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FHWA-SA-11-08

Intersection Safety

A Manual for Local Rural Road Owners
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FHWA-SA-11-08

Intersection Safety: A Manual for Local Rural Road Owners

The Task Manager for this document was Rosemarie Anderson, FHWA Office of Safety.

The Technical Oversight Working Group included John Dewar, Ed Rice, Joe Bared, and Fred Ranck, FHWA; 

Betsey Tramonte, FHWA Louisiana Division; David Anderson, Delaware Valley Regional Planning Commission; Bruce Drewes, Idaho Technology Transfer Center; Joe Fiocco, McMahon Associates, Inc.; Wayne 

Schoonover, Ionia County, Michigan Road Commission; and Bob Sperry, Iowa LTAP/CTRE.

According to the Federal Highway Administration, over 6 million lane-miles of roadway are in rural 

areas, and more than two-thirds of these rural roads are owned and operated by local entities. In 2008 

56 percent of the 37,261 fatalities on U.S. roadways occurred in rural areas. Rural areas face a number of 

highway safety challenges due to the nature of their facilities.

More than 20 percent of all traffic fatalities in the United States occur at intersections and over 80 percent 

of intersection-related fatalities in rural areas occur at unsignalized intersections. This document provides information on effectively identifying intersection safety issues in local areas, choosing the countermeasures that address them, and evaluating the benefits of those treatments. It is geared toward local 

road managers and other practitioners with responsibility for operating and maintaining their roads. 

It offers information on the procedures and processes to improve the safety of local rural unsignalized 

intersections and to reduce the potential for future crashes. 

Science Applications International Corporation (SAIC)

Mail Stop E-12-3

8301 Greensboro Drive

McLean, VA 22102-3600

Office of Safety

Federal Highway Administration

1200 New Jersey Ave, SE

Washington, DC 20590-9898

Golembiewski, G.A. and Chandler, B.

Intersection Safety, Intersections, Local, Rural, 

Unsignalized Intersections, Data, Field Review, Signs, 

Pavement Markings, Practitioner, Crashes, Implementation.

No restrictions. 

Unclassified Unclassified 60 N/A

January, 2011

DFTH61-05-D-00025, T-09-003

HSSP

2. Government Accession No. 3. Recipient’s Catalog No.
Table of Contents

Table of Contents................................................................................................ i

1 Introduction and Purpose ......................................................................1

1.1. The Intersection Crash Problem ............................................................1

1.2. State Intersection Safety Implementation Plans.............................3

1.3. Implementation Approaches..................................................................3

1.3.1. Systematic Approach.................................................................................3

1.3.2. Spot Location Approach..........................................................................4

1.3.3. Comprehensive Approach.....................................................................5

1.4. Information in this Document................................................................6

2 Identifying Safety Issues.......................................................................10

2.1. State and Local Crash Databases........................................................ 11

2.2. Law Enforcement Crash Reports and Citations............................. 11

2.3. Observational Information................................................................... 12

2.4. Public Notifications................................................................................. 14

2.5. Roadway Data ........................................................................................... 14

2.6. Exposure Data ........................................................................................... 15

3 Safety Analysis........................................................................................16

3.1. Crash Frequency....................................................................................... 16

3.2. Crash Rates................................................................................................. 16

3.3. Geometric Issues...................................................................................... 18

3.3.1. Sight Distance .............................................................................................18

3.3.2. Skewed Geometry....................................................................................20

3.4. Field Reviews............................................................................................. 21

4 Countermeasures ...................................................................................23

4.1. Enhanced Sign and Pavement Marking Improvements............ 23

4.2. Select Intersection Countermeasures.............................................. 25

4.3. Funding Intersection Safety Countermeasures............................ 43

5 Evaluation .............................................................................................44

6 Summary .............................................................................................46

Appendix A Resources and References ...................................................A-1

Appendix B MUTCD Compliance Issues at Rural, Two-Way 

 Stop-Controlled Intersections.............................................B-1

i | Intersection Safety
List of Tables

Table 1 Sample Spreadsheet to Monitor Crashes/Observations

at Local Intersections ..................................................................13

Table 2 Example of the Intersection Crash Rate Calculation..............17

Table 3 Design Intersection Sight Distance – Left Turn, Right Turn, 

and Crossing from a Stop............................................................20

Table 4 Example Spreadsheet to Monitor Countermeasure 

Application History and Crash/Observational Data...............45

List of Figures

Figure 1 Intersection Fatalities by Year................................................... 7-8

Figure 2 Steps to Address Intersection Safety ..........................................9

Figure 3 Sight Distance Triangles for 4-Leg Stop-controlled 

Intersections ..................................................................................19

Figure 4 Skewed Intersection.....................................................................20

Figure 5 Basic Package for Intersections Experiencing Crashes..........24

Intersection Safety | ii
1 | Intersection Safety

1 Introduction and Purpose

Three million miles of local roads are maintained and operated by local 

administrators, township managers, and public works officials in more 

than 38,000 counties, cities, villages, towns, and tribal governments 

across the United States.1 One issue common to all local agencies is 

traffic safety.

One of the most pressing traffic safety issues on local roads is 

intersection safety. Intersections can vary widely in terms of size, 

shape, number of entering legs, and number of turn lanes. According 

to the American Association of State Highway and Transportation 

Officials’ (AASHTO) A Policy on Geometric Design of Highways and 

Streets, an intersection is defined as the general area where two or 

more highways join or cross, including the roadway and roadside 

facilities for traffic movements within the area. Each highway radiating 

from an intersection and forming part of it is an intersection leg. The 

most common intersection where two highways cross has four legs. 

Intersections generally involve through- or cross-traffic movements and 

typically involve turning movements between the highways. There are 

three general types of highway crossings – at-grade intersections, grade 

separations without ramps, and interchanges. This document addresses 

safety issues related to at-grade intersections.

Local rural roads also encompass a wide range of surface types, 

including paved facilities, gravel roads, and dirt roads. Many local rural 

intersections lack suitable design standards, delineation, and signing 

that may be provided on higher volume roadways. Further, many were 

not officially designed, but rather “evolved” over time to their current 

geometric configuration. 

1.1. The Intersection Crash Problem

In 2008 the National Highway Traffic Safety Administration (NHTSA) 

indicated that 56 percent of the 37,261 fatalities on U.S. roadways 

occurred in rural areas.2

 This figure is disproportionate since only 23 

percent of Americans live in rural areas3 and rural roadways account for 

just 40 percent all vehicle miles traveled nationally.4 

1 McNinch, T.L. and Colling, T.K. “Traffic Safety Education for Nonengineers.” Public Roads, May/June, 

2009, pp. 32-39. Available at: http://www.fhwa.dot.gov/publications/publicroads/09june/05.cfm 

2 National Highway Traffic Safety Administration, Traffic Safety Facts: 2008 Data (Washington, DC: 

2009). Available at: http://www-nrd.nhtsa.dot.gov/Pubs/811164.pdf

3 U.S. Department of Transportation, “Rural Safety Initiative,” web page, February 2008. Available at: 

http://www.dot.gov/affairs/ruralsafety/ruralsafetyinitiativeplan.htm

4 U.C. Berkeley, Safe Transportation Research & Education Center, “Rural Road Safety” web page. 

Available at: http://www.tsc.berkeley.edu/research/ruralroads.html
Intersection Safety | 2

More than 20 percent of all traffic fatalities in the United States occur at 

intersections, both signalized and unsignalized. As shown in Figure 1, the 

number of intersection-related fatalities has been decreasing since 2005, 

yet the overall number is still very high. 

More than 80 percent of rural intersection fatalities occur at unsignalized 

intersections. Due to this high proportion of crashes at these types of 

intersections, unsignalized intersections will be the focus of this report. 

For information on safety at signalized intersections, please refer to 

Signalized Intersections: Informational Guide5

 and NCHRP Report 500, 

Volume 12, A Guide for Reducing Collisions at Signalized Intersections.

