U.S. Department of Transportation

Federal Highway Administration

AN EVALUATION OF RSA PROGRAMS AND PROJECTS

FHWA-SA-12-037

Road Safety Audits:
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Technical Report Documentation Page

1. Report No.

FHWA‐SA‐12‐037 4. Title and Subtitle

   

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

5. Report Date

Road Safety Audits: An Evaluation of RSA

Programs and Projects

October 2012 6. Performing Organization Code

7. Author(s)

Dan Nabors, Frank Gross, Kevin Moriarty, Mike Sawyer, and Craig Lyon

9. Performing Organization Name and Address

Vanasse Hangen Brustlin, Inc.

8300 Boone Boulevard, Suite 700

Vienna, VA 22182‐2626

8. Performing Organization Report No.

10. Work Unit No. (TRAIS)

11. Contract or Grant No.

DTF61‐05‐D‐00024

12. Sponsoring Agency Name and Address

Federal Highway Administration

Office of Safety

1200 New Jersey Ave. S.E.

Washington, DC 20590

13. Type of Report and Period Covered

Final Report

September 2009 – October 2012

14. Sponsoring Agency Code

15. SupplementaryNotes

The Federal Highway Administration Office of Safety sponsored the Road Safety Audits reported in this document. The

FHWA Office of Safety Contract Task Order Manager was Becky Crowe.

16. Abstract

Road Safety Audits (RSAs) are an effective tool for proactively improving the future safety performance of a road project

during the planning and design stages and for identifying safety issues in existing transportation facilities. To demonstrate

the effectiveness of RSAs, the Federal Highway Administration (FHWA) Office of Safety sponsored an evaluation of RSAs at the

program and project levels. The aim of these evaluations is to provide State, local, Federal, and Tribal agencies with examples

of RSA programs and quantifiable results from specific RSA projects that can help in implementing RSAs and further their

growth and success.

Six jurisdictions were reviewed for their unique ability to sustain an RSA program at the State, regional, or local level. Key

strategies underpinning the success of these RSA programs are described in this document. At the project level, five RSAs

were evaluated to quantify the safety benefit of specific improvements that were implemented as a result of the RSAs.

Statistical analyses were conducted using observational before‐after methods. Costs of conducting the RSA and of

implementing countermeasures are also presented and used in conjunction with the before‐after analysis to determine the

benefit/cost (B/C) ratio of each project.  

17. Key Words

Safety, Road Safety Audit, Road Safety Assessment,

Evaluation, Benefit/Cost

18. Distribution Statement

No restrictions. This document is available to the public

through the National Technical Information Service,

Springfield, Virginia 22161.

19. Security Classif. (of this report)

Unclassified

20. Security Classif. (of this page)

Unclassified

21. No. of Pages

86

22. Price
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ACKNOWLEDGEMENT

Information obtained for this document involved transportation agencies at the State, county,

and city levels. FHWA and the authors greatly appreciate the participation and cooperation of

the following agencies for their willingness to provide the information to make this document

possible: Arizona Department of Transportation (ADOT); Bullhead City, Arizona; Collier County,

Florida; Cumberland County, Tennessee; Florida Department of Transportation (FDOT); Kansas

Department of Transportation (KDOT); Lee County, Florida; Massachusetts Department of

Transportation (MassDOT); Montgomery County (Maryland) Department of Transportation

(MCDOT); Nevada Department of Transportation (NDOT); Ocean City, New Jersey; Rhode

Island Department o f Transportation (RIDOT); South Jersey Transportation Planning

Organization (SJTPO); and Tennessee Department of Transportation (TDOT).
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TABLE OF CONTENTS		

SUMMARY.........................................................................................................................................................................1

Agencies................................................................................................................................................................1

Focus.....................................................................................................................................................................1

Benefit...................................................................................................................................................................1

INTRODUCTION ................................................................................................................................................................3

Background...........................................................................................................................................................3

Purpose.................................................................................................................................................................4

Focus.....................................................................................................................................................................5

NOTEWORTHY RSA PROGRAMS......................................................................................................................................6

Rhode Island DOT: Focus on High‐Benefit, Low‐Cost Safety and Mobility Improvements.............................7

Nevada DOT: Establish RSA Champions..............................................................................................................9

Kansas DOT: Recurring Systemwide RSA Program...........................................................................................10

Massachusetts DOT: Linking RSAsto HSIP........................................................................................................10

Montgomery County, Maryland: Improving Pedestrian and Bicycle Safety...................................................10

Arizona DOT: Collaborative and Proactive Approach to Statewide Safety.....................................................11

Tennessee DOT: Formalized and Uniform RSA Process...................................................................................11

Collier County, Florida: Adoption of RSA Policy Including Design Permit Requirement................................11

South Jersey Transportation Planning Organization: Comprehensive Site Selection Processes...................11

THE EFFECTIVENESS OF RSA PROJECTS.........................................................................................................................12

RSA Projects Evaluated ......................................................................................................................................16

Methodology......................................................................................................................................................16

Key Findings........................................................................................................................................................17

APPENDIX A: DETAILED OVERVIEW OF EVALUATION METHODOLGIES ........................................................... 19

Empirical Bayes Methodology...........................................................................................................................19

Comparison Group Methodology .....................................................................................................................20

Naïve Methodology............................................................................................................................................21

APPENDIX B: RSA CASE STUDIES....................................................................................................................... 22

Bullhead Parkway: Bullhead City, Arizona....................................................................................................... 22

Background.........................................................................................................................................................23

Key Findings and Suggestions............................................................................................................................24

RSA Outcomes....................................................................................................................................................29

Program Review.................................................................................................................................................34

State Route 101 (Peavine Road): Cumberland County, Tennessee ................................................................. 35

Background.........................................................................................................................................................35

Key Findings and Suggestions............................................................................................................................37

RSA Outcomes....................................................................................................................................................38

Program Review.................................................................................................................................................42

Collier Boulevard at Golden Gate Parkway: Collier County, Florida ................................................................ 48

Background.........................................................................................................................................................48

Key Findings and Suggestions............................................................................................................................50
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RSA Outcomes....................................................................................................................................................53

Program Review.................................................................................................................................................56

Immokalee Road: Collier County, Florida ........................................................................................................ 57

Background.........................................................................................................................................................57

Key Findings and Suggestions............................................................................................................................58

RSA Outcomes....................................................................................................................................................60

Program Review.................................................................................................................................................63

Ninth Street: Ocean City, New Jersey .............................................................................................................. 64

Background.........................................................................................................................................................64

Key Findings and Suggestions............................................................................................................................66

RSA Outcomes....................................................................................................................................................69

Program  Review ................................................................................................................................................75

List of Figures

Figure 1. Typical RSA Process.............................................................................................................................. 4

Figure 2. Aerial Map of Bullhead Parkway........................................................................................................ 23

Figure 3. Treatment Site Crash Totals Over Time. ............................................................................................30

Figure 4. Aerial Map of State Route 101........................................................................................................... 36

Figure 5. RSAR Review Flow Chart: Development Phase..................................................................................45

Figure 6. RSAR Review Flow Chart: Implementation Phase. ............................................................................46

Figure 7. Aerial Map of Collier Boulevard/Golden Gate Parkway. ...................................................................49

Figure 8. Aerial Map of Immokalee Road RSA Location. ..................................................................................58

Figure 9. Aerial Map of Ninth Street................................................................................................................. 65

Figure 10. Route 52 Construction Changes to Ninth Street..............................................................................69

Figure 11. Corridor‐Level Crash Totals Over Time. ...........................................................................................72

Figure 12. Signalized Intersection Crash Totals Over Time...............................................................................72

Figure 13. Overview of the South Jersey Transportation Planning Organization's RSA Site Selection Process.

..........................................................................................................................................................................77

List of Tables

Table 1. Summary of RSA Programs Evaluated................................................................................................... 1

Table 2. Summary of RSA Projects Evaluated..................................................................................................... 2

Table 3. RSA Programs Evaluated. ...................................................................................................................... 5

Table 4. RSA Projects Evaluated. ........................................................................................................................ 6

Table 5. Type of Safety Review Based on Number of Crashes. ........................................................................13

Table 6. Type of Project Based on Number of Crashes.....................................................................................15

Table 7. Quantitative Evaluation of RSA Outcomes..........................................................................................18

Table 8. Summary of Safety Issues and Suggestions: .......................................................................................24

Table 9. Summary of Arizona Data. .................................................................................................................. 29

Table 10. Comparison Group Results from Arizona Including Total Before‐Period. ........................................31

Table 11. Comparison Group Results from Arizona, Excluding 2004 to 2006. .................................................32
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Table 12. Naïve Results from Arizona, Including all Before‐Period Years. .......................................................32

Table 13. Naïve Results from Arizona, Excluding 2004 to 2006. ......................................................................32

Table 14. Summary of Results from Arizona..................................................................................................... 33

Table 15. Summary of Safety Issues and Suggestions: RSA of State Route 101...............................................37

Table 16. Summary of Tennessee Treatment and Reference Site Data. ..........................................................39

Table 17. Estimated SPFs for Tennessee........................................................................................................... 40

Table 18. EB Corridor Results for Tennessee.................................................................................................... 40

Table 19. Analysis of Proportion of Crash Types in Tennessee. .......................................................................41

Table 20. Summary of Safety Issues and Suggestions: .....................................................................................51

Table 21. Summary of Florida (Collier Boulevard) Data. ..................................................................................53

Table 22. Estimated SPFs for Florida................................................................................................................. 54

Table 23. EB Results from Florida. .................................................................................................................... 55

Table 24. Summary of Safety Issues and Suggestions: RSA of Immokalee Road..............................................62

Table 25. Summary of Florida (Immokalee Road) Data....................................................................................61

Table 26. Estimated SPFs for Florida................................................................................................................. 61

Table 27. Corridor Results for Florida (Immokalee Road). ...............................................................................62

Table 28. Summary of Safety Issues and Suggestions: RSA of Ninth Street. ....................................................67

Table 29. Summary of New Jersey Corridor Data.............................................................................................70

Table 30. Summary of New Jersey Signalized Intersection Data......................................................................71

Table 31. Corridor Results for New Jersey........................................................................................................ 73

Table 32. Signalized Intersection Results for New Jersey.................................................................................74
Road Safety Audits: An Evaluation of RSA Programs and Projects

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SUMMARY

Road Safety Audits (RSAs) are an effective tool at addressing safety for all users. This document

provides the evaluation results of RSAs at both the program and project level. As part of this

study, nine jurisdictions were reviewed for their unique ability to sustain an RSA program

at the State, regional, or local level (see Table 1). These jurisdictions were selected based on the

presence of an RSA program and their willingness to share their experiences. The key strategies

underpinning these successful RSA programs are described in this document.

Table 1. Summary of RSA Programs Evaluated.

Agencies Focus Benefit

Rhode Island Department of

Transportation (RIDOT)

Low‐Cost, High‐Benefit Safety and

Mobility

Rapid deployment of RSA team and

implementation of recommendations.

Nevada Department of

Transportation (NDOT)

Establish RSA Champions and

Stakeholder Relations

Trained over 60 transportation

professionals on the basic and

advanced techniques for conducting

RSAs.

Kansas Department of

Transportation (KDOT)

Recurring System‐wide RSA Program Efficient use of personnel and

consistent updating of traffic control

devices.

Massachusetts Department of

Transportation (MassDOT)

Linking RSAs to Highway Safety

Improvement Program

RSAs linked to funding and projects are

programmed quickly.

Montgomery County, Maryland

Department of Transportation

(MCDOT)

Improving Pedestrian and Bicycle

Safety

Crash data and observations in the

field used to understand and address

pedestrian and bicyclist safety.

Arizona Department of

Transportation (ADOT)

Collaborative and Proactive

Approach to Statewide Safety

Findings from RSAs have been used to

update DOT policies and standards.

Tennessee DOT (TDOT) Formalized and uniform RSA process RSAs are conducted in a more efficient

and cost‐effective manner.

Collier County, Florida Adoption of an RSA policy including

a RSA requirement for design

permits

Improvements to design result in

savings over the life of a project.

South Jersey Transportation

Planning Organization (SJTPO)

Creating a comprehensive site

selection processes.

The process was able to identify

locations for quick, low‐cost

improvements that would lead to the

highest reduction in severe crashes.
Road Safety Audits: An Evaluation of RSA Programs and Projects

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At the project level, five areas (four roadways and one intersection projects) were reviewed to

quantify the safety benefits of specific improvements that were implemented as a result of an

RSA. These projects were selected based on having implemented safety measures suggested as

part of the RSA, as well as the availability of data for similar “comparison” sites within the

agency’s jurisdiction. Statistical analyses were conducted using observational before‐after

methods. As shown in Table 2, there was a significant reduction in crashes as a result of the

suggestions implemented from the five RSAs. Total crash reductions ranged from 10 to 50

percent.  For most RSA projects, benefit/cost (B/C) ratios—which compare the benefits derived

from crash reduction to the cost of conducting the RSA and implementing the

countermeasures—were calculated as an additional measure of the project’s success. All

of the evaluated RSA projects had a B/C ratio greater than 1.0, meaning the project benefits

outweighed the project costs. Many of these RSA projects were also discussed in the context of

the overall RSA program for each location.  

Table 2. Summary of RSA Projects Evaluated.

Location Results

Bullhead Parkway

Bullhead City, Arizona

 54% reduction in total crashes

 50% reduction in fatal / incapacitating injury crashes

 30% reduction in intersection‐related crashes

 B/C ratio of 20:1 (total crashes)

State Route 101 (Peavine Road)

Cumberland County, Tennessee

 13.7% reduction in total crashes

 31.3% reduction in injury crashes  

 B/C ratio of 51:1 (total crashes)

Intersection of Collier Boulevard and Golden

Gate Parkway

Collier County, Florida

 11% reduction in total crashes, two intersections

 B/C ratio of 5:1 (total crashes, two intersections)

Immokalee Road

Collier County, Florida

 10.8% reduction in total crashes

Ninth Street

Ocean City, New Jersey

 25.6% reduction in total crashes

 B/C ratio of 1.2:1 (total crashes)

The RSA programs and projects reviewed for this report represent a small sample of RSA activity

throughout the U.S. Many Federal, State, local, and Tribal agencies have experience conducting

RSAs and are creating or have created RSA programs. Moving forward, more agencies will be

implementing safety measures as a result of RSAs, which will, in turn, provide more

opportunities to evaluate the effectiveness of these measures in addressing safety.
Road Safety Audits: An Evaluation of RSA Programs and Projects

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INTRODUCTION

BACKGROUND

Road Safety Audits (RSAs) are an effective tool for proactively improving roadway safety. The

RSA process may be employed on any type of facility and during any stage of the project

development process, including existing facilities that are open to traffic. A decade ago, few

States had experience in conducting RSAs. Now, almost every State has had some experience

with the RSA process.

The Federal Highway Administration (FHWA) defines an RSA as a “formal safety performance

evaluation of an existing or future road or intersection by an independent, multidisciplinary

team.” The primary focus of an RSA is safety, while working within the context of other aspects,

such as mobility, access, surrounding land use, and aesthetics. An RSA conducted by a team that

is independent of the design and operations of the facility can address safety through a thorough

review of roadway, traffic, environmental, and human factors conditions. By using an unbiased

and multidisciplinary team to perform a comprehensive review and an evaluation of physical,

operational, and human‐factors‐related safety issues for a given study area, RSAs make sure that

safety is adequately considered.   

RSAs typically follow the procedures outlined in the FHWA Road Safety Audit Guidelines

document (Publication Number FHWA‐SA‐06‐06). The procedures involve an eight‐step RSA

process that is shown in Figure 1 and can be done at any stage in a project’s life:

• A pre‐construction RSA (planning and design stages) examines a road before it is built,

either at the planning/feasibility stage or the design (preliminary or detailed design) stage.

An RSA at this stage identifies potential safety issues before crashes occur. The earlier a

preconstruction RSA is conducted, the more potential it has to efficiently remedy possible

safety concerns.

• Construction RSAs (work zone, changes in design during construction, and preopening)

examine temporary traffic management plans associated with construction or other

roadwork and changes in design during construction. RSAs at this stage can also be

conducted when construction is completed, but before the roadway is opened to traffic.

• A post‐construction or operational RSA (existing road) examines a road that is operating

and is usually conducted to address a demonstrated crash problem.
Road Safety Audits: An Evaluation of RSA Programs and Projects

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The multidisciplinary RSA team is typically composed of at least three members having

expertise in road safety, traffic operations, and road design. Other potential team members

may have a background in (but not limited to) enforcement, emergency medical services,

maintenance, human factors analysis, transportation planning, pedestrian safety, and bicyclist

safety. It is important that members of the RSA team are independent of the design and

operations of the facility being assessed. The RSA team’s independence assures two things:

1) there is no bias in the assessment, and 2) the project is reviewed with “fresh eyes.”  

PURPOSE

The purpose of this document is to provide State, local, Federal, and Tribal agencies with

examples of RSA programs and quantifiable results from RSA projects that can help in

Figure 1. Typical RSA Process.
Road Safety Audits: An Evaluation of RSA Programs and Projects

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implementing RSAs and further their growth and success. This project evaluated nine sustained

RSA programs and the improvements implemented as a result of five specific RSA projects. The

RSA programs (shown in Table 3) were reviewed from a programmatic perspective to identify

key factors for success, and the RSA projects were evaluated to quantify the safety effectiveness

of the improvements suggested through the RSAs in reducing crashes. Table 4 provides a brief

summary of the characteristics of the specific RSA projects evaluated. The evaluation consisted

of a rigorous before‐after analysis to measure the project’s success through the development

of benefit/cost (B/C) ratios, which describe the benefits derived from crash reduction versus

the cost of conducting the RSA and implementing the recommended

countermeasures. The methodology used in the analysis is described in Appendix A. Appendix

B includes a project description, a summary of key findings and suggestions, and photographs

to illustrate before and after conditions of each of the RSA projects evaluated.  Specifics about

why RSAs were initiated are also discussed.  

Table 3. RSA Programs Evaluated.

