horizontal curve locations with 

a high frequency of roadway departure crashes.

Top Recommended Resources:

1. FHWA, Low Cost Treatments for Horizontal Curve Safety, December 2006. Available at: 

http://safety.fhwa.dot.gov/roadway_dept/horicurves/fhwasa07002/.

2. FHWA, “Proven Safety Countermeasures: Longitudinal Rumble Strips and Stripes on 2-Lane Roads,” 

April 2012. Available at: http://safety.fhwa.dot.gov/provencountermeasures/fhwa_sa_12_008.htm.

Safety Treatment

Initial 

Implementation 

Cost

NCHRP 500 

Performance 

Rating

Crash 

Modification 

Factor (CMF)

Install Targeted Longitudinal Rumble Strips at 

Key Locations (Such as on the Outside of 

Horizontal Curves Only)

$5,001 to $50,000 Tried 0.85

Install Targeted Longitudinal Rumble Strips at Key Locations 
Federal Highway Administration | Office of Safety 

92

Install or Maintain a Graded Shoulder 

Installing an earth or graded shoulder 

adjacent to the travel lane provides a 

recovery area for vehicles should they depart 

the roadway. The shoulder serves as an 

opportunity for the driver to correct their 

direction of travel by either re-entering 

the roadway or serving as a buffer before 

traversing the sideslope.

Where to Use: This treatment may be used 

at locations where no shoulders exist and/or 

where roadway departure crashes frequently 

occur.

Top Recommended Resource:

1. FHWA, Low Cost Treatments for Horizontal Curve Safety, December 2006. Available at: 

http://safety.fhwa.dot.gov/roadway_dept/horicurves/fhwasa07002/.

Safety Treatment

Initial 

Implementation 

Cost

NCHRP 500 

Performance 

Rating

Crash 

Modification 

Factor (CMF)

Install or Maintain a Graded Shoulder $5,001 to $50,000 Proven 0.52

Install or Maintain a Graded Shoulder 
Manual for Selecting Safety Improvements on High Risk Rural Roads

 93

Provide Turnout Areas 

Turnout areas are additional pavement beyond the travel 

way used for slower moving traffic to allow following 

traffic to pass.

Where to Use: This treatment may be used in low-volume 

rural locations where farm equipment and other slow 

moving vehicles are common. Because turnout areas 

can cause extreme speed differentials, they should not be 

installed at locations with high traffic volumes.

Safety Treatment

Initial 

Implementation 

Cost

NCHRP 500 

Performance 

Rating

Provide Turnout Areas $5,001 to $50,000 Tried

Provide Turnout Areas 
Federal Highway Administration | Office of Safety 

94

Improve Pavement Friction/Increase Skid Resistance 

Vehicles often leave the road due to lack of friction—especially 

in wet conditions when water between the tires and pavement 

could cause hydroplaning. Pavement friction treatments can 

reduce the number of wet-road crashes by improving friction at 

specific locations. 

Where to Use: Treatments such as epoxy-based, micro-surface, 

or chip seal overlays can address spot locations (e.g., a single 

curve, interchange ramp, bridge, or short roadway section). 

Friction treatments should be applied at locations with severe 

slick conditions that could benefit from increased friction.

Top Recommended Resource:

1. FHWA, Roadway Departure Safety: A Manual for Local Rural Road Owners, January 2011. Available at: 

http://safety.fhwa.dot.gov/local_rural/training/fhwasa1109/fhwasa1109.pdf.

Improve Pavement Friction/Increase Skid 

Resistance 

- Initial Investment: $53,335

- Cost of Maintenance: n/a

- Frequency of Maintenance: 10 years (2 applications)

Benefit-Cost 

Ratio

NCHRP 500 

Performance 

Rating

Crash 

Modification 

Factor (CMF)

Lower Volume Optimal Conditions 3.3 Proven 0.25–0.60

Higher Volume Optimal Conditions 26.7 Proven 0.25–0.60

Lower Volume Narrower Conditions 4.1 Proven 0.25–0.60

Higher Volume Narrower Conditions 40.3 Proven 0.25–0.60

Improve Pavement Friction/Increase Skid Resistance 
Manual for Selecting Safety Improvements on High Risk Rural Roads

 95

Add Paved Shoulder 

The addition of a paved shoulder to an existing road can help 

to reduce run-off-road crashes. Benefits can be realized for 

any HRRR without paved shoulders regardless of existing lane 

pavement width. Adding a paved shoulder within horizontal 

curve sections may help agencies maximize use of the treatment 

while minimizing costs as opposed to adding paved shoulders to 

an entire corridor.

Where to Use: This treatment may be used on any HRRR 

without a paved shoulder.

Top Recommended Resource:

1. FHWA, Low Cost Treatments for Horizontal Curve Safety, December 2006. Available at: 

http://safety.fhwa.dot.gov/roadway_dept/horicurves/fhwasa07002/.

Add Paved Shoulder 

- Initial Investment: $400,000

- Cost of Maintenance: $20,000

- Frequency of Maintenance: 2 years

Benefit-Cost 

Ratio

NCHRP 500 

Performance 

Rating

Crash 

Modification 

Factor (CMF)

Lower Volume Optimal Conditions n/a Proven 0.86

Higher Volume Optimal Conditions n/a Proven 0.86

Lower Volume Narrower Conditions 0.5 Proven 0.86

Higher Volume Narrower Conditions 4.5 Proven 0.86

Add Paved Shoulder 
Federal Highway Administration | Office of Safety 

96

Widen Existing Travel Lanes by Two Feet or Less per Lane 

Increasing lane width on HRRR from 9- or 10-feet wide to 11- or 12-feet wide can result in up to a 50 percent 

reduction in crashes. Drivers on rural two-lane highways may shift closer to the center line as they become 

less comfortable next to a narrow shoulder. At other times, they may shift closer to the shoulder edge and are 

at greater risk of driving off the paved portion of the roadway as they meet oncoming traffic. Lane widening in 

horizontal curve sections may help agencies maximize use of the treatment while minimizing costs as opposed to 

widening lanes through an entire corridor. 

Where to Use: This treatment may be used at locations where the width of travel lane is less than 12 feet.

Top Recommended Resource:

1. FHWA, Mitigation Strategies for Design Exceptions, “Chapter 3. The 13 Controlling Criteria,” July 2013. 

Available at: http://safety.fhwa.dot.gov/geometric/pubs/mitigationstrategies/chapter3/3_lanewidth.htm.

Widen Existing Travel Lanes by Two Feet or Less 

per Lane 

- Initial Investment: $500,000

- Cost of Maintenance: $25,000

- Frequency of Maintenance: 10 years

Benefit-Cost 

Ratio

NCHRP 500 

Performance 

Rating

Crash 

Modification 

Factor (CMF)

Lower Volume Optimal Conditions n/a Proven 0.95

Higher Volume Optimal Conditions n/a Proven 0.95

Lower Volume Narrower Conditions 0.3 Proven 0.95

Higher Volume Narrower Conditions 2.8 Proven 0.95

Widen Existing Travel Lanes by Two Feet or Less per Lane 
Manual for Selecting Safety Improvements on High Risk Rural Roads

 97

Install Passing or Climbing Lanes 

Passing or climbing lanes are auxiliary lanes that are 

provided in short segments to accommodate the passage of 

single-directional traffic.

Where to Use: This treatment can be provided where 

additional capacity is needed, in segment locations where 

head-on collisions occur as a result of passing vehicles, or 

locations where particularly slow moving traffic exists.

Install Passing or Climbing Lanes 

- Initial Investment: $1,000,000

- Cost of Maintenance: $50,000

- Frequency of Maintenance: 10 years

Benefit-Cost 

Ratio

NCHRP 500 

Performance 

Rating

Lower Volume Optimal Conditions 0.3 Proven

Higher Volume Optimal Conditions 2.3 Proven

Lower Volume Narrower Conditions 0.4 Proven

Higher Volume Narrower Conditions 3.5 Proven

Install Passing or Climbing Lanes 
Federal Highway Administration | Office of Safety 

98

Increase Shoulder Width 

Increasing shoulder width may offer the following 

benefits:

•	 Provide an area for drivers to maneuver to avoid 

crashes;

•	 Increase safety by providing a stable, clear recovery 

area for drivers who have left the travel lane;

•	 Improve stopping sight distance at horizontal curves 

by providing an offset to objects such as barrier and 

bridge piers;

•	 Improve bicycle accommodations; and

•	 Provide space for emergency storage of disabled 

vehicles.

The benefits seen by increasing shoulder width vary based on before and after conditions, road classification, 

speed, and the presence of multiple road user types. Increasing shoulder width within horizontal curve sections 

may help agencies maximize use of the treatment while minimizing costs as opposed to widening shoulders along 

an entire corridor.

Where to Use: For narrow pavement widths, it is beneficial to provide narrower lanes with wider shoulders at 

low AADTs (less than 1,000 vpd), while the configuration with 12-foot lanes and no shoulders appears to be most 

beneficial for large AADTs (greater than 1,000 vpd).

Top Recommended Resource:

1. FHWA, Safety Evaluation of Lane and Shoulder Width Combinations on Rural, Two-Lane, Undivided Roads, 

June 2009. Available at: http://www.fhwa.dot.gov/publications/research/safety/09031/09031.pdf.

Safety Treatment

Initial 

Implementation 

Cost

NCHRP 500 

Performance 

Rating

Crash 

Modification 

Factor (CMF)

Increase Shoulder Width $100,000 and up Proven 0.90–0.97

Increase Shoulder Width 
Manual for Selecting Safety Improvements on High Risk Rural Roads

 99

Improve Superelevation at Horizontal Curve Locations 

Superelevation is the rotation of the 

pavement on the approach to and through 

a horizontal curve and is intended to 

assist the driver in negotiating the curve 

by counteracting the lateral acceleration 

produced by tracking. In other words, 

the road is designed so that the pavement 

rises as it curves, offsetting the horizontal 

sideways momentum of the approaching 

vehicle.

Where to Use: Superelevation is expressed as a decimal representing the ratio of the pavement slope to width, 

ranging from 0 to 0.12 feet. The adopted criteria allow for the use of maximum superelevation rates from 0.04 to 

0.12. Maximum superelevation rates for design are established by policy by each State. Selection of a maximum 

superelevation rate is based on several variables, such as climate, terrain, highway location (urban vs. rural), and 

frequency of very slow-moving vehicles. Specific guidance on superelevation rates can be found in AASHTO’s A 

Policy on Geometric Design of Highways and Streets and Guidelines for Geometric Design of Very Low-Volume Local 

Roads (ADT ≤ 400). 

Top Recommended Resources:

1. FHWA, Mitigating Strategies for Design Exceptions, July 2007. Available at: 

http://safety.fhwa.dot.gov/geometric/pubs/mitigationstrategies/.

2. AASHTO, Guidelines for Geometric Design of Very Low-Volume Local Roads (ADT ≤ 400), January 2001.

3. AASHTO, A Policy on Geometric Design of Highways and Streets, November 2011.

Safety Treatment

Initial 

Implementation 

Cost

NCHRP 500 

Performance 

Rating

Improve Superelevation at Horizontal Curve Locations $100,000 and up Proven

Improve Superelevation at Horizontal Curve Locations 
Federal Highway Administration | Office of Safety 

100

4.6. Pavement Marking

Pavement markings provide directional guidance and sometimes inconspicuous warnings as drivers approach 

intersections and horizontal curves. Over time, these markings may fade, or increases in traffic volume may warrant 

pavement markings where none existed previously. This section covers safety improvement treatments that can be 

applied in the form of pavement marking procedures. Some treatments in this section also appear in the sections on 

intersection improvements, horizontal curve improvements, and roadside safety.1 2

32 As discussed in Section 1.2, a BCR is only shown where data were available to calculate the ratio. Where data were unavailable, the BCR has been left blank.

33 As stated in NCHRP Series 500 Reports (http://safety.transportation.org/guides.aspx). Proven: The safety effect for other similar applications has shown a proven benefit. Tried: The 

treatment has indications that it can be expected to reduce crashes, but has some conflicting reports as to its associated safety effects or has been deployed and observed to be effective. 

Experimental: New treatments that still need to be tested and for which the safety effect is unknown. Unknown: Not enough is known about an associated safety performance.