6

8689

8922

9273

9362

9176

9238

8850

8703

7809

7500

7700

7900

8100

8300

8500

8700

8900

9100

9300

9500

2000 2001 2002 2003 2004 2005 2006 2007 2008

Figure 1 – Intersection Fatalities by Year

According to FHWA, the most severe crash type at unsignalized 

intersections is a right-angle crash. This crash type typically occurs 

when two vehicles approaching at a perpendicular angle collide due 

to one vehicle failing to stop or yield right of way from a Stop or Yield 

sign. In recent data analyses commissioned by the Federal Highway 

Administration (FHWA), every 100 reported angle crashes at unsignalized 

intersections resulted in approximately 1 to 3 fatalities and 5 to 15 serious 

injuries.7

5 U.C. Berkeley, Safe Transportation Research & Education Center, “Rural Road Safety” web page. 

Available at: http://www.tsc.berkeley.edu/research/ruralroads.html

6 Antonucci, N. et al., A Guide for Reducing Collisions at Signalized Intersections, TRB, National Research 

Council, NCHRP Report 500, Vol. 12, 2004. Available at:

http://onlinepubs.trb.org/onlinepubs/nchrp/nchrp_rpt_500v12.pdf

7 Federal Highway Administration, “State Intersection Safety Implementation Plans,” 2008-2010. 

(unpublished studies)
3 | Intersection Safety

1.2. State Intersection Safety Implementation Plans

FHWA recognized that while a number of States had intersection 

safety as an emphasis area in their Strategic Highway Safety Plans 

(SHSP), they lacked an action plan to guide their intersection safety 

implementation activities on State and local roads. To date, FHWA has 

worked with 11 States to develop Intersection Safety Implementation 

Plans (Arizona, Florida, Georgia, Indiana, Louisiana, Mississippi, Missouri, 

Ohio, Pennsylvania, South Carolina, and Tennessee).8

 The plans 

include the activities, countermeasures, strategies, deployment levels, 

implementation steps, and estimate of funds necessary to achieve the 

intersection component of the State’s SHSP goal. Local road practitioners 

should consult their State’s Intersection Safety Implementation Plan, if 

available, before embarking on an improvement strategy.

1.3. Implementation Approaches

Local practitioners should consider implementation methodology when 

seeking to address intersection safety within their jurisdiction. Typical 

approaches include:

•	 Systematic approach;

•	 Spot location approach; and

•	 Comprehensive approach incorporating human behavior issues.

1.3.1. Systematic Approach

For the systematic approach, the analysis is based on crash types and 

proven safety countermeasures selected based on those types. 

In one application of the systematic approach, common crash types are 

selected from analysis. Locations experiencing these crash types and 

locations with similar geometric features as those experiencing selected 

crash types are selected and treated systematically with low-cost safety 

countermeasures. 

Another application of the systematic approach begins with identifying 

low-cost, effective countermeasures to common traffic safety issues. 

Once a basic set of countermeasures is identified, the crash data system 

is analyzed to choose locations where the countermeasures can be costeffectively deployed. Estimates of the impacts of implementation can be 

made in terms of deployment cost and the benefits measured in traffic 

crash reduction. 

8 An example Intersection Safety Implementation Plan is available at:

http://safety.fhwa.dot.gov/intersection/resources/sfty_imp_pln0709/index.cfm#toc 
Intersection Safety | 4

Benefits of the systematic approach may include:

•	 Widespread effect. The systematic approach can impact safety issues at 

a large number of locations on an entire local roadway network.

•	 Crash type prevention. Using predominant crash types with a high 

or moderate level of crashes, an agency can address locations that have 

not yet experienced these crash types, but have similar characteristics 

to locations with such crash histories (e.g., geometric conditions, traffic 

volume).

•	 Cost-effectiveness. Implementing low-cost solutions across an entire 

system can be a more cost-effective approach to addressing system-wide 

safety.

•	 Reduced data needs. The systematic approach can be used without 

detailed crash history for specific locations, reducing data needs. 

Drawbacks of the systematic approach may include:

•	 Justifying improvements can be difficult. Because this approach 

does not always address locations with a history of crashes with 

recommended treatments, it can be difficult to justify improvements at 

locations without crash history. The systematic approach will rarely include 

a recommendation for a large-scale safety improvement at a single location. 

Since these are the types of projects that garner attention from decision 

makers, the media, elected officials, and the general public, it can require 

additional effort from the safety practitioner to explain the systematic 

approach and its benefits to those groups.

1.3.2.Spot Location Approach

The spot location approach has typically been based exclusively on 

an analysis of crash history. Due to the fact that some locations in a 

jurisdiction may have a significantly higher number of crashes than most 

of the others, it is important to identify those locations and treat them 

accordingly. 

The benefits to the spot location approach may include:

•	 Focus on demonstrated needs. The spot location approach focuses 

directly on locations with a history of crashes and addresses them.

Drawbacks of the spot location approach may include:

•	 Assumption that the past equals the future. This approach assumes 

locations with a history of crashes will continue to have the same number 

and type of crashes in the future.

•	 Minimal overall benefit. This approach often focuses on specific 

locations, and because of this, it is difficult to have a significant impact on 

the entire network.
5 | Intersection Safety

The spot location approach to traffic safety can be implemented in 

parallel with the systematic approach to provide the best combination 

of safety treatments in a jurisdiction. In addition, the spot location 

approach could be applied to those locations that have had low-cost 

countermeasures installed systematically but, after an assessment, 

continue to show a higher than average crash rate.

1.3.3.Comprehensive Approach

The comprehensive approach introduces the concept of the 4 E’s 

of Safety; Engineering, Enforcement, Education, and Emergency 

Medical Services. This approach recognizes that not all locations can 

be addressed solely by infrastructure improvements. Incorporating 

other elements is often required to achieve marked improvement in 

intersection safety.

Some intersections will be identified that have frequent driving violations 

for which targeted enforcement is an appropriate countermeasure. In 

general, the most common violations at intersections are speeding, 

failure-to-yield, aggressive driving, failure to wear safety belts, and 

driving while impaired. When locations are identified that have reports 

and observations of these violations, coordination with the appropriate 

law enforcement agencies is needed to deploy visible targeted 

enforcement at the identified intersections to reduce the potential for 

future driving violations and related crashes. Education and outreach 

efforts should supplement enforcement to improve the effect of each. 
Intersection Safety | 6

1.4. Information in this Document

The purpose of this document is to provide information on effectively 

identifying intersection safety issues and countermeasures that address 

them, leading to the effective implementation of safety projects. This 

includes pertinent information regarding the Manual on Uniform Traffic 

Control Devices (MUTCD) requirements, guidance on conducting field 

reviews, identification of unsignalized intersections with multiple crashes 

and/or high potential for future crashes, selection of the appropriate 

low-cost improvement at these intersections, and evaluation of safety 

projects and processes.

This document is intended to provide appropriate intersection safety 

information in one report. Some practitioners responsible for the safety 

of the local road network may not have formal safety-specific highway 

training; this can present a challenge in reducing the risk of crashes at 

rural unsignalized intersections on local roads. In addition, the person 

responsible for highway safety may have multiple responsibilities 

including public works functions, such as water and/or wastewater 

treatment, trash collection, and snow removal. In these cases, roadway 

safety and infrastructure maintenance may be only a small part of the 

job. 

The report is not intended as a comprehensive guide for intersection 

design and improvement. It does, however, provide a framework that 

can be used to assess the safety of existing intersections and determine 

whether additional countermeasures should be installed.

This document suggests a process for the planning and implementation 

of intersection safety improvements. The processes discussed in this 

document are summarized in Figure 2.
7 | Intersection Safety

Safety issues can be identified by collecting crash history, 

roadway, and exposure information from the following 

sources:

•	State and local crash databases

•	Law enforcement crash reports and citations

•	Observations by law enforcement or road maintenance crews

•	Public notifications

•	Hospital records

•	State and local roadway databases

•	Traffic count records

Compile information in a table that includes the source of 

the information, the type of problem, and other attributes of 

the crash, observation, or notification.

Step 1

Identify Intersection Safety Issues

(Manual: Section 2)

Step 2

Record Information for Safety Analysis

(Manual: Table 1)

Steps 3 & 4

Data Analysis, Countermeasure Selection, 

and Installation

Depending on the approach, the order of data analysis, 

countermeasure selection, and countermeasure installation 

steps may vary.

Spot Location Approach 

and Systematic Approach 

(Crash Type Focus)

Systematic Approach 

(Countermeasure Focus)
Intersection Safety | 8

Data can be analyzed in the 

following ways, based on 

available information:

•	Crash frequency

•	Crash rate calculations

•	Qualitative analysis

Details from crash data and 

analysis feeds the countermeasure selection process.