Agencies Program

Level

Focus

Rhode Island Department of Transportation

(RIDOT)

State Low‐Cost, High‐Benefit Safety and

Mobility

Nevada Department of Transportation

(NDOT)

State Establish Champions

Kansas Department of Transportation

(KDOT)

State Recurring System‐wide RSA Program

Massachusetts Department of

Transportation (MassDOT)

State Linking RSAs to Highway Safety

Improvement Program

Montgomery County Department of

Transportation (MCDOT‐ Montgomery

County, Maryland)

County Improving Pedestrian and Bicycle Safety

Arizona Department of Transportation

(ADOT)

State Collaborative and Proactive Approach to

Statewide Safety

Tennessee DOT (TDOT) State Formalized and uniform RSA process

Collier County, Florida County Adoption of an RSA policy including a RSA

requirement for design permits

South Jersey Transportation Planning

Organization (SJTPO)

Regional Creating a comprehensive site selection

processes.
Road Safety Audits: An Evaluation of RSA Programs and Projects

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Table 4. RSA Projects Evaluated.

Location RSA Stage Project Description

Bullhead Parkway

Bullhead City, Arizona

Existing

roadway

 10.2‐mile section

 Paved, four‐lane divided rural roadway

 4 signalized intersections, 13 unsignalized intersections

 AADT: 10,000 – 15,000 vehicles per day (2007)

 50 mph posted speed limit

State Route 101   

(Peavine Road)

Cumberland County,

Tennessee

Existing

roadway

 3.84‐mile section

 Paved, two‐lane rural roadway

 Two unsignalized intersections

 AADT: 12,860 vehicles per day (2007)

 45 mph posted speed limit

Collier Boulevard at

Golden Gate Parkway

Collier County, Florida

Existing

roadway

 Three‐legged signalized intersection

 Paved, four‐lane divided roadway

 Adjacent unsignalized intersection at Collier County Boulevard and

25th Avenue

 AADT: 18,000 – 24,000 vehicles per day (2005)

 45 mph posted speed limit

Immokalee Road  

Collier County, Florida

Design stage  3.25‐mile section

 Paved, four‐lane divided roadway (existing)

 Paved, six‐lane divided roadway (planned)

 Six signalized intersections

 AADT: 45,488 vehicles per day (2005)

 45 mph posted speed limit

Ninth Street

Ocean City, New Jersey

Existing

roadway

 0.47‐mile section

 Paved, four‐lane arterial roadway

 6 signalized intersections, 1 unsignalized intersection

 AADT: 13,870 vehicles per day (2007)

 25 mph posted speed limit

NOTEWORTHY RSA PROGRAMS

RSA programs were reviewed to understand the key strategies underpinning successful program

implementation at the State, regional, or local level. The RSA programs reviewed as part of this

project were selected based on the presence of an RSA program that has resulted in multiple

RSAs and the parent agencies’ willingness to share their experiences. The key strategies

underpinning the following noteworthy RSA programs are described in this document:  

• State of Rhode Island.

• State of Nevada.

• State of Kansas.

• Commonwealth of Massachusetts.

• Montgomery County, Maryland.
Road Safety Audits: An Evaluation of RSA Programs and Projects

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• State of Arizona.

• State of Tennessee.

• Collier County, Florida.

• South Jersey Transportation Planning Organization.

RHODE ISLAND DOT: FOCUS ON HIGH‐BENEFIT, LOW‐COST SAFETY AND MOBILITY

IMPROVEMENTS

The Rhode Island Department of Transportation (RIDOT) initiated its RSA Program through

RI*STARS—Rhode Island’s Strategically Targeted Affordable Roadway Solutions. This program

borrows from a Federal program in the 1970s and the Virginia Department of Transportation’s

similarly‐named STARS program. Traditionally, the transportation planning process has focused

on long‐term, high‐cost capital improvements for the transportation system. RI*STARS is

focused on rapidly delivering high‐benefit, low‐cost safety and mobility improvements in

response to today’s safety, mobility, and funding challenges.

Funding for RI*STARS is included in the Transportation Improvement Program (TIP), which is its

own line item under the RIDOT Traffic Safety Program. The program is funded $1,000,000 a

year for study, design, and near‐term construction. Construction of additional near‐term and

intermediate term recommendations may utilize other safety dollars, as well, such as Highway

Safety Improvement Program (HSIP) funds.

RI*STARS was piloted on Aquidneck Island, which is made up of the Towns of Portsmouth and

Middletown and the City of Newport. Aquidneck Island was selected for the pilot because of

the significant amount of data available from the recently‐started Aquidneck Island

Transportation Study (AITS)‐ this was a regional, comprehensive, multimodal transportation

planning study that evaluated roadway, transit, and pedestrian and bicycle travel.  During the

pilot effort, "hot spots" were identified in each of the three municipalities based on data that

were compiled as part of the AITS, including crash data, congestion mapping, and input from

public and local municipalities. Potential locations were then ranked based on crash history

(including frequency and severity) and delay to identify 50 candidate locations exhibiting the

greatest safety and/or congestion concerns. Candidates that were already under construction

were dropped from further consideration, resulting in 17 ”hot spot” corridors and intersections.

RSAs were conducted by an interdisciplinary RSA Team consisting of engineers and officials

from the municipalities, RIDOT, the Rhode Island Statewide Planning Program, law

enforcement, and FHWA. The team identified crash contributing factors and developed

strategies to address these factors for each “hot spot.” These strategies were comprehensive‐ 

covering the 4 E’s of safety (engineering, enforcement, education, and emergency services)‐ and
Road Safety Audits: An Evaluation of RSA Programs and Projects

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grouped into near‐term, intermediate term, and long‐term implementation time frames.

Planning‐level order‐of‐magnitude construction cost estimates were developed for the

recommended improvements, as were crash reduction benefits. B/C ratios were then calculated

to evaluate the economic feasibility and effectiveness of the proposed safety improvements at

each location.

Once the RI*STARS team reviewed all countermeasures and developed a list of

recommendations, the team developed a list of implementation mechanisms to be used for the

identified recommendations. RIDOT Traffic Engineering will be implementing all the optimized

signal timings in the field. RIDOT Maintenance will be responsible for addressing issues such as

silted catch basins and missing signal head hoods. Recommendations at four locations are

being incorporated into the design stage of identified projects. All remaining improvements will

be implemented through two separate design‐bid‐build construction contracts. The first

contract will focus on improvements not requiring permitting, such as basic signing, striping,

and pedestrian facility enhancements. The second contract will cover the remaining

improvements that may require permitting or input from the municipality or general public. The

first contract was advertised for construction in

March 2012 and the second is scheduled to be

advertised at the end of 2012. Enforcement and

education recommendations were developed in

conjunction with appropriate stakeholders to

maximize the opportunity for successful

implementation.

One example of a recommended improvement

from RI*STARS that will be implemented within

a year is the retrofit of the City of Newport

Rotary. As illustrated in the photograph at left,

the nondelineated rotary will be enhanced with

modern roundabout features, primarily by

implementing low‐cost measures like signing, striping, and minor curbing. In addition to

enhancing safety, the retrofitted rotary is projected to operate with less delay than it does

under existing conditions. However, this retrofit is an interim measure, as the intermediate‐

range plan is to reconstruct the intersection into a modern roundabout as part of an adjacent

bridge project. Another example of a recommended improvement is the conversion of a four‐

lane roadway to two lanes with a two‐way‐left‐turn‐lane and shoulders that can be used by

cyclists.

An aerial view of the City of Newport Rotary

with enhanced pavement marking plan.
Road Safety Audits: An Evaluation of RSA Programs and Projects

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The successes of the RI*STARS program hinges upon the rapid implementation of the proposed

countermeasures. This is critical in gaining momentum for the program and maintaining support

from stakeholders (i.e., municipalities, community groups, and first responders). This pilot

program has a goal to implement most near‐term improvements within one year from the

issuance of the final report and less than two years from the time the RSAs were conducted.

Other improvements being included in planned projects will be implemented over the next few

years, as those specific projects go to construction.

NEVADA DOT: ESTABLISH RSA CHAMPIONS

The Nevada DOT (NDOT) has a well‐established RSA Program. NDOT Safety Engineering

established a dedicated RSA Coordinator to implement the RSA program statewide. To

supplement these efforts, NDOT developed guidelines for RSAs of new transportation project

plans (i.e., preconstruction RSAs) such as capacity projects at various design stages, as well as

for RSAs along existing roads (i.e., post‐construction RSAs) that are undergoing safety

improvements or resurfacing‐restoration‐rehabilitation (3‐R) projects. In starting its program,

NDOT leveraged the National Highway Institute (NHI) and FHWA RSA courses to train over 60

transportation professionals in the basic and advanced techniques in conducting RSAs. RSA

teams focus on providing low‐cost, crash‐reducing improvements that can often be put into

place by maintenance crews. NDOT also starts the RSA process in the prescoping phase of

design projects such that safety improvements have the best chance for inclusion. NDOT

also utilizes consulting firms to perform RSAs.

An aerial view of the four‐lane to two‐lane roadway conversion concept.
Road Safety Audits: An Evaluation of RSA Programs and Projects

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KANSAS DOT: RECURRING SYSTEMWIDE RSA PROGRAM

The Kansas DOT (KDOT) conducts county‐wide RSAs on the entire State highway system. With a

goal of completing a comprehensive RSA every five years on each State route, U.S. route, and

the Interstate system. The RSA is comprised of three components: an office review, a field

review, and a final report. It provides a proactive process to recognize issues immediately and

to take corrective action. The RSA process also allows for the responsible engineer to meet with

local officials and KDOT personnel to gain additional insight to improve safety. KDOT found that

a well‐managed RSA program can achieve more efficient use of personnel, as well as promote

the consistent and up‐to‐date use of traffic control devices across the State.

MASSACHUSETTS DOT: LINKING RSAS TO HSIP

There are multiple benefits to linking an RSA program to the Highway Safety Improvement

Program (HSIP).  The RSA program can identify high quality, affordable, multi‐modal safety

projects and be used as a tool to advance HSIP implementation efforts and reduce fatalities and

serious injuries within a jurisdiction.  The Massachusetts DOT (MassDOT) considers RSA

programs to be a “low‐cost opportunity to make significant safety improvements” and uses

them at all stages of a facility’s life‐cycle, an approach that stemmed from its Strategic Highway

Safety Plan (SHSP). MassDOT’s HSIP is linked to its RSA program by requiring that "all HSIP

candidate locations will require an accompanying RSA report, or an engineering or planning

report to determine eligibility." For example, roadway departure crashes were identified as

an SHSP emphasis area and high severe crash locations were identified as part of the HSIP. The

RSA program studied severe crossover median crashes and recommended and prioritized low‐

cost median treatments at these locations. MassDOT is looking to expand its RSA program to

cover non‐motorized high‐crash locations as a result of the successful RSA median program.

MONTGOMERY COUNTY, MARYLAND: IMPROVING PEDESTRIAN AND BICYCLE SAFETY

Montgomery County DOT is leading an RSA program for pedestrians and bicyclists for the

County. A consultant‐led team identifies candidate locations for the pedestrian and bicycle

safety assessments through the County’s High Incident Area (HIA) Program. Up to four HIAs are

selected for evaluation each year, usually on major corridors throughout the County. Once study

areas are defined, a multidisciplinary team is assembled that includes representatives from the

Maryland State Highway Administration (MD SHA), neighboring local agencies, community

members, and Montgomery County DOT staff. During the course of the assessment, the RSA
Road Safety Audits: An Evaluation of RSA Programs and Projects

11

team analyzes data, conducts site visits, and examines the issues and preliminary findings,

which are discussed among the various stakeholders. A report is produced documenting the

issues, and the RSA team presents it to the key stakeholders and roadway owners, a group that

typically includes the County, MD SHA, and local/regional transit agencies. The RSA team

coordinates improvements with each agency and monitors and pursues actions to implement

improvements, such as completing preliminary designs, developing cost estimates, and

completing work orders.

ARIZONA DOT: COLLABORATIVE AND PROACTIVE APPROACH TO STATEWIDE SAFETY

Program details can be found in Appendix B.

TENNESSEE DOT: FORMALIZED AND UNIFORM RSA PROCESS

Program details can be found in Appendix B.

COLLIER COUNTY, FLORIDA: ADOPTION OF RSA POLICY INCLUDING DESIGN PERMIT REQUIREMENT

Program details can be found in Appendix B.

SOUTH JERSEY TRANSPORTATION PLANNING ORGANIZATION: COMPREHENSIVE SITE SELECTION

PROCESSES

Program details can be found in Appendix B.

   
Road Safety Audits: An Evaluation of RSA Programs and Projects

12

THE EFFECTIVENESS OF RSA PROJECTS

BACKGROUND

The RSA project costs and benefits must be understood to determine the effectiveness of an RSA

in improving safety. This section discusses basic techniques to compare RSA project costs and

benefits to determine a project B/C ratio and provides programmatic guidance when selecting a

location to conduct an RSA.            

RSA COSTS

Three main factors contribute to the cost of an RSA:

 RSA team costs.

 Design team and owner costs.

 Implementation costs.

The RSA team costs reflect the size of the team and the time required for the RSA, which

in turn are dependent on the complexity of the RSA project. In the RSA projects evaluated as

part of this project, the team size may have been larger than necessary to expose more

professionals to the RSA process.

The design team and owner costs reflect the time required for staff to attend the start‐up and

preliminary findings meetings and to subsequently read the RSA report and respond to its

findings. In addition, staff time is required to compile project or site materials for the RSA team.

The final cost component is implementation costs. These are the costs resulting from the

design and construction of measures suggested as part of the RSA. These can range from low‐

cost measures (e.g., signing and pavement markings) to higher‐cost measures that require

design and construction. Measures suggested for each of the RSAs reviewed for this project are

included in Appendix B.

RSA BENEFITS

The primary benefit of RSAs is the reduction in crashes as road safety is improved. The U.S.

Department of Transportation’s1 estimated costs of automotive crashes are shown below:

																																																												

1 Duvall, Tyler D. Memorandum to Secretarial Officers, Modal Administrators, U.S. Department of 

Transportation Office of the Assistant Secretary for Transportation Policy, “Treatment of the Value of 

Preventing Fatalities and Injuries in Preparing Economic Analyses”. 5 Feb. 2008. 
Road Safety Audits: An Evaluation of RSA Programs and Projects

13

 $6,000,000 for a traffic fatality (category K).

 $4,422,500 for a critical injury (category A1).

 $1,087,500 for a severe injury (category A2).

 $333,500 for a serious injury (category B1).

 $89,900 for a moderate injury (category B2).

 $11,600 for a minor injury (category C).

 $6,500 for property damage only (PDO).

The process for determining whether a measure or project is effective at reducing crashes is a

B/C analysis that compares the total expected benefits of a measure or project to the total

expected costs for a specific measure or project. The output of the analysis, called a B/C ratio, is

the cost savings from the reduction in crashes (achieved through the safety measures) divided

by the cost of the safety reviews and safety measures implemented (in dollars). A B/C ratio

greater than 1.0 represents the project benefits outweighing the project costs. Table 5

illustrates how the cost of various types of safety reviews can be justified for an existing

location based on crash history. The table indicates the number of crashes o f moderate‐

(B2), minor‐(C), or PDO‐(O) severity that need to be reduced as a result of the safety review to

achieve a B/C ratio of at least 1.0 based on the average cost of the safety review alone. It is

assumed that each type of safety review has a service life of three years. As such, the statistics

in Table 5 refer to the number of crashes in a three‐year period. The table highlights that, by

addressing a few moderate to property‐damage‐only crashes, an agency can justify the cost of a

simple to complex RSA.

Table 5. Type of Safety Review Based on Number of Crashes.

Type of Safety Review

(Existing Roadway)

Average Cost

B2 C O

Moderate Minor PDO

Associated Crash Cost

$89,900 $11,600 $6,500

Traditional Safety Review $1,000 1 1 1

RSA ‐ Simple $10,000 1 1 2

RSA ‐ Intermediate $15,000 1 2 3

RSA ‐ Complex $25,000 1 3 4

Detailed Safety Review $50,000 1 5 8

Notes: Any type of safety review can achieve a B/C over 1.0 if there is just one moderate or more severe injury.

Each study type is assumed to have a three‐year service life.  A traditional safety review is typically a quick review

of a project conducted by a transportation agency with in‐house staff.  A detailed safety review refers to a more

expansive form of traditional safety review.  

In the past, it was difficult to quantify the benefits of design‐stage RSAs, especially on new

facilities that have no crash record, since they aim to prevent crashes from occurring. Now,
Road Safety Audits: An Evaluation of RSA Programs and Projects

14

through the use of the Highway Safety Manual (HSM) and related tools such as the Interactive

Highway Safety Design Model (IHSDM), there are methods to estimate the expected crashes for

a new facility based on its design and operational characteristics. The benefits of RSAs on

improved facilities and existing roads can be quantified based on observed pre‐ and post‐

improvement collision histories, but there are potential biases related to simple before‐after

comparisons. The HSM identifies methods for incorporating the average crash history at

similar sites with the observed crashes at the location of interest to address the potential

biases associated with before‐after evaluations.

Whether design‐stage or existing‐stage, when compared to the high cost of automotive

crashes, changes implemented from an RSA only need to prevent a few moderate‐ or high‐

severity crashes to be cost effective. Table 6 illustrates how different project implementation

levels can achieve a favorable B/C ratio for various crash severities. The table indicates the

number of crashes (by severity) that need to be reduced over the service life of the project to

achieve a B/C ratio of at least 1.0 based on project implementation cost. It is assumed that

maintenance projects have a service life of three years and HSIP projects have a service life

of 10 years. For example, a low‐level maintenance project would prove to be beneficial given

at least one PDO crash is eliminated. A medium‐level HSIP candidate project would prove to

be beneficial if at least one serious injury or three moderate injury crashes were eliminated.

Capital projects addressing highway safety issues without the guidance of an RSA may be

similarly beneficial, but RSAs provide an opportunity to address multiple issues and coordinate

safety‐related projects to optimize costs and improve the potential effectiveness in reducing

crashes and severity.  

There are many other benefits that can be realized from conducting an RSA or safety review

other than relying completely on achieving a B/C ratio greater than 1.0. Other benefits of RSAs

include reduced life‐cycle project costs (i.e., the total cost over the life of a project that

includes activities like design and engineering, land acquisition, construction, reconstruction

and rehabilitation, and preservation and routine maintenance).2 This can be attributed to

the fact that, as crashes are reduced and there is less need to make changes to the roadway or

project, a greater awareness of safety is realized through the development of good safety

engineering and design practices within an agency, including consideration of potential

multimodal safety issues and integrating human factors into the design, operations, and

maintenance of roads.  