Safet

y Treatment

For more information, 

visit page

C

ost

Frequency of 

Maintenance (years)

Safet

y

Benefit

Benefit-Cost

Ratio 32

Initial 

Implementation

Ongoing 

Maintenance

NCHRP 500 

Performance Rating

Crash Modification 

Factor (CMF)

Lower Volume*, 

Optimal Conditions***

Higher Volume**, 

Optimal Conditions***

Lower Volume*, 

Narrower Conditions****

Higher Volume**, 

Narrower Conditions****

Provide a Stop Bar on Minor Road Approaches 101 $ $ 5 P 337.7 1175.8 287.1 1484.1

Install Stop Ahead Pavement Markings 102 $ P 0.44-0.69

Relocate an Existing Stop Bar on Minor Approach 103 $

T

Use of Optical Speed Bars 104 $Install Raised Pavement Markers 105 $-$$ T ≤0.76Install Edge Line Markings 106 $$ – 5 P 0.56-0.62 27.9 222.8 34.1 336.1Install Center Line Markings 107 $$ – 5 P 0.67 35.1 281.0 43.0 424.0

Install Wider Pavement Markings (With or Without Rumble Strips) 108 $$ E 0.65-0.96

Implement Lane Narrowing Through Rumble Strips and Painted Median at Rural Stop-controlled Approaches

109 $$-$$$

T 0.60-0.80

Install Center Line and Edge Line Markings 110 $$$ – 5 P 16.5 132.1 20.2 199.3

Convert a Four-Lane Two-Way Road into a Three-Lane Road With One Lane in Each Direction of Travel Plus a Continuous Two-Way Left Turn Lane (Road Diet)

111 $$$-$$$$ P 0.71-0.95

Convert a Four-Lane Two-Way Road into a Five-Lane Road with Two Lanes in Each 

Direction of Travel Plus a Continuous Two-Way Left Turn Lane OR Convert a Two-Lane Two-Way Road into a Three-Lane Road Plus a Continuous Two-Way Left Turn Lane

112 $$$-$$$$

T

Cost:$ = $0 to $5,000$$ = $5,001 to $20,000$$$ = $20,001 to $50,000$$$$ = $50,001 to $100,000$$$$$ = $100,001 and up

NCHRP 500 Performance Rating33

P – ProvenT – TriedE – ExperimentalU – Unknown

*Lower Volume ≤1000 vpd**Higher Volume = Between 1,001 and 8000 vpd***Optimal Conditions = 12-foot lanes, 6-foot paved shoulders****Narrower Conditions = 10-foot lanes and no shoulders

Pavement Marking
Manual for Selecting Safety Improvements on High Risk Rural Roads

 101

Provide a Stop Bar on Minor Road Approaches 

Providing visible stop bars on minor road approaches 

to unsignalized intersections can help direct the 

attention of drivers to the presence of the intersection.

Where to Use: Apply on minor road approaches 

where conditions allow the stop bar to be seen by an 

approaching driver at a significant distance from the 

intersection. Locations should be identified by patterns 

of crashes related to lack of driver recognition of the 

intersection.

Top Recommended Resource:

1. FHWA, Intersection Safety: A Manual for Local Rural Road Owners, January 2011. Available at: 

http://safety.fhwa.dot.gov/local_rural/training/fhwasa1108/fhwasa1108.pdf.

Provide a Stop Bar on Minor Road Approaches

- Initial Investment: $1,000 (4-Way), $500 (3-Leg)

- Cost of Maintenance: $0

- Frequency of Maintenance: 5 years (4 applications)

Benefit-Cost 

Ratio

NCHRP 500 

Performance 

Rating

Lower Volume 4-Way Intersections 337.7 Proven

Higher Volume 4-Way Intersections 1175.8 Proven

Lower Volume 3-Leg Intersections 287.1 Proven

Higher Volume 3-Leg Intersections 1484.1 Proven

Provide a Stop Bar on Minor Road Approaches 
Federal Highway Administration | Office of Safety 

102

Install Stop Ahead Pavement Markings 

Providing pavement markings with supplementary 

messages (such as Stop Ahead) can help alert drivers on the 

stop-controlled approach to the presence of an intersection.

Where to Use: It is likely that Stop Ahead pavement 

markings will be most effective at locations with a 

high frequency of target collisions (i.e., right-angle and 

rear-end), particularly where driver awareness may be an 

issue.

Top Recommended Resource:

1. FHWA, Techbrief: Safety Evaluation of STOP AHEAD Pavement Markings, March 2008. Available at: 

http://www.fhwa.dot.gov/publications/research/safety/08045/index.cfm.

Safety Treatment

Initial 

Implementation 

Cost

NCHRP 500 

Performance 

Rating

Crash 

Modification 

Factor (CMF)

Install Stop Ahead Pavement Markings $0 to $5,000 Proven 0.44–0.69

Install Stop Ahead Pavement Markings 
Manual for Selecting Safety Improvements on High Risk Rural Roads

 103

Relocate an Existing Stop Bar on Minor Approach

A minor approach may have an existing stop bar 

that is located where vehicles stopping at the bar 

have limited sight distance at the intersection. 

The stop bar may be relocated closer to the 

intersection at a point where the stopped vehicle 

would have better sight distance for approaching 

traffic. 

Where to Use: This treatment may be used 

at locations where existing sight distance may 

obstructed or where sight distance may be 

significantly improved by moving the stop bar.

Top Recommended Resource:

1. FHWA. NCHRP Report 500 / Volume 5: A Guide for Addressing Unsignalized Intersection Collisions, “Strategy 

E4. Provide a Stop Bar (or Provide a Wider Stop Bar) on Minor Road Approaches,” July 2003. Available at: 

http://safety.fhwa.dot.gov/intersection/resources/intsafestratbro/ue4.cfm.

Safety Treatment

Initial 

Implementation 

Cost

NCHRP 500 

Performance 

Rating

Relocate an Existing Stop Bar on Minor Approach $0 to $5,000 Tried

Relocate an Existing Stop Bar on Minor Approach
Federal Highway Administration | Office of Safety 

104

Use of Optical Speed Bars 

Optical Speed Bars are transverse stripes spaced at gradually decreasing 

distances. The rationale for using them is to increase drivers’ perception 

of speed and cause them to reduce speed, which can be helpful near 

intersections or horizontal curves. The Optical Speed Bar name comes 

from this intended visual effect on drivers’ speed as they react to the 

spacing of the painted lines. These white transverse stripes are 18 inches 

long and 12 inches wide. The preferred material is thermoplastic 

because of the exposure to traffic volume over time. 

Where to Use: This treatment may be used at locations where speed reductions are needed such as near 

intersections and horizontal curves.

Top Recommended Resource:

1. FHWA, Low Cost Treatments for Horizontal Curve Safety, December 2006. Available at: 

http://safety.fhwa.dot.gov/roadway_dept/horicurves/fhwasa07002/.

Safety Treatment

Initial 

Implementation 

Cost

Use of Optical Speed Bars $0 to $5,000

Use of Optical Speed Bars 
Manual for Selecting Safety Improvements on High Risk Rural Roads

 105

Install Raised Pavement Markers 

Raised pavement markers are designed to supplement 

the delineation provided by pavement markings. During 

certain conditions, particularly on wet roads in the dark, 

motorists may have difficulty determining the location 

of the center line and edge line pavement markings, 

increasing the likelihood of roadway departure. By 

installing raised pavement markers, the pavement 

markings are much more prominent in adverse weather 

conditions, providing important information to the driver. 

Where to Use: Raised pavement markers should be installed on routes with sufficient pavement quality to hold 

the devices in place. The type of raised pavement marker to install is dependent on regional climate. For example, 

in areas that experience snowfall, snow plowable RPMs should be used.

Top Recommended Resource:

1. FHWA, Roadway Departure Safety: A Manual for Local Rural Road Owners, January 2011. Available at: 

http://safety.fhwa.dot.gov/local_rural/training/fhwasa1109/fhwasa1109.pdf.

Safety Treatment

Initial 

Implementation 

Cost

NCHRP 500 

Performance 

Rating

Crash 

Modification 

Factor (CMF)

Install Raised Pavement Markers $0 to $20,000 Tried ≤ 0.76

Install Raised Pavement Markers 
Federal Highway Administration | Office of Safety 

106

Install Edge Line Markings 

Edge line markings separate the travel lane from 

the shoulder and communicate the intended 

roadway alignment and travel path to the driver. 

The MUTCD states that edge line markings must 

be white. A standard edge line marking is 4 inches, 

and wider edge line markings can range from 

4 inches to 8 inches in width.

Where to Use: According to Massachusetts DOT 

guidance, edge lines shall be placed on paved rural 

arterials with a traveled way of 20 feet or more and 

an ADT of 6,000 vpd or greater.

Top Recommended Resources:

1. Massachusetts DOT, Pavement Markings: Centerlines and Edgelines, January 2008. Available at: 

http://www.mhd.state.ma.us/safetytoolbox/downloads/PavementMarkings_CL_EL.pdf.

2. FHWA, Roadway Departure Safety: A Manual for Local Rural Road Owners, January 2011. Available at: 

http://safety.fhwa.dot.gov/local_rural/training/fhwasa1109/fhwasa1109.pdf.

Install Edge Line Markings 

- Initial Investment: $16,000

- Cost of Maintenance: n/a

- Frequency of Maintenance: 5 years (2 applications)

Benefit-Cost 

Ratio

NCHRP 500 

Performance 

Rating

Crash 

Modification 

Factor (CMF)

Lower Volume Optimal Conditions 27.9 Proven 0.56–0.62

Higher Volume Optimal Conditions 222.8 Proven 0.56–0.62

Lower Volume Narrower Conditions 34.1 Proven 0.56–0.62

Higher Volume Narrower Conditions 336.1 Proven 0.56–0.62

Install Edge Line Markings 
Manual for Selecting Safety Improvements on High Risk Rural Roads

 107

Install Center Line Markings 

Center line markings separate two opposing traffic streams on a roadway, 

guide the road user, and delineate travel lanes. The MUTCD states that 

center line markings must be yellow. A single solid center line is used to 

discourage crossing, a double line prohibits crossing, and a broken center 

line is used to indicate a passing zone.

Where to Use: According to Massachusetts DOT guidance, center 

lines are required on all paved urban arterials and collectors that have a 

traveled way of 20 feet or more in width and an ADT volume of 6,000 vpd 

or greater.

Top Recommended Resources:

1. Massachusetts DOT, Pavement Markings: Centerlines and Edgelines, January 2008. Available at: 

http://www.mhd.state.ma.us/safetytoolbox/downloads/PavementMarkings_CL_EL.pdf.

2. FHWA, Roadway Departure Safety: A Manual for Local Rural Road Owners, January 2011. Available at: 

http://safety.fhwa.dot.gov/local_rural/training/fhwasa1109/fhwasa1109.pdf.

Install Center Line Markings 

- Initial Investment: $16,000

- Cost of Maintenance: n/a

- Frequency of Maintenance: 5 years (2 applications)

Benefit-Cost 

Ratio

NCHRP 500 

Performance 

Rating

Crash 

Modification 

Factor (CMF)

Lower Volume Optimal Conditions 35.1 Proven 0.67

Higher Volume Optimal Conditions 281.0 Proven 0.67

Lower Volume Narrower Conditions 43.0 Proven 0.67

Higher Volume Narrower Conditions 424.0 Proven 0.67

Install Center Line Markings 
Federal Highway Administration | Office of Safety 

108

Install Wider Pavement Markings (With or Without Rumble Strips) 

Pavement markings provide continuous information to road users related to the roadway alignment, vehicle 

positioning, and other important driving-related tasks. Edge line width has been found to statistically lower 

nighttime fatal and injury crashes. A standard edge line marking is 4 inches, and wider edge line markings can 

range from 4 inches to 8 inches in width. 

Where to Use: This treatment may be beneficial for locations that experience run-off-road and opposite-direction 

crashes that occur at night or on curves.

Top Recommended Resource:

1. Carlson, P., E. Park, and C. Anderson, “The Benefits of Pavement Markings: A Renewed Perspective Based on 

Recent and Ongoing Research,” Paper No. 09-0488, August 2008.

Safety Treatment

Initial 

Implementation 

Cost

NCHRP 500 

Performance 

Rating

Crash 

Modification 

Factor (CMF)

Install Wider Pavement Markings (With or Without 

Rumble Strips) $5,001 to $20,000 Experimental 0.65–0.96

Install Wider Pavement Markings (With or Without Rumble Strips) 
Manual for Selecting Safety Improvements on High Risk Rural Roads

 109

Implement Lane Narrowing Through Rumble Strips and Painted Median at 

Rural Stop-Controlled Approaches 

Lane narrowing features the introduction of rumble strips on 

the outside shoulders and in a painted yellow median island on 

the major road approaches. The objective of lane narrowing is 

to induce drivers on major roads to reduce approach speeds at 

intersections by effectively reducing the lane width.

Where to Use: This practice has greater potential for 

effectiveness for intersections on high-speed roadways. 

However, the treatment can also be applied to intersections with lower posted speed limits.

Top Recommended Resource:

1. FHWA, Summary Report: Two Low-Cost Safety Concepts for Two-Way STOP-Controlled, Rural Intersections 

on High-Speed Two-Lane, Two-Way Roadways, December 2008. Available at: 

http://www.fhwa.dot.gov/publications/research/safety/08063/.

Safety Treatment

Initial 

Implementation 

Cost

NCHRP 500 

Performance 

Rating

Crash 

Modification 

Factor (CMF)

Implement Lane Narrowing Through 

Rumble Strips and Painted Median at Rural 

Stop-Controlled Approaches

$5,001 to $50,000 Tried 0.60–0.80

Implement Lane Narrowing Through Rumble Strips and Painted Median at Rural Stop-Controlled Approaches
Federal Highway Administration | Office of Safety 

110

Install Center Line and Edge Line Markings 

This treatment refers to installing both center line and edge line 

markings on a roadway. 

Where to Use: Any road with a history of run-off-road-right, 

head-on, opposite-direction-sideswipe, or run-off-road-left 

crashes is a candidate for this treatment. Depending on the 

width of the roadway, various combinations of edge line and/or 

center line pavement markings may be the most appropriate. 

Top Recommended Resource:

1. FHWA, Roadway Departure Safety: A Manual for Local Rural Road Owners, January 2011. Available at: 

http://safety.fhwa.dot.gov/local_rural/training/fhwasa1109/fhwasa1109.pdf.