•	 Enhanced signing

•	 Transverse rumble strips

•	 Clear sight triangles

•	 Other

Step 3

Analyze Data

(Manual: Section 3)

Step 4

Select and Install

Countermeasures

(Manual: Section 4)

Step 5

Assessment and Follow-up

(Manual: Section 5)

Evaluate intersection safety treatments after installation.

•	 Track countermeasure installations

•	 Monitor crash experience at treated locations

Step 3

Select Countermeasures

(Manual: Section 4)

Develop a list of

countermeasures and

thresholds for their

application (e.g. crash

frequency, crash type,

traffic volumes).

Step 4

Analyze Data and Install 

Countermeasures

(Manual: Section 3 and 4)

•	Search crash data for the 

criteria identified in Step 3.

•	Determine cost-effective 

level of deployment for each 

countermeasure.

Spot Location Approach 

and Systematic Approach 

(Crash Type Focus)

Systematic Approach 

(Countermeasure Focus)

Figure 2 – Steps to Address Intersection Safety
9 | Intersection Safety

Section 2 of this manual provides an overview of the types of data to 

collect for the identification of intersection safety issues. It discusses the 

sources of crash data and how they can be used. Additionally, types of 

roadway data used in safety analyses are introduced.

Section 3 summarizes the types of analysis that can feed the issue 

identification and countermeasures selection process. This discussion 

builds on the types of information and data discussed in Section 2 

and provides definitions and examples of the factors that should be 

considered. 

Section 4 provides a description of selected countermeasures that have 

been shown to improve safety at unsignalized intersections on local rural 

roads. It includes a basic set of strategies – supplementary warning signs 

and pavement markings – to install at locations experiencing a history 

of crashes. The section also introduces additional safety strategies, 

including flashing beacons on Stop signs and turn lane modifications. 

The steps to complete an evaluation are presented in Section 5. 

After the countermeasures are installed, assessing their effectiveness 

will provide valuable information and can help determine which 

countermeasures should continue to be installed on other intersections 

to make them safer as well.

In Section 6 a summary of the overall content of the manual is 

presented.

A list of resources and references is presented in Appendix A. It includes 

publications that focus on intersection countermeasures, research that 

supports their use, and various studies that document their effectiveness. 

The appendix also includes references that focus on the use of datadriven processes for countermeasure selection, assessment procedures 

and strategies, descriptions of successful programs, and national 

programs that may help identify resources to support local efforts. 

Appendix B addresses compliance with MUTCD minimum requirements 

for rural unsignalized intersections. The MUTCD provides the standards 

used by road managers nationwide to install and maintain traffic control 

devices on all public streets, highways, bikeways, and private roads open 

to public traffic.
Intersection Safety | 10

2 Identifying Safety Issues

Determining what the problems are and where they are occurring will 

assist in making the most informed decisions regarding countermeasure 

selection and implementation to address intersection safety issues. 

When conducting a safety analysis, a minimum of 3 years of data is 

desired to obtain an accurate picture of the crash history within a 

jurisdiction, since crashes are relatively rare events and are not universally 

distributed across all intersections. A relatively large representative 

sample size for crashes in the jurisdiction will increase the chance that 

locations with the most severe safety issues will be identified. Due to the 

possibility of changes in traffic patterns and the roadway itself, data more 

than 5 years old are typically not desirable for assessing safety issues. 

Analysis can range from simple “push pin” maps for identifying crash 

clusters to statistical analyses of crash rates, depending on the crash 

history and other data available. 

There are a number of information sources used to identify crashes and 

risk factors at rural intersections. These include:

•	 State and local crash databases;

•	 Law enforcement crash reports and citations; 

•	 Observational information from road maintenance crews and law 

enforcement; and 

•	 Public notification of safety concerns.

In order to determine the intersections with a history of crashes (and 

those with a potential for future crashes), it is important to consider the 

types of data available and how those data can be used. In addition 

to the location of the crashes, the data can also provide information 

regarding crash causation to help identify potentially effective 

countermeasures. 

The types of data available can range from anecdotal information, such 

as public input, to crash databases provided by State or local agencies. In 

some cases it may be beneficial to collect data from multiple sources to 

identify safety issues occurring at intersections.

The following discussion presents the most common information 

sources and recommendations for their use. 
11 | Intersection Safety

2.1. State and Local Crash Databases

Each State has a central repository for storing crash data that identifies 

locations with crash occurrences. Information found in a typical crash 

database includes; time and date of the crash, location, crash type, 

crash severity, and weather conditions. These data can be used to help 

compare a jurisdiction’s intersections with others in the State. This 

comparison can help determine the level of need as it relates to similar 

locations in the region. Often States will provide or assist local agencies 

with their crash data analysis needs. Crash data is typically stored by the 

State Department of Transportation (DOT), Department of Public Safety 

(DPS), or Department of Revenue (DOR). 

In addition, some local jurisdictions keep their own crash and roadway 

databases. If these exist, the information can be used as described above.

Action: Depending on your State’s organizational structure, contact 

the county, regional, or State engineer or your State’s Local Technical 

Assistance Program (LTAP) representative to determine if crash data 

within your jurisdiction is available for your use. If available, obtain 3 to 5 

years of crash and roadway characteristic data. Develop a spreadsheet 

for intersections with a history of crashes (see Table 1). This can serve 

as a basic database to help identify common crash characteristics and 

identify appropriate countermeasures. 

2.2. Law Enforcement Crash Reports and Citations

If an agency does not have access to State crash databases, law 

enforcement crash reports can be a valuable tool to identify the location 

and contributing circumstances to intersection crashes. The following 

variables (at a minimum) should be extracted and compiled from the 

crash reports:

•	 Location;

•	 Date and time;

•	 Crash type;

•	 Crash severity;

•	 Weather conditions;

•	 Sequence of events; and

•	 Contributing circumstances.
Intersection Safety | 12

Review of law enforcement crash reports can support decisions 

regarding the locations to improve and the safety treatments to select. 

While the information collected by law enforcement personnel may 

differ by jurisdiction, the basic elements should provide sufficient data to 

identify intersections that need improvement. 

Citation records by law enforcement can provide information regarding 

driver behavior issues within a jurisdiction. Though not correlated 

directly to crash locations, citation information can indicate overall issues 

in the region that can potentially be addressed with enforcement and 

education strategies.

Police reports should be reviewed periodically in order to compile the 

necessary information for conducting an analysis. This information can 

also be stored in the spreadsheet shown in Table 1.

Action: Develop a relationship with law enforcement officials responsible 

for enforcement and crash investigation on their roads. This could 

foster cooperation in sharing crash reports and safety information and 

collaboration on problem intersections. 

2.3. Observational Information

The crews who maintain the roads and law enforcement officers can 

serve as valuable resources to identify problem areas. Since they travel 

extensively on the local roads, they are able to continuously monitor 

the region for actual or potential problems (e.g., reduced sight distance 

due to vegetation growth, missing signs). Road maintenance crews 

often keep logs of their work activities connected to traffic safety issues, 

including sign replacements and edge drop-off repairs. These logs can 

assist safety practitioners in identifying recurring safety issues.

Law enforcement personnel are sometimes aware of problem areas 

that may not show up in the crash database or be known by public 

works staff, especially issues occurring at night or on weekends. This 

supplemental information about intersection safety can be beneficial to 

the safety improvement process. 

Action: Develop a system for maintenance crews to report and record 

observed intersection safety issues and a mechanism to address them. 