																																																												

2Economic	Analysis	Primer	

	http://www.fhwa.dot.gov/infrastructure/asstmgmt/primer04.cfm	
15	

Road Safety Audits: An Evaluation ofRSAPrograms and Projects

Table 6. Type of Project Based on Number of Crashes.

Project Type Average Cost

K A1 A2 B1 B2 

Killed Critical Severe Serious Moderate 

Associated Crash Cost

$6,000,000 $4,422,500 $1,087,500 $333,500 $89,900 

Maintenance – Low1 $1,000 1 1 1 1 1 Maintenance – Medium1 $10,000 1 1 1 1 1 Low‐Cost Safety Improvement2 $10,000 1 1 1 1 1 Maintenance – High1 $100,000 1 1 1 1 2 HSIP – Medium2 $250,000 1 1 1 1 3 HSIP – Med/High2 $500,000 1 1 1 2 6 HSIP – High2 $1,000,000 1 1 1 3 12 

Notes:1. Assumes a 3‐year service life.

2. Assumes a 10‐yearservice life.

Through safety management activities, one should strive for the greatest concentration of severe crashes to t

RSA. The number of crashes shown is the absolute minimum to achieve a positive benefit/cost ratio (i.e., greate

Strong Candidate for RSA and Countermeasures

Likely Candidate for RSA and Countermeasures

Questionable Candidate for RSA and Countermeasures

Weak Candidate for RSA and Countermeasures
Road Safety Audits: An Evaluation of RSA Programs and Projects

16	

RSA PROJECTS EVALUATED

Five RSAs were selected for detailed quantitative evaluations as part of this project, based on

having implemented safety measures suggested as part of the RSA, as well as the availability of

data for similar “comparison” sites within the agency’s jurisdiction. The RSA sites selected for

detailed evaluation include the following:

• Bullhead Parkway – Bullhead City, Arizona.

• State Route 101 – Cumberland County, Tennessee.

• Collier Boulevard at Golden Gate Parkway – Collier County, Florida.

• Immokalee Road – Collier County, Florida.

• Ninth Street – Ocean City, New Jersey.

The information presented for each RSA was gathered through direct communication with the

responsible RSA agency.  The specific objective of the quantitative analysis was to estimate the

safety effects of engineering improvements that were implemented as a result of conducting

RSAs. The expected annual benefits were then compared to the annualized cost of the

treatments, including the cost to conduct the RSA, to estimate a B/C ratio. Safety effects were

measured with respect to total crashes. Specific crash types were considered whenever

possible, based on the individual locations, availability of detailed data, and sample size.  

METHODOLOGY

Three evaluation methods were employed in this study depending on the availability of data.

All three methods were based on an observational before‐after study design where a site

was selected for study, an RSA was conducted, treatments were implemented based on the RSA

findings, and the crash history of the site was compared before and after treatment.

There are several potential biases to account for in before‐after studies for which one should

account:

• Regression‐to‐the‐mean. Regression‐to‐the‐mean is the tendency for high crash

frequency periods to be followed by a low crash frequency period and vice‐versa.

• Traffic volume. Changes in traffic volume can affect the number of crashes on a roadway

and, therefore, should be accounted for in the analysis.

• Temporal trends. Temporal trends are factors that may change from the before to the

after period, such as weather, driver behavior, and crash reporting practices.

If these potential biases are not properly addressed (or at least dismissed), the results could

over‐ or underestimate the safety effects of the treatment.

The following is a brief summary of primary attributes of each evaluation methodology used in

the evaluation of RSA outcomes:
Road Safety Audits: An Evaluation of RSA Programs and Projects

17	

 Empirical Bayes. The empirical Bayes (EB) before‐after method is used to estimate and

compare the expected number of crashes without implementation of specific RSA

treatments to the number of reported crashes after RSA treatments have been

implemented. EB is the primary, and preferred, study design for this evaluation and is

considered the state‐of‐the‐practice for conducting observational before‐after studies

because it properly accounts for regression‐to‐the‐mean and other potential sources of

bias.

 Comparison Group. This method uses data from the RSA site (having implemented

treatments) and a comparison group of untreated RSA sites (having similar characteristics

and crash histories to the treated RSA site) to develop before/after comparisons of

observed and expected crash incidence. This method can account for several potential

sources of bias but does not effectively address regression‐to‐the‐mean.

 Naïve. The naïve (or simple) before‐after method uses before and after crash data only

from the RSA site to compare observed and expected crash incidence. This method does

not address regression‐to‐the‐mean and is typically the last option for a before‐ after

study; however, it can be useful to identify the general effectiveness of a treatment (i.e.,

substantial increase or decrease in crashes), particularly if the treatment effect is large.

A detailed overview of the attributes, advantages, and disadvantages of each evaluation

method can be found in Appendix A. More details can be found in FHWA’s A Guide to

Developing Quality Crash Modification Factors (Gross et al., 2010).                                   

KEY FINDINGS

Each of the five RSA sites evaluated exhibited an overall reduction in crashes as a result of the

suggestions implemented from the RSAs. Reductions in total crashes ranged from 10 percent to

50 percent, with varying levels of statistical significance. Furthermore, each of the RSA sites for

which project cost information was provided showed a B/C ratio greater than 1.0, meaning that

the benefits of the treatments implemented as a result of the RSAs exceeded the total RSA and

implementation costs. B/C ratios ranged from 1.2:1 to 116:1; the greater the B/C ratio, the

greater the benefit compared to the project cost. Areas with high B/C ratios either had a high

reduction in crashes (e.g., a reduction in total crashes of 50 percent) or had low project costs

(e.g., implementing signing and pavement markings). Areas with lower B/C ratios typically had

higher project costs.

Table 7 summarizes the safety improvement measures implemented as a result of the RSAs, the

statistical evaluation methods applied, the project costs, and the safety benefits and resulting

B/C ratios based on the analysis of the crash types addressed. Appendix A provides further

details on the methodologies used to quantify RSA treatment benefits for each case study site.

Further details about each RSA project site (i.e., a project description, summary of key findings
Road Safety Audits: An Evaluation of RSA Programs and Projects

18	

and suggestions, photographs for each location, the methodology used in the evaluation, data,

analysis, and findings) are included in Appendix B. If it was available, additional information is

also provided about the agency’s RSA procedures and experience outside of the specific RSA

project considered for this effort.

           Table 7. Quantitative Evaluation of RSA Outcomes.

Location & Measures

Primary Method:

Biases Addressed Results

Bullhead Parkway

Bullhead City, Arizona

 Roadside improvements

 Guardrail

 Signing and marking

 Traffic signals

 Drainage

Comparison Group:

Traffic volume

changes, temporal

changes

 Total cost of $869,478 (plus several nominal fee projects)

 $785,000 of additional projects scheduled

 54% reduction in total crashes

 50% reduction in fatal/incapacitating injury crashes

 30% reduction in intersection‐related crashes

 B/C ratio of 20:1 (total crashes)

 B/C ratio of 16:1 (injury crashes)

 B/C ratio of 2:1 (intersection‐ related crashes)

State Route 101 (Peavine Rd.)

Cumberland County, Tennessee

 Signing and marking

 Sight distance enhancements  

 Vegetation removal

Empirical Bayes:

Regression‐to‐the‐

mean, traffic volume

changes, temporal

changes

 Total cost of $35,000

 13.7% reduction in total crashes

 31.3% reduction in injury crashes

 B/C ratio of 51:1 (total crashes)

 B/C ratio of 116:1 (injury crashes)

Intersection of Collier Boulevard and

Golden Gate Parkway

Collier County, Florida

 Signing and marking

 Geometric modifications

 Vegetation removal

 Pedestrian enhancements

Empirical Bayes:

Regression‐to‐the‐

mean, traffic volume

changes, temporal

changes

 Total cost of $265,000

 11% reduction in total crashes, both intersections

 B/C ratio of 5:1 (total crashes, both intersections)

Immokalee Road

Collier County, Florida

 Access management  

 Pedestrian signals

 Median fence

 Geometric modifications

 Bicycle facilities

Naïve (with

adjustments): Traffic

volume changes,

temporal changes,

other changes (4‐ to

6‐lane conversion)

 10.8% reduction in total crashes

Ninth Street

Ocean City, New Jersey

 Traffic signal improvements

 Pedestrian signals

Comparison Group:

Traffic volume

changes, temporal

changes

 Total cost of $921,000

 25.6% reduction in total crashes

 B/C ratio of 1.2:1 (total crashes)

  
Road Safety Audits: An Evaluation of RSA Programs and Projects

19	

APPENDIX A: DETAILED OVERVIEW OF EVALUATION

METHODOLGIES

EMPIRICAL BAYES METHODOLOGY

The empirical Bayes (EB) method can be used to account for regression‐to‐the‐mean bias in

before‐after studies. Other advantages are that it can be used to accomplish the following:

• Overcome the difficulties of using crash rates to normalize for differences in traffic

volumes between the before and after periods.

• Reduce the level of uncertainty in the estimates of safety effect.

• Provide a foundation for developing guidelines for estimating the likely safety

consequences of contemplated installations.

• Properly account for differences in crash experience and reporting practices.

The premise of the EB method is to estimate the expected number of crashes that would

have occurred in the after period had the treatment not been implemented (π) and compare

that with the number of reported crashes in the after period once the treatment is actually

installed (λ). The number of crashes before a treatment by itself is not a good estimate of π 

because of changes in safety that may result from changes in traffic volume, regression‐to‐the‐

mean, and trends in crash reporting and other factors. Instead, π is estimated from an EB

procedure where information from the treatment site and a group of similar reference sites are

combined. The following steps are used to estimate π:

1. Identify a reference group of untreated sites that is otherwise similar to the treatment group.   

2. Use the reference group data to estimate safety performance functions (SPFs) (i.e.,

mathematical equations that predict crash frequency by type/severity as a function of traffic

volumes and other site characteristics). Typically, SPFs are negative binomial regression

models that are estimated using generalized linear modeling (GLM).

3. Calibrate annual multipliers (time‐related factors) to account for temporal trends (e.g.,

variations in weather, demography, and crash reporting).

4. Use the SPFs and annual multipliers to compute the predicted number of crashes in each year

of the before period for each treatment site.

5. Use the predicted number of crashes in the before period (from step 4) and the observed

crashes in the before period at each treatment site to estimate the expected number of

crashes in the before period at each site. This step applies the EB weighting scheme to adjust

for possible bias due to regression‐to‐the‐mean.
Road Safety Audits: An Evaluation of RSA Programs and Projects

20	

6. Estimate π (i.e., the expected number of crashes in the after period had the treatment not

been implemented) as the product of the expected number of crashes in the before period

(from step 5) and the ratio of the sum of annual SPF predictions for the after period divided

by the sum of these predictions for the before period.

7. The estimate of π is then summed over all sites in a treatment group of interest and

compared with the count of crashes during the after period.

The estimate of π and its variance are then used, along with the crash counts after the

implementation of the treatment, to estimate the treatment effect.

COMPARISON GROUP METHODOLOGY

The comparison group method does not effectively account for regression‐to‐the‐mean but can

be effective in accounting for other nontreatment effects, such as those due to changes in traffic

volume and other temporal trends. This method makes use of a comparison group that is

untreated and for which an RSA was not conducted but is otherwise similar to the treatment

sites. The data from the comparison group are used to adjust the before period crash count at

the treated site to reflect the length of after period (relative to the before period), as well as

other extraneous factors. Implicit in the use of a comparison group is the assumption that the

comparison group is subject to extraneous factors affecting crashes in a way that is sufficiently

similar to the treatment sites. This can be tested by tracking the yearly crash counts at treatment

and comparison sites.

Similar to the EB method, the premise of the comparison group method is to estimate the

expected number of crashes that would have occurred in the after period had the treatment not

been implemented (π) and compare that with the number of reported crashes in the after period

once the treatment is actually installed (λ). The departure from the EB method is that π is based

on the observed crashes in the before period at the treatment site. This estimate could be biased

if sites are selected for treatment because of a randomly high observed crash count (i.e.,

regression‐to‐the‐mean).

General temporal trends are accounted for using crash data from the comparison group.

Specifically, the ratio of crashes after treatment to before treatment is computed for the

comparison sites and multiplied by the observed crashes before treatment at the treatment site.

This is generally insufficient to account for changes in traffic volume from the before period to

the after period. To properly account for traffic volume changes, another factor is applied to the

result of the previous step. The comparison group is first used to develop an SPF, and the factor

is computed as the ratio of predicted crashes in the after period divided by the predicted crashes

in the before period for the treatment sites.
Road Safety Audits: An Evaluation of RSA Programs and Projects

21	

NAÏVE METHODOLOGY

The naïve (or simple) before‐after method does not effectively account for regression‐to‐the‐

mean and is also less effective than the EB and comparison group methods in accounting for

other nontreatment effects, such as those due to changes in traffic volume and other temporal

trends. This method does not utilize a reference or comparison group and simply uses before

and after data from the treatment sites.

Similar to the previous two methods, the naïve before‐after method estimates the expected

number of crashes that would have occurred in the after period had the treatment not been

implemented (π) and compares that with the number of reported crashes in the after period

once the treatment is actually installed (λ). Similar to the comparison group method, π is based

on the observed crashes in the before period at the treatment site, but there is no use of a

comparison group to adjust this estimate. Again, this estimate could be biased if sites are

selected for treatment based on a randomly high crash count (i.e., regression‐to‐the‐mean).

The naïve before‐after method accounts for the length of the before and after periods and

roughly adjusts for changes in traffic volumes. There is no account for other temporal trends that

could change from the before to the after period. To account for traffic volume changes, a simple

linear relationship between crashes and traffic volume is often assumed. In this case, the ratio of

traffic volume in the after period to the before period would be calculated. The ratio of years

after treatment to years before treatment is also computed to adjust for the number of years in

each period. The observed crash count before treatment is then multiplied by the two ratios to

estimate π.  

                                                                                  
Road Safety Audits: An Evaluation of RSA Programs and Projects

22	

APPENDIX B: RSA CASE STUDIES

BULLHEAD PARKWAY: BULLHEAD CITY, ARIZONA

Road: Existing 10.2‐mile section of paved, 4‐lane, divided, rural roadway

RSA Sites: • 4 signalized intersections, 13 unsignalized intersections

• AADT: 10,000 – 15,000 vehicles per day (2007)

• 50 mph posted speed limit

Environment:  urban/urbanized  suburban  rural

Owners: Bullhead City, Arizona

Road Safety Audit

Date of RSA: 23‐25 October 2007

RSA Stage(s):  planning/design stage  RSA of existing roads

RSA Team:

RSA Cost:

Implementation Cost:

Crash Reduction:

Benefit / Cost Ratio:

5 members representing ADOT Traffic Safety, ADOT Traffic Design, ADOT Kingman

District, FHWA, and the City of Yuma

$30,000

$839,478

54% total; 50% fatal / incapacitating; 30% intersection‐related

20:1 total; 16:1 injury; 2:1 intersection‐related
Road Safety Audits: An Evaluation of RSA Programs and Projects

23	

BACKGROUND

An RSA was conducted along a 10.2‐mile section of Bullhead Parkway in Bullhead City, Arizona

(Figure 2). Bullhead Parkway is a four‐lane, divided, rural roadway with a posted speed

limit of 50 mph for the entire length. Four signalized intersections are present along the

Parkway. At the time of the RSA, the annual average daily traffic along the Parkway was

reported to range between 10,000 and 15,000 vehicles per day (vpd).

The RSA was requested by the Bullhead City Department of Public Works. The Parkway

appeared on Arizona’s 2006 Five Percent Report. The section was also one of the City’s top

safety priority locations.

Figure 2. Aerial Map of Bullhead Parkway.

The RSA was conducted in October 2007. The RSA team was comprised of five members

representing the Arizona Department of Transportation (ADOT) Traffic Safety, ADOT Traffic

Design, ADOT Kingman District, City of Yuma, and Federal Highway Administration (FHWA).

Information used by the RSA team to conduct the review included the following:

• Crash data (August 1, 2003 – July 31, 2006) from the ADOT Motor Vehicle

Division.

• Traffic data (2007 and 2009) from Bullhead City.

• Roadway data (lane, median, and shoulder widths).
Road Safety Audits: An Evaluation of RSA Programs and Projects

24	

For this RSA, 3.5 hours (total) were required to hold the opening and closing meetings. The RSA

team spent 7 hours in the field reviewing the roadway segment. Analysis prior to and following

the field review required 10 hours. Documenting the findings of the RSA required 12 hours. Four

hours of travel each way were required to complete the RSA. In total, the RSA of Bullhead

Parkway took 40.5 hours and cost $30,000.  

KEY FINDINGS AND SUGGESTIONS

The key findings and suggestions of the RSA are summarized in Table 8. Several of the measures

were initiated in 2007, shortly after the completion of the RSA. A number of measures have

since been implemented or are programmed for coming years. Out of all the measures

suggested, only the flattening of roadside slopes is not being considered or evaluated

further due to a lack of available right‐of‐way and cost issues.

Table 8. Summary of Safety Issues and Suggestions:

RSA of Bullhead Parkway (part 1 of 3).

Suggestions Implementation Location/Extent Cost Roadside and Edge Drop‐offs

Flatten embankment slopes to 4:1; lay back cut

slopes

Not Implemented N/A N/A

Install guardrail where embankment slopes are

steeper than 4:1

Implemented (Jan to Jun

2008)

All over Parkway Approx. $100,000

Request that developers move concrete blocks Implemented (Jan 2008) North of Lauglin Ranch

Boulevard

Nominal

In addition to constructing 8‐ft shoulders with

rumble strips along the outside lanes, provide

4‐ft shoulders with rumble strips along the

median lanes; in interim, maintain and

stabilize shoulders

Paving shoulders, inside

and outside with rumble

strips (May 2008)

All over Parkway $565,228  

Median

If median crossover crashes increase, consider

median barrier, particularly on the southern

end

Not implemented,

crossover crashes have

been zero

N/A N/A

At non‐traversable median drains, raise the

catch basin and provide a concrete apron with

6:1 slopes; then remove object markers and

delineators

All center median storm

drains raised to grade per

ADOT standards; all posts

and signs removed (Jan to

Oct 2008)

All over Parkway 20 x $1,000 each

$20,000

Perform routine maintenance on catch basins,

pipes, and grates

Being implemented (Jan

through Dec 2008)

All over Parkway Ongoing operational

costs

If landscaping median, use vegetation that

grows no higher than 4 ft with mature trunk

diameters no larger than 4 in

Decided not to landscape

median

N/A N/A
Road Safety Audits: An Evaluation of RSA Programs and Projects

25	

       Table 8. Summary of Safety Issues and Suggestions:  

RSA of Bullhead Parkway (part 2 of 3).