Install Center Line and Edge Line Markings

- Initial Investment: $32,000

- Cost of Maintenance: n/a

- Frequency of Maintenance: 5 years (2 applications)

Benefit-Cost 

Ratio

NCHRP 500 

Performance 

Rating

Lower Volume Optimal Conditions 16.5 Proven

Higher Volume Optimal Conditions 132.1 Proven

Lower Volume Narrower Conditions 20.2 Proven

Higher Volume Narrower Conditions 199.3 Proven

Install Center Line and Edge Line Markings 
Manual for Selecting Safety Improvements on High Risk Rural Roads

 111

Convert a Four-Lane Two-Way Road into a Three-Lane Road With One Lane in Each 

Direction of Travel Plus a Continuous Two-Way Left Turn Lane (Road Diet) 

A road diet involves converting an undivided four-lane roadway into three lanes made up of two through lanes 

and a center Two-Way Left Turn Lane (TWLTL). The reduction of lanes allows the roadway to be reallocated for 

other uses such as bike lanes, pedestrian crossing islands, and/or parking. Road diets have multiple safety and 

operational benefits for vehicles as well as pedestrians, such as:

•	 Decreasing vehicle travel lanes for pedestrians to cross, therefore reducing the multiple-threat crash (when 

one vehicle stops for a pedestrian in a travel lane on a multi-lane road, but the motorist in the next lane does 

not, resulting in a crash) for pedestrians;

•	 Providing room for a pedestrian crossing island;

•	 Improving safety for bicyclists when bike lanes are added (such lanes also create a buffer space between 

pedestrians and vehicles);

•	 Providing the opportunity for on-street parking (also a buffer between pedestrians and vehicles);

•	 Reducing rear-end and side-swipe crashes; and

•	 Improving speed limit compliance and decreasing crash severity when crashes do occur.

Where to Use: Road diets can be low cost if planned in conjunction with reconstruction or simple overlay 

projects, since a road diet mostly consists of restriping. Roadways with Average Daily Traffic (ADT) of 20,000 or 

less may be good candidates for a road diet and should be evaluated for feasibility. It has been shown that roads 

with 15,000 ADT or less had very good results in the areas of safety, operations, and livability. Driveway density, 

transit routes, the number and design of intersections along the corridor, as well as operational characteristics are 

some considerations to be evaluated before deciding to implement a road diet.

Top Recommended Resource:

1. FHWA, Proven Safety Countermeasures: Road Diet (Roadway Reconfiguration), December 2011. Available at: 

http://safety.fhwa.dot.gov/provencountermeasures/fhwa_sa_12_013.htm.

Safety Treatment

Initial 

Implementation 

Cost

NCHRP 500 

Performance 

Rating

Crash 

Modification 

Factor (CMF)

Convert a Four-Lane Two-Way Road into a Three-Lane 

Road With One Lane in Each Direction of Travel Plus a 

Continuous Two-Way Left Turn Lane (Road Diet)

$20,001 to 

$100,000 Proven 0.71–0.95

Convert a Four-Lane Two-Way Road into a Three-Lane Road With One Lane in Each Direction of Travel
Federal Highway Administration | Office of Safety 

112

Convert a Four-Lane Two-Way Road into a Five-Lane Road with Two Lanes in Each 

Direction of Travel Plus a Continuous Two-Way Left Turn Lane OR Convert a Two-Lane 

Two-Way Road into a Three-Lane Road Plus a Continuous Two-Way Left Turn Lane 

A Two-Way Left Turn Lane (TWLTL) is a lane placed 

between opposing lanes of traffic for the purpose of 

allowing traffic from either direction to make left 

turns off of a roadway.

TWLTLs remove left turning vehicles from the 

through lanes, which can reduce delay to through 

vehicles and can lead to a reduction in rear-end and 

sideswipe collisions. Second, TWLTLs provide spatial 

separation between opposing lanes of traffic, which 

can lead to a reduction in head-on collisions. The 

TWLTLs can also function as a lane for emergency 

vehicles.

Where to Use: Current and future operational conditions such as capacity and level of service, safety conditions, 

traffic volumes (including trucks), and left turn volumes, along with type of land use, future development, and 

driveway and intersection densities should be considered before implementation.

Lower cost installations of TWLTLs can be a cost-effective treatment for two-lane rural locations, especially those 

with a high frequency of rear-end collisions involving a lead vehicle desiring to make a turn.

Top Recommended Resources:

1. Iowa DOT. Design Manual, “Chapter 6,” December 2010. Available at: 

http://www.iowadot.gov/design/dmanual/manual.html. 

2. FHWA, Safety Evaluation of Installing Center Two-Way Left Turn Lanes on Two-Lane Roads, March 2007. 

Available at: http://www.fhwa.dot.gov/publications/research/safety/08042/08042.pdf. 

Safety Treatment

Initial 

Implementation 

Cost

NCHRP 500 

Performance 

Rating

Convert a Four-Lane Two-Way Road into a Five-Lane 

Road with Two Lanes in Each Direction of Travel Plus 

a Continuous Two-Way Left Turn Lane OR Convert a 

Two-Lane Two-Way Road into a Three-Lane Road Plus 

a Continuous Two-Way Left Turn Lane

$20,001 to 

$100,000 Tried

Convert a Four-Lane Two-Way Road into a Five-Lane Road with Two Lanes in Each Direction of Travel
Manual for Selecting Safety Improvements on High Risk Rural Roads

 113

4.7. Roadside

Improvements cited in this section include removal of hazards, redesigning obstacles, relocating obstacles, 

reducing impact severity with breakaway devices, shielding obstacles, or delineation. These are common hazards 

on rural roadways. Some treatments in this section also appear in the sections on pavement and shoulder 

treatments.12

34 As discussed in Section 1.2, a BCR is only shown where data were available to calculate the ratio. Where data were unavailable, the BCR has been left blank.

35 As stated in NCHRP Series 500 Reports (http://safety.transportation.org/guides.aspx). Proven: The safety effect for other similar applications has shown a proven benefit. 

Tried: The treatment has indications that it can be expected to reduce crashes, but has some conflicting reports as to its associated safety effects or has been deployed and 

observed to be effective. Experimental: New treatments that still need to be tested and for which the safety effect is unknown. Unknown: Not enough is known about an 

associated safety performance.

Safet

y Treatment

For more information, 

visit page

C

ost

Frequency of 

Maintenance (years)

Safet

y

Benefit

Benefit-Cost

Ratio 34

Initial 

Implementation

Ongoing 

Maintenance

NCHRP 500 

Performance Rating

Crash Modification 

Factor (CMF)

Lower Volume*, 

Optimal Conditions***

Higher Volume**, 

Optimal Conditions***

Lower Volume*, 

Narrower Conditions****

Higher Volume**, 

Narrower Conditions****

Install a Safety Edge 114 $ – 20 P 0.85-0.92 33.4 267.2 40.9 403.2Improve Sight Distance by Controlling Roadside Vegetation 115 $-$$

T

Convert Culvert Headwalls to Traversable End Treatments 116 $-$$ PRemove Guardrail 117 $-$$

U

Install or Maintain a Graded Shoulder 118 $$$ P 0.52Relocate Select Hazardous Utility Poles 119 $$$-$$$$ P ≤0.71Install Median Guardrail 120 $$$-$$$$

Modify End Treatments of Existing Guardrail 121 $$$-$$$$ PInstall Impact Attenuation Devices at Select Roadside Hazard Locations (Such as Exposed Bridge Columns)

122 $$$-$$$$ P 0.31-0.54

Remove or Shield Obstacles in Clear Zone 123 $$$$ $$ 5 P ≤0.71 3.3 26.7 4.6 45.2

Increase Shoulder Width 124 $$$$-$$$$$ P 0.90-0.97

Widen Existing Median or Construct Median 125 $$$$-$$$$$ PInstall Median Cable Barrier 126 $$$-$$$$ P 0.71Flatten Road Sideslope 127 $$$$$ – 10 P 0.58 n/a n/a 0.2 1.9

Create or Increase Clear Zone 128 $$$$$ – – P 0.56-0.87 1.0 7.9 1.5 14.6

Add Paved Shoulder 129 $$$$$ $$ 2 P 0.86 n/a n/a 0.5 4.5Install Concrete Median Barrier 130 $$$$$ P

Cost:$ = $0 to $5,000$$ = $5,001 to $20,000$$$ = $20,001 to $50,000$$$$ = $50,001 to $100,000$$$$$ = $100,001 and up

NCHRP 500 Performance35 

Rating P – ProvenT – TriedE – ExperimentalU – Unknown

*Lower Volume ≤1000 vpd**Higher Volume = Between 1,001 and 8000 vpd***Optimal Conditions = 12-foot lanes, 6-foot paved shoulders****Narrower Conditions = 10-foot lanes and no shoulders

Roadside
Federal Highway Administration | Office of Safety 

114

Install a Safety Edge 

When a vehicle leaves the traveled way and encounters a pavementshoulder drop-off, it can be difficult for the driver to return safely to 

the roadway. They often overcorrect when returning to the pavement 

and subsequently lose control and run off the road. A safety edge is 

a treatment intended to minimize drop-off-related crashes. With this 

treatment, the pavement edge is sloped at an angle (30-35 degrees) 

to make it easier for a driver to safely re-enter the roadway after 

inadvertently driving onto the shoulder. This treatment is designed to 

be a standard policy for any overlay project. 

Where to Use: Each State should implement policies and procedures to incorporate the Safety Edge where 

pavement and non-pavement surfaces interface on all paving and resurfacing projects with surface differentials 

of 2.5 inches or more. The differentials should be measured from the pavement surface to the adjacent nonpavement surface, accounting for grading along the pavement edge during construction and including existing 

drop-offs. The Safety Edge is appropriately used at locations where pavement edge drop-offs occur through 

everyday use, particularly on rural roads with unpaved shoulders. 

Note: In general, the Safety Edge is used the entire length of a project, rather than only in locations where a drop-off 

exists for a short distance.

Top Recommended Resources:

1. FHWA, Summary Report: Safety Evaluation of the Safety Edge Treatment, February 2011. Available at: http://

www.fhwa.dot.gov/publications/research/safety/hsis/11025/11025.pdf.

2. FHWA, “Proven Safety Countermeasures: Safety Edge,” January 2012. Available at: 

http://safety.fhwa.dot.gov/provencountermeasures/fhwa_sa_12_010.htm.

3. FHWA, Roadway Departure Safety: A Manual for Local Rural Road Owners, January 2011. Available at: 

http://safety.fhwa.dot.gov/local_rural/training/fhwasa1109/fhwasa1109.pdf.

Install a Safety Edge 

- Initial Investment: $2,145

- Cost of Maintenance: n/a

- Frequency of Maintenance: 20 years

Benefit-Cost 

Ratio

NCHRP 500 

Performance 

Rating

Crash 

Modification 

Factor (CMF)

Lower Volume Optimal Conditions 33.4 Proven 0.85–0.92

Higher Volume Optimal Conditions 267.2 Proven 0.85–0.92

Lower Volume Narrower Conditions 40.9 Proven 0.85–0.92

Higher Volume Narrower Conditions 403.2 Proven 0.85–0.92

Install a Safety Edge 
Manual for Selecting Safety Improvements on High Risk Rural Roads

 115

Improve Sight Distance by Controlling Roadside Vegetation 

Vegetation control helps lessen the likelihood of 

fixed-object crashes. Proper maintenance of tall grass, 

weeds, brush, and tree limbs and can help improve 

drivers’ sight distance of the road ahead, traffic control 

devices, approaching vehicles, wildlife and livestock, and 

pedestrians and bicycles.

Where to Use: This treatment is appropriate to use at all 

locations, especially those in rural areas where vegetation 

growth is high.

Top Recommended Resource:

1. FHWA, Vegetation Control For Safety: A Guide for Local Highway and Street Maintenance Personnel, 

August 2008. Available at: http://safety.fhwa.dot.gov/local_rural/training/fhwasa07018/vegetationfv1108.pdf.

Safety Treatment

Initial 

Implementation 

Cost

NCHRP 500 

Performance 

Rating

Improve Sight Distance by Controlling Roadside 

Vegetation $0 to $20,000 Tried

Improve Sight Distance by Controlling Roadside Vegetation 
Federal Highway Administration | Office of Safety 

116

Convert Culvert Headwalls to Traversable End Treatments 

Culvert headwalls may act as a fixed object once vehicles leave the roadway. By installing traversable culvert end 

treatments, vehicles may be able to drive over them without rolling over or experiencing an abrupt change in 

speed.

Where to Use: This treatment is applicable for locations where culvert headwalls are perpendicular to and lie in 

close proximity to the traveled way.

Safety Treatment

Initial 

Implementation 

Cost

NCHRP 500 

Performance 

Rating

Convert Culvert Headwalls to Traversable End 

Treatments $0 to $20,000 Proven

Convert Culvert Headwalls to Traversable End Treatments 

Top Recommended Resource:

1. FHWA, Maintenance of Drainage Features for Safety: A Guide for Local Street and Highway Maintenance 

Personnel, July 2009. Available at: http://safety.fhwa.dot.gov/local_rural/training/fhwasa09024/fhwasa09024.pdf.
Manual for Selecting Safety Improvements on High Risk Rural Roads

 117

Remove Guardrail 

Removal of guardrail that no longer provides a safety benefit can help 

eliminate a roadside obstacle. Each removal should be evaluated on a 

case-by-case basis.

Where to Use: This treatment may be used at locations where guardrails 

no longer provide a safety benefit (e.g., locations where sideslopes have 

been improved behind the guardrail or where roadside obstacles have 

been removed).

Safety Treatment

Initial 

Implementation 

Cost

NCHRP 500 

Performance 

Rating

Remove Guardrail $0 to $20,000 Unknown

Remove Guardrail
Federal Highway Administration | Office of Safety 

118

Install or Maintain a Graded Shoulder 

Installing a stabilized earth or graded shoulder adjacent to the travel lane provides a recovery area for vehicles 

if they should depart the road. The shoulder provides as an opportunity for drivers to correct their direction of 

travel by re-entering the roadway. It may also serve as a buffer before traversing the sideslope.