Set up a regular meeting with local law enforcement to discuss their 

observations of traffic safety issues in the local jurisdiction. 
13 

| Intersection Safety

Source of 

Information

Date 

(MM/DD/

YYYY)

Type of 

Information Problem Crash? Nature of Crash Time of Day (24 hr time) Weather Conditions Traffic Conditions Intersetion Reviewed? Action? Date of Action

Local 

Newspaper 3/8/2008 Citizen Complaint Speeding N Y Pending

Local Police 4/8/2008 Police Report Crash Report Y

Vehicle traveling 

North on Route 

657 hit while 

making left turn 

onto Glade Drive

11:39 Clear Light Volume N

Local Police 11/12/2009 Police Report Crash Report Y

Vehicle traveling 

West on Glade 

collided with 

vehicle on Route 

657

23:04 Rain No Traffic N

Maintenance 

Crew 12/12/2009 Observation Missing Stop Sign N Y Replaced Stop Sign 12/19/2009

State Police 11/24/2008 Crash Report Y

Vehicle traveling 

West on Clifton 

Road rear-ended 

at intersection

19:21 Rain Light Volume N

Table 1. Sample Spreadsheet to Monitor Crashes/Observations at Local Intersections
Intersection Safety | 14

2.4. Public Notifications

Information about observed near misses or other perceived problems 

can support identification of intersections with safety issues and the 

potential for severe crashes. Occasionally, when near misses occur or an 

unsafe situation is observed, a citizen may notify the local government 

through an email, letter, telephone call, or public meeting. While this is 

anecdotal information, these sources can serve as important indicators 

that a problem may exist and would warrant further review and analysis 

to determine its extent. 

Public notification of intersection safety issues can come from 

community or regional newspapers and newsletters, or correspondence 

from local homeowner associations, neighborhood groups, or 

individuals. Receiving this information could help pinpoint which 

intersections are candidates for review and establish links and 

relationships with the community to foster communication on safety 

related issues.

Action: Acknowledge input and, depending on the nature of the 

problem, establish a plan to review the identified sites. Keep a record of 

notifications and periodically monitor them.

2.5. Roadway Data

It is also valuable to obtain information about the roadway infrastructure. 

The following roadway data are often used to assist practitioners in 

safety analyses at intersections:

•	 Roadway surface (dirt, aggregate, asphalt, concrete);

•	 Lane information for approaches (number, width);

•	 Median (type, width);

•	 Number of intersection legs;

•	 Configuration of intersection legs; and

•	 Traffic control devices present (signs, pavement marking, traffic signals).

This information can be combined with crash data to help local 

practitioners identify appropriate locations and treatments to improve 

safety. For example, if a local rural intersection is experiencing a high 

number of right angle crashes, analysis of the inventory of roadway 

elements could reveal that the roadway does not have Stop signs on any 

approaches. An appropriate countermeasure could be to install Stop 

signs to provide traffic control at that location.
15 | Intersection Safety

2.6. Exposure Data

The raw number of crashes can sometimes provide misleading 

information about the most appropriate locations for treatment. 

Introducing exposure data helps to create a more accurate comparison 

of locations. Exposure data provide a common metric to the crash data 

so intersections can be compared more appropriately.

The most common type of exposure data used at intersections is 

entering traffic volume. A count of the number of vehicles entering an 

intersection can provide information to the practitioner for comparison. 

For example, if two intersections have the same number of crashes but 

different entering traffic volumes, the location with fewer vehicles (i.e., 

less exposure) will have a higher crash rate, meaning that vehicles were 

more likely to have experienced a crash at that location. This rate reflects 

the fact that an increase in the number of vehicles has an effect on the 

expected number of crashes.
Intersection Safety | 16

3 Safety Analysis

Conducting safety analyses will assist the practitioner in identifying 

intersections with safety issues and selecting countermeasures to 

improve them. The types of analysis can be qualitative or quantitative. 

This section outlines steps to identifying intersections with safety issues 

and making data-supported decisions as to the type, deployment levels, 

and locations of countermeasures. These steps build on the previous 

discussion of overall safety implementation approaches and sources 

of information for identifying safety problems. Additional information 

on analysis procedures and data can be reviewed in “Road Safety 

Information Analysis: A Manual for Local Rural Road Owners.”

3.1. Crash Frequency

Crash frequency represents the number of crashes that have occurred at 

a particular intersection over a period of time. It can be determined from 

the State or local crash database (or law enforcement crash reports).

This allows the practitioner to:

•	 Summarize the crashes by type and location;

•	 Spatially display crash locations on a map using push pins or a computer 

software package; and

•	 Provide a report identifying intersections with a history of crashes.

Once this information is collected and displayed, the local practitioner 

can compare intersections using cluster analysis to determine crash 

experience by frequency levels. 

3.2. Crash Rate

Crash frequency alone is often inadequate when comparing multiple 

intersections or prioritizing locations for improvement. Crash rates 

can be an effective tool to measure the relative safety at a particular 

intersection. The ratio of crash frequency (crashes per year) to vehicle 

exposure (number of vehicles entering the intersection) results in a crash 

rate. Crash rate analysis can be a useful tool to determine how a specific 

intersection compares to the average intersection on the roadway 

network. 

For example, it is possible that two intersections in a jurisdiction 

(Intersection A and Intersection B) each have a similar number of crashes. 

However, Intersection A may have many more vehicles entering 
17 | Intersection Safety

the intersection on a typical day than Intersection B, as shown in Table 

2. In order to effectively compare the safety of the two locations, the 

practitioner must factor in the level of exposure to crashes for each 

intersection. Exposure data here is represented by the number of 

vehicles entering the intersection. Population and number of licensed 

drivers within a jurisdiction are other types of exposure data that can be 

used depending on the circumstances and availability.

Crash rate is often used to prioritize locations for safety improvements 

when working with limited budgets to achieve the greatest safety 

benefits with available resources.

Crash rates can be calculated using the following widely accepted 

equation. This equation can be used for any crash type or severity. The 

intersection crash rate based on vehicles entering the intersection is 

calculated as:

R = 1,000,000 x C

365 x N x V

Where:

R = Crash rate for the intersection expressed as crashes per million entering 

vehicles (MEV)

C= Total number of intersection-related crashes in the study period

N = Number of years of data

V = Traffic volumes entering the intersection daily 

This equation relies on traffic volume information. Actual and estimated 

traffic volumes are often compiled and kept by State highway agencies, 

local governments and property developers.

In the following example shown in Table 2, two intersections have 

approximately the same number of crashes but different entering 

traffic volumes. By factoring in traffic volume (exposure), the calculation 

indicates that Intersection B may be a more promising roadway for safety 

treatments due to its higher intersection crash rate (measured in number 

of crashes for every 1 million entering vehicles).

Location Intersection 

Crashes (C)

Entering Traffic 

Volume Years of Data (N) Intersection Crash Rate (R)*

Intersection A 25 14,000 5 0.98

Intersection B 22 6,500 5 1.85

*Measured as the number of crashes per 1 million entering vehicles.

Table 2. Example of the Intersection Crash Rate Calculation
Intersection Safety | 18

Intersection A

R = (1,000,000) (25) = 0.98 crashes per million entering vehicles

(365) (5) (14,000)

Intersection B

R = (1,000,000) (22) = 1.85 crashes per million entering vehicles

(365) (5) (6,500)

Action: Calculate the crash rates for intersections experiencing crashes 

in the jurisdiction, and then use that crash rate to prioritize locations for 

investigation and possible treatments. 

Develop a database to record crash rate calculations over time for 

comparison with intersections that have potential safety issues in the 

future. This can provide practitioners with a jurisdiction-specific average 

intersection crash rate for varying situations.

3.3. Geometric Issues

The geometric design of intersections can create navigational problems 

for motorists, potentially contributing to crashes at these locations. 

Among geometric design elements, two specific issues can cause safety 

concerns: sight distance limitations and skewed geometry.

3.3.1. Sight Distance

Insufficient sight distance can be a contributing factor in intersection 

traffic crashes. Intersection sight distance is typically defined as the 

distance a motorist can see approaching vehicles before their line of 

sight is blocked by an obstruction near the intersection. The driver 

of a vehicle approaching or departing from a stopped position at an 

intersection should have an unobstructed view of the intersection, 

including any traffic control devices, and sufficient lengths along the 

intersecting roadway to permit the driver to anticipate and avoid 

potential collisions. Examples of obstructions include crops, hedges, 

trees, parked vehicles, utility poles, or buildings. In addition, the 

horizontal and vertical alignment of the roadway approaching the 

intersection can reduce the sight triangle of vehicles navigating the 

intersection.

It is important for approaching motorists on the major road to see side 

street vehicles approaching the Stop sign, and for minor road motorists 

to see approaching major road vehicles before entering the intersection. 

Poor sight distance can lead to rear-end crashes on the approaches 
19 | Intersection Safety

and to angle crashes within the intersection because motorists may be 

unable to see and react to traffic control devices or approaching vehicles. 

The area needed for provision of this unobstructed view is called the 

Clear Sight Triangle (see Figure 3). 