Suggestions Implementation Location/Extent Cost Median

Extend guardrail at locations where hazards

are not adequately shielded

Guardrail installed in front of new

traffic signals standards on East side

(Mar 2008)

75‐ft. on Montano

Place

$5,000  

Remove unwarranted guardrail just south of

Montano Place

Guardrail removed on W side (Feb

2008)

South of Montano

Place

$500  

Stiffen guardrail in front of power pole just

south of Montano Place

Double guardrail installed (Mar 2008) South of Montano

Place

$250  

Address erosion problems at guardrail

sections near milepost 9

Implemented (Apr 2008) Milepost 9 $1,000  

Remove unneeded curb sections Still to be done N/A N/A

Provide post block‐outs at remaining

curb/guardrail locations

Implemented (Jan thru Dec

2007/2008)

Several areas on

Parkway

$5,000  

For future curb installations, use sloping curb

no higher than 4 inches installed flush with or

behind the guardrail

No more curb installed N/A N/A

When replacing terminals, install energy‐

absorbing terminals

Replaced about 30 in 2008 ‐ 2010, 20

planned for FY 2011 using HSIP Grant

All over Parkway 20 x $4,000

per terminal

$80,000

Signage

Install hill signs showing percent grade with a

45 mph speed plaque on southbound section

south of North Oatman Road

Still to be done N/A N/A

Use 150‐ft spacing for flexible delineators in

curves

Implemented (May 2008) 300‐ft spacing $14,000  

Install two‐direction large arrow signs on far

side of T intersections

W1‐7 sign installed at T intersections

(Feb & Mar ‘08)

All over Parkway $2,000  

Remove unnecessary intersection warning

signs

D‐3 signs installed for advance

warning; all yellow advance warning

signs removed (Jan to Oct 2008)

All over Parkway Nominal

Install advance street name signs in advance

of side streets

Y‐ D‐3 signs installed for advance

warning; all yellow advance warning

signs removed (Sep and Oct 2008)

All over Parkway $1,500  

At southbound approach to Desert Hills

Boulevard, replace the intersection warning

sign with the existing signal ahead sign

Southbound signal ahead sign moved

150 ft north around curve (Jan 2008)

At Desert Foothills

Boulevard

Nominal

Where signs are closely spaced, move farther

apart

Implemented (Feb 2009) All over Parkway Nominal

Where signs are within 10 ft of the road,

move farther away

All signs in shoulders moved to 8+ ft

from travel lane (May 2008)

All over Parkway Included in

cost of

shoulder

work

Install object markers at Circle K driveway

island

Delineation installed on porkchop

island (Jan 2008)

At Circle K on

Adobe Road

Nominal

When replacing signs, use higher intensity

sheeting and next larger size

Started using current standard Jan

2009

All over Parkway Nominal

extra cost
Road Safety Audits: An Evaluation of RSA Programs and Projects

26	

Table 8. Summary of Safety Issues and Suggestions:  

RSA of Bullhead Parkway (part 3 of 3).

Suggestions Implementation Location/Extent Cost Markings

Extend the northbound right‐turn lane at Adobe

Road and the southbound right‐turn lane at

North Oatman Road

Right‐turn lane EB to SB

lengthened (Mar 2008)

At Adobe Road &

North Oatman

Road

$5,000  

Provide "dribble lines" for northbound right‐turn

lane at Adobe Road

White blocks installed across

entrance to guide around curve

(Mar 2008)

At Adobe Road Nominal

Update pavement markings and consider using

thermoplastic markings and 6‐inch wide edge

and lane lines

Scheduled for 2010 All over Parkway $300,000

HSIP Grant

Install RPMs on the inside edge line (20‐ft

spacing) and on the lane lines (40‐ft spacing)

Reflective RPMs will be installed

on both sides of Parkway.

Scheduled for 2010.

All over Parkway $50,000

HSIP Grant

Use grinding for future pavement marking

eradication

None needed N/A N/A

In the future, consider use of offsets for left‐turn

lanes

None needed N/A N/A

Signals

Inspect signal display brightness level on

northbound approach to Silver Creek Road

Implemented (Jan 2008) Silver Creek Road

signal

Nominal

Remove pedestrian signals at Silver Creek Road,

Laughlin Ranch Boulevard, and Montano Place

Still evaluating N/A N/A

If pedestrian activity increases, provide ADA‐

compliant pedestrian signals and

accommodations where needed

No increase in pedestrians N/A N/A

Remove middle signals from the mast arms for

the approaches from Adobe Road and replace

with far left signal heads

Signal heads moved (Feb 2009) Adobe Road signal Nominal

For the northbound approach at Adobe Road,

install a longer mast arm and adjust the signal

head locations for proper lane alignment

Purchased arm but still need to

install

N/A N/A

Other Observations

Measure superelevation in the field and if found

insufficient, address in future paving projects

Will do part of future paving N/A N/A

Replace temporary stop sign at Montano Place

with a higher sign (5‐ to 7 ft high)

Implemented (Jan 2008) Montano Ridge

signal

Nominal

Initiate discussion with Laughlin casinos/area

employers to address fatigued driver problem

Implemented (Mar 2007 and Oct

2008)

N/A None, as no

action taken
Road Safety Audits: An Evaluation of RSA Programs and Projects

27	

The following photos illustrate safety issues observed during the RSA (“before” on left) and the

subsequent improvements resulting from the RSA suggestions (“after” on right).

Nontraversable median drains. Raised traversable median drains.

Out‐of‐date end terminals. Current standard end terminals.

T‐intersection signing. Enhanced T‐intersection signing.
Road Safety Audits: An Evaluation of RSA Programs and Projects

28	

Short right‐turn lane. Extended right‐turn lane.

The cost, to date, of the suggestions implemented based on the findings totaled

$839,478 (plus several nominal fee projects). These measures were paid for largely through

Bullhead City’s Capital Improvement Program. To cover the cost of programmed projects directly

related to the RSA, the City completed local government Highway Safety Improvement Program

(HSIP) grant applications and submitted to ADOT in the amount of $403,000. An additional

$382,000 was also applied for to complete projects along the Parkway that were outside of the

RSA suggestions. This amount included $200,000 for signal design and construction at the

intersection with N. Oatman Road; $170,000 for the construction of a southbound right‐turn lane

at the intersection with Silver Creek Road; and $12,000 for the construction of ADA‐compliant

ramps at the corners of the intersection with Adobe Road.

In general, ADOT and Bullhead City viewed the RSA as a great success. For its efforts in garnering

funds and implementing improvements, Bullhead City was presented with an “RSA Champion”

award by ADOT and FHWA during the inaugural Arizona Traffic Safety Summit in 2009. ADOT

district personnel have seen the value in RSAs, as the representative team member for this RSA

has participated in several others since. The City has also accepted the RSA process and its

benefits; two additional RSAs have been conducted in Bullhead City since the completion of the

one along Bullhead Parkway. The City has also received some educational benefit from this RSA

in terms of roadway and roadside hazard safety. For example, the City had previously installed

trees along a low‐speed facility as landscaping. A similar application was suggested by the City for

use along the median of Bullhead Parkway; however, the use of large‐diameter trees (i.e.,

greater than four inches wide) along the roadside of a high‐speed facility is not conducive to

safety, as the landscaping presents fixed object hazards.
Road Safety Audits: An Evaluation of RSA Programs and Projects

29	

RSA OUTCOMES

Geometric, traffic volume, and crash data were collected for both treatment and comparison

sites in Arizona. The treatment site consisted of two consecutive segments that were divided at

the point where the traffic volume changed. Data were provided by direction for the

comparison site because certain roadway characteristics differed between the two directions.

Similar to the treatment site, the comparison site was split into two segments at the point

where the traffic volume changed. Table 9 provides a summary of the treatment and

comparison site data.

Table 9. Summary of Arizona Data.

Variable

Treatment

Site

Comparison

Site SB

Comparison

Site NB

Number of segments 2 2 2

Months before 60 60 60

Months after1 23 23 23

Total crashes/mile‐year before 4.76 0.58 0.66

Total crashes/mile‐year after1 2.25 0.99 0.61

Injury crashes/mile‐year before 2.35 0.28 0.29

Injury crashes/mile‐year after1 1.13 0.40 0.29

Intersection‐related crashes/mile‐year before 1.75 0.04 0.06

Intersection‐related crashes/mile‐year after1 1.64 0.05 0.08

AADT

Before

Average 13,092 3,767 3,767

Minimum 12,874 3,050 3,050

Maximum 13,310 4,456 4,456

AADT

After

Average 11,615 3,908 3,908

Minimum 11,490 3,609 3,609

Maximum 11,740 4,511 4,511

Area type Rural Rural Rural

Number of Lanes 4 2 2

Median Type Unpaved Unpaved Unpaved

Median Width (ft) 16 80 80

Shoulder Type Unpaved Unpaved Paved

Shoulder Width (ft) 8 8 10

Posted Speed (mph) 50 65 65

1

Includes 2008 and 11 months in 2009
Road Safety Audits: An Evaluation of RSA Programs and Projects

30	

In Arizona, the countermeasures implemented as a result of the RSA were mostly implemented in

2008; however, some countermeasures were implemented in 2009 and after. Thus, the after

period conditions were continuously changing for the treated segments. Recognizing the

changing conditions and the limited after period, the analysis was run for two after periods.

The first after period was based on data from 2008 and the first 11 months of 2009. The

second after period only considered the first 11 months of 2009.

The analysis did not account for regression‐to‐the‐mean because the empirical Bayes (EB)

approach could not be applied. However, it was possible to investigate the potential for

regression‐to‐the‐mean. Specifically, the yearly crash counts for both total and injury crashes

were plotted over time for the treatment site, as shown in Figure 3. The period from 2003 to

2007 is relevant to the potential for regression‐to‐the‐mean. If present, one would expect to see

a spike in crash counts prior to the RSA being conducted in 2007. The plot indicates the potential

for regression‐to‐the‐mean for both total and injury crashes. Notably, the annual crash counts

appear to spike for the three‐year period from 2004 to 2006 and then decrease in 2007, prior to

the implementation of any countermeasures from the RSA.

In this case, the potential regression‐to‐the‐mean bias could result in an overestimation of the

expected safety effects of the treatments. As such, the analyses were run with and without

the three years of suspect data (2004 to 2006) to investigate the magnitude of the regression‐to‐

the‐mean bias.

Figure 3. Treatment Site Crash Totals Over Time.
Road Safety Audits: An Evaluation of RSA Programs and Projects

31	

The following points should also be noted with respect to the analysis:

• For the comparison group method, total crashes in the before and after period at the

comparison sites were used to account for general temporal trends in total and intersection‐

related crashes. Note that total crashes at the comparison sites were used to adjust the

intersection‐related crashes at the treatment sites due to limited intersection‐related

crashes at the comparison sites. Injury crashes at the comparison sites were used to adjust

for injury crashes at the treatment site.

• When accounting for changes in traffic volume, a linear relationship was assumed between

crashes and traffic volume. With a limited variation in traffic volumes it was not possible to

develop an SPF or evaluate the suitability of existing SPFs to model the true relationship.

Given the inherent uncertainty in other aspects of the analysis, and the relatively small

changes in annual average daily traffic (AADT), this assumption was not deemed crucial.

• The suitability of the comparison group could not be rejected using the methods described

by Hauer (1997). As such, the comparison site is deemed reliable for use in the comparison

group method.

The results of the Arizona analyses are presented in Tables 10 – 13. Note that separate results

are provided for each of the following:

1. Comparison‐group method, including entire before period.

2. Comparison‐group method, excluding years 2004 to 2006 from the before period.

3. Naïve method, including entire before period.

4. Naïve method, excluding years 2004 to 2006 from the before period.

Note that each table includes two sets of results, one considering 2008 in the after period and

another excluding 2008 from the after period. Results that are statistically significant at the five

percent level are noted in bold.

Table 10. Comparison Group Results from Arizona Including Total Before‐Period.

Crash Type

C‐G Method Including 2008 C‐G Method Without 2008

Observed

Crashes

After

Expected

Crashes

After

CMF

(Standard

Error)

Observed

Crashes

After

Expected

Crashes

After

CMF

(Standard

Error)

Total 44 116.29 0.339 (0.113) 17 54.96 0.277 (0.104)

Injury 22 52.05 0.361 (0.143) 7 26.90 0.221 (0.106)

Intersection‐Related 32 39.21 0.683 (0.272) 15 21.24 0.572 (0.254)
Road Safety Audits: An Evaluation of RSA Programs and Projects

32	

Table 11. Comparison Group Results from Arizona, Excluding 2004 to 2006.

Crash Type

Observed

Crashes

After

Expected

Crashes

After

CMF

(Standard

Error)

Observed

Crashes

After

Expected

Crashes

After

CMF

(Standard

Error)

Total 44 84.53 0.462

(0.159)

17 38.98 0.386

(0.149)

Injury 22 36.72 0.501

(0.206)

7 18.48 0.315

(0.154)

Intersection‐ 

Related

32 36.56 0.698

(0.297)

15 19.26 0.604

(0.280)

Table 12. Naïve Results from Arizona, Including all Before‐Period Years.

Crash Type

Observed

Crashes

After

Expected

Crashes

After

CMF

(Standard

Error)

Observed

Crashes

After

Expected

Crashes

After

CMF

(Standard

Error)

Total 44

83.12

0.527

(0.086)

17

39.75

0.426

(0.106)

Injury 22

41.02

0.532

(0.122)

7

19.62

0.354

(0.136)

Intersection‐ 

Related

32 30.16 1.049

(0.214)

15 14.42 1.028 (0.284)

Table 13. Naïve Results from Arizona, Excluding 2004 to 2006.

Crash Type

Observed

Crashes

After

Expected

Crashes

After

CMF

(Standard

Error)

Observed

Crashes

After

Expected

Crashes

After

CMF

(Standard

Error)

Total 44

71.09

0.612

(0.113) 17 34.00

0.494

(0.130)

Injury 22

102.54

0.213

(0.049) 7 49.04

0.142

(0.055)

Intersection‐ 

Related

32 75.40 0.420

(0.086)

15 36.06 0.411

(0.114)

The results indicate a general safety benefit of conducting the RSA and implementing the

treatments suggested in the RSA report. For total and injury crashes, the estimated crash

modification factor (CMF) is consistently less than 1.0 for all variations of the analysis,

indicating a reduction in expected crashes. Further, the reductions in total and injury crashes

are substantial and highly significant. With respect to intersection‐related crashes, the results

generally indicate a safety benefit with two exceptions, which are not statistically significant.
Road Safety Audits: An Evaluation of RSA Programs and Projects

33	

While there are several variations of the analysis, the results from the comparison group

method are preferred over the naïve before‐after results. The estimated crash reductions are

generally larger for the comparison group method than for the naïve method. This is due to

the observed increase in crashes at the comparison site in accounting for time trends.

However, the naïve method does appear to corroborate the results of the comparison group

method. The remainder of the discussion is focused on the results of the comparison group

method but generally applies to the naïve results, as well.

The estimated crash reductions are generally smaller when the 2004 to 2006 data are not

included in the before period. This confirms the suspicion that regression‐to‐the‐mean may be

present. Therefore, the results from Table 11 (Comparison Group Results Excluding 2004 to

2006) provide a more conservative estimate of the safety effects than Table 10. Within each

table, the estimated crash reductions are larger when 2008 is excluded from the after

period. This is not surprising, as countermeasures were implemented throughout 2008 and

2009. As such, the analyses that include 2008 in the after period provide conservative

estimates of the safety effect.

Table 14 presents a summary of the safety benefits estimated from the treatment site in

Arizona. The conservative estimates are based on the comparison group method, excluding

2004 to 2006 from the before period and including 2008 in the after period. The range of

results from both methods and all variations is also presented. The results indicate a 54

percent reduction in total crashes, a 50 percent reduction in injury crashes, and a 30 percent

reduction in intersection‐related crashes.

Table 14. Summary of Results from Arizona.

Conservative Estimate (S.E.) Range of Estimates

Total 0.462 (0.159) 0.277 to 0.612

Injury 0.501 (0.206) 0.142 to 0.532

Intersection‐related 0.698 (0.297) 0.411 to 1.049

The annualized costs and benefits were then compared. Based on the comparison group

method, there was an annual reduction of 21.1 total crashes, 7.7 injury crashes, and 2.4

intersection‐related crashes. Using the FHWA crash costs document, Crash Cost Estimates by

Maximum Police‐Reported Injury Severity within Selected Crash Geometries (Publication Number

FHWA‐HRT‐05‐051), the annual benefits are $1,973,395, $1,582,195, and $222,025 for total,

injury, and intersection‐related crashes, respectively. Assuming a total cost of $869,478

($30,000 for the RSA and $839,478 for the improvements), a discount rate of 2.2 percent, and a

service life of 10 years, the annualized cost is $97,812. Therefore, the B/C ratio of the
Road Safety Audits: An Evaluation of RSA Programs and Projects

34	

improvements made as a result of the RSA is 20:1, 16:1, and 2:1 for total, injury, and

intersection‐related crashes, respectively.

PROGRAM REVIEW

The Arizona DOT (ADOT) uses its RSA program to build collaborative partnerships that

proactively improve safety. RSAs have brought together State, county, and tribal transportation

practitioners to solve complex safety issues.   This has led to long‐standing partnerships

between ADOT, counties, and the tribes where each agency has a better understanding of each

agencies concerns, limitations, and abilities.  This collaborative approach applied through RSAs

has also been helpful in educating local agencies about the risks associated with various crash

types and bringing attention to safety issues at locations that may be lacking crash data.  For

example, a pedestrian crash may be a rare occurrence, but when one occurs, there is often a

high probability of severe injury or death.  ADOT staff brings perspectives to local agencies to

help provide context on the types of operational and geometric characteristics that can

adversely impact pedestrian safety.  In an example of safety issues at locations lacking crash

data, most non‐fatal crashes occurring on tribal reservations are not entered into the state DOT

crash database.  This skews the crash frequencies and rates on reservation roads, many of which

are state‐owned and maintained, making it appear that these roads do not have a crash

problem.  The proactive nature of the RSA provides an opportunity to identify safety issues

without the benefit of crash data and develop appropriate countermeasures to improve road

safety.    