Where to Use: This treatment may be used at locations where no shoulders exist and/or where roadway departure 

crashes frequently occur.

Safety Treatment

Initial 

Implementation 

Cost

NCHRP 500 

Performance 

Rating

Crash 

Modification 

Factor (CMF)

Install or Maintain a Graded Shoulder $20,001 to 

$50,000 Proven 0.52

Install or Maintain a Graded Shoulder 
Manual for Selecting Safety Improvements on High Risk Rural Roads

 119

Relocate Select Hazardous Utility Poles 

Relocating or removing utility poles from within the clear zone 

alleviates the potential for fixed-object crashes. If utility poles cannot 

be completely eliminated from within the clear zone, efforts can be 

made to either relocate the poles to a greater offset from the road or 

delineated.

Where to Use: This treatment may be used at locations where utility 

pole fixed-object crashes occur or are more likely to occur due to the 

proximity of the poles to the roadway, such as along the outside of 

horizontal curves. 

Top Recommended Resource:

1. Transportation Research Board. NCHRP Report 500 / Guidance for Implementation of the AASHTO Strategic 

Highway Safety Plan, Volume 8: A Guide for Reducing Collisions Involving Utility Poles, June 2004. Available at: 

http://onlinepubs.trb.org/Onlinepubs/nchrp/nchrp_rpt_500v8.pdf. 

Safety Treatment

Initial 

Implementation 

Cost

NCHRP 500 

Performance 

Rating

Crash 

Modification 

Factor (CMF)

Relocate Select Hazardous Utility Poles $20,001 to 

$100,000 Proven ≤ 0.71

Relocate Select Hazardous Utility Poles 
Federal Highway Administration | Office of Safety 

120

Install Median Guardrail 

The installation of median guardrail is most 

suitable for use in traversable medians having 

no or little change in grade and cross slope. 

While these systems may not reduce the 

frequency of crashes due to roadway departure, 

they can help prevent a lane-departure crash 

from becoming a head-on collision.

Where to Use: This treatment may be used on 

divided highways with 20,000 ADT or greater 

that have a system-wide history of cross-median 

crashes. Highways with medians less than 50 

feet wide. The treatment should be applied 

systemically using logical end points, not at 

specific locations.

Top Recommended Resource:

1. FHWA, Median Barriers, September 2010. Available at: 

http://safety.fhwa.dot.gov/roadway_dept/policy_guide/road_hardware/ctrmeasures/median_barriers/.

Safety Treatment

Initial 

Implementation 

Cost

Install Median Guardrail $20,001 to 

$100,000

Install Median Guardrail 
Manual for Selecting Safety Improvements on High Risk Rural Roads

 121

Modify End Treatments of Existing Guardrail 

The installation of a crashworthy end treatment can be used to prevent impact with guardrail ends by safely 

decelerating the vehicle or by safety redirecting it around the object of concern.

Where to Use: This treatment may be used at guardrail locations that have experienced severe crashes or have not 

performed as desired when hit. Also, any currently-installed “turn-down” or blunt guardrail ends.

Safety Treatment

Initial 

Implementation 

Cost

NCHRP 500 

Performance 

Rating

Modify End Treatments of Existing Guardrail $20,001 to 

$100,000 Proven

Modify End Treatments of Existing Guardrail 
Federal Highway Administration | Office of Safety 

122

Install Impact Attenuation Devices at Select Roadside Hazard Locations (Such as 

Exposed Bridge Columns) 

An impact attenuator, also known as a crash cushion or 

crash attenuator, is a device intended to reduce the damage 

to vehicles, motorists, and structures as a result of a motor 

vehicle collision. Attenuators may be installed to protect 

bridge columns and other narrow roadside obstacles.

Where to Use: This treatment may be used at locations 

where roadside hazards are relatively close to the road, or 

where fixed object crashes have occurred.

Safety Treatment

Initial 

Implementation 

Cost

NCHRP 500 

Performance 

Rating

Crash 

Modification 

Factor (CMF)

Install Impact Attenuation Devices at Select Roadside 

Hazard Locations (Such as Exposed Bridge Columns)

$20,001 to 

$100,000 Proven 0.31–0.54

Install Impact Attenuation Devices at Select Roadside Hazard Locations 
Manual for Selecting Safety Improvements on High Risk Rural Roads

 123

Remove or Shield Obstacles in Clear Zone 

Removing, redesigning, marking, or relocating 

fixed objects within the clear zone reduces 

the likelihood of a crash. If a crash occurs, 

adding breakaway features, crash cushions, or 

redirection devices reduces crash severity.

Where to Use: Depending on the type and 

location of the obstacle, several methods to 

improve the clear zone exist. 

These include:

1. Removing the obstacle;

2. Redesigning the obstacle so it can be safely traversed;

3. Relocating the obstacle to a point where it is less likely to be struck;

4. Reducing impact severity by using an appropriate breakaway device;

5. Protecting the driver by redirecting the errant vehicle with guardrail or reducing the severity of the crash with 

an impact attenuation device; and

7. Marking the object to provide motorist information.

Top Recommended Resources:

1. FHWA, Toolbox of Countermeasures and Their Potential Effectiveness for Roadway Departure Crashes, August 2008. Available at: http://safety.fhwa.dot.gov/tools/crf/resources/briefs/rdwydepartissue.cfm.

2. FHWA, Roadway Departure Safety: A Manual for Local Rural Road Owners, January 2011. Available at: 

http://safety.fhwa.dot.gov/local_rural/training/fhwasa1109/fhwasa1109.pdf.

Remove or Shield Obstacles in Clear Zone

- Initial Investment: $70,000

- Cost of Maintenance: $7,000

- Frequency of Maintenance: 5 years

Benefit-Cost 

Ratio

NCHRP 500 

Performance 

Rating

Crash 

Modification 

Factor (CMF)

Lower Volume Optimal Conditions 3.3 Proven ≤ 0.71

Higher Volume Optimal Conditions 26.7 Proven ≤ 0.71

Lower Volume Narrower Conditions 4.6 Proven ≤ 0.71

Higher Volume Narrower Conditions 45.2 Proven ≤ 0.71

Remove or Shield Obstacles in Clear Zone 
Federal Highway Administration | Office of Safety 

124

Increase Shoulder Width 

Increasing shoulder width may offer the following benefits:

•	 Provide an area for drivers to maneuver to avoid crashes;

•	 Increase safety by providing a stable, clear recovery area for drivers who have left the travel lane;

•	 Improve stopping sight distance at horizontal curves by providing an offset to objects such as barrier and 

bridge piers;

•	 Provide shelf for snow in northern climates;

•	 Improve bicycle accommodation; and

•	 Provide space for emergency storage of disabled vehicles

The benefits seen by increasing shoulder width vary based on before and after conditions, road classification, 

speed, and the presence of multiple road user types. Increasing shoulder width within horizontal curve sections 

may help agencies maximize use of the treatment while minimizing costs, as opposed to adding widening 

shoulders to an entire corridor.

Where to Use: For narrow pavement widths, it is beneficial to provide narrower lanes with wider shoulders at 

low AADTs (less than 1,000 vpd), while the configuration with 12-foot lanes and no shoulders appears to be most 

beneficial for large AADTs (greater than 1,000 vpd).

Top Recommended Resource:

1. FHWA, Safety Evaluation of Lane and Shoulder Width Combinations on Rural, Two-Lane, Undivided Roads, 

June 2009. Available at: http://www.fhwa.dot.gov/publications/research/safety/09031/09031.pdf.

Safety Treatment

Initial 

Implementation 

Cost

NCHRP 500 

Performance 

Rating

Crash 

Modification 

Factor (CMF)

Increase Shoulder Width $50,001 to 

$100,000 Proven 0.90–0.97

Increase Shoulder Width
Manual for Selecting Safety Improvements on High Risk Rural Roads

 125

Widen Existing Median or Construct Median

Use of these treatments helps to provide additional lateral distance between opposing traffic.

Where to Use: This treatment may be applicable when high frequencies of head-on collisions exist.

Safety Treatment

Initial 

Implementation 

Cost

NCHRP 500 

Performance 

Rating

Widen Existing Median or Construct Median $50,001 to 

$100,000 Proven

Widen Existing Median or Construct Median
Federal Highway Administration | Office of Safety 

126

Install Median Cable Barrier 

Median cable barrier systems are considered the most versatile 

and forgiving barrier systems available for reducing the severity 

of median crossover crashes. While these systems may not 

reduce the frequency of crashes due to roadway departure, 

they can help prevent a lane-departure crash from becoming a 

head-on collision.

Where to Use: This treatment may be used on divided 

highways that have a system-wide history of cross-median 

crashes and highways with medians less than 50 feet wide. The 

treatment should be applied systemically using logical end 

points, not at specific locations.

Top Recommended Resource:

1. FHWA, Median Barriers. Available at: 

http://safety.fhwa.dot.gov/roadway_dept/policy_guide/road_hardware/ctrmeasures/median_barriers/

Safety Treatment

Initial 

Implementation 

Cost

NCHRP 500 

Performance 

Rating

Crash 

Modification 

Factor (CMF)

Install Median Cable Barrier $120,000 Proven 0.71

Install Median Cable Barrier 
Manual for Selecting Safety Improvements on High Risk Rural Roads

 127

Flatten Road Sideslope 

By reducing the amount of road sideslope, vehicles are 

better able to recover after leaving the travelway. The flatter 

the slope, the more traversable the sideslope becomes.

Where to Use: This treatment may be used at locations that 

have experienced overturn crashes, on the outside of curves 

with small radii, where the sideslope has a slope of greater 

than 3:1.

Top Recommended Resources:

1. FHWA, Toolbox of Countermeasures and Their Potential Effectiveness for Roadway Departure Crashes, 

August 2008. Available at: http://safety.fhwa.dot.gov/tools/crf/resources/briefs/rdwydepartissue.cfm.

2. FHWA, Roadway Departure Safety: A Manual for Local Rural Road Owners, January 2011. Available at: 

http://safety.fhwa.dot.gov/local_rural/training/fhwasa1109/fhwasa1109.pdf.

Flatten Road Sideslope

- Initial Investment: $1,000,000

- Cost of Maintenance: n/a

- Frequency of Maintenance: 10 years

Benefit-Cost 

Ratio

NCHRP 500 

Performance 

Rating

Crash 

Modification 

Factor (CMF)

Lower Volume Optimal Conditions n/a Proven 0.58

Higher Volume Optimal Conditions n/a Proven 0.58

Lower Volume Narrower Conditions 0.2 Proven 0.58

Higher Volume Narrower Conditions 1.9 Proven 0.58

Flatten Road Sideslope 
Federal Highway Administration | Office of Safety 

128

Create or Increase Clear Zone 

A clear zone is an unobstructed, traversable roadside area 

that allows a driver to stop safely or regain control of a 

vehicle that has left the roadway. The width of the clear 

zone should be based on risk (also called exposure). Key 

factors in assessing risk include traffic volumes, speeds, and 

slopes, in accordance to the AASHTO Roadside Design 

guide. Clear roadsides consider both fixed objects and 

terrain that may cause vehicles to rollover. Creating or 

increasing clear zones within horizontal curve sections 

may help agencies maximize use of the treatment while 

minimizing costs, as opposed to providing a clear zone 

throughout an entire corridor.

Where to Use: A clear zone should be developed on every roadway where space is available. In situations where 

public right-of-way is limited, steps should be taken to request assistance from property owners or seek volunteer 

easements, as appropriate.

Top Recommended Resources:

1. FHWA, Clear Zones, Available at: http://safety.fhwa.dot.gov/roadway_dept/clear_zones/

2. FHWA, Roadway Departure Safety: A Manual for Local Rural Road Owners, January 2011. Available at: 

http://safety.fhwa.dot.gov/local_rural/training/fhwasa1109/fhwasa1109.pdf.

3. AASHTO, Roadside Design Guide, September 2011.

Create or Increase Clear Zone

- Initial Investment: $300,000

- Cost of Maintenance: n/a

- Frequency of Maintenance: n/a

Benefit-Cost 

Ratio

NCHRP 500 

Performance 

Rating

Crash 

Modification 

Factor (CMF)

Lower Volume Optimal Conditions 1.0 Proven 0.56–0.87

Higher Volume Optimal Conditions 7.9 Proven 0.56–0.87

Lower Volume Narrower Conditions 1.5 Proven 0.56–0.87

Higher Volume Narrower Conditions 14.6 Proven 0.56–0.87

Create or Increase Clear Zone 
Manual for Selecting Safety Improvements on High Risk Rural Roads

 129

Add Paved Shoulder 

The addition of a paved shoulder to an existing road can help 

to reduce run-off-road crashes. Benefits can be realized for 

any HRRR without paved shoulders, regardless of existing lane 

pavement width. Adding a paved shoulder within horizontal 

curve sections may help agencies maximize use of the treatment 

while minimizing costs as opposed to adding paved shoulders to 

an entire corridor.

Where to Use: This treatment may be used on any HRRR 

without a paved shoulder.