Source: Modified from A Policy on Geometric Design of Highway and Streets, 5th Edition, 

American Association of State Highway and Transportation Officials (AASHTO), 2004.

Figure 3 – Sight Distance Triangles for 4-Leg Stop-controlled Intersections

The Intersection Sight Distance (ISD) is measured along the major road 

beginning at a point that coincides with the location of the minor road 

vehicle. Table 3 provides the recommended values for ISD, based on the 

following assumptions:

•	 Stop control of the minor road approaches;

•	 Using driver eye and object heights associated with passenger cars;

•	 Both minor and major roads are considered at level grade;

•	 Considers a left-turn from the minor road as the worst-case scenario (i.e., 

requiring the most sight distance); and

•	 The major road is an undivided, two-way, two-lane roadway with no turn 

lanes.

If conditions at the intersection being evaluated differ from these 

assumptions, an experienced traffic engineer or highway designer 

should be consulted to determine whether different ISD values should 

be used.

Clear Sight Triangle 

Looking Left

ISD

Clear Sight Triangle 

Looking Right

Location of Driver’s Eye 

(Use 15 feet from edge 

of nearest through lane)

ISD
Intersection Safety | 20

Speed (mph) Stopping Sight Distance 

(ft.)

Design Intersection

Sight Distance (ft.)

25 155 280

30 200 335

35 250 390

40 305 445

45 360 500

50 425 555

55 495 610

60 570 665

65 645 720

Source: A Policy on Geometric Design of Highway and Streets, 5th Edition, American 

Association of State Highway and Transportation Officials (AASHTO), 2004.

Table 3 – Sight Distance at Intersections

Stopping Sight Distance (SSD) provides sufficient distance for drivers to 

anticipate and avoid collisions. However, in some cases this may require 

a major road vehicle to stop or slow to accommodate the maneuver 

by a minor road vehicle. To enhance traffic operations, sight distances 

that exceed the recommended SSD (as shown in Table 3) are desirable. 

Note that design intersection sight distance criteria for stop-controlled 

intersections are longer than stopping sight distance to ensure the 

intersection operates smoothly.

3.3.2.Skewed Geometry

Optimally, an intersection should be designed to have roadways cross 

at a 90-degree angle. In situations where the intersecting angles are 60 

degrees or less, the intersections are considered skewed (see Figure 4).

Figure 4 – Skewed Intersection
21 | Intersection Safety

Potential problems associated with skewed intersections include:

•	 Vehicles may have a longer distance to traverse while crossing or turning 

onto the intersecting roadway, resulting in an increased period of exposure 

to the cross-street traffic; 

•	 Older drivers may find it more difficult to turn their heads, necks, or upper 

bodies for an adequate line of sight down an acute-angle approach; 

•	 The driver’s sight angle for convenient observation of opposing traffic and 

pedestrian crossings is decreased; 

•	 Drivers may have more difficulty aligning their vehicles as they enter the 

cross street to make a right or left turn; 

•	 Drivers making right turns around an acute-angle radius may encroach on 

lanes intended for oncoming traffic from the right; 

•	 The larger intersection area may confuse drivers and cause them to deviate 

from the intended path;

•	 Motorists on the major road making left turns across an obtuse angle may 

attempt to maintain a higher than normal turning speed and cut across the 

oncoming traffic lane on the intersecting street; and

•	 The vehicle body may obstruct the line of sight for drivers with an acuteangle approach to their right. 

When crashes are occurring at skewed intersections, it may be desirable 

to reduce or eliminate the skew angle of the approaches. Treatments 

include pavement marking, delineator islands, and roadway realignment.

3.4. Field Reviews

Regardless of implementation approach, a field review should be 

conducted at identified locations. Intersection field reviews have the 

potential to identify safety issues and solutions. Field reviews can be 

conducted as informal field assessments or formal Road Safety Audits 

(RSAs). An informal field assessment is generally performed by an 

in-house team with available personnel. The team will spend time 

at identified intersections and document safety issues to develop 

recommendations for improvement. 

An RSA is a formal safety performance examination of an existing or 

future road or intersection by an independent, multidisciplinary team. 

The process includes a formal report on existing or potential road safety 

issues and identifies opportunities for safety improvements for all road 

users.9

9 More information on RSA’s can be found in Appendix A: Resources and References.
Intersection Safety | 22

When conducting field reviews at intersections, one source of 

information to reference is the MUTCD. It provides the minimum 

standards for the installation and maintenance of traffic control devices 

on all public streets, highways, bikeways, and private roads open to 

public traffic.10 Complying with the MUTCD standards is an important 

step toward a safer transportation system. If the intersection is not in 

compliance with the MUTCD, it should be brought up to standard. Noncompliance is an important consideration that can affect road safety and 

may have liability implications.

There are several elements to consider for this review, as listed below. 

The appropriate MUTCD sections are noted in parentheses and summary 

information pertinent to intersections is found in Appendix B. These 

elements are:

•	 Signs

» Retroreflectivity requirements (Section 2A.07, Section 2A.08)

◊ All regulatory, warning, and guide signs should display the same colors 

both day and night. Retroreflectivity (reflecting light back to its source) 

allows signs to do this.

» Stop and Yield sign placement (Section 2B.10)

◊ Stop and Yield signs should be installed as close as practical to the 

intersection and on the right-hand side of the approach to which it 

applies.

» Sign types (regulatory, warning) (Section 2A.05)

◊ The MUTCD defines specific functions for each category of sign. 

» Sign sizes (Section 2A.11)

◊ The MUTCD defines minimum dimensions for all signs.

» Number of signs and clutter (Section 2A.04)

◊ The installation of signs should be a conservative process as 

unnecessary signs could cause a loss of effectiveness for all signs.

•	 Pavement Markings

» Retroreflectivity (Section 3A.03)

Action: Analyze crash data to determine crash frequency and crash 

clusters. 

Calculate the crash rate of identified locations for comparison and 

prioritization. 

Identify intersections with common safety-related characteristics for 

potential systematic treatment of safety strategies.

Conduct field reviews of selected locations to determine their 

compliance with the MUTCD and identify any other potential safety 

issues and countermeasures. 

10 Federal Highway Administration, Manual on Uniform Traffic Control Devices, Washington, DC: 

December 2009. The MUTCD can be accessed at http://mutcd.fhwa.dot.gov
23 | Intersection Safety

4 Countermeasures

To make the most informed decision regarding countermeasure 

selection, an agency should begin with the crash history data, 

observational information, and public notifications. After an analysis of 

that information, the local practitioner can choose appropriate safety 

treatments. The decision regarding which countermeasures to install to 

address a safety issue can be challenging. When appropriate, an agency 

should seek engineering expertise from a State or local engineer or 

through the State Local Technical Assistance Program (LTAP). 

For isolated high crash locations, the spot location approach is most 

appropriate. For those areas with a number of intersections with varying 

levels of crashes, systematic implementation of safety countermeasures 

is often the most effective approach. For locations that have yet to 

experience crashes, systematically applying safety treatments based on 

other criteria such as geometric configuration can prevent future crashes.

For example, a high proportion of crashes may occur at intersections that 

share common geometric or operational elements.11 Installing the same 

low-cost countermeasures at multiple intersections (where appropriate) 

could, in many cases, improve the cost effectiveness of the safety 

improvement. 

The countermeasures presented here represent strategies that have 

been used by State and local jurisdictions to improve rural unsignalized 

intersection safety. 

4.1. Enhanced Sign and Pavement Marking Improvements

For a conventional unsignalized intersection, a typical enhancement of 

sign and pavement markings as shown in Figure 5 should be considered. 

This installation is recommended for intersection locations that have 

experienced a high or moderate level of crashes. Depending on the 

crash type(s), crash frequency and roadway geometry at the location, 

one or more of the following treatments may be appropriate:

•	 For the minor road stop approach of the intersection, two Stop Ahead 

signs (mounted left and right) and a painted stop bar are recommended 

to warn the driver of a stop condition ahead. The first Stop sign is installed 

at the traditional right side location; a second is recommended in the 

median (if available) of the approach. To accommodate this left-mounted 

Stop sign, a small mountable curb is suggested. This curb and associated 

pavement markings provide the motorist with additional information that 

11 Federal Highway Administration, Low-Cost Safety Enhancements for Stop-Controlled and Signalized 

Intersections, FHWA-SA-09-020, (Washington, DC: May 2009).
Intersection Safety | 24

he or she is entering an intersection. At a three-leg T-intersection, a Double 

Arrow Board is installed on the far side of the intersection facing the minor 

approach to warn drivers that the roadway does not continue straight past 

the intersecting roadway.