Over time, the RSA program has successfully communicated to design engineers that merely

following standards does not necessarily produce a safe design. The collaborative and

independent approach of the RSA teams to improving safety is changing how design engineers

initially viewed RSAs—from a strict adherence to design standards to a more open discussion

about the safety implications of various designs. The findings from the RSA program have

been used to update the DOT’s policies and standards. The ADOT experience has shown a need

for better upfront coordination with the road owner as a key element to obtain better data and

reports and to determine who should be invited to the RSA meetings. ADOT also recommends a

nighttime site review, even if the crash data does not indicate any issues, and to obtain the law

enforcement perspective in each RSA.
Road Safety Audits: An Evaluation of RSA Programs and Projects

35	

STATE ROUTE 101 (PEAVINE ROAD): CUMBERLAND COUNTY, TENNESSEE

Road: Existing 3.84‐mile section of paved, two‐lane, rural roadway

RSA Sites: • 2 unsignalized intersections

• AADT: 12,860 vehicles per day (2007)

• 45 mph posted speed limit

Environment:  urban/urbanized  suburban  rural

Owners: Tennessee DOT (TDOT); Cumberland County

Road Safety Audit

Date of RSA: 1 November 2005

RSA Stage(s):  planning/design stage  RSA of existing roads

RSA Team:

RSA Cost:

Implementation Cost:

Crash Reduction:

Benefit / Cost Ratio:

9 members representing FHWA and TDOT

$12,000

$23,000

13.7% total; 31.3% injury

51:1 total; 116:1 injury

BACKGROUND

An RSA was conducted along a 3.84‐mile section of State Route 101 (Peavine Road) in

Cumberland County, Tennessee (Figure 4). Throughout this section, State Route 101 is a two‐

lane, rural roadway with a posted speed limit of 45 mph. The AADT was reported as 12,860 vpd

in 2007.

The area of concern was brought to attention by local citizens who perceived the

section of roadway to be dangerous. Consequently, Tennessee DOT (TDOT) Planning staff were

asked to evaluate this section of State Route 101 to determine the need for appropriate safety

measures. Upon reviewing the crash data, the number of reported crashes supported the

public’s concern.
Road Safety Audits: An Evaluation of RSA Programs and Projects

36	

The RSA was conducted along State Route 101 in November 2005 from Peavine Firetower Road

(L.M. 18.31) to Tuttle Lane (L.M. 22.15). The RSA team was comprised of nine members

representing the FHWA, TDOT Headquarters, TDOT Traffic Engineering, and TDOT Planning.

The efforts of the team were led by the TDOT Regional Engineer.

Figure 4. Aerial Map of State Route 101.

Information used by the RSA team to conduct the review included roadway data (i.e.,

geometrics, functional class, route features, etc.), traffic data, and crash data. A comprehensive

list of the available information is as follows:

• Crash data and ambulance call records.

• General statements from citizens.

• Cumberland County general highway map.

• Tennessee Roadway Information Management System (TRIMS) Route Feature

Description Listing.

• TRIMS Photolog.

• TRIMS Crash Data (2001 – 2003, and any available from 2004 and 2005).

• TRIMS Crash Rate Summary Report (01/01/2001 – partial 2005).

• TRIMS Crash Summary Report (01/01/2001 – partial 2005).

• Maps pinpointing crash locations (01/01/2001 – partial 2005).

While no cost information (i.e., consultant fees, time for public officials, etc.) was recorded with

regard to completing the RSA on State Route 101, a typical RSA of this extent costs in the range
Road Safety Audits: An Evaluation of RSA Programs and Projects

37	

of $10,000 to $12,000. For RSAs on the scale of five miles or more, the cost to complete the

entire RSA process increases.

KEY FINDINGS AND SUGGESTIONS

The key findings and suggestions of the RSA are summarized in Table 15. TDOT responded that

all of the suggested measures in the RSA report were installed in May 2006, six months after

the RSA was completed and documented. There were no additional improvements made

beyond those suggested in the RSA report. The cost of the measures implemented based on

the findings of the RSA totaled $23,000. There were no locations along the study corridor that

were eligible for funding by the Hazard Elimination Safety (HES) Program. However, the

segment from L.M. 18.50 to L.M. 18.70 and the location at L.M. 20.81 were eligible for funding

by the High Risk Rural Roads (HRRR) Program, as fatal and/or injury crash rates were in excess

of statewide averages.

Table 15. Summary of Safety Issues and Suggestions: RSA of State Route 101.

Location Safety Issues Suggestions

L.M. 18.50 to

L.M. 18.70

Horizontal

curvature and

vertical

alignment

 Add chevron signs and advance curve warning signs

 Provide extra wide (8‐inch) thermoplastic edgelines

 Restripe 0.2 mi of project limits with new thermoplastic

L.M. 20.81 Limited sight

distance

 Move stop bar to increase sight distance

 Remove trees from right‐of‐way

 Relocate “Beach & Marina →” sign

Horizontal curvature looking south at L.M. 18.50 to

L.M. 18.70.

Vertical alignment looking north at L.M. 18.50 to

L.M. 18.70.
Road Safety Audits: An Evaluation of RSA Programs and Projects

38	

       Limited sight distance looking south at  

L.M. 20.81.

Limited sight distance looking north at  

L.M. 20.81.

In general, the suggestions emerging from the RSA were well‐received by TDOT, local

transportation personnel, and the public. While the RSA was well‐received, TDOT indicated that

they did not observe a noticeable reduction in crashes after the measures were implemented.

The cursory review did not, however, account for other potential changes over time. TDOT also

stated that the effect of the implementation measures may be altered since the time of the

study (i.e., signs are no longer in their suggested locations, vegetation has grown back, etc.). It

was clear that a more formal analysis would be necessary to determine the safety impacts of the

RSA and implemented strategies.

RSA OUTCOMES

Geometric, traffic volume, and crash data were collected for both treatment and reference sites

in Tennessee. The treatment site consisted of a 3.84 mile corridor, and the specific treatments

included the following:

• Segment treatments: add chevron signs, advance curve warning signs, extra‐wide (8‐inch)

thermoplastic edge lines, and new thermoplastic for a portion of the project.

• Intersection treatments: move stop bar to increase sight distance, remove trees from the

right‐of‐way, and relocate sign (“Beach & Marina →”).

The reference sites included 21.46 miles of similar corridors that were selected to match the

treatment site by number of lanes, speed limit, illumination, and shoulder width. Table 16

provides a summary of the treatment and reference site data.

The initial before period included the years 2000 to 2005 and a relatively large multi‐

jurisdictional reference group. Based on an initial examination of the data, it was determined

that some of the years in both the treatment and reference group exhibited an unusual change
Road Safety Audits: An Evaluation of RSA Programs and Projects

39	

in crashes. There was also a wide variation in the annual crash trends among the jurisdictions

from which the reference group was selected. The DOT confirmed this finding and noted that in

2001 they changed the structure of their crash database, which resulted in a loss of data due to

trouble reconciling the two systems. In addition, they developed a new paper report and

implemented it during the period from 2001 to 2002. As a result, it was determined that years

2004 to 2005 would be more suitable for the before period as there were no changes during this

timeframe and the previous changes had taken effect. Due to inconsistencies among the

jurisdictions, it was also determined that the reference group would only include sites from

Cumberland County, the same jurisdiction as the treatment site.  

There was some concern regarding the integrity of the data in the after period. In the period

from 2006 to 2007, TDOT switched to an electronic crash reporting system, and some of the

location information was lost in the report processing (i.e., transferring the data entered by the

police officers to the central database). There are some crash data missing for 2006 and

approximately 10 percent of crashes missing statewide for 2007. Additional crash data were

obtained for 2008 to 2009, and these data are more complete than those from 2006 to 2007.

Table 16. Summary of Tennessee Treatment and Reference Site Data.

Variable

Treatment Group

(2004‐2005 before period)

Cumberland County

Reference Group

Total mileage 3.84 21.46

Mile‐Years Before 7.68 171.68

Mile‐Years After 3.84 171.68

Crashes/Million Vehicle Miles Before 2.77 4.00

Crashes/Million Vehicle Miles After 2.56 3.34

Injury Crashes/Million Vehicle Miles Before 1.00 1.31

Injury Crashes/Million Vehicle Miles After 0.72 4.00

Access Points/Mile (Driveways + Intersections) 4.69

Average 4.67

Min. 0.00

Max. 25.00

AADT Before (vpd) 11,738

Average 2,899

Min. 648

Max. 10,366

AADT After (vpd) 12,860

Average 2,899

Min. 648

Max. 10,366

The analysis considered the entire corridor. The reference group of similar corridors was

used to develop SPFs for use in the EB process. Generalized linear modeling was used to
Road Safety Audits: An Evaluation of RSA Programs and Projects

40	

estimate model coefficients, assuming a negative binomial error distribution, which is

consistent with the state of research. Separate SPFs were calibrated for total and injury crashes.

The general model form for all models is given by Equation 1. Note that annual multipliers were

estimated and added to each model for the appropriate year. The coefficients for each SPF are

presented in Table 17.

Crashes/mile/year = expln(a)(AADT)b expc(dd) (1)

Where:

AADT = annual average daily traffic (vehicles per day).

dd = driveway density (total number of driveways and intersections divided by the segment

length in miles).

a, b, and c = coefficients estimated from the model.

Table 17. Estimated SPFs for Tennessee.

Variable

Crash Type

Total Injury

a (s.e.)  ‐6.1428 (0.6891)  ‐6.7849 (0.6674)

b (s.e.) 0.8602 (0.0961) 0.8089 (0.0899)

c (s.e.) 0.0706 (0.0128) 0.0639 (0.0115)

k (s.e.) 0.4083 (0.0889) 0.2362 (0.0820)

Year Yearly Multipliers

2000 1.16 0.93

2001 1.60 1.97

2002 1.33 1.70

2003 1.76 1.82

2004 1.75 1.55

2005 1.49 1.63

2006 1.56 1.68

2007 1.39 1.54

2008 1.03 0.90

2009 1.22 1.10

The results of the Tennessee analyses are presented in Table 18 for total and injury crashes.

Table 18. EB Corridor Results for Tennessee.

Crash Type Observed

Crashes After

Expected

Crashes After

CMF

(S.E.)

Total 128 146.69 0.863 (0.116)

Injury 36 50.92 0.687 (0.159)
Road Safety Audits: An Evaluation of RSA Programs and Projects

41	

The results indicate a general safety benefit of conducting the RSA and implementing the

treatments suggested in the RSA report. The estimated CMF is consistently less than 1.0 for

both total and injury crashes, indicating a reduction in expected crashes. The reduction in injury

crashes is statistically significant at the 95 percent confidence level, but the reduction in total

crashes is statistically insignificant. Due to the limited crash counts for other crash types, it was

not possible to conduct separate EB analyses for additional target crash types. Instead, a

cursory analysis of the proportion of crash types was undertaken to see if any insights could be

gleaned. Recall that the treatments included both segment‐ and intersection‐related

improvements.

Given the nature of the treatments, the intersection improvements may target rear‐end and

angle crashes, and the segment improvements may target run‐off‐road crashes. The crash

data do not identify run‐off‐road crashes specifically but do indicate single‐ vehicle crashes that

were analyzed as a substitute. Table 19 presents the analysis of crash proportions. There are no

apparent insights in terms of changes in proportions of the various target crash types. Although

there are reductions in the proportion of rear‐end and angle crashes, the apparent effects are

based on numbers that are much too small from which to draw definitive conclusions.

Table 19. Analysis of Proportion of Crash Types in Tennessee.

Crash Type

Treated Site Crash

Count

Treated Site

Proportion Treated Site

Entire Reference

Group

Before After Before After Difference Count Proportion

Total 203 128 1.00 1.00 N/A 1741 1.00

Rear‐end 72 43 0.35 0.34 ‐0.01 359 0.21

Angle 40 15 0.20 0.12 ‐0.08 251 0.14

Single‐vehicle 52 57 0.26 0.45 0.19 670 0.38

The annualized costs and benefits were then compared. Based on the EB methodology for

observational before‐after studies, this study indicated a 13.7 percent reduction in total crashes

and a 31.3 percent reduction in injury crashes over a three‐year “after” period. Using the FHWA

crash costs document, Crash Cost Estimates by Maximum Police‐Reported Injury Severity within

Selected Crash Geometries (Publication Number FHWA‐HRT‐05‐051), the annual reduction of 6.23

crashes results in an annual benefit of $200,830. Assuming a total cost of $35,000 ($12,000 for

the RSA and $23,000 for the improvements), a discount rate of 2.2 percent, and a service life of

10 years, the estimated annual cost is $3,937. Therefore, the B/C of the improvements made as a

result of the RSA is 51:1 based on the estimated change in total crashes.

The annual reduction in injury crashes is 4.97 crashes per year. This results in a range of

annual benefits, from $199,301 per injury crash (assuming all Type C injuries) to $968,432 per
Road Safety Audits: An Evaluation of RSA Programs and Projects

42	

injury crash (assuming all Type A injuries). The estimated cost of a generic injury crash is

$367,668. Based on the same annual cost from above, the injury B/C ranges from 51:1 (Type

C) to 246:1 (Type A). The B/C is estimated as 116:1 for generic injury crashes. These results

indicate a positive effect on safety as a result of the RSA performed on State Route 101.

PROGRAM REVIEW

Selection Process

Each year, TDOT’s safety section generates a list of candidate projects. On average,

approximately 60 projects are selected statewide annually. These projects qualify as either a

Hazard Elimination Safety Project (HESP) or an HRRR project. Three conditions must be met to

qualify as a HESP: 1) locations must have experienced fatal and/or incapacitating injury crashes;

2) a total of seven crashes must have occurred in a three‐year period; and 3) the actual crash

rate must be at least four times the critical rate. (NOTE: crash rates are typically

calculated on a per‐million‐ vehicle‐ miles‐ traveled basis.) Instances that may remove

projects from the HESP list include an unsupportive crash history due to a miscoding of

incidents or other projects already programmed for the location in which a review has been or

will be conducted.

HRRR projects consist of intersection, spot, or short segment locations. Like HESPs, these

locations must have experienced fatal and/or incapacitating injury crashes, three total crashes

must have occurred in a three‐year period, and the severe crash rate must exceed the statewide

average severe crash rate for similar locations.

In addition to the approximate 60 projects each year, additional localized projects are request‐

based. Requests are typically submitted via the comments section on TDOT’s website, through

locally‐elected officials, or by public contact with TDOT regional offices. To be considered for

review, crash data must indicate that the location has experienced a fatal and/or incapacitating

injury crash, a total of three crashes must have occurred during a three‐year period, the total

crash rate must exceed the statewide average crash rate, and the severe crash rate must exceed

the statewide average severe crash rate for similar sections. Although the statistics are

calculated for a three‐year period, it is recommended that data be studied for at least a six‐

year period to get a more thorough understanding of the severe crash history. The

qualifying statistics can be developed based on any consecutive three years of the six‐year

period. On average, approximately 10 request‐based projects are selected each year. Those

locations that do not meet the requirements or are not selected are passed on to the regional

engineer for a maintenance review or to be included in the “Spot Safety” program.

RSA Process

TDOT conducts spot or section RSAs – called Road Safety Audit Reviews (RSARs) by TDOT – on

Interstates, State roads, and local functionally‐classified roadways. For non‐classified roadways,
Road Safety Audits: An Evaluation of RSA Programs and Projects

43	

TDOT depends on the county or city to provide the appropriate data. RSAs on these facilities

are generally request‐based. The total number of RSAs conducted throughout the State

typically varies from year to year.

Since the RSA on State Route 101 in 2005, the TDOT safety team has become more defined;

thus, RSAs are conducted in a more efficient and cost effective manner. In‐house RSAs are

typically led and written by the project planning team. When consultants are involved, the team

manages consultant activities. TDOT conceptual and National Environmental Policy Act (NEPA)

planning personnel handle the RSA improvement cost estimates and development of layout

sheets (design plans scaled down for field review purposes).

The size of an RSA team is typically 10 to 12 people. The team members represent TDOT

Traffic Engineering, Planning, Design, Maintenance, Right‐of‐way, and Construction. Other

agencies represented include regional metropolitan planning organizations (MPOs), rural

planning organizations (RPOs), and law enforcement. The TDOT Bike and Pedestrian

Coordinator is also generally contacted for input. Generally, the RSA team is led by the TDOT

Regional Engineer.

Information typically requested for purposes of conducting RSAs includes crash data, traffic

data, and design plans. In terms of crashes, data from the most recent five years are

used for HRRR projects, and the most recent three years of crash data are used for HESP

projects. The most recent year of traffic data is used. When applicable, turning movement

counts are analyzed or may be conducted. Lastly, design plans are used to generate layout

sheets to show problematic areas/issues and locations for potential improvements (e.g., sign

placement, geometric/alignment changes, etc.).

In general, TDOT indicates that the time from when crash data reports are first pulled to the

time when the RSA report is officially signed is typically between 2 and 2‐1/2 months. The

following is a list of the order of events and the associated time requirements:

1. Candidate projects are ranked in order of their severity index ( from the most

severe to the least severe), as calculated from the HSIP list.

2. A packet of crash reports and crash rate summary sheets are received. Crash rate

sheets are supplied for in‐house RSAs only; consultants generate their own.

Information is distributed to the RSA team prior to the pre‐brief meeting.

3. The pre‐brief/background meeting is scheduled and the RSA time and location are set.

Usually the RSA is conducted within one week of the pre‐brief meeting.

4. For an RSA of one location, the draft report is developed within two weeks of the site

visit. For a n RSA conducted at multiple locations or along a corridor, the draft

report is developed within three to four weeks of the site visit.

5. The draft report is reviewed over a one‐ to two‐week period.
Road Safety Audits: An Evaluation of RSA Programs and Projects

44	

6. The draft report is edited within a two‐week period.

7. The project manager (typically the TDOT Regional Engineer) verifies that changes

have been made and then submits the RSA report to the director for review. At this

point, the director may accept and sign the report; however, it is typical that the

director will have comments to be addressed.

8. The report is typically finalized within one week of the Director’s review.

9. The report is distributed to all RSA team members, both electronically and by

hard copy.