Add Paved Shoulder 

- Initial Investment: $400,000

- Cost of Maintenance: $20,000

- Frequency of Maintenance: 2 years

Benefit-Cost 

Ratio

NCHRP 500 

Performance 

Rating

Crash 

Modification 

Factor (CMF)

Lower Volume Optimal Conditions n/a Proven 0.86

Higher Volume Optimal Conditions n/a Proven 0.86

Lower Volume Narrower Conditions 0.5 Proven 0.86

Higher Volume Narrower Conditions 4.5 Proven 0.86

Add Paved Shoulder 
Federal Highway Administration | Office of Safety 

130

Install Concrete Median Barriers

Concrete median barriers are longitudinal barriers used to 

separate opposing directions of traffic. While these systems 

may not reduce the frequency of crashes due to roadway 

departure, they can help prevent a lane-departure crash from 

becoming a head-on collision.

Where to Use: Concrete median barriers can be used in urban 

or rural locations that experience frequent head-on collisions 

when:

•	 Constructing a median is not possible, and

•	 There exists sufficient distance between opposing travel 

lanes to install the barrier

Safety Treatment

Initial 

Implementation 

Cost

NCHRP 500 

Performance 

Rating

Install Concrete Median Barriers $100,001 and up Proven

Install Concrete Median Barriers
Manual for Selecting Safety Improvements on High Risk Rural Roads

 131

4.8. Signing

Improved signing and sign conspicuity can provide warnings to drivers as they approach potentially hazardous 

scenarios, such as intersections and horizontal curves. Some treatments in this section also appear in the sections 

on intersection improvements and horizontal curve improvements.1 2

36 As discussed in Section 1.2, a BCR is only shown where data were available to calculate the ratio. Where data were unavailable, the BCR has been left blank.

37 As stated in NCHRP Series 500 Reports (http://safety.transportation.org/guides.aspx). Proven: The safety effect for other similar applications has shown a proven benefit. 

Tried: The treatment has indications that it can be expected to reduce crashes, but has some conflicting reports as to its associated safety effects or has been deployed and 

observed to be effective. Experimental: New treatments that still need to be tested and for which the safety effect is unknown. Unknown: Not enough is known about an 

associated safety performance.

Safet

y Treatment

For more information, 

visit page

C

ost

Frequency of 

Maintenance (years)

Safet

y

Benefit

Benefit-Cost

Ratio 36

Initial 

Implementation

Ongoing 

Maintenance

NCHRP 500 

Performance Rating

Crash Modification 

Factor (CMF)

Lower Volume*, 

Optimal Conditions***

Higher Volume**, 

Optimal Conditions***

Lower Volume*, 

Narrower Conditions****

Higher Volume**, 

Narrower Conditions****

Install/Upgrade Curve Warning Signs with Fluorescent Yellow Sheeting 132 $ – 5 P 0.66 63.1 490.4 75.1 739.9

Install Curve Warning Signs 133 $ $ 5 P 0.70 33.8 270.1 43.5 428.4

Install Retroreflective Strips on Sign Posts 134 $

T

Double Use of Advanced Warning Signs for Curves or Intersections 135 $

T

Provide Upcoming Road Names on Advanced Warning Signs 136 $ T 0.90-0.99

Install Advanced Intersection Warning Signs 137 $

T

Upgrade to Larger Stop Signs 138 $ P

Double Use of Stop Signs 139 $

T

Use of Supplemental Warning Signs 140 $

T

Install Chevron Signs 141 $$ $ 5 P 0.75 10.6 84.7 13.0 127.7

Cost:$ = $0 to $5,000$$ = $5,001 to $20,000$$$ = $20,001 to $50,000$$$$ = $50,001 to $100,000$$$$$ = $100,001 and up

NCHRP 500 Performance Rating37 

P – ProvenT – TriedE – ExperimentalU – Unknown

*Lower Volume ≤1000 vpd**Higher Volume = Between 1,001 and 8000 vpd***Optimal Conditions = 12-foot lanes, 6-foot paved shoulders****Narrower Conditions = 10-foot lanes and no shoulders

Signing
Federal Highway Administration | Office of Safety 

132

Install/Upgrade Curve Warning Signs with Fluorescent Yellow Sheeting 

Fluorescent yellow sheeting can improve the effectiveness of curve warning and delineation signs by increasing the 

conspicuity of the sign, especially during dark conditions.

Where to Use: Connecticut DOT used fluorescent yellow sheeting to improve signing at horizontal curves 

between 2002 and 2006. These curves were selected through a regular program called the Suggested List of 

Surveillance Study Sites (SLOSSS), which uses crash data, traffic volumes, and roadway characteristics to identify 

intersections and road segments with higher than expected crash rates.

Top Recommended Resources:

1. FHWA, Safety Evaluation of Improved Curve Delineation, September 2009. Available at: 

http://www.fhwa.dot.gov/publications/research/safety/09045/09045.pdf

2. FHWA, Low Cost Treatments for Horizontal Curve Safety, December 2006. Available at: 

http://safety.fhwa.dot.gov/roadway_dept/horicurves/fhwasa07002/.

Install/Upgrade Curve Warning Signs with 

Fluorescent Yellow Sheeting 

- Initial Investment: $1,280

- Cost of Maintenance: n/a

- Frequency of Maintenance: 5 years (2 applications)

Benefit-Cost 

Ratio

NCHRP 500 

Performance 

Rating

Crash 

Modification 

Factor (CMF)

Lower Volume Optimal Conditions 63.1 Proven 0.66

Higher Volume Optimal Conditions 490.4 Proven 0.66

Lower Volume Narrower Conditions 75.1 Proven 0.66

Higher Volume Narrower Conditions 739.9 Proven 0.66

Install/Upgrade Curve Warning Signs with Fluorescent Yellow Sheeting 
Manual for Selecting Safety Improvements on High Risk Rural Roads

 133

Install Curve Warning Signs 

Some of the most serious crashes on rural roads occur 

at horizontal curves. Horizontal alignment signs, 

informally called curve warning signs, can improve 

safety by alerting drivers to changes in roadway 

geometry that may not be apparent or expected. These 

signs provide visual information for the driver about 

the nature of the curve they are approaching, letting 

them know whether it’s a gradual curve, a sharp turn, a 

hairpin turn, or some combination. Different types of 

curve warning signs are identified in the MUTCD.

Where to Use: Curve warning signs should be applied to any curve or turn 

with a history of roadway departure crashes and curves or turns with similar 

geometry or traffic volume yet to experience crashes. According to the 2009 

MUTCD, warning signs are required on curves or turns where the advisory 

speed is 10 mph less than the posted speed.

Studies have shown that reductions in crashes due to the installation of 

curve warning signs are more prominent at locations with higher traffic 

volumes, sharper curves, or hazardous roadsides.

Top Recommended Resources:

1. University of California, Berkley, Institute of Transportation Studies, Technology Transfer Program, Tech 

Transfer Newsletter, “Signs for Curves and Turns.” Available at: 

http://www.techtransfer.berkeley.edu/newsletter/08-2/signs-for-curves-and-turns.php.

2. FHWA, Roadway Departure Safety: A Manual for Local Rural Road Owners, January 2011. Available at: 

http://safety.fhwa.dot.gov/local_rural/training/fhwasa1109/fhwasa1109.pdf.

Install Curve Warning Signs 

- Initial Investment: $2,400

- Cost of Maintenance: $1,280

- Frequency of Maintenance: 5 years

Benefit-Cost 

Ratio

NCHRP 500 

Performance 

Rating

Crash 

Modification 

Factor (CMF)

Lower Volume Optimal Conditions 33.8 Proven 0.70

Higher Volume Optimal Conditions 270.1 Proven 0.70

Lower Volume Narrower Conditions 43.5 Proven 0.70

Higher Volume Narrower Conditions 428.4 Proven 0.70

Install Curve Warning Signs 
Federal Highway Administration | Office of Safety 

134

Install Retroreflective Strips on Sign Posts 

The use of retroreflective strips on sign posts may be beneficial when there 

is a need to draw additional attention to the signs, especially at night. 

Reflective strips may be added to Stop signs, curve or intersection warning 

signs, regulatory or guidance signs, etc. 

Where to Use: The MUTCD provides the following guidance for the use of 

reflective strips on sign posts: “the material must be at least 2 inches wide 

and must be placed the full length of the post from the sign to within 2 feet 

above the horizontal surface into which the sign is fixed. In addition, the 

color of the material must match the background color of the sign except 

that the color of the strip for Yield and Do Not Enter signs must be red.”

Top Recommended Resource:

1. FHWA, “Intersection Safety Implementation Plan Workshop,” presentation, July 2009. Available at: http://

safety.fhwa.dot.gov/intersection/resources/ex_wksp_pres0109/.

Safety Treatment

Initial 

Implementation 

Cost

NCHRP 500 

Performance 

Rating

Install Retroreflective Strips on Sign Posts $0 to $5,000 Tried

Install Retroreflective Strips on Sign Posts 
Manual for Selecting Safety Improvements on High Risk Rural Roads

 135

Double Use of Advanced Warning Signs for Curves or Intersections 

Doubling the use of either Intersection Ahead 

warning signs or Curve Ahead warning signs (on 

the left and right) is recommended for locations 

where the crash rate has not been reduced after 

installation of a single advanced warning sign.

Where to Use: This treatment may be used at 

locations where crashes indicate that motorists 

do not heed existing advanced warning signs and 

additional conspicuity is needed.

Top Recommended Resource:

1. FHWA, Low Cost Treatments for Horizontal Curve Safety, December 2006. Available at: 

http://safety.fhwa.dot.gov/roadway_dept/horicurves/fhwasa07002/.

Safety Treatment

Initial 

Implementation 

Cost

NCHRP 500 

Performance 

Rating

Double Use of Advanced Warning Signs for Curves or 

Intersections $0 to $5,000 Tried

Double Use of Advanced Warning Signs for Curves or Intersections 
Federal Highway Administration | Office of Safety 

136

Provide Upcoming Road Names on Advanced Warning Signs 

At locations where Intersection Ahead warning signs are used, it is 

recommended that street name signs be placed underneath each intersection 

warning sign. These street name plaques provide the driver with additional 

information about the street the motorist is approaching so he or she can make 

an early decision regarding potential turning movements.

Where to Use: This treatment may be used at locations where crashes could 

potentially be reduced by providing advanced turn information.

Safety Treatment

Initial 

Implementation 

Cost

NCHRP 500 

Performance 

Rating

Crash 

Modification 

Factor (CMF)

Provide Upcoming Road Names on Advanced Warning 

Signs $0 to $5,000 Tried 0.90–0.99

Provide Upcoming Road Names on Advanced Warning Signs 
Manual for Selecting Safety Improvements on High Risk Rural Roads

 137

Install Advanced Intersection Warning Signs 

Advanced intersection warning signs can help alert drivers 

to the upcoming presence of an intersection. Signs can be 

placed with sufficient distance prior to the intersection to 

allow drivers to perceive and react and can be installed on 

both sides of the roadway to solicit greater awareness.

Where to Use: Advanced intersection warning signs 

are to be applied predominantly on single through lane, 

high-crash, stop-controlled State intersections in both 

rural and urban areas. They may also be applied on dual 

through lane, high-crash, stop-controlled intersections 

with lower traffic volumes (less than about 25,000 average 

annual daily traffic (AADT)) where the use of J-treatments 

are not appropriate and the frequency of acceptable gaps 

for entering traffic is such that long waiting and higher 

risk taking are not present at the intersection.

Top Recommended Resource:

1. FHWA, Stop-Controlled Intersection Safety: Through Route Activated Warning Systems, February 2011. 

Available at: http://safety.fhwa.dot.gov/intersection/resources/fhwasa11015/traws.pdf.

Safety Treatment

Initial 

Implementation 

Cost

NCHRP 500 

Performance 

Rating

Install Advanced Intersection Warning Signs $0 to $5,000 Tried

Install Advanced Intersection Warning Signs 
Federal Highway Administration | Office of Safety 

138

Upgrade to Larger Stop Signs 

A high number of crashes relate to the driver’s 

inability or failure to see the Stop sign at 

stop-controlled intersections. To improve 

recognition of the signs, larger Stop signs can 

be installed. Sizes can range from 30 inches, to 

36 inches, to 48 inches and larger, if needed.

Where to Use: While roadway classification 

and speed can help determine proper Stop sign 

size, larger sizes may be used when crash types 

indicate that Stop sign visibility may be an issue.

Top Recommended Resource:

1. FHWA, Stop Sign-Controlled Intersections: Enhanced Signs and Markings—A Winston-Salem Success Story, 

November 2009. Available at: http://safety.fhwa.dot.gov/intersection/resources/casestudies/fhwasa09010/.

Safety Treatment

Initial 

Implementation 

Cost

NCHRP 500 

Performance 

Rating

Upgrade to Larger Stop Signs $0 to $5,000 Proven

Upgrade to Larger Stop Signs 
Manual for Selecting Safety Improvements on High Risk Rural Roads

 139

Double Use of Stop Signs 

Two Stop signs (mounted left and right) can be used to 

call greater attention to the need for motorists to stop 

at an intersection. The first Stop sign is installed at the 

traditional right side location; a second is recommended 

in the median (if available) of the approach. To 

accommodate this left-mounted Stop sign, a small 

mountable curb is suggested. This curb and associated 

pavement markings provide the motorist with additional 

information that he or she is entering an intersection. 

Where to Use: This treatment may be used at locations where crashes indicate that motorists do not obey existing 

Stop signs and additional intersection conspicuity is needed.

Top Recommended Resources:

1. FHWA, Intersection Safety: A Manual for Local Rural Road Owners, January 2011. Available at: 

http://safety.fhwa.dot.gov/local_rural/training/fhwasa1108/fhwasa1108.pdf.

2. FHWA, Stop Sign-Controlled Intersections: Enhanced Signs and Markings—A Winston-Salem Success Story, 

November 2009. Available at: http://safety.fhwa.dot.gov/intersection/resources/casestudies/fhwasa09010/.