•	 For the major road approach, Intersection Ahead warning signs are 

recommended (mounted left and right). In addition, it is recommended 

that street name signs be placed underneath each intersection warning 

sign. These street name plaques provide the driver with additional 

information about the street the motorist is approaching so he or she can 

make an early decision regarding potential turning movements.

•	 The installation of edge line and centerline pavement markings are also 

recommended on the main line approach, with a gap in the centerline 

pavement marking to indicate the presence of an intersecting roadway.

Even if all signs cannot be feasibly installed at a given intersection, 

enhancement of traffic control devices with installation of part of 

this sign and pavement marking package can provide some level of 

improved safety.

Figure 5 – Basic Package for Intersections Experiencing Crashes12

In addition to this basic package, supplemental enhancements can be 

installed as needed. For example, Stop signs can be oversized (typically 

48 inches wide, but sometimes up to 60 inches is acceptable), with a 

reflective red strip on the post, or with a flashing red beacon installed 

above the sign to increase recognition of the intersection. Flashing 

12 Federal Highway Administration, Low-Cost Safety Enhancements for Stop-Controlled and Signalized 

Intersections, FHWA-SA-09-020, (Washington, DC: May 2009).
25 | Intersection Safety

amber beacons and yellow reflective post strips can be added to 

warning signs. 

Additional enhancements to pavement markings include raised 

pavement markers (RPMs) and pavement legends, including the word 

“STOP” painted on the roadway just before the stop bar.

For intersections identified for safety improvements, additional analysis 

may be needed to determine the most appropriate countermeasures 

to reduce future crashes. The information compiled from the database 

will help determine, for each intersection, the contributing crash 

and roadway attributes that will form the foundation for selecting 

appropriate countermeasures.

4.2. Select Intersection Countermeasures

This section contains specific information on a number of select 

countermeasures to prevent future crashes at unsignalized intersections. 

These individual treatments should be considered in addition to, or 

in lieu of, the basic package discussed previously to address specific 

safety issues. This does not represent an all-inclusive list of intersection 

countermeasures; for additional countermeasures see the following 

documents.

•	 NCHRP Report 500, Volume 5. “A Guide for Addressing Unsignalized 

Intersection Collisions.”

•	 Federal Highway Administration, “Objectives and Strategies for Improving 

Safety at Unsignalized and Signalized Intersections.”

•	 Federal Highway Administration, “Intersection Safety Strategies Brochure.”

Each countermeasure discussed includes the following information:

•	 Crash Type Addressed – In order to effectively reduce the number and 

severity of intersection crashes, it is necessary to match countermeasures 

to the crash types they are intended to address. For example, if the most 

frequent crash types are angle crashes due to poor sight distance with an 

overgrowth of foliage, the most effective countermeasure would be to clear 

the intersection’s sight triangles to improve sight distance.

•	 Where to use – Some countermeasures will have specific types of 

intersections where their benefit is greater than others. For example, the 

addition of a turn lane is most likely to benefit an intersection with a high 

number of turning vehicles.

•	 Why it works – A discussion of the benefit of a countermeasure is important 
Intersection Safety | 26

to determine its appropriateness to address certain intersection crash types.

•	 Timeline for Implementation – This category refers to the relative 

approximate time it can take to implement the countermeasure. 

•	 Estimated cost – Most countermeasures included in this report are 

considered low-cost; low to moderate cost; or moderate cost. These 

categories represent relative costs of the countermeasures to each other. 

Costs can vary considerably due to local conditions.

•	 Crash Reduction Factor – The crash reduction factor (CRF) for a given 

countermeasure is an indication of how many crashes a treatment is 

expected to reduce if installed. It is calculated based on research conducted 

on the pre- and post-crash frequencies at sites where the countermeasure 

has been installed specifically to address a certain crash type. For example, 

an oversized Stop sign may be installed to improve recognition of the 

intersection. In this case, it is expected that right-angle crashes at the 

intersection will be reduced. The higher the CRF, the greater the expected 

reduction in crashes. For instance a CRF of 20 percent is interpreted 

as an expected reduction of 20 percent of crashes.13, 14 The effect of a 

countermeasure on crashes can also be expressed as a Crash Modification 

Factor (CMF). It is defined mathematically as 1 – CRF. In the example above, 

a 20 percent reduction of crashes is represented by a CMF of 0.80. This 

effect of the countermeasure can be calculated by multiplying its value by 

the number of current crashes to determine an expected number of future 

crashes. For instance, if there are 50 current crashes, by multiplying the CMF 

of 0.80 times 50, one could expect 40 future crashes. 

13 Unless otherwise noted, CRFs in this document were from “Issue Brief: Toolbox of Countermeasures 

and Their Potential Effectiveness for Intersection Crashes.” Available at: 

http://safety.fhwa.dot.gov/intersection/resources/fhwasa10005/brief_8.cfm 

14 Additional CRFs can be found at the Crash Modification Factors Clearinghouse. Available at:

http://www.cmfclearinghouse.org 

Short Time Period

Moderate Time Period

Long Time Period
Unless otherwise noted, all Crash Reduction Factors (CRFs) in this document are from “Issue Brief 8: Toolbox of Countermeasures and Their Potential 

Effectiveness for Intersection Crashes,” FHWA, 2009.

27 | Intersection Safety Crash type addressed Right-angle and rear-end crashes attributed to drivers unaware of the intersection. Time: Cost: Low

CRF: 40%

Where to useUnsignalized intersections that are not clearly visible to approaching motorists, particularly approaching motorists on the major road. The strategy is particularly appropriate for intersections with patterns of rear-end, right-angle, or turning crashes related to lack of driver awareness of the presence of the intersection.Why it worksInstallation of signing in advance of and at intersections will provide approaching motorists with additional information at these locations. Drivers should be more aware that the intersection is coming up, and therefore make safer decisions as they approach the intersection.

Improve Visibility of Intersections by Providing Enhanced Signing and Delineation
Unless otherwise noted, all Crash Reduction Factors (CRFs) in this document are from “Issue Brief 8: Toolbox of Countermeasures and Their Potential 

Effectiveness for Intersection Crashes,” FHWA, 2009.

Intersection Safety | 28

Crash type addressedRight-angle crashes attributed to drivers unaware of the intersection or failing to stop at the Stop sign.

Time:Cost: Low

CRF: Unknown 

Where to useAll stop-controlled intersections should be addressed with this treatment. Damaged signs should be replaced without undue delay, and a suitable schedule for inspection, cleaning, and replacement of Stop signs should be established. Why it worksThe Stop sign is often the only indication to drivers that conflicting traffic could be approaching at an intersection. Maintenance of Stop signs must be at a high standard to ensure that the effectiveness of the signs is retained.

Provide Improved Maintenance of Stop Signs
Unless otherwise noted, all Crash Reduction Factors (CRFs) in this document are from “Issue Brief 8: Toolbox of Countermeasures and Their Potential 

Effectiveness for Intersection Crashes,” FHWA, 2009.

29 | Intersection Safety Crash type addressed Right-angle crashes attributed to drivers unaware of the intersection or failing to stop at the Stop sign. Time: Cost: Low 

CRF: 19%

Where to useMinor road approaches where conditions allow the stop bar to be seen by an approaching driver at a significant distance from the intersection. Locations should be identified by patterns of crashes related to lack of driver recognition of the intersection. Why it worksProviding visible stop bars on minor road approaches to unsignalized intersections can help direct the attention of drivers to the presence of the intersection.

Provide a Stop Bar on Minor Road Approaches
Unless otherwise noted, all Crash Reduction Factors (CRFs) in this document are from “Issue Brief 8: Toolbox of Countermeasures and Their Potential 

Effectiveness for Intersection Crashes,” FHWA, 2009.

Intersection Safety | 30

Crash type addressedRight-angle and rear-end crashes attributed to drivers unaware of the intersection or failing to stop.