10. The report is submitted to the TDOT environmental section, which typically takes one

to two weeks to issue a “programmatic categorical exclusion (CE).”

11. The report is submitted to the TDOT funding section, where a project number is

received. The project is then submitted for implementation.

Figure 5 illustrates TDOT’s RSA process through the development phase.
Road Safety Audits: An Evaluation of RSA Programs and Projects

45	

Figure 5. RSAR Review Flow Chart: Development Phase.
Road Safety Audits: An Evaluation of RSA Programs and Projects

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Implementation

On average, implementation occurs approximately 18 months from the start of the RSA process.

TDOT indicates that this time period is highly variable, as “political motivation” occasionally

drives implementation scheduling. Figure 6 illustrates TDOT’s RSA process through the

implementation phase.

Figure 6. RSAR Review Flow Chart: Implementation Phase.

Funding for implementing RSA improvement measures may come from HRRR funds or HESP

funds. For HRRR projects, TDOT has a self‐imposed “soft cap” of $50,000 per project. For HESP

projects, TDOT has a self‐imposed “soft cap” of $1,000,000 per project. This self‐imposed cap is

intended to limit the project extents and the type of improvement measures to be

considered. Funding in excess of the cap will be approved when necessary, but these

occurrences are very rare. Local officials generally exhibit an interest in RSAs due to funding
Road Safety Audits: An Evaluation of RSA Programs and Projects

47	

obligations. For projects not on TDOT’s 100 percent funding list, locals have to match 10

percent of the total project cost.

At the time of the State Route 101 RSA, the implementation was somewhat rapid, being only six

months from approval. This quick turnaround time was likely due to TDOT Maintenance

involvement. However, since that time, all projects (including signing and marking) are let out to

contract. Projects with a lower dollar amount are bundled together, adding time to

implementation because of the need to wait for multiple projects to accumulate. Projects with a

higher dollar amount may be implemented in a shorter timeframe, unless right‐of‐way

acquisition is involved. In either case, contracting the work rather than using State forces has

added significantly to implementation time. TDOT Maintenance divisions—which are

responsible for implementation—are trying to reestablish the means to use on‐call contractors

rather than let out every project to contract.

TDOT is not aware of any problems with implementing RSA suggestions. Typical questions of

“concern” include, “Why aren’t we spending more (in terms of improvements)?” and “Why can’t

we (TDOT Maintenance) pay to do the work now and get reimbursed later?” In general,

suggestions and improvements at all RSAs are well received. All stakeholders (i.e., TDOT, local

agencies, and the public) seem pleased to see that strides are being made to improve roadway

safety.

TDOT monitors each RSA location for a three‐year period from the notice of completion. If there

is a recurring problem within the three‐year period, TDOT reevaluates the improvement

measures and makes adjustments, as necessary. Each year, the locations from the HRRR and

HSIP lists are reentered into TDOT’s database to see if they come up again as repeat critical

locations.

Since the time of this project in 2005, the RSA process has become more formalized and

uniform. TDOT has developed a manual to guide the RSA process, to explain project and data

needs, and to establish a “boilerplate” report format. TDOT has described the RSA as a “living

process”; TDOT is consistently finding ways to improve the RSA process, making it better along

the way.  
Road Safety Audits: An Evaluation of RSA Programs and Projects

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COLLIER BOULEVARD AT GOLDEN GATE PARKWAY: COLLIER COUNTY, FLORIDA

Road: Existing intersections along paved, four‐lane, divided roadway

RSA Sites: • Three‐legged, signalized intersection

• Adjacent unsignalized intersection at Collier Boulevard / 25th Avenue

• AADT: 18,000 – 24,000 vehicles per day (2005)

• 45 mph posted speed limit

Environment:  urban/urbanized  suburban  rural

Owners: Florida Department of Transportation (FDOT); Collier County

Road Safety Audit

Date of RSA: 12 July 2005

RSA Stage(s):  planning/design stage  RSA of existing roads

RSA Team:

RSA Cost:

Implementation Cost:

Crash Reduction:

Benefit / Cost Ratio:

2 teams of 4 – 5 members representing the consultant, County engineers, non‐ 

engineers (i.e., technician), and law enforcement (County Sherriff Department)

$15,000

$250,000

11% total; ‐10% injury (note the “‐“ sign denotes an increase)

5:1 total; ‐3:1 injury

BACKGROUND

An RSA was conducted at the intersection of Collier Boulevard and Golden Gate Parkway in

Collier County, Florida (Figure 7). The intersection was chosen based on a definitive crash issue.

Consequently, Collier County decided to evaluate this intersection to determine the need for

appropriate safety measures. Additionally, upgrades desired at this particular location were

wrapped into the RSA process. Due to its close proximity, the RSA team also evaluated the

adjacent unsignalized intersection at Collier Boulevard/25th Avenue. The County used the RSA

for a n in‐house design of median closures and directional turns.
Road Safety Audits: An Evaluation of RSA Programs and Projects

49	

Figure 7. Aerial Map of Collier Boulevard/Golden Gate Parkway.

The RSA was conducted by two teams, with each having four to five members. The teams were

comprised of consulting staff, County engineers, nonengineers (technicians), and law

enforcement (County sheriff’s department). The efforts of the teams were led by the consultant

with direct oversight by County personnel.

Information used by the RSA teams to conduct the review included the following:

• Crash data (2002 – 2004, potentially partial 2005).

• Traffic data (2002 – 2004, potentially partial 2005).

• Aerial imagery.

Overhead maps were provided for use by the consultant to indicate problem areas and issues

and to draw potential improvements (e.g., sign placement, geometric/alignment changes, etc.).

If design plans were used, County personnel indicate that they were probably very old and out

of date.

For this RSA, three hours (total) were required to hold the opening and closing meetings. The

two RSA teams spent two days in the field reviewing the study locations. Both teams reviewed

the same locations: one team started on Collier Boulevard, while the other started on Golden
Road Safety Audits: An Evaluation of RSA Programs and Projects

50	

Gate Parkway. A night review was also conducted by members of each team, although not all

members from each participated. Each team completed RSA reports immediately following the

site visits. The consultant compiled the reports written by the RSA teams. If one team felt more

strongly about a particular issue or observation than the other team, the team’s remarks were

identified as “Team A” or “Team B” in the report. The draft report was submitted by the

consultant to the County within one week after completion of the field reviews. In addition to

meeting and field review time, the consultant traveled four hours each way to perform the RSA.

Total cost to complete the RSA (including consultant fees) was $15,000.

KEY FINDINGS AND SUGGESTIONS

The key findings and suggestions of the RSA are summarized in Table 20. County personnel

responded that all of the suggested improvement measures in the RSA report were installed

between January and March 2006, approximately six months after the RSA was completed and

documented. There were no additional improvements made beyond those suggested in the

RSA report. The costs of the measures implemented based on the findings of the RSA

totaled $250,000. This amount covered design through construction activities. These

improvements were funded by gas tax revenues. County personnel indicated that the tax source

may be County and State, as well as Federal.
Road Safety Audits: An Evaluation of RSA Programs and Projects

51	

Table 20. Summary of Safety Issues and Suggestions:

RSA of Collier Boulevard & Golden Gate Parkway.

Safety Issues Suggestions

Signing and Marking

 Object markers obscured by signal poles on EB Golden

Gate Pkwy

 End of Golden Gate Pkwy not clearly defined. Need to

enhance signing

 NB approach not well marked

 Route markers on all approaches poorly placed and

obscured

 Street name signs poorly placed. NB visibility is particularly

poor

 Relocate obscured object markers

 Install overhead signing

 Add supplemental plaque for 25th Ave. SW

to cross street sign on NB approach

 Review and revise placement of route

marker and destination signing

 Improve placement of street name signs

Intersection Geometry

 EB left‐turn lane confusing: (1) opportunity to make two

left‐ turn movements out of a single lane (41st St. SW, alley

to east); (2) possible misinterpretation of lane use

 U‐turns observed to cross over island at plaza just east of

41st St. SW

 Provision for SB left turns to 25th Ave. SW impacts queue

space on Collier Blvd

 WB to SB left turn can be blocked by 2‐stage left‐turn

movements

 Cut median nose back to facilitate U‐turns

just east of 41st St. SW.

 Modify median opening providing access to

25th Ave. SW.

 Consider median closure

Visibility, SightDistance  SB sight distance issues from inside lane with NB through.

Problem compounded when left‐turning vehicle from 25th

Ave. SW to SB.

 Median hedges impact visibility for NB and SB left‐ turn and

U‐turn movements

 Trim vegetation in median

PedestrianAccommodations  No sidewalk on south side  Review sidewalk needs

 Confirm pedestrian phasing will be installed
Road Safety Audits: An Evaluation of RSA Programs and Projects

52	

The following photos illustrate safety issues observed during the RSA (“before” on left) and the

subsequent improvements resulting from the RSA suggestions (“after” on right).

SB left‐turn lane to 25th Ave. SW (before).    SB left‐turn lane to 25th Ave. SW (after). SB left

only; no WB left.

EB median nose at plaza just east of 41st St. SW

(before).

EB median nose at plaza just east of 41st St. SW

(after). Nose cut back.

In general, the suggestions resulting from the RSA were well‐received by County personnel, law

enforcement, and the public. Residents near the study intersection were satisfied with the

changes, as access into the residential area across the canal at 25th Street was improved.

Overall, a qualitative improvement in safety has been observed. County personnel also

indicate that, in the long term, the measures implemented have eased traffic flow through the

intersection. Drivers are now more expectant of the maneuvers to be made, enhancing the

traffic flow and overall intersection safety.

Those involved with this RSA were also satisfied with the process. In the end, the County

decided that they probably didn’t need two teams to complete this RSA. County personnel

indicated that one team could complete the same amount of work required and still come up

with the same conclusions.
Road Safety Audits: An Evaluation of RSA Programs and Projects

53	

RSA OUTCOMES

Geometric, traffic volume, and crash data were collected for both treatment and reference sites

in Florida. The treatment sites consisted of one signalized intersection (Collier

Boulevard/Golden Gate Parkway) and the nearby unsignalized intersection (Collier

Boulevard25th Avenue Southwest). The RSA considered both locations because the

improvements at 25th Avenue Southwest included the prohibition of left‐turns from one

direction, which now requires that those vehicles first turn right and make a U‐turn at the

intersection with Golden Gate Parkway. The reference sites consisted of 22 untreated signalized

intersections that were otherwise similar to the treated signalized intersection. A specific

reference group was not available for the unsignalized treatment site, but the signalized

reference group was utilized to adjust for specific trends. (This is discussed further in analysis

section.) Table 21 provides a summary of the treatment and reference site data.

Table 21. Summary of Florida (Collier Boulevard) Data.

Variable Signalized

Intersection

Unsignalized

Intersection

Signalized Reference

Group (22 Sites)

Years before 1 1 4.58 years/site

Years after 2.75 2.75 4.58 years/site

Total Crashes/year before 43.0 22.0 Average 21.8/site/yr

Total Crashes/year after 35.3 7.3 Average 21.8/site/yr

Injury Crashes/year before 4.0 3.0 Average 1.8/site/yr

Injury Crashes/year after 4.0 1.5 Average 1.8/site/yr

Left‐Turn Crashes/year before 6.0 4.0 Average 1.4/site/yr

Left‐Turn Crashes/year after 3.6 0.7 Average 1.4/site/yr

Rear‐End Crashes/year before 18.0 3.0 Average 9.3/site/yr

Rear‐End Crashes/year after 10.9 2.2 Average 9.3/site/yr

Sideswipe Crashes/year before 5.0 3.0 Average 2.4/site/yr

Sideswipe Crashes/year after 4.4 0.7 Average 2.4/site/yr

Major AADT before 29,160 30,552 Average 32,564

Major AADT after 26,130 27,173 Average 32,564

Minor AADT before n/a 20,501 Average 18,452

Minor AADT after n/a 18,455 Average 18,452
Road Safety Audits: An Evaluation of RSA Programs and Projects

54	

The signalized reference group was used to develop SPFs for use in the EB process. Generalized

linear modeling was used to estimate model coefficients, assuming a negative binomial error

distribution, which is consistent with the state of research. Separate SPFs were calibrated for

each target crash type. Since minor road AADTs were only available for some of the reference

sites, only the major road AADT was considered as an exposure variable in the models.

The general model form for all models is given by Equation 2. Note that annual multipliers were

estimated and added to each model for the appropriate year. The coefficients for each SPF are

presented in Table 22.

Crashes/year = exp(a)(MajAADT)b (2)

Where:

MajAADT = major road AADT

a and b = coefficients estimated from the model

Table 22. Estimated SPFs for Florida.

Crash Type A (s.e) B (s.e.) K (s.e.) Yearly Multipliers

Total ‐5.4177

(3.6207)

0.8194

(0.3501)

0.2903

(0.0868)

2005=1.24

2006=1.19

2007=1.11

2008=0.81

Injury ‐3.33078

(4.0671)

0.3766

(0.3929)

0.2277

(0.1063)

Left‐Turn ‐10.0017

(4.3556)

0.9919

(0.4191)

0.2509

(0.1213)

Rear‐End ‐4.1189

(3.5534)

0.6126

(0.3435)

0.2599

(0.0825)

Sideswipe ‐14.7367

(5.9866)

1.4985

(0.5774)

0.6233

(0.2119)

The EB method could not be applied to estimate the number of crashes without treatment at

the unsignalized intersection because a suitable reference group was not provided. For this

location, the expected number of crashes without treatment was estimated by the before

period crash counts and several factors. The first factor was used to adjust for the different

lengths of the before and after periods and was computed as the ratio of the duration of the

after period to the before period. The second factor was used to adjust for the change in traffic

volume between the before and after period and was computed as the ratio of AADT in the

after period to before period. (Note that this adjustment assumes a linear relationship between

traffic volume and crashes, which may not be valid for large changes from the before to the
Road Safety Audits: An Evaluation of RSA Programs and Projects

55	

after period). The final factor was used to adjust for general temporal trends and was computed

as the ratio of SPF estimates in the after period to the before period.

The results of the Florida analyses for Collier Boulevard are presented in Table 23. Note that

specific results are provided for total, injury, left‐turn, rear‐end, and sideswipe crashes. Results

are presented separately for the unsignalized treatment site, the signalized treatment site, and

the two sites combined.

The results indicate a general safety benefit of implementing the treatments at the unsignalized

intersection. As expected, the elimination of westbound left‐turns resulted in a substantial and

significant reduction in several crash types, including total, injury, left‐turn, and sideswipe

crashes. There was also a reduction in rear‐end crashes, but the result was not statistically

significant.

As might be expected, there was an increase in several crash types at the signalized intersection,

potentially due to the increase in turning movements after the westbound left‐turns were

eliminated at the adjacent unsignalized intersection. Specifically, there was an increase in total,

injury, left‐turn, and sideswipe crashes at the signalized intersection; however, these increases

are highly insignificant. There does appear to be a reduction in rear‐end crashes at the signalized

intersection, but, again, the result is highly insignificant.

Table 23. EB Results from Florida.

Crash Type

25th Avenue Southwest Golden Gate Parkway Both Locations Combined

Observed

Crashes

After

Expected

Crashes

CMF

(S.E.)

Observed

Crashes

After

Expected

Crashes

CMF

(S.E.)

Observed

Crashes

After

Expected

Crashes

CMF

(S.E.)

Total 20 45.19 0.423

(0.125)

97 84.06 1.130

(0.197)

117 129.25 0.892

(0.134)

Injury 4 6.16 0.487

(0.279)

11 6.08 1.616

(0.662)

15 12.25 1.100

(0.419)

Left‐Turn 2 8.22 0.195

(0.135)

10 5.70 1.594

(0.648)

12 13.92 0.781

(0.306)

Rear‐End 6 6.16 0.735

(0.387)

30 34.19 0.839

(0.226)

36 40.36 0.857

(0.215)

Sideswipe 2 6.16 0.243

(0.167)

12 7.76 1.342

(0.565)

14 13.93 0.904

(0.348)
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56	

Overall, there appears to be a reduction in several crash types based on the results for both

sites combined. The reduction in crashes at the unsignalized intersection is partly offset by an

increase in crashes at the signalized intersection, but the results still show an overall reduction

in total crashes. Specifically, the net effect is an 11 percent reduction in total crashes over the

two intersections, which is significant at the 58 percent confidence level. The combined results

also indicate a reduction in left‐turn, rear‐end, and sideswipe crashes. These results are highly

insignificant, as is the increase in injury crashes.

The annualized costs and benefits were then compared based on the results of the two

intersections combined and focusing on total crashes. Based on the analysis, this study

indicated an 11 percent reduction in total crashes over a 2.75‐year after period. Using the FHWA

crash costs document, Crash Cost Estimates by Maximum Police‐Reported Injury Severity within

Selected Crash Geometries (Publication Number FHWA‐HRT‐05‐051), the annual reduction

of 4.45 total crashes results in an annual benefit of approximately $143,597. The analysis was

conducted based on a total cost of $265,000 ($15,000 for the RSA and $250,000 for the

improvements), a discount rate of 2.2 percent, and a service life of 10 years, resulting in an

annual cost of $29,811. Therefore, the collective B/C of the improvements made as a result of

the RSA is 5:1, indicating an overall positive effect on safety in terms of total crashes.

PROGRAM REVIEW

The Board of Collier County Commissioners in the State of Florida adopted an RSA Policy that

included RSAs for 30 percent and 60 percent design plans for their capital improvement

projects, as well as a predetermined number of existing high‐crash locations or roadways. RSAs

are also required for new site development permits. The County utilizes an annual

professional services contract to deliver the RSA program. The consultant serves as the team

leader with agency staff and other experts serving as the RSA team. The contract is negotiated

for each specific RSA project with typical consultant costs between $6,000 and $15,000. The

County has found that the life‐cycle savings far outweigh the RSA cost. The services contract is

an effective method to train county staff on how to perform an RSA. The contract has also

institutionalized the RSA process, which has adapted to meet local needs and focuses on what is

implementable.

The County has also trained locally‐based groups o f highway safety advocates to

form Community Traffic Safety Teams (CTSTs) to complete RSAs. An example of CTST

involvement was a predesign RSA on a greenway. Members of the CTST were avid cyclists who

provide a safety perspective from a cyclist’s standpoint. The CTST is not always called upon to

assist in intersection or corridor reviews. The County has also had members of RSA teams in

wheelchairs. Again, this adds another perspective to RSA reviews, as such a team member can

enhance the RSA team’s understanding of issues that affect people with mobility restrictions.