Safety Treatment

Initial 

Implementation 

Cost

NCHRP 500 

Performance 

Rating

Double Use of Stop Signs $0 to $5,000 Tried

Double Use of Stop Signs 
Federal Highway Administration | Office of Safety 

140

Use of Supplemental Warning Signs 

When specialized conditions exist, supplemental warning signs may be used to notify 

road users of the possibility that slower and more susceptible road users may be ahead. 

Examples include Share The Road, Trail Crossing, and Equestrian Crossing signs. 

Where to Use: These signs may be used whenever road users need to be notified that 

slower traffic crosses the roadway or exists on or very near the roadway.

Safety Treatment

Initial 

Implementation 

Cost

NCHRP 500 

Performance 

Rating

Use of Supplemental Warning Signs $0 to $5,000 Tried

Use of Supplemental Warning Signs 
Manual for Selecting Safety Improvements on High Risk Rural Roads

 141

Install Chevron Signs

Chevron signs (or curve delineation signs) 

indicate to drivers the alignment of the 

roadway when they are within the actual 

horizontal alignment of a curve. The signs 

show the shape and degree of curvature 

and guide drivers through the entire curve 

or turn.

Where to Use: Chevrons should be 

installed at any curve or turn with a history 

of roadway departure crashes and curves 

or turns with similar geometry or traffic 

volume that have yet to experience crashes. 

According to the 2009 MUTCD, alignment 

delineation (or a one direction large arrow) 

is required on curves or turns where the advisory speed is 15 mph less than the posted speed limit. They can be 

installed at locations where no chevrons currently exist or to supplement those that are already in place.

Top Recommended Resource:

1. FHWA, Roadway Departure Safety: A Manual for Local Rural Road Owners, January 2011. Available at: 

http://safety.fhwa.dot.gov/local_rural/training/fhwasa1109/fhwasa1109.pdf.

Install Chevron Signs 

- Initial Investment: $7,200

- Cost of Maintenance: $3,600

- Frequency of Maintenance: 5 years

Benefit-Cost 

Ratio

NCHRP 500 

Performance 

Rating

Crash 

Modification 

Factor (CMF)

Lower Volume Optimal Conditions 10.6 Proven 0.75

Higher Volume Optimal Conditions 84.7 Proven 0.75

Lower Volume Narrower Conditions 13.0 Proven 0.75

Higher Volume Narrower Conditions 127.7 Proven 0.75

Install Chevron Signs
Federal Highway Administration | Office of Safety 

142

4.9. Vertical Curves

Safety improvement treatments on vertical curves range from low-cost improvements (such as signing) to 

high-cost improvements (such as modifying road geometry). This section covers safety improvement treatments 

that can be applied at vertical curve locations. Some treatments in this section also appear in the sections on 

intersection improvements, signing, and roadside safety. 1 2

38 As discussed in Section 1.2, a BCR is only shown where data were available to calculate the ratio. Where data were unavailable, the BCR has been left blank.

39 As stated in NCHRP Series 500 Reports (http://safety.transportation.org/guides.aspx). Proven: The safety effect for other similar applications has shown a proven benefit. 

Tried: The treatment has indications that it can be expected to reduce crashes, but has some conflicting reports as to its associated safety effects or has been deployed and 

observed to be effective. Experimental: New treatments that still need to be tested and for which the safety effect is unknown. Unknown: Not enough is known about an 

associated safety performance.

Safet

y Treatment

For more information, 

visit page

C

ost

Frequency of 

Maintenance (years)

Safet

y

Benefit

Benefit-Cost

Ratio 38

Initial 

Implementation

Ongoing 

Maintenance

NCHRP 500 

Performance Rating

Crash Modification Factor 

(CMF)

Lower Volume*, 

Optimal Conditions***

Higher Volume**, 

Optimal Conditions***

Lower Volume*, 

Narrower Conditions****

Higher Volume**, 

Narrower Conditions****

Install Advanced Intersection Warning Signs 143 $ P

Install Dynamic Advanced Intersection Warning System 144 $$ P 0.10-0.76

Modify Horizontal/Vertical Geometry 145 $$$$$ P

Relocate Driveways, Entrances, and Intersections 146 $$$$$

T

Cost:$ = $0 to $5,000$$ = $5,001 to $20,000$$$ = $20,001 to $50,000$$$$ = $50,001 to $100,000$$$$$ = $100,001 and up

NCHRP 500 Performance Rating39

P – ProvenT – TriedE – ExperimentalU – Unknown

*Lower Volume ≤1000 vpd**Higher Volume = Between 1,001 and 8000 vpd***Optimal Conditions = 12-foot lanes, 6-foot paved shoulders****Narrower Conditions = 10-foot lanes and no shoulders

Vertical Curves
Manual for Selecting Safety Improvements on High Risk Rural Roads

 143

Install Advanced Intersection Warning Signs 

Advanced intersection warning signs can help alert drivers 

to the presence of an intersection ahead. Signs can be placed 

with sufficient distance prior to the intersection to allow 

drivers to perceive and react and can be installed on both 

sides of the roadway to solicit greater awareness. Advanced 

intersection signing can be used to improve notice of upcoming 

intersections where vertical curves impede visibility to the 

intersection.

Where to Use: Advanced intersection warning signs are to 

be applied predominantly on single through lane, high-crash, 

stop-controlled State intersections in both rural and urban 

areas. They may also be applied on dual through lane, high-crash, 

stop-controlled intersections with lower traffic volumes (less 

than about 25,000 average annual daily traffic (AADT)) where 

the use of J-treatments are not appropriate and the frequency of 

acceptable gaps for entering traffic is such that long waiting and 

higher risk taking are present at the intersection.

Top Recommended Resource:

1. FHWA, Stop-Controlled Intersection Safety: Through Route Activated Warning Systems, February 2011. 

Available at: http://safety.fhwa.dot.gov/intersection/resources/fhwasa11015/traws.pdf.

Safety Treatment

Initial 

Implementation 

Cost

NCHRP 500 

Performance 

Rating

Install Advanced Intersection Warning Signs $0 to $5,000 Proven

Install Advanced Intersection Warning Signs 
Federal Highway Administration | Office of Safety 

144

Install Dynamic Advanced Intersection Warning System 

Infrastructure-based Intelligent Transportation System (ITS) 

technologies can be used to significantly improve the safety at 

stop-controlled intersections with visibility limited by vertical 

curves. These systems provide enhanced safety warning 

information for approaching drivers compared to passive 

warning systems. A dynamic advanced intersection warning 

system can provide:

•	 Enhanced warning to the through driver that there is a 

vehicle on a cross road stop approach that may enter the 

intersection.

•	 Enhanced warning to drivers on a stop approach that their 

trajectory speed is high and that they may run the Stop 

sign.

•	 Enhanced warning to through drivers that they are 

traveling at too high an intersection entry speed and 

advising them to slow down.

•	 Enhanced warning to drivers on the stop approach of 

entering vehicles on the through approach, inferring 

potential unsafe gaps.

Where to Use: This treatment may be provided at intersections that experience severe intersection-related crashes 

due to speed, low visibility, or insufficient gaps.

Safety Treatment

Initial 

Implementation 

Cost

NCHRP 500 

Performance 

Rating

Crash 

Modification 

Factor (CMF)

Install Dynamic Advanced Intersection Warning System $5,001 to $20,000 Proven 0.10–0.76

Top Recommended Resource:

1. FHWA, Stop-Controlled Intersection Safety: Through Route Activated Warning Systems, February 2011. 

Available at: http://safety.fhwa.dot.gov/intersection/resources/fhwasa11015/traws.pdf.

Install Dynamic Advanced Intersection Warning System
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Modify Horizontal/Vertical Geometry

Horizontal and vertical geometry may be reconstructed in a variety of ways. For example, horizontal and vertical 

curves may benefit from increased radii, thereby increasing sight distance. Modifying road geometry may also 

include eliminating horizontal or vertical curves and providing a more direct alignment. 

Where to Use: This treatment may be used at locations where improved sight distance is needed and at locations 

that experience head-on and run-off-road crashes. This treatment can also be used at unsignalized intersections 

with restricted sight distance due to horizontal or vertical geometry and those with patterns of crashes related to 

that lack of sight distance that cannot be ameliorated by less expensive methods.

Safety Treatment

Initial 

Implementation 

Cost

NCHRP 500 

Performance 

Rating

Modify Horizontal/Vertical Geometry $100,001 and up Proven

Modify Horizontal/Vertical Geometry
Federal Highway Administration | Office of Safety 

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Relocate Driveways, Entrances, and Intersections

Relocating or removing private and public driveways, commercial 

entrances, and road or street intersections just beyond the crest of 

vertical curves in the direction of travel isn’t always feasible but does 

ensure that conflicts at locations with limited sight distances are 

removed or remediated.

Where to use: This treatment may be used near vertical curve crests 

where sight distance to driveways, entrances, or intersections is 

limited or obstructed.

Safety Treatment

Initial 

Implementation 

Cost

NCHRP 500 

Performance 

Rating

Relocate Driveways, Entrances, and Intersections $100,001 and up Tried

Relocate Driveways, Entrances, and Intersections
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 147

4.10. Other Treatments

Treatments in this section may be applied at specific locations to improvement safety and do not fit into any of the 

previous categories. 1 2

40 As discussed in Section 1.2, a BCR is only shown where data were available to calculate the ratio. Where data were unavailable, the BCR has been left blank.

41 As stated in NCHRP Series 500 Reports (http://safety.transportation.org/guides.aspx). Proven: The safety effect for other similar applications has shown a proven benefit. 

Tried: The treatment has indications that it can be expected to reduce crashes, but has some conflicting reports as to its associated safety effects or has been deployed and 

observed to be effective. Experimental: New treatments that still need to be tested and for which the safety effect is unknown. Unknown: Not enough is known about an 

associated safety performance.

Safet

y Treatment

For more information, 

visit page

C

ost

Frequency of 

Maintenance (years)

Safet

y

Benefit

Benefit-Cost

Ratio 40

Initial 

Implementation

Ongoing 

Maintenance

NCHRP 500 

Performance Rating

Crash Modification 

Factor (CMF)

Lower Volume*, 

Optimal Condition***

Higher Volume**, 

Optimal Condition***

Lower Volume*, 

Narrower Condition****

Higher Volume**, 

Narrower Condition****

Mitigate Ground Water to Prevent Ponding and/or Icing 148 $$$-$$$$

E

Widen Functionally Obsolete Bridges 149 $$$$$

Cost:$ = $0 to $5,000$$ = $5,001 to $20,000$$$ = $20,001 to $50,000$$$$ = $50,001 to $100,000$$$$$ = $100,001 and up

NCHRP 500 Performance Rating41 

P – ProvenT – TriedE – ExperimentalU – Unknown

*Lower Volume ≤1000 vpd**Higher Volume = Between 1,001 and 8000 vpd***Optimal Condition = 12-foot lanes, 6-foot paved shoulders****Narrower Condition = 10-foot lanes and no shoulders

Other Treatments
Federal Highway Administration | Office of Safety 

148

Mitigate Ground Water to Prevent Ponding and/or Icing 

Good site drainage is needed to keep ponding and icing from 

occurring. This can be accomplished through a change in runoff 

conditions, whether by increasing the storm drainage capacity, 

re-grading ditches for better flow, or making changes to the 

roadway superelevation.

Where to Use: This treatment is applicable at locations where 

roadway ponding occurs.

Safety Treatment

Initial 

Implementation 

Cost

NCHRP 500 

Performance 

Rating

Mitigate Ground Water to Prevent Ponding and/or Icing $20,001 to 

$100,000 Experimental

Mitigate Ground Water to Prevent Ponding and/or Icing 
Manual for Selecting Safety Improvements on High Risk Rural Roads

 149

Widen Functionally Obsolete Bridges 

Widening narrow bridges on HRRR that are unable to accommodate traffic, either as a one-lane two-way 

operation or lanes too narrow to accommodate two-way traffic, may help to prevent head-on and sideswipe 

collisions.

Where to Use: This treatment can be used at locations that experience a high frequency of head-on or sideswipe 

collisions due to narrow lane width or one-lane two-way operations.

Safety Treatment

Initial 

Implementation 

Cost

Widen Functionally Obsolete Bridges $100,001 and up

Widen Functionally Obsolete Bridges 
Federal Highway Administration | Office of Safety 

150

5. Safety Management, the Funding Process, and 

Funding Sources

Safety Management includes overall program direction and project prioritization, funding identification, project 

development, project implementation, and evaluation.

5.1. Safety Management

5.1.1. Safety Project Prioritization and Development 

To prioritize and identify projects for funding, safety professionals must determine comparison criteria for this 

purpose. In many cases an economic appraisal is used to provide a fair comparison among projects competing for 

safety funds. In a basic economic appraisal, an analyst will calculate the monetary cost of the treatment and the 

estimated monetary value of the benefits, such as reduced number and severity of crashes. The analyst can then 

calculate a benefit-to-cost ratio for each potential project to compare their relative effectiveness.421

In addition to the calculated value, other prioritization criteria may include:

•	 Connecting the treatment to State Strategic Highway Safety Plan strategies;

•	 Leveraged funding through cost sharing with other agencies (or other similar methods that decrease 

treatment cost);

•	 Local needs of MPOs, RPCs, or local roadway agencies;

•	 Benefits of combining safety and non-safety funding sources (e.g., adding rumble strips to an already-funded, 

non-safety project); and

•	 Public perception of safety treatments.