Time:Cost: Low

CRF: Unknown

Where to useUnsignalized intersections with patterns of right-angle crashes related to lack of driver awareness of the presence of the intersection. In particular, it might be appropriate to use this strategy at the first stopcontrolled approach (possibly of a series) located on a long stretch of highway without any required stops, or at an intersection located after a sharp horizontal curve.Why it worksInstallation of an additional Stop sign above the roadway will provide approaching motorists a clear message that they must stop at the intersection. This reduces the opportunity for right-angle crashes attributed to a driver inadvertently running the Stop sign.

Provide Supplementary Stop Signs Mounted Over the Roadway
Unless otherwise noted, all Crash Reduction Factors (CRFs) in this document are from “Issue Brief 8: Toolbox of Countermeasures and Their Potential 

Effectiveness for Intersection Crashes,” FHWA, 2009.

31 | Intersection Safety Crash type addressed Right-angle and rear-end crashes attributed to drivers unaware of the intersection or failing to stop at the Stop sign. Time: Cost: Low 

CRF: 12-58%

Where to useUnsignalized intersections with patterns of right-angle crashes related to lack of driver awareness of the intersection on an uncontrolled approach and lack of driver awareness of the Stop sign on a stopcontrolled approach. Why it worksFlashing beacons provide a visible signal to the presence of an intersection and can be very effective in rural areas where there may be long stretches between intersections as well as locations where nighttime visibility of intersections is an issue.

Install Flashing Beacons at Stop-Controlled Intersections

Angle crashes
Unless otherwise noted, all Crash Reduction Factors (CRFs) in this document are from “Issue Brief 8: Toolbox of Countermeasures and Their Potential 

Effectiveness for Intersection Crashes,” FHWA, 2009.

Intersection Safety | 32

Crash type addressedRight-angle and rear-end crashes attributed to drivers unaware of the intersection.

Time:Cost: Moderate

CRF: 35-45%

Where to useMinor road approaches to unsignalized intersections where the presence of the intersection or the stop sign is not readily visible to approaching motorists. The strategy is particularly appropriate for intersections where the speeds on the minor road are high.Why it worksThe installation of splitter islands allows for the addition of a stop sign in the median to make the intersection more conspicuous. Additionally, the splitter island on the minor-road provides for a positive separation between turning vehicles on the through road and vehicles stopped on the minorroad approach.

Install Splitter Islands on the Minor Road Approach to an Intersection

Injury crashes
Unless otherwise noted, all Crash Reduction Factors (CRFs) in this document are from “Issue Brief 8: Toolbox of Countermeasures and Their Potential 

Effectiveness for Intersection Crashes,” FHWA, 2009.

33 | Intersection Safety

Unless otherwise noted, all Crash Reduction Factors (CRFs) in this document are from “Issue Brief 8: Toolbox of Countermeasures and Their Potential Effectiveness for Intersection Crashes,” FHWA, 2009.

Crash type addressedRight angle and roadway departure crashes attributed to motorists unaware of Stop or Yield signs as they approach an intersection.

Time:Cost: Moderate

CRF: 28-35%

Where to useTransverse rumble strips are installed in the travel lane for the purposes of providing an auditory and tactile sensation for each motorist approaching the intersection. They can be used at any stop or yield approach intersection, often in combination with advance signing to warn of the intersection ahead. Due to the noise generated by vehicles driving over the rumble strips, care must be taken to minimize disruption to nearby residences and businesses. Why it worksWhen motorists are traveling along the roadway, they are sometimes unaware they are approaching an intersection. This is especially true on rural roads, as there may be fewer cues indicating an intersection ahead. Transverse rumble strips warn motorists that something unexpected is ahead that they need to pay attention to.

Install Transverse Rumble Strips
Unless otherwise noted, all Crash Reduction Factors (CRFs) in this document are from “Issue Brief 8: Toolbox of Countermeasures and Their Potential 

Effectiveness for Intersection Crashes,” FHWA, 2009.

Intersection Safety | 34

Crash type addressedRight-angle and left-turn crashes attributed to poor sight distance at the intersection. Minor road vehicles could be turning right, left, or going straight.

Where to useUnsignalized intersections with restricted sight distance and patterns of crashes related to lack of sight distance where sight distance can be improved by clearing roadside obstructions without major construction.Why it worksBy removing sight distance restrictions (e.g., vegetation, parked vehicles, signs, buildings) from the sight triangles at stop or yield-controlled intersection approaches, drivers will be able see approaching vehicles on the main line, without obstruction and therefore make better decisions about entering the intersection safely.

Time:Cost: ModerateCRF: 14-26%

Clear Sight Triangles on Stop- or Yield-Controlled Approaches to Intersections
Unless otherwise noted, all Crash Reduction Factors (CRFs) in this document are from “Issue Brief 8: Toolbox of Countermeasures and Their Potential 

Effectiveness for Intersection Crashes,” FHWA, 2009.

35 | Intersection Safety Crash type addressed Rear-end crashes attributed to right turning vehicles hit from behind. Time: Cost: Moderate

CRF: 14-26%

Where to useUnsignalized intersections with a high frequency of rear-end crashes resulting from conflicts between (1) vehicles turning right and following vehicles and (2) vehicles turning right and through vehicles coming from the left on the cross street.Why it worksProviding right-turn lanes at intersections will allow vehicles that are traveling through the intersection to continue without stopping while turning vehicles will use the right-turn lanes. Assuming turn lanes are of adequate length, vehicles will not be stopped on the travel lanes which allows for through traffic to continue without stopping for vehicles turning at an intersection.

Provide Right-Turn Lanes at Intersections
Unless otherwise noted, all Crash Reduction Factors (CRFs) in this document are from “Issue Brief 8: Toolbox of Countermeasures and Their Potential 

Effectiveness for Intersection Crashes,” FHWA, 2009.

Intersection Safety | 36

Crash type addressedRear-end crashes attributed to left turning vehicles hit from behind.

Time:Cost: LowCRF: 24%

Where to useAt three-legged unsignalized intersections on two-lane highways with moderate through and turning volumes, especially intersections that have a pattern of rear-end collisions involving vehicles waiting to turn left from the mainline.Why it worksProviding bypass lanes on the shoulder will allow vehicles that are traveling through the intersection to continue without stopping, thus reducing the potential for stopped vehicles waiting to make the turn from being hit from behind.

Right-angle injury crashes

Provide Bypass Lanes on Shoulder at T-Intersections
Unless otherwise noted, all Crash Reduction Factors (CRFs) in this document are from “Issue Brief 8: Toolbox of Countermeasures and Their Potential 

Effectiveness for Intersection Crashes,” FHWA, 2009.

37 | Intersection Safety Crash type addressed Rear-end crashes attributed to left-turning vehicles hit from behind. Time: Cost: Moderate

CRF: 28-48%

Where to useUnsignalized intersections with a high frequency of crashes resulting from the conflict between (1) vehicles turning left and following vehicles and (2) vehicles turning left and opposing through vehicles.Why it worksProviding left-turn lanes at intersections will allow vehicles that are traveling through the intersection to continue without stopping while turning vehicles will use the left-turn lanes. Assuming turn lanes are of adequate length, vehicles will not be stopped on the travel lanes which allows for through traffic to continue without stopping for vehicles turning at an intersection.

Provide Left-Turn Lanes at Intersections
Unless otherwise noted, all Crash Reduction Factors (CRFs) in this document are from “Issue Brief 8: Toolbox of Countermeasures and Their Potential 

Effectiveness for Intersection Crashes,” FHWA, 2009.

Intersection Safety | 38

Crash type addressedHead-on and angle crashes due to left-turning motorists pulling out in front of opposing through traffic.

Time:Cost: Moderate-High

CRF: 20-26%

Where to useUnsignalized 4-legged intersections with a high frequency of crashes between vehicles turning left and opposing through vehicles. This treatment can be applied at intersections on divided highways with medians wide enough to provide the appropriate positive offset, and also on approaches without medians if sufficient width exists.Why it works Positive offset turn lanes provide the left-turning motorist a line of sight to opposing through vehicles. Instead of attempting to look around opposing left-turning vehicles, the motorist can clearly see oncoming traffic.

Provide Offset Left-Turn Lanes at Intersections

Urban locations
Unless otherwise noted, all Crash Reduction Factors (CRFs) in this document are from “Issue Brief 8: Toolbox of Countermeasures and Their Potential 

Effectiveness for Intersection Crashes,” FHWA, 2009.