   
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IMMOKALEE ROAD: COLLIER COUNTY, FLORIDA

Road: Planned widening of 3.25‐mile section from four‐lane to six‐lane arterial road

RSA Site:  3.25‐mile section

 Paved, four‐lane divided roadway (existing)

 Paved, six‐lane divided roadway (planned)

 6 signalized intersections

 AADT: 45,488 vehicles per day (2005)

 45 mph posted speed limit

Environment:  urban/urbanized  suburban  rural

Owners: Collier County, Florida

Road Safety Audit

Date of RSA: 15‐19 November 2004

RSA Stage(s):

 planning/design stage  RSA of existing roads

RSA Team:

Crash Reduction:

Members representing the consultant, Collier County, and Federal Highway Administration

Resource Center

10.8% total

BACKGROUND

An RSA was conducted along Immokalee Road from Interstate (I‐) 75 to Collier Boulevard in

Collier County, Florida (Figure 8). To accommodate current and forecasted future demand, the

County was considering widening the road. The proposed upgrade entailed widening the road

from a four‐lane to a six‐lane divided urban arterial. At the time of the RSA, the widening project

was at a conceptual stage. Design documentation consisted of State design practices and the

County’s typical section for a six‐lane divided urban arterial.  
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58	

The RSA was conducted by a team of experts representing staff from the consultant, Collier

County, and the FHWA Resource Center. The efforts of the teams were led by the consultant,

with direct oversight by County personnel.

Signalized intersections shown.

Figure 8. Aerial Map of Immokalee Road RSA Location.

Conceptual design plans (less than 30 percent complete), the State’s design standards, and aerial

photos were used to conduct this RSA.   

Three hours (total) were required to hold the opening and closing meetings. The RSA team spent

two days in the field reviewing the study locations. A night review was also conducted, although

not all members participated.  

KEY FINDINGS AND SUGGESTIONS

The RSA findings were divided into the following two parts:

1. Issues arising from the proposed upgrade: These issues reflected concerns arising from the

proposed upgrading from a four‐lane mixed urban/rural arterial to a six‐lane urban arterial

cross section and dealt with properties or specific conditions of the Immokalee Road

widening project that could influence design details or require the modification of design

standards.

2. Further opportunities for improvement: Additional opportunities for improvements that

could be incorporated during the upgrade were also identified. Although these

improvements were not specifically related to the proposed widening, they responded to

issues observed along the corridor by the RSA team. These improvements could be

“piggybacked” onto the upgrade project at relatively limited effort and expense.

The key findings and suggestions as a result of the RSA are summarized in Table 24. County

personnel indicated that most of the suggested improvement measures in the RSA report were

installed between March 2006 and March 2009.   Northbrooke Drive Oakes Blvd Valewood Drive Laurel Oaks Elementary 

Road 

High School East Access 

Collier Blvd 
Road Safety Audits: An Evaluation of RSA Programs and Projects

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Table 24. Summary of Safety Issues and Suggestions: RSA of Immokalee Road.

Safety Issue Suggestions

Issues arising from the proposed upgrade

Access Along

Arterial Road

Movements at driveways and local

road intersections interfere with

traffic on Immokalee Road, an

arterial road.

 Consult County’s access management manual.  

 Consider closure of some median breaks.

 Introduce right‐turn acceleration lanes.

 Introduce devices and designs to prevent wrong‐way movements.

School‐Related

Pedestrian and

Vehicle Traffic

Increased volumes, lanes, and width

may increase the collision risk for

vehicle and pedestrian traffic

associated with adjacent schools.

 Revise flashing signal operation at adjacent intersections.

 Consider median treatment to obstruct midblock crossings.

 Implement a continuous pedestrian network.

 Reduce curb return radii at adjacent intersections.

Pedestrian

Facilities

Pedestrians need to be safely

accommodated on the upgraded

roadway.

 Provide a continuous and convenient pedestrian network.

 Provide pedestrian countdown signal heads.

 Reduce return radii at intersections and driveways.

Cycling Facilities

Cyclists need to be safely

accommodated on the upgraded

roadway.

 Replace 4‐ft bike lanes with wider paved shoulder.

 Provide sufficient bike lane width at intersections.

Barriers with

Curb

The design of roadside barriers must

accommodate the proposed barrier

curb.

 Consider anticipated speeds when designing barrier system.

Stakeholder

Consultation

Widening Immokalee Road may

affect the North Naples fire station

and may generate an increased need

for speed enforcement.

 Consult fire station to determine the need for a fire signal.

 Consult with police to identify their enforcement requirements.

Median

Treatments

The impact of median treatments on

road safety should be considered in

this urbanized transition area.

 Avoid fixed‐object safety issues in the median.

 Avoid sight‐line obstructions in the median.

 Consider median treatments that obstruct midblock crossings.

 Minimize median maintenance requirements.

 Consider angled left turn lanes in wide medians.

Road Shoulders

Shoulders may be desirable for

emergency use, especially where fire‐

station traffic is expected.

 Confirm whether shoulders are desirable for fire department and

other emergency use.

Signal Display Signal displays should be visible and

conspicuous at all times.

 Mount overhead signals on mast arms.

 Consider redundant signal displays and/or double red display for

left‐turn signals.

 Consider one signal head for each lane.

 Use a backplate with reflective border.

Accommodation

of Older and

Unfamiliar

Drivers

Older and unfamiliar drivers require

enhanced signing, pavement

marking, and signal displays.

 Follow recommended practices of the Florida DOT Elder Road User

program.
Road Safety Audits: An Evaluation of RSA Programs and Projects

60	

The following photos illustrate safety issues observed during the RSA.

Immokalee Road near Valewood Drive. Immokalee Road in front of schools.

In general, the suggestions resulting from the RSA were well‐received. In design‐stage RSAs, a

wider scope for safety enhancements exists. This opportunity is even more pronounced for

designs that are early in the planning process (e.g., a conceptual design).

This RSA was conducted very early in the planning stage, when the only design documentation

was the County’s typical section for a six‐lane divided urban roadway. As a result, the RSA was

able to not only consider issues related specifically to the proposed widening from four to six

lanes but could also suggest additional opportunities to enhance road safety that were not

necessarily related to the specified widening. Of particular significance was the opportunity to

include several measures to accommodate older drivers, which will help the County to

implement elements of the Florida DOT’s “Elder Road User Program” on County roads.

RSA OUTCOMES

Geometric, traffic volume, and crash data were collected for both treatment and comparison

sites in Florida. The treatment site consisted of 3.25‐mile corridor that included six signalized

and several unsignalized intersections and driveways. The comparison sites consisted of six

untreated corridors that were otherwise similar to the treated site. The comparison group was

utilized to adjust for specific trends. (This is discussed further in analysis section.) Table 25

provides a summary of the treatment and reference site data.
Road Safety Audits: An Evaluation of RSA Programs and Projects

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Table 25. Summary of Florida (Immokalee Road) Data.

Variable Treatment Color Comparison

Years Before 1 1.0 Year/Site

Years After 1.6 1.0 Year/Site

Total Crashes/Year Before 68.0 Average 268.3/Site/Yr.

Total Crashes/Year After 72.1 Average 281.7/Site/Yr.

AADT Before 45,488 34,564

AADT After 43,389 34,564

The analysis considered the corridor in its entirety, including the signalized and unsignalized

intersections. A naïve before‐after analysis was conducted but included adjustments from a

comparison group and also employed an EB technique to assess the potential for regression‐to‐

the‐mean bias. It was only possible to analyze total crashes because data were not provided for

other crash categories.

The EB method was used to assess the potential for regression‐to‐the‐mean bias. Based on a

relatively limited reference group, an SPF was developed for total crashes. Generalized linear

modeling was used to estimate model coefficients, assuming a negative binomial error

distribution, which is consistent with the state of research. The general model form for the SPF is

given by Equation 3 and the model coefficients are presented in Table 26.

Crashes/year = Length*exp(a+b*lanes)( AADT)c       (3)

Where:

AADT = total two‐way traffic volume (vehicles per day)

Lanes = indicator variable for the number of lanes (1 if 4‐lanes; 0 if 6‐lanes)

Length = segment length (miles)

a, b, and c = coefficients estimated from the model

Table 26. Estimated SPFs for Florida.

Crash Type a b c

Total 0.2365 ‐0.0436 0.2857

While the coefficients from the SPF were not statistically significant, it was possible to investigate

the potential for regression‐to‐the‐mean. The EB‐adjusted expected crash count in the before

period was 70.74 as opposed to 68 observed crashes indicating that regression‐to‐the‐mean is

not a significant consideration. Based on the lack of evidence to suggest the potential for

regression‐to‐the‐mean and the fact that the SPF and Collier County reference data are suspect
Road Safety Audits: An Evaluation of RSA Programs and Projects

62	

for some locations, it was decided to use the naïve before‐after method with observed crash

counts in the analysis.

The naive before‐after method was used to estimate the overall change in safety at the

treatment site. However, there were other improvements made to the treatment site in addition

to the suggestions from the RSA. Specifically, the corridor was widened from a four‐lane to a six‐

lane cross section. As such, it was necessary to adjust for the lane conversion to isolate the

effects associated with the RSA. An adjustment factor was derived from the most relevant CMF

information in the Highway Safety Manual (HSM).3 The HSM provides separate CMFs for four‐ to

five‐lane conversions and five‐ to six‐lane conversions as follows:

CMF for 4‐lane to 5‐lane conversion = 1.10 (standard error =0.07)

CMF for 5‐lane to 6‐lane conversion = 1.04 (standard error = 0.11)

The estimated effect of converting from four to six lanes is obtained by multiplying the two CMFs

(CMF = 1.10*1.04 = 1.14).

A final factor was used to adjust for general temporal trends and was computed as the ratio of

number of crashes in the after period to number of crashes occurring in the before period for the

comparison group. The time trend factor is 1.05 and represents the change from 2004 to 2009. It

was assumed that this calculated time trend was applicable to the treatment site for which the

before period is 2005 and the after period is January 2010 to July 2011.

The results of the Florida analyses for Immokalee Road are presented in Table 27 for the

corridor. Note that Table 27 contains three sets of results, including 1) the naïve before‐after

analysis without adjustment, 2) adjustment for the lane conversion, and 3) adjustment for the

lane conversion and time trend.  

Table 27. Corridor Results for Florida (Immokalee Road).

Method

Observed

Crashes After

Expected  

Crashes After

CMF (S.E.)

Naïve (without adjustment) 117 107.67 1.071 (0.161)

Naïve (with adjustment for lane

conversion)

117 123.17 0.936 (0.141)

Naïve (with adjustment for lane

conversion and time trends)

117 129.33 0.892 (0.134)

																																																												

3	American	Association	of	State	Highway	Safety	Officials.	(2010).	The Highway Safety Manual.	

Washington,	D.C.:	American	Association	of	State	Highway	Safety	Officials.		
Road Safety Audits: An Evaluation of RSA Programs and Projects

63	

The results indicate a general safety benefit of implementing the treatments suggested in the

RSA report.  

While the unadjusted naïve analysis indicates an insignificant increase in total crashes, the results

show an expected reduction in crashes once adjustments are made to account for the effects of

the four‐ to six‐lane conversion and time trends. Specifically, the analysis indicates an expected

10.8 percent reduction in total crashes as a result of the RSA and associated improvements after

adjusting for time trends and the lane conversion. Note that this result is statistically insignificant

at the 95 percent confidence level. Using the FHWA crash costs document, Crash Cost Estimates

by Maximum Police‐Reported Injury Severity within Selected Crash Geometries (Publication

Number FHWA‐HRT‐05‐051), the annual reduction of 12.33 total crashes results in an annual

benefit of approximately $397,470. It was not possible to compute the B/C ratio for the

improvements made as a result of the RSA because cost data were not provided, but there

appears to be an overall positive effect on safety in terms of total crashes. As long as the annual

costs are less than approximately $400,000, there will also be a positive return on investment.

PROGRAM REVIEW

See information in the previous section for Collier Boulevard.

   
Road Safety Audits: An Evaluation of RSA Programs and Projects

64	

NINTH STREET: OCEAN CITY, NEW JERSEY

Road: Existing 0.47‐mile section of paved, four‐lane arterial roadway

RSA Sites: • 5 signalized, 1 unsignalized “major” intersections

• 6 unsignalized other intersections and alleyways

• AADT: 13,870 vehicles per day (2007)

• 25 mph posted speed limit

Environment:  urban/urbanized  suburban  rural

Owners: Ocean City, New Jersey

Road Safety Audit

Date of RSA: 28 May 2004

RSA Stage(s):  planning/design stage  RSA of existing roads

RSA Team:

RSA Cost:

Implementation Cost:

Crash Reduction:

Benefit / Cost Ratio:

14 members representing Cape May County, FHWA, NJ Division of Highway Traffic Safety,

New Jersey Department of Transportation (NJDOT), Ocean City, South Jersey

Transportation Planning Organization (SJTPO), and Orth‐Rodgers & Associates, Inc.

$21,000

$900,000

25.6% total

1.2:1 total

BACKGROUND

An RSA was conducted along a 0.47‐mile section of Ninth Street in Ocean City, New Jersey from

Bay Avenue to Atlantic Avenue (Figure 9). Throughout this section, Ninth Street is a four‐lane

arterial roadway with a posted speed limit of 25 mph. Five signalized intersections and one

“major” unsignalized intersection are present within the study area; six other unsignalized

intersections/alleyways are also present. The AADT along Ninth Street was reported as 13,870

vehicles per day in 2007. Ninth Street is owned and maintained by Ocean City.
Road Safety Audits: An Evaluation of RSA Programs and Projects

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Figure 9. Aerial Map of Ninth Street.

In November 2003, a preliminary list of six candidate locations for RSAs was submitted by the

Cape May County Engineer and forwarded to the NJDOT Bureau of Data Development for

further analysis. At this time, the Local Safety Program provided only

$0.5 million to each NJ metropolitan planning organization annually. Due to time constraints for

using the available metropolitan planning (PL) funding, all RSA work needed to be completed by

June 30, 2004. Data‐driven approaches to the RSA process had not yet been well developed;

therefore, the SJTPO used outreach, local knowledge, and limited data analysis to identify

Ninth Street as a high‐crash corridor. As a result, Ninth Street was one of two locations

selected for an initial pilot project by the SJTPO for a formal RSA to determine safety

deficiencies and appropriate countermeasures. SJTPO proceeded with the expectation that

the RSA was likely to yield low‐cost, quick‐turnaround improvements, as opposed to high‐cost,

construction‐intensive projects requiring extensive NEPA processing.

A kickoff meeting was held in March 2004 and attended by 24 individuals. RSAs were relatively

new to New Jersey, and there was a strong desire to see the process expanded to other parts

of South Jersey. In May 2004, the RSA was conducted by a team of 14 individuals from

various agencies, including representatives from Ocean City, Cape May County, SJTPO,

NJDOT, the New Jersey Division of Transportation Safety, and FHWA.
Road Safety Audits: An Evaluation of RSA Programs and Projects

66	

The team was comprised of consulting staff, engineers, planners, and law enforcement. The

efforts of the team were led by the consultant with direct oversight by County personnel.

Information used by the RSA team to conduct the review included the following:

• Aerial imagery and maps.

• Traffic volume data (2000).

• Bicycle and pedestrian counts.

• Level of Service (LOS) analysis.

• Crash data (2001‐2004).

• Traffic signal plans.

• Video logs.

Aerial maps (including an 11‐inch by 14‐inch sheet scaled at 1 inch =500 ft and additional maps

at 1 inch =60 ft) were provided for use by the County to indicate problem areas and issues and

to draw potential improvements (e.g., sign placement, traffic signal improvements, etc.). Traffic

volumes indicated a large presence of nonmotorized traffic, with peak demand occurring during

the midday period. A capacity analysis demonstrated that all intersections were operating at

acceptable levels of service, except for the Bay Avenue intersection. Approximately 200 crashes

were submitted for review; 128 were identified as having occurred within the study area (which

included an influence area around the intersections as determined by the consultant).

In the morning, after a brief introduction, a three‐hour brainstorming session allowed

participants to review the existing data and discuss several operational and congestion‐related

issues. In the afternoon, the team conducted the field review. It was estimated that five hours

were utilized to complete the field review. The total cost to complete the RSA (including

consultant fees) was approximately $21,000.

KEY FINDINGS AND SUGGESTIONS

The consultant prepared a draft report to document the RSA, the key findings, and suggestions.

In total, 42 issues were identified with 53 safety measures suggested. The measures cover a

wide range of actions, from maintenance‐level tasks to capital‐intensive projects. Each measure

was ranked in priority high to low based upon the level of effort required and the potential

safety benefit. Of the 53 suggestions, 33 (62 percent) were projected to have a high safety

benefit, and 13 (25 percent) were projected to have a medium safety benefit. Fifteen of the

proposed suggestions could be implemented within one year, whereas the remaining 38

suggestions were intended to be incorporated into longer‐range design plans. Those suggestions

that were implemented are summarized in Table 28.
Road Safety Audits: An Evaluation of RSA Programs and Projects

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Table 28. Summary of Safety Issues and Suggestions: RSA of Ninth Street.

Safety  

Issues Suggestions

Implementation

(Y/N) Date Location Cost

Pedestrian behavior is not

consistent

Install Walk/Don't Walk

signals at all signalized

intersections

Y 2006: Ninth &

West; 2008:

other

intersections

Portion of

$170K

(West);

$659K

(others)

With the exception of Bay Ave.,

traffic signals along the Ninth St.

corridor do not provide clear

indication for pedestrians

Redesign each of the six

signals within the corridor

to provide man/hand

signals. Pedestrian

countdown signals

should be considered

Y

Pavement surface along entire

Ninth St. corridor is in general

state of disrepair. Much of the

aggregate has been exposed and

polished, indicating a lower level

of skid resistance

Resurface the roadway to

improve skid resistance

and improve travel surface

for all modes of

transportation

Partial Asbury to

Boardwalk

Portion of

$170K

(West)

The traffic signal at Ninth St. and

West Ave. is not pedestrian‐

friendly. Some crossings have no

signals readily visible to

pedestrians

Modify the traffic signal

installation to better serve

pedestrians. (This item is

already being done by ORA

at the direction of the

County Engineer.)