5.1.2. Initial and Ongoing Treatment Costs

When selecting safety improvements to deploy, practitioners should weigh the treatments among several criteria: 

estimated safety benefit, feasibility or applicability of installing the treatment at a specific site or sites, how to fund 

the initial installation and ongoing maintenance costs while considering the ranges of those costs, and how often 

the treatment will need routine maintenance in order to maintain the safety benefits associated with deployment.

Typically, the initial installation of safety treatments can be financed through dedicated safety funds in additional 

to other funding sources used for highway construction and reconstruction. However, ongoing maintenance costs 

associated with the initial installation become the responsibility of the agency and are typically funded through 

internal operations and maintenance budgets. 

Recurring maintenance costs should be considered and weighed as practitioners decide among potential 

treatments to deploy on HRRR. The HRRR Treatment Matrix located in this manual presents the initial 

deployment cost and recurring maintenance costs associated with safety treatments presented in Chapter 4 to aid 

in the decision-making process.

42 AASHTO, Highway Safety Manual, First Edition, 2010.
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5.2. The Funding Process

State DOTs typically program safety (and other transportation) projects through their multi-year Statewide 

Transportation Improvement Program (STIP). A State’s Planning Division is often the leader of this process, so 

safety-focused staff must provide project recommendations for potential funding. Specific policies, procedures, 

and practices vary widely by State. 

Non-State agencies, such as counties, municipalities, and Tribal entities, work through regional planning 

commissions (RPCs), regional planning organizations (RPO), councils of government (COGs), or metropolitan 

planning organizations (MPOs) to identify, plan, and program transportation safety projects. Each RPC, RPO, 

COG, and MPO develops a Transportation Improvement Program (TIP) in conjunction with the State DOT that 

cites the region or area’s top transportation priorities for new projects. Transportation safety projects are typically 

a portion of the TIP.

5.3. Legislation and Funding Sources

A number of sources for funding are available at the Federal, State, and local levels. Processes vary widely from 

State-to-State and year-to-year based on the current level of funding and legislation, so the best sources of 

information in an individual State is the State DOT Safety Engineer, State DOT Local Programs Office, FHWA 

Division Office, and LTAP Center.

The following sections provide background information regarding current legislation and funding sources at the 

time of this writing. All are subject to change.

5.3.1. Legislation and Federal Funding Sources

In 2005, the Safe, Accountable, Flexible, Efficient Transportation Equity Act: A Legacy for Users (SAFETEA-LU) 

established the HSIP as a core Federal-aid funding program. As part of the HSIP, SAFETEA-LU introduced a setaside provision, the High Risk Rural Roads Program (HRRRP). The HRRRP provided $90 million as an annual 

set-aside from a State’s HSIP apportionment and was developed to help States implement solutions on the lower 

functional classes of rural roadways, a segment of the system often overlooked.432

On July 6, 2012, President Barak Obama signed into law P.L. 112-141, the Moving Ahead for Progress in the 21st 

Century Act (MAP-21). MAP-21 continues the Highway Safety Improvement Program with nearly double the 

funding from SAFETEA-LU. MAP-21 removes the HRRRP set-aside provision and also revises the definition of 

“High Risk Rural Road,” but continues the inclusion of construction and operational improvements on HRRR as 

eligible HSIP projects.443

 While the $90 million set-aside for HRRR was not continued, MAP-21 contains a special 

rule454 requiring obligation of funds for HRRR projects if the fatality rate on rural roads in a State is increasing. If 

the special rule applies to a State for a fiscal year, it must obligate projects on HRRR of an amount equal to at least 

200 percent of the amount of funds the State received for FY 2009 for the HRRRP.465

 

43 23 U.S.C. §148(a)(1) defines a “high risk rural road” as: “...any roadway functionally classified as a rural major or minor collector or a rural local road (a) on which the 

accident rate for fatalities and incapacitating injuries exceeds the statewide average for those functional classes of roadway; or (b) that will likely have increases in traffic volume 

that are likely to create an accident rate for fatalities and incapacitating injuries that exceeds the statewide average for those functional classes of roadway.”

44 Section 1112 of MAP-21 changed the definition of a “high risk rural road” in 23 USC 148(a)(1) to: “any roadway functionally classified as a rural major or minor collector or a 

rural local road with significant safety risks, as defined by a State in accordance with an updated State strategic highway safety plan.”

45 23 U.S.C. 148(g)(1)

46 FHWA, “Highway Safety Improvement Program, MAP-21 High Risk Rural Roads Guidance.”
Federal Highway Administration | Office of Safety 

152

There are multiple funding resources that can be used to fund recommendations for HRRR projects, depending 

on the nature of the suggestion. Funding for safety projects may come from a variety of Federal, State, and local 

sources. Some of the programs include:476

•	 Highway Safety Improvement Program (HSIP) – The HSIP emphasizes a data-driven, strategic approach to 

improving highway safety on all public roads and focuses on performance. The foundation for this approach 

is a safety data system, which each State is required to have to identify key safety problems, establish their 

relative severity, and then adopt strategic and performance-based goals to maximize safety. Every State is 

required to develop a Strategic Highway Safety Plan (SHSP) that lays out strategies to address these key safety 

problems. The HSIP has average annual funding of $2.4 billion, including $220 million per year for the 

Railway-Highway Crossing Program. 

For more information, refer to the HSIP Fact Sheet: http://www.fhwa.dot.gov/map21/hsip.cfm

•	 23 U.S.C. 130: Railway-Highway Crossing Program (Section 130) – The program funds safety 

improvements to eliminate hazards at public railway-highway grade crossings. This includes projects on 

HRRR and could be a potential funding source. This program is funded with a $220 million set-aside of the 

Highway Safety Improvement Program (HSIP). 

•	 Surface Transportation Program (STP) – The STP provides an annual average of $10 billion in flexible 

funding that may be used by States and localities for projects to preserve or improve conditions and 

performance on any Federal-aid highway, bridge projects on any public road, facilities for non-motorized 

transportation, transit capital projects and public bus terminals, and facilities. 

For more information, refer to the STP Fact Sheet: http://www.fhwa.dot.gov/map21/stp.cfm

•	 Transportation Alternatives Program (TAP) – MAP-21 established a new program to provide for a 

variety of alternative transportation projects that were previously eligible activities under separately funded 

programs. This program is funded at a level equal to two percent of the total of all MAP-21 authorized 

Federal-aid highway and highway research funds, with the amount for each State set aside from the State’s 

formula apportionments. For HRRR, this funding may be utilized for the Safe Routes to School Program.

For more information, refer to the TAP Fact Sheet: http://www.fhwa.dot.gov/map21/tap.cfm 

•	 Federal Lands and Tribal Transportation Programs – MAP-21 continues to acknowledge the importance 

of access to Federal and Tribal lands. Recognizing the need for all public Federal and Tribal transportation 

facilities to be treated under uniform policies similar to the policies that apply to Federal-aid highways and 

other public transportation facilities, MAP-21 creates a unified program for Federal lands transportation 

facilities, Federal lands access transportation facilities, and Tribal transportation facilities. 

For more information, refer to the Tribal Transportation Program (TTP) Fact Sheet: http://www.fhwa.dot.

gov/map21/ttp.cfm

•	 Federal Lands Transportation Program – The program provides $300 million annually for projects 

that improve access within the Federal estate, such as national forests and national recreation areas, on 

infrastructure owned by the Federal government. This program combines the former Park Roads and Refuge 

Roads programs, and adds three new Federal Land Management Agency (FLMA) partners. A portion of the 

funds will support traditional partner agencies at current funding levels, with new partners competing for a 

modest portion. 

For more information, refer to the Federal Lands Transportation Program (FLTP) Fact Sheet: 

http://www.fhwa.dot.gov/map21/fltp.cfm. 

47 FHWA, Moving Ahead for Progress in the 21st Century Act (MAP-21), A Summary of Highway Provisions. Available at: http://www.fhwa.dot.gov/map21/summaryinfo.cfm.
Manual for Selecting Safety Improvements on High Risk Rural Roads

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•	 Federal Lands Access Program – The program provides $250 million annually for projects that improve 

access to the Federal estate on infrastructure owned by States and local governments. Replacing and 

expanding the Forest Highways program, projects providing access to any Federal lands are eligible for this 

new comprehensive program. Funds are distributed by formula based on recreational visitation, Federal land 

area, Federal public road mileage, and the number of Federal public bridges. 

•	 Tribal Transportation Program – This program provides $450 million annually for projects that improve 

access to and within Tribal lands. This program generally continues the existing Indian Reservation Roads 

program, while adding new set-asides for Tribal bridge projects (in lieu of the existing Indian Reservation 

Road Bridge program) and Tribal safety projects. It continues to provide set-asides for program management 

and oversight and Tribal transportation planning.

•	 Tribal High Priority Projects Program – This program is a discretionary program modeled on an earlier 

program that was funded by set-asides from the Indian Reservation Roads Program. MAP-21 provides $30 

million per year from the General fund (subject to appropriation) for this new program. 

For more information, refer to the Tribal High Priority Projects Program Fact Sheet: 

http://www.fhwa.dot.gov/map21/thpp.cfm

•	 Appalachian Development Highway System (ADHS) – The ADHS program is continued, but without 

separate funding. Portions that are on the NHS are eligible for National Highway Performance Program 

(NHPP) funding, and ADHS routes, including local access roads, are eligible for STP funding. To encourage 

the completion of the ADHS, States are required to submit plans for completion of the system and an 

increased Federal share is provided. 

For more information, refer to the ADHS Fact Sheet: http://www.fhwa.dot.gov/map21/adhs.cfm 

•	 Bridge and Tunnel Inspection – The program provides for continued improvement to bridge and tunnel 

conditions essential to protect the safety of the traveling public and allow for the efficient movement of people 

and goods on which the U.S. economy relies. MAP-21 requires inspection and inventory of highway bridges 

and tunnels on public roads. No dedicated funds are provided for inspections, but it is an eligible use of 

NHPP, STP, HSIP, FHWA administrative, Tribal Transportation, and Research funds. MAP-21 authorizes 

$400 million per year for the following six programs: Highway Research and Development, Technology 

and Innovation Deployment, Training and Education, Intelligent Transportation Systems, University 

Transportation Research, and the Bureau of Transportation Statistics. 

For more information, refer to the Bridge and Tunnel Inspection Fact Sheet: http://www.fhwa.dot.gov/map21/bti.cfm

•	 Research and Technology Development and Deployment – MAP-21 provides $115 million per year for 

the Highway Research and Development program. Research areas include highway safety, infrastructure 

integrity, planning and environment, highway operations, exploratory advanced research, and the TurnerFairbank Highway Research Center.

•	 Technology Innovation and Deployment Program – The program provides $62.5 million per year to 

accelerate implementation and delivery of new innovations and technologies that result from highway 

research and development to benefit all aspects of highway transportation. At least $12 million per year of 

these funds must be used to accelerate the deployment and implementation of pavement technology.

•	 Training and Education – MAP-21 authorizes $24 million per year for continuation of training and 

education programs, including the National Highway Institute, the Local Technical Assistance Program 

(LTAP), the Tribal Technical Assistance Program (TTAP), the Dwight D. Eisenhower Transportation 

Fellowships, the Garrett A. Morgan Technology and Transportation Education Program, the Transportation 

Education Development Program, and the Freight Capacity Building Program. Also funded from the 

Training and Education funds are the competitively selected centers for transportation excellence in the areas 

of the environment, surface transportation safety, rural safety, and project finance. The Federal share for 

LTAP and TTAP centers remains at 50 percent and 100 percent respectively.
Federal Highway Administration | Office of Safety 

154

•	 State Planning and Research (SP&R) – MAP-21 continues the SP&R, as a two percent takedown of four core 

programs: National Highway Performance Program, Surface Transportation Program, Congestion Mitigation 

Air Quality program, and Highway Safety Improvement Program. At least 25 percent of these funds have to 

be used for research purposes. 

For more information, refer to the State Planning and Research (SP&R) Fact Sheet: 

http://www.fhwa.dot.gov.map21/spr.cfm 

In addition to the major highway program funding sources, other Federal safety resources may assist with HSIP 

implementation. These grant programs are administered by NHTSA and FMCSA and can be used to assist with 

law enforcement efforts and improve traffic record data collection, data systems, and hazard elimination. The 

funding includes:48,49 78

•	 23 U.S.C. 154 and 164 Transfer Funds – States in which Federal-aid highway funds are transferred based 

on noncompliance with 23 U.S.C. 154 Open Container Requirements or 23 U.S.C. 164 Minimum Penalties 

for Repeat Offenders for Driving While Intoxicated or Under the Influence can use the transfer funds on 

approved projects for alcohol-impaired driving countermeasures or direct the funds to State/local law 

enforcement to increase impaired driving enforcement. States also may elect to use the funds for hazard 

elimination activities eligible under 23 U.S.C. 152.

•	 23 U.S.C. 402: State and Community Highway Safety Grants – Supports a full range of highway safety 

behavioral programs, including alcohol countermeasures, occupant protection, police traffic services 

(e.g., enforcement), emergency medical services, traffic records, motorcycle safety pedestrian and bicycle 

safety, non-construction aspects of road safety, and speed enforcement and management programs. A 

minimum of 40 percent of a State’s Section 402 funds must be expended by local governments, or be used for 

the benefit of local governments. To receive Federal highway safety grant funds, State Highway Safety Offices 

must submit an annual Highway Safety Plan (HSP) to the NHTSA.

5.3.2. Other Funding Sources

In some States the DOT sets aside a certain amount of safety funding for State and local rural road projects. 