Y 2006 Ninth &

West

There is no advance notice

regarding the lane configuration

on the Asbury Ave. approaches

to Ninth St.

Place advance lane use

control signs (R3‐8) on the

approaches

Y One is

partially

obscured by

tree

A crosswalk at the corner of

Wesley Ave. leads to a full‐face

curb without depression for

users with mobility restrictions

Install a curb depression

for users with mobility

restrictions

Y

There is no northbound

pedestrian signal on the

northeast corner at the

intersection of Ocean Ave. and

Ninth St.

Upgrade the traffic signals

to better serve the

pedestrians

Y

The crosswalk at Atlantic Ave.

leads to a full‐face curb without

depression for users with

mobility restrictions

Install a curb depression

for users with mobility

restrictions

Y‐3,

N‐1
Road Safety Audits: An Evaluation of RSA Programs and Projects

68	

One of the major changes suggested as a result of the RSA was to implement a roadway diet,

converting Ninth Street from a four‐lane section to a three‐lane section with a two‐way left‐

turn lane and bicycle lanes. Another suggestion resulting from the RSA was to install a traffic

signal at the intersection of Ninth Street and West Avenue. The improvements included an

uninterruptible power supply, all new signal hardware, 12‐inch LED lenses, accessible

countdown pedestrian signals with ramps, sidewalk improvements, and signing and pavement

marking enhancements. A preliminary before‐after study indicated a 50 percent reduction in

crashes and injuries at the intersection. This study provides the results of a more rigorous

evaluation. The cost of this improvement was $172,000 and was completed on June 15, 2005.

Further traffic signal improvement work was

implemented based on the RSA suggestions. The

existing traffic signals were outdated and did not

provide pedestrian accommodations. The work

consisted of installing countdown pedestrian

traffic signals at the intersections of Asbury,

Central, Wesley, and Ocean Avenues. The work

also interconnected signal controller

communications with all five traffic signals

between West Avenue and Ocean Avenue. This

was a joint project between Cape May County and

Ocean City and was funded by the HSIP program.

The Ninth Street Signals Improvement Project was completed in May 2007 at a cost of

$728,000.

In addition to the traffic signal upgrades, several other safety measures will be implemented

with the Route 52 Causeway construction project to the immediate west of the study corridor.

The Route 52 project will replace two drawbridges and tie into the Ninth Street corridor at

West Avenue. Included within this project is the raising of portions of Ninth Street where

flooding causes periodic closures, new raised medians, and new pedestrian sidewalk along the

Traffic signal mast arms and signal display alignments prior to improvements.

New traffic signal mast arms and signal

display alignments resulting from the RSA.
Road Safety Audits: An Evaluation of RSA Programs and Projects

69	

south side of the roadway (Figure 10). Construction began in August 2006 and is scheduled for

completion in December 2012 at a cost of $400 million. Ocean City was aware that the Route

52 construction would affect the western portion of the corridor, particularly in terms of

significantly altering traffic patterns. Additional improvements will be made beyond those

suggested in the RSA report, as the causeway is a significant gateway to Ocean City.

Figure 10. Route 52 Construction Changes to Ninth Street.

In general, the suggestions resulting from the RSA were well‐received by County personnel,

law enforcement, and the public. Those involved with this RSA were pleased with the process

and sought to expand this pilot into a full RSA program. Additionally, residents near the study

area were happy with the outcomes. According to local officials, the public was especially

receptive of the traffic signal improvements.  

RSA OUTCOMES

Geometric, traffic volume, and crash data were collected for both treatment and comparison

sites in New Jersey. The treatment site consisted of a 0.47‐mile corridor that was divided into

two consecutive segments based on geometric changes. Data were obtained for each

segment of the corridor and the signalized intersections within the corridor. Several

comparison sites were identified for the corridor and signalized intersection analyses. A total

of 4.32 miles of corridor were identified for the comparison group. Tables 29 and 30 provide a

summary of the treatment and comparison site data for the corridors and signalized

intersections, respectively. Note that two before periods were analyzed separately: 2003 to

2004 and 2003 to 2007. This approach was based on the implementation period in which

most changes were implemented in 2008, but the intersection of Ninth Street/West Street

was also modified in 2005. It is preferable to include more than two years of data in the

before period; hence, the analysis considers a before period of 2003 to 2007. The additional

years in the before period provide a more stable estimate of the safety performance prior to

the treatment’s installation. The period from 2003 to 2004 was used to account for changes

due to the improvements made in 2005.
Road Safety Audits: An Evaluation of RSA Programs and Projects

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Table 29. Summary of New Jersey Corridor Data.

Variable Treatment Site Comparison Site

Number of segments 2 5

Before Period1 2003‐2004

2003‐2007

2003‐2004

2003‐2007

After Period 2009 2009

Length (miles)

Average 0.24 0.86

Minimum 0.06 0.10

Maximum 0.41 2.70

Total Crashes/

mile‐year

before (2003‐

2004)

Average 80.3 21.8

Minimum 43.9 5.0

Maximum 116.7 35.0

Total

Crashes/mile‐

year before

(2003‐2007)

Average 66.8 20.1

Minimum 46.8 12.0

Maximum 86.7 31.0

Total

Crashes/mile‐

year after

Average 44.5 8.5

Minimum 39.0 0.0

Maximum 50.0 15.6

AADT Before2

Average 9,251; 11,231

Minimum 9,251; 11,231 7,631

Maximum 9,251; 11,231 6,078

AADT After2

Average 16,513 8,666

Minimum 16,513

Maximum 16,513

Area Type Urban Urban

Number of Lanes 4 2 (0.82 miles)

4 (3.50 miles)

Median Type None (0.41 miles)

TWLTL (0.06 miles) None

Median Width (ft) 0 (0.41 miles)

15 (0.06 miles) 0

Shoulder Type None None

Shoulder Width (ft) 0 0

Posted Speeds (mph) 25

25 (1.42 miles)

30 (0.20 miles)

35 (2.70 miles)

1

Two before periods were used. One of the signalized intersections was treated in 2005 while the rest were treated in 2008.

2

Only one count was available for the comparison site; treated site had counts available in 2004 and 2007, other years were estimated assuming a

linear trend over time
Road Safety Audits: An Evaluation of RSA Programs and Projects

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Table 30. Summary of New Jersey Signalized Intersection Data.

Variable Treatment Sites Comparison Sites

Number of Sites 6 41

Years Before

Average 4.7 Appropriate years for

all sites used for each

comparison site

Minimum 3.0

Maximum 5.0

Years After

Average 1.3 Appropriate years for

all sites used for each

comparison site

Minimum 1.0

Maximum 3.0

Total Crashes/Year Before

Average 2.8

Minimum 1.7 1.0

Maximum 3.8 0.0

Total Crashes/Year After1

Average 2.4 2.6

Minimum 0.0

Maximum 4.7

Major Road AADT Before1

Average 11,011

Minimum 9,911 7,899

Maximum 11,231 6,078

Major Road AADT After

Average 16,293 8,666

Minimum 15,192

Maximum 16,513

Area Type Urban Urban

Number of Approaches 4 4

1

Treated sites had major road counts available in 2004 and 2007, other years were estimated assuming a linear trend over time. Minor road AADTs

were not available.

In New Jersey, the countermeasures implemented as a result of the RSA were mostly

implemented in 2008; however, one intersection was modified in 2005. Thus, the after period

conditions changed at two different times for the treated segments. Recognizing the changing

conditions, the analysis was run for two after periods. The first after period was based on data

from 2003 to 2007 (i.e., the period before most of the major changes occurred). The second

after period only considered the period from 2003 to 2004 (i.e., the period before any changes

occurred).

The analysis considered the corridor in its entirety, including the signalized intersections, and

separately considered the signalized intersections within the corridor. Comparison group and

naïve before‐after analyses were conducted for both scenarios. It was only possible to analyze

total crashes for each scenario because there were too few crashes in the other categories.
Road Safety Audits: An Evaluation of RSA Programs and Projects

72	

The analysis did not account for regression‐to‐the‐mean because the EB approach could not be

applied. However, it was possible to investigate the potential for regression‐to‐the‐mean.

Specifically, total crashes were plotted over time for the corridor and signalized intersections, as

shown in Figures 11 and 12. If regression‐to‐the‐ mean is present, one would expect to see a

spike in crashes just prior to 2005 and/or 2008 (recall that the majority of changes occurred in

2008, with modifications to a signalized intersection in 2005). Figures 11 and 12 do not indicate

such a spike in crashes but rather reflect a consistent oscillation around some mean value. Thus,

for the purposes of the analysis, it is concluded that regression‐to‐the‐mean is not likely to

introduce significant bias.

Figure 11. Corridor‐Level Crash Totals Over Time.

Figure 12. Signalized Intersection Crash Totals Over Time.
Road Safety Audits: An Evaluation of RSA Programs and Projects

73	

The following points should also be noted with respect to the analysis.

• A linear relationship was assumed between crashes and traffic volume when

accounting for changes in traffic volume. With a limited variation in traffic volumes, it

was not possible to develop an SPF or evaluate the suitability of existing SPFs to model

the true relationship. Given the inherent uncertainty in other aspects of the analysis

and the relatively small changes in AADT, this assumption was not deemed crucial.

• The suitability of the comparison group could not be rejected using the methods

described by Hauer (1997). As such, the comparison site is deemed reliable for use in

the comparison group method.

The results of the New Jersey analyses are presented in Table 31 and Table 32 for the corridor

and signalized intersections, respectively. Results that are statistically significant at the five

percent level are noted in bold. Note that Table 31 contains results for the comparison group

and naïve before‐after analyses; separate results are provided for each of the following:

1. Comparison group and naïve before‐after methods, including entire before period.

2. Comparison group and naïve before‐after methods, excluding years 2005 to 2007 from

the before period.

Table 32 contains results for the comparison group and naïve before‐after analyses, and

separate results are provided for each of the following:

1. Comparison group and naïve before‐after methods, including the signalized

intersection of Ninth Street and West Avenue.

2. Comparison group and naïve before‐after methods, excluding the signalized

intersection of Ninth Street and West Avenue.

Table 31. Corridor Results for New Jersey.  

C‐G Method Naïve Method

Before Period

Observed

Crashes

After

Expected

Crashes

After

CMF

(Standard

Error)

Observed

Crashes

After

Expected

Crashes

After

CMF

(Standard

Error)

2003 to 2004 19 26.3 0.643

(0.240)

19 44.6 0.417

(0.110)

2003 to 2007 19 22.8 0.744

(0.277)

19 35.9 0.525

(0.129)
Road Safety Audits: An Evaluation of RSA Programs and Projects

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Table 32. Signalized Intersection Results for New Jersey.  

C‐G Method Naïve Method

Before Period

Observed

Crashes

After

Expected

Crashes

After

CMF

(Standard

Error)

Observed

Crashes

After

Expected

Crashes

After

CMF

(Standard

Error)

Including Ninth

and West

24 24.3 0.895

(0.308)

24 29.7 0.791

(0.194)

Excluding Ninth

and West

10 17.7 0.510

(0.209)

10 22.1 0.447

(0.149)

The results indicate a general safety benefit of conducting the RSA and implementing the

treatments suggested in the RSA report. The estimated CMF is consistently less than 1.0 for

all variations of the analysis, indicating a reduction in expected crashes. While the estimated

reductions in total crashes for the corridor are substantial, they are insignificant for the

comparison group method. With respect to the treated signalized intersections, the results

indicate a safety benefit, although not statistically significant when the intersection of Ninth

Street and West Avenue is included.

While there are several variations of the analysis, the results from the comparison group

method are preferred over the naïve before‐after results. The estimated crash reductions are

consistently smaller for the comparison‐group method than for the naïve method and could be

considered conservative. However, the naïve method does appear to corroborate the results of

the comparison group method.

While the EB methodology could not be applied in this evaluation, the results are consistent

among the various approaches, even when considering the potential for regression‐to‐the‐

mean. The estimated crash reductions are also large enough to justify confidence in the RSA

process, especially considering that the evaluation was based on only one project and on

relatively low crash counts. The confidence level in the RSA process will be increased as the

results of other projects developed from RSAs are amalgamated with the results in this report.

The annualized costs and benefits were then compared based on the results of the comparison

group before‐after study. For the corridor as a whole, the analysis indicated a 25.6 percent

reduction in total crashes over a one‐year “after” period. Using the FHWA crash costs

document, Crash Cost Estimates by Maximum Police‐Reported Injury Severity within Selected

Crash Geometries (Publication Number FHWA‐HRT‐05‐051), the annual reduction of 3.8 total

crashes results in an annual benefit of $122,497. Assuming a total cost of $921,000 ($21,000 for

the RSA and $900,000 for the improvements), a discount rate of 2.2 percent, and a service life

of 10 years, the annualized cost is $103,608. Therefore, the B/C ratio of the improvements

made as a result of the RSA is 1.2:1 for the corridor, indicating an overall positive effect on

safety in terms of total crashes.
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PROGRAM  REVIEW

Transportation safety is one of the SJTPO’s top priorities. Since completing its first RSA on

Ninth Street in 2004 without the benefit of rigorous corridor‐selection criteria, the SJTPO

created a comprehensive process for the evaluation of future candidate RSA locations. In its

fiscal year 2005 Planning Work Program, SJTPO began to gear the RSA program towards

identifying locations where quick, low‐cost safety improvements could be implemented. A

process was established to program approximately $1 million in HSIP funding towards efforts

that would have the highest reduction on severe crashes.

In 2005, two procedures were adopted as a means to select sites for RSAs.

Nomination Selection Process

The nomination selection process uses a “bottom up” approach. County engineers and officials

qualitatively nominate sites based on their knowledge of high‐crash locations. Geographic

considerations, local control and cooperation, and available funding sources are several factors

used to determine suitable locations. The following questions also help to identify locations

that would likely have a high return on the investment of conducting an RSA and quickly

implementing safety improvements:

• Are there few State road intersections in the corridor?

• Are there few municipalities involved, and are they responsive to safety projects?

• Is the corridor length compact enough to make for a good concentrated RSA?

• Are planning funds available for this project?

Crash Data Selection Process

The crash data selection process uses a “top down” approach. The process began with the

SJTPO reviewing two years of crash data for every road in the region and identifying high crash‐

density locations as suitable sites. Crash data were reviewed based on crash density per

mile, prior high‐crash locations, and high‐crash segments versus intersections. Of the three,

crash density was given the most weight.

In 2006, the selection process became more refined. Fiscal year 2006 RSA corridors were

selected using a balance of qualitative and quantitative elements. The SJTPO engaged local

experts to nominate locations that could be improved quickly with inexpensive

countermeasures. The South Jersey Traffic Safety Alliance and the SJTPO’s Technical Advisory

Committee solicited nominations from engineers, planners, and traffic officers who possessed

first‐hand knowledge of the local roadways, driving habits, and crash documentation. Once

nominations were received, four factors were used as a filter:
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• Geographic compactness of the corridor.

• High degree of local control.

• Good local cooperation.

• Potential for safety improvements.

The sites that met the above criteria were considered as top candidates and continued to

SJTPO’s quantitative analysis. A high‐crash corridor was considered to experience at least 15

crashes per mile per year and a minimum of 100 total crashes. Injuries and fatalities were also

considered. The top candidates from this step of the process were compared to all routes in

the region on the basis of crash density. A sliding window technique was utilized to find the

crash clusters. An overview flowchart of the process is illustrated in Figure 13.
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Figure 13. Overview of the South Jersey Transportation Planning Organization's RSA Site

Selection Process.
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NJDOT is very supportive of the SJTPO RSA program, working to enable the authorization of

HSIP funds and assisting with unobligated HSIP funding issues. The NJ Division of

Transportation Safety has also devoted a considerable amount of time to partnering with the

SJTPO to conduct RSAs. Over the past several years, this RSA program has been highlighted

by FHWA. In 2005, the program received an Honorable Mention in the National Roadway Safety

Awards:

“It is one of the first local programs of its kind, utilizing Federal planning funds to

systemically identify local road segments of concern, organizing a team of independent

specialists under the auspices of a metropolitan planning organization, engaging a

consultant team for the audits and securing Federal funding for the resulting

recommended improvement packages.”

Additionally, in 2007, the SJTPO Director received the Dave Powell Excellence Award. This

award is given to recognize partnerships with the FHWA New Jersey Division Office.

Transportation Safety Planning Results

In 2005, the results yielded four corridors from the nomination selection process and one

corridor from the crash data selection process. The corridors ranged from 1.2 miles to 5.3 miles

in length. In 2006, the results yielded five corridors from the qualitative and quantitative

selection process. These corridors ranged from 1.9 miles to 4.3 miles in length.

In recent years, the SJTPO has shifted from using consultant support for the actual RSA to more

project development tasks. The RSAs are now conducted by the localities as the SJTPO flexes

regional Surface Transportation Program (STP) funds to metropolitan planning funds to

conduct the RSA. In the near future, to ensure independent teams are being used, localities

will begin a pilot effort to conduct peer expert exchanges in neighboring counties. For

example, an established RSA team based in one county would conduct an independent

safety assessment in a neighboring county in return for in‐kind services.

Roadway Safety Scans

Since 2007, the SJTPO has also been using a “Road Safety Scan” (RSS) process. An RSS is a

scaled‐down version of an RSA and is more comparable to a traditional safety review. The scans

allow experienced highway safety engineers to cover significantly more road mileage than a

formal RSA. Local participation is also encouraged.

For an RSS, each section of study roadway is first driven at normal operating speeds and then at

slower speeds to stop as necessary to take pictures and measurements. Particular items the

engineers are looking for include traffic control device deficiencies,
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clear zone issues, sight distance issues, pavement drop‐offs, guardrail end treatment

deficiencies, etc. Voice‐over video‐recording devices are also used extensively for

documentation and further office review.

There are three parts to the scan:

• Data collection – crash data printouts are reviewed by engineers to identify

potential safety issues.

• Field review – conducted by the traffic engineer with local participation; each

location is documented as accurately as possible.

• Preparation of the report and findings – documentation of findings and any

recommended actions.

In 2007, a scan was completed for 31 sections (totaling 122 miles) in Cumberland, NJ and 13

sections (totaling 46 miles) in Atlantic, NJ. Each section had several safety issues identified,

proposed remedial actions, an estimate of the level of effort required to implement the

measures, and the potential safety benefit. A map with additional photographs and the

reviewed crash data were also included to complete the scan.