Funding sources and amounts vary from State to State, so the best resources for finding out more in a particular 

State are the State DOT Safety Engineer, FHWA Division Office, and LTAP Center. For example, safety efforts in 

Iowa on State and local roads are funded with a combination of Federal and State funds. A portion of their Road 

Use Tax Fund (0.5% as of 2005) has been set aside for safety projects. This gives Iowa about $7 million of State 

funds per year—on top of their Federal safety funding—to address the State’s most pressing safety needs. Previous 

projects have included experimental pavement marking, data software development, the small town signing 

program, and research projects at local universities.509

 

5.4. Evaluation

Evaluation of safety treatments is a necessary step in the safety management process. Calculating effectiveness 

provides safety officials with the information needed to determine if the treatment(s) should be used in similar 

situations in the future.

48 FHWA, Highway Safety Improvement Program Manual. Available at: http://safety.fhwa.dot.gov/hsip/resources/fhwasa09029/sec5.cfm

49 Iowa Department of Transportation, “National Priority Safety Programs Under MAP-21, Section 405.” Available at: http://www.iowadot.gov/pol_leg_services/federalregisternotices/NHTSA%20Sec.%20405%20regulatory%20analysis.pdf

50 Chandler, B., Midwest Safety Scanning Tour, Missouri Department of Transportation, 2005. Available at: http://www.modot.org/safety/Safety_Engineering/documents/2005SafetyScanningTour.pdf
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Pre- and post-installation crash history and a record of treatment installations support performance assessment 

of each safety treatment. It is important to keep a current list of installed treatments with associated details to 

support these analyses. Periodic assessments will help drive decisions about whether each treatment contributed 

to safety improvements and why they were successful. 

Required information may include crash history data (with associated details related to the treatment—crash type, 

frequency, severity); public input and complaints; and observations from maintenance crews or law enforcement.

Once calculated, the quantified benefits of certain treatments can be used to develop crash modification factors 

(CMF) to improve the analysis during project prioritization and selection.5110 

6. Navigating the Safety Treatments

The HRRR safety treatments summarized in this manual can be systematically considered; however, only a 

subset of the large number of candidate treatments can potentially help to reduce crashes for a given location. 

One approach for selecting safety enhancements is to identify study sites, perform a descriptive statistical 

safety diagnosis, execute a treatment analysis, evaluate economic feasibility, and prioritize and select promising 

improvements suitable for consideration. The contents of this manual can be used to perform this type of 

assessment. The following sections briefly review each of these key steps that will enable the selection of potential 

safety enhancements for a study location.

6.1. Identify Study Sites

The safety treatments summarized in this manual are specifically targeted for HRRR locations and assumed to 

apply to two-lane highways with varying traffic volume and road characteristics. Prior to initiating the safety 

assessment, practitioners should identify the specific sites or site types for which the analysis will be applied. In 

many cases, the study may focus only on an intersection while in other cases the analysis could be targeted to a 

corridor or a systemic modification. Consequently, it is important in this first step to clearly identify where the 

analysis will apply and why this location has been selected for consideration. Figure 1 (Flowchart A) introduces an 

overall approach to this safety enhancement analysis. Once the study location and focus has been established, the 

next step is to perform a preliminary safety diagnosis.

For discussion related to spot versus systemic treatment application, see Chapter 3.2.

6.2. Perform Safety Diagnosis

The steps for the initial safety diagnosis are depicted in Figure 2 (Flowchart B). The user should develop a series 

of descriptive statistics regarding safety at the study location(s). In an effort to provide a statistically robust 

evaluation, crash data that extends across a period of 3-5 years should be used for these summaries. Crash data 

should be compiled so that a summary of crash frequencies per year for total crashes as well as fatal and injury 

only crashes can be used in subsequent analysis. In addition, crash information should be summarized by crash 

types. This crash type information will be used as a key diagnostic input in subsequent tasks.

51 FHWA, Road Safety Information Analysis: A Manual for Local Rural Road Owners, FHWA-SA-11-10 (Washington, DC, 2011).
Federal Highway Administration | Office of Safety 

156

Figure 1. Flowchart A – HRRR Safety Enhancement Analysis

YES

Identify Characteristics

for Candidate Two-Lane

High Risk Rural Road

Perform

Safety

Diagnosis [See 

Flowchart B]

Initiate the Low Volume

(<1000 vpd)

HRRR Evaluation

Is the

Facility Low

Volume

(<1000 vpd)?

Initiate the Standard

(1000<AADT<8000 vpd)

HRRR Evaluation

NO

Assemble Findings

and Compile

Recommendations

Perform

Treatment

Analysis [See

Flowchart C]
Manual for Selecting Safety Improvements on High Risk Rural Roads

157

The crash types should be divided into the following general categories and proportional values should be assigned 

based on total crashes or fatal plus injury crashes (depending on the objective of the safety enhancement effort):

•	 Rear-end	 	 	 	 	 • Sideswipe

•	 Angle	 	 	 	 	 • Turning

•	 Head-on	 	 	 	 	 • Run-off-road

•	 Fixed object	 	 	 	 	 • Animal

•	 Out-of-control	 	 	 	 • Work zone

•	 Other 

Following the development of the crash type summary for the study site, the user should identify the two or more 

most common crash types that occurred for the severity type targeted for reduction. If the intent is to reduce the 

number of fatal plus serious injury crashes, then the two or more crash types most often involved in that subset 

of crashes should be identified. If, on the other hand, the intent is to reduce total crashes or crashes of a specific 

nature, then the two most significant crash types for this group of crashes should be selected.

During the safety diagnosis step, the user should also compile information that may be contributing to the crash 

condition. This would include physical road features and traffic volume. In addition, unusual features identified 

by examining the crash history may be noted. These could include an unexpected number of crashes at dawn or 

dusk, inclement weather crashes, or similar.

Compile Crash Descriptive 

Statistics Frequency, 

Severity, Roadway & 

Environmental Conditions

Identify the Two Most

Frequent Crash Types

Summarize and Report

Diagnosis Statistics 

Perform

Safety

Diagnosis

FROM FLOW CHART A:

Figure 2. Flowchart B – Safety Diagnosis
Federal Highway Administration | Office of Safety 

158

6.3. Initiate Treatment Analysis

It may be likely that the preliminary improvement selection criteria are availability of funding, either for the initial 

installation or for ongoing maintenance. Additionally, the economic feasibility of a specific treatment is strongly 

influenced by traffic exposure at a location. Consequently, the treatments provided in this manual are further 

divided into lower volume (assumed to be represented by AADT=1000 vpd) and higher volume (assumed to 

be represented by AADT=8000 vpd) treatments. In general, the lower volume locations are also characterized 

by relaxed design standards such as narrower lanes and shoulders. As a result, prior to initiating the treatment 

analysis the user needs to clearly define which traffic volume threshold best applies to the study location. As 

shown in Figure 1 (Flowchart A), facilities with more than 1000 vpd are considered “Standard” or higher volume 

and evaluated separately from their lower volume counterparts. Figure 3 (Flowchart C) demonstrates the 

treatment analysis steps that can be applied to either traffic volume threshold.

Each facility should be divided into a category of intersection or segment. For locations that include entire corridors 

or systemic improvements, the characteristics of the prevailing targeted crash types will help determine the facility 

type of interest. This manual includes the following 10 general categories for the potential safety treatments:

•	 Horizontal curves	 	 	 	 	 • Signalized intersections

•	 Unsignalized intersections	 	 	 	 • Signing

•	 Pavement marking	 	 	 	 	 • Pavement and shoulder resurfacing and widening

•	 Roadside infrastructure	 	 	 	 • Non-motorized user

•	 Vertical curves	 	 	 	 	 • Others

Select the Type of Facility 

(Intersection versus Segment)

Perform 

Economic 

Analysis [See

Flowchart D]

Identify the Target Crash 

Severity Level to Reduce at 

This Site (Crash Type 

Identify in Safety Diagnosis)

Select Nature of

Proposed Improvement

(Systemic, Single Location)

Summarize Safety

Analysis Results

Perform 

Treatment 

Analysis

FROM FLOW CHART A:

Figure 3. Flowchart C – Treatment Analysis
Manual for Selecting Safety Improvements on High Risk Rural Roads

159

In many cases, an individual treatment can be included in more than one of these 10 categories. As an example, 

installing advanced intersection warning signs would be included in both the intersection category as well as 

the signing category. Within each category, the treatments tend to be further reduced into infrastructure-based 

treatments, traffic control treatments, and other enhancements.

Based on the two most significant crash types previously identified in the safety diagnosis, potential treatments can 

be identified; however, before the treatment analysis can be completed, the user should also consider the economic 

feasibility of a treatment for the specific study location. For example, one possible improvement that may be 

identified is widening a shoulder. If the study site already has a shoulder that is reasonably wide, this candidate 

treatment may not be practical if a different treatment can more substantially help to reduce crashes resulting in a 

more economically justified treatment selection. Therefore, the final step in the treatment analysis is to initiate the 

economic assessment for the subset of treatments identified.

6.4. Perform Economic Analysis

The benefit-cost ratio is one common method for evaluating the economic feasibility of a treatment. In addition, 

issues such as substantial initial investments, short life cycles, and extensive treatment maintenance must be 

considered to determine practical application of a treatment. The benefit-cost ratio is a numeric value that helps 

to capture these influences. A benefit-cost ratio value of 2.0, for example, suggests that there would be a $2 return 

for every $1 invested. For more information on how to calculate a benefit-cost ratio, see FHWA’s Benefit-Cost 

Analyses Guidance for TIGER Grant Applicants.52 11

In addition to the benefit-cost ratio are other potential economic metrics. Two of these candidate cost-effectiveness 

values in the user guide include the equivalent annual dollars spent for fatal plus injury crashes prevented and the net 

annual benefit. This manual includes these economic values for each of the candidate treatments.

Of course, many safety enhancement projects are constrained by targeted funds that must be used for specific 

purposes or that are systemic rather than site specific. Figure 4 (Flowchart D) summarizes the basic steps required 

to perform the economic analysis component of the treatment selection process. 

In many cases, a maximum initial investment can be a driving force in the selection of feasible treatments. 

The practitioner should first identify this maximum value and determine if there are any funding constraints 

associated with the available resources or candidate improvements. Once these economic analysis questions are 

answered, the practitioner can then evaluate the previously identified list of potential treatments and determine 

their associated economic assessment values. This information can then be used to develop a list of priorities. 

Many agencies will restrict the economic analysis priority selection to a specific economic metric, so the 

practitioner will need to identify if this constraint applies. As an example, some agencies solely use the 

benefit-cost ratio for final economic decisions.

52 FHWA’s Benefit-Cost Analyses Guidance for TIGER Grant Applicants. Available at: http://www.dot.gov/tiger/guidance.
Federal Highway Administration | Office of Safety 

160

Figure 4. Flowchart D – Economic Analysis

6.5. Summarize Recommendations

Following these safety enhancement analysis steps, the user should have a short, prioritized list of candidate 

safety treatments. It is important to note that the intent of this HRRR safety analysis is to identify potential 

safety enhancements for additional consideration. Consequently, transportation agencies would then use this 

information as one key input into a final safety project study. Additional issues that should be considered and that 

are not captured as part of this analysis include, but are not limited to, potential impacts to the roadway capacity, 

air quality, contextually sensitive characteristics, local or regional construction preferences, and local driving laws 

and regulations. A final engineering study is necessary to capture these broader issues associated with a specific 

improvement project. 

Identify Maximum

Initial Investment that

is Feasible

Identify Economically 

Viable Candidate

Treatments to 

Consider from HSIP 

Funding Options

Identify Economically 

Viable Candidate 

Treatments to 

Consider From All 

Funding Options

Qualify for

All Funds?

Qualify for

HSIP Funds?

What Funding

Constraints Apply

To Candidate

Improvements

Identify Economically Viable 

Candidate Treatments to 

Consider from 23 USC120 

Funding Options

Prioritize Treatment

Options Based on 

Economic Appraisal

Summarize Economic

Appraisal Results

Perform

Economic

Analysis 

FROM FLOW CHART C:
Manual for Selecting Safety Improvements on High Risk Rural Roads

161

Glossary

Local Technical Assistance Program (LTAP) – In each State, a LTAP center and/or a Tribal Technical Assistance 

Program Center can provide technical information and training for local governments and agencies that own and 

maintain public roads. These centers are partially funded by the Federal Highway Administration (FHWA) and 

provide resources to local agencies and Tribal governments.

Roadway Feature Type – Characteristics of the roadway present at a specific site. For the purposes of this 

document, roadway feature types may include an intersection, a roadside, horizontal curves, driving lane or 

shoulder, etc.

Safety Treatment or Improvement – A treatment that, once installed, helps to improve a defined safety need.

Tribal Technical Assistance Programs (TTAP) – The TTAP is a training and technology transfer resource 

for Native American tribes in the United States and is funded by the FHWA and the Bureau of Indian Affairs. 

Through technology transfer and training, research, and cultural consideration, the TTAP aims to distribute 

technical assistance and training activities at the Tribal level; help implement administrative procedures and new 

transportation technology at the Tribal level; provide training and assistance in transportation planning and 

economic development; and develop educational programs to encourage and motivate interest in transportation 

careers among Native American students.5312

53 LTAP/TTAP website. Accessed October 14, 2013. http://www.ltap.org/about/ttap.php


For More Information

Visit http://safety.fhwa.dot.gov/hsip/hrrr/manual

FHWA, Office of Safety

James Dahlem

james.dahlem@dot.gov

202-366-9265

FHWA-SA-14-075

2014