39 | Intersection Safety Crash type addressed Skew reduction or elimination is appropriate at unsignalized intersections with a high frequency of crashes resulting 

from insufficient sight distance caused by the skew.

Time:Cost: Moderate - HighCRF: Varies

Where to useSkew realignment is appropriate at unsignalized intersections with a high frequency of crashes resulting from insufficient intersection sight distance and awkward sight lines at a skewed intersection. Why it worksReducing or eliminating the skew at intersection approaches helps address problems like vehicle alignment, long exposure in the intersection, and potential driver confusion. Treatments include pavement markings, channelizing islands, and realignment.

Realign Skewed Intersection

* The CRF varies by the degree of skew. Details are available at

http://safety.fhwa.dot.gov/intersection/resources/intsafestratbro/ub16_intersection_skew.pdf

*The CRF varies by the degree of skew.
Unless otherwise noted, all Crash Reduction Factors (CRFs) in this document are from “Issue Brief 8: Toolbox of Countermeasures and Their Potential 

Effectiveness for Intersection Crashes,” FHWA, 2009.

Intersection Safety | 40

Crash type addressedRight-angle, left-turn, and rearend crashes attributed to dark conditions.

Time:Cost: Moderate-HighCRF: 38%

Where to useUnsignalized, unlit intersections with substantial patterns of nighttime crashes. In particular, patterns of rear-end, right-angle, or turning crashes on the major road approaches to an unsignalized intersection may indicate that approaching drivers are unaware of the presence of the intersection.Why it worksAt night in rural areas, the only source of lighting for roadways is generally provided by vehicle headlights. Roadway lighting allows for greater visibility of the intersection which makes the intersection more conspicuous to motorists and provides aid in helping drivers determine their paths through the intersection by making signs and markings more visible.

Improve Visibility of the Intersection by Providing Lighting

Injury crashes
Unless otherwise noted, all Crash Reduction Factors (CRFs) in this document are from “Issue Brief 8: Toolbox of Countermeasures and Their Potential 

Effectiveness for Intersection Crashes,” FHWA, 2009.

41 | Intersection Safety Vehicle on side street Original alignment Modied alignment Sight distance before realignment

Sight distance after realignment

Crash type addressed

Right-angle and rear-end crashes attributed to poor sight distance.

Time:Cost: High

CRF: 5-17%

Where to useUnsignalized intersections with restricted sight distance due to horizontal and/or vertical geometry and with patterns of crashes related to that lack of sight distance that cannot be ameliorated by less expensive methods.Why it works Although changing alignment is a high cost treatment, in some cases sight distance is restricted by horizontal and vertical curvature. Straightening a roadway will increase sight distance and allow for better visibility of other vehicles and the intersection itself.

Change Horizontal and/or Vertical Alignment of Approaches toProvide More Sight Distance
Unless otherwise noted, all Crash Reduction Factors (CRFs) in this document are from “Issue Brief 8: Toolbox of Countermeasures and Their Potential 

Effectiveness for Intersection Crashes,” FHWA, 2009.

Intersection Safety | 42

Crash type addressedRight-angle and left-turn crashes attributed to motorists unaware of Stop or Yield signs, unaware of conflicting traffic at the intersection, or misjudging gaps in the mainline traffic.

Time:Cost: High

CRF: 71%

Where to useRoundabouts can be installed in a wide variety or rural locations. In particular, unsignalized intersections with a history of right angle crashes are good candidates for roundabout installation. Sufficient agency-owned right-of-way is necessary to install the roundabout, as its geometric footprint differs from a traditional intersection. Why it worksRoundabouts are a proven safety treatment for intersection crashes due to a reduced number of conflict points and reduced intersection speeds. A motorist approaching the intersection looks in only one direction for conflicting traffic before entering the roundabout. The geometry of the approach legs and the inner circle keep speeds low, reducing the severity of any crash that might occur.

Install Roundabout Intersection
43 | Intersection Safety

4.3. Funding Intersection Safety Countermeasures

Each State has a Strategic Highway Safety Plan (SHSP) as a requirement of 

the Federal funding legislation: the Safe, Accountable, Flexible, and Efficient 

Transportation Equity Act: A Legacy for Users (SAFETEA-LU). As part of that 

requirement, Federal funds are set aside for transportation safety projects. 

Some sources of Federal safety funding include the following:

•	 Highway Safety Improvement Program (HSIP). The HSIP is a Federal 

Aid program focused on improving traffic safety on all public roads with 

infrastructure solutions.

•	 High Risk Rural Roads Program (HRRRP). The HRRRP is a set aside from 

the HSIP funds. It focuses on addressing rural road safety needs on rural 

major and minor collectors and local rural roads with construction and 

operational improvements. 

•	 Safe Routes to School (SRTS) Program. The SRTS Program empowers 

communities to make walking and bicycling to school a safe and routine 

activity. The program makes funding available for a wide variety of programs 

and projects, from building safer street crossings to establishing programs 

that encourage children and their parents to walk and bicycle safely to 

school.

Human behavior-related funding sources for traffic safety include the 

following:

•	 NHTSA Programs. The National Highway Traffic Safety Administration 

(NHTSA) provides a number of funding sources focused on human behavior 

aspects of traffic safety with emphases on speeding, safety belt use, child 

passenger safety, and impaired and distracted driving.15

•	 GHSA Programs. Programs promoted by the Governors Highway Safety 

Association (GHSA) target unsafe driving practices at the State level.16 

In addition, potential access to other transportation funding sources 

(not directly focused on safety) for safety projects may also be available. 

Further information about Federal funding sources can be accessed at 

the FHWA Office of Safety website: http://safety.fhwa.dot.gov. 

Outside the Federal funding sources, State safety funds may be available 

to a jurisdiction for intersection safety projects.

Action: Contact the State DOT or LTAP Center to find out more 

information about how Federal and State safety funds are used and could 

potentially be used to support safety projects at local intersections. 

15 For details on NHTSA funding sources, see National Highway Traffic Safety Administration, 

“SAFETEA-LU Information and Facts Sheets” available at: http://www.nhtsa.gov/About+NHTSA/

Programs+&+Grants/SAFETEA-LU+Information+and+Facts+Sheets 

16 For details on GHSA Program funding sources, visit http://www.ghsa.org.
Intersection Safety | 44

5 Evaluation

It is important to evaluate intersection safety treatments after installation 

to determine their effectiveness. The effort that goes into conducting 

the assessment will help guide future decisions regarding intersection 

countermeasures.

A record of crash histories, if available, and countermeasure installations 

forms the foundation for assessing how well implemented strategies 

have performed. It is important to keep a current list of installed 

intersection countermeasures with documented “when/where/why” 

information. Periodic assessments will provide the necessary information 

to make informed decisions on whether each countermeasure 

contributed to an increase in safety, whether the countermeasure could 

or should be installed at other locations, and which factors may have 

contributed to the strategy’s success.

To perform the assessment it is necessary to collect the required 

information for a period of time after strategies were deployed at the 

intersection. The time period varies, but should be no less than one 

full year (with 3 years preferred). The information required may consist 

of public input and complaints, police reports, and observations from 

maintenance crews. The most important information is crash data 

before and after implementation.

It is important to keep the list of strategy installations up to date since 

it will serve as a record of countermeasure history. By using this type of 

system, assessment dates can be scheduled to review the crashes and 

other pertinent information at intersections where treatments have been 

installed (see Table 4). 

Action: Develop a spreadsheet to track future safety project installations 

and record 3 years of “before” crash information at those locations.
45 

| Intersection Safety

Table 4. Example Spreadsheet to Monitor Countermeasure Application History and Crash/Observational Data

Intersection Specific Location Type of Countermeasures Installed Date Installed Date Removed (If Appl.) Comments

3 Years Prior to Installation 1 Year After Installation

Number 

of Public 

Comments

Number 

of 

Crashes

Number 

of Near 

Misses

Number 

of Public 

Comments

Number 

of 

Crashes

Number 

of Near 

Misses

Middlebrook 

Pike and 

Waples Mill 

Road

Waples 

Mill –

West 

Approach

Stop Sign 12/19/2009 Sign was old and faded 0 0 0

Rt. 123 and 

Fox Mill Road

Fox Mill 

Road – 

South 

Approach

Stop Bars 7/9/2008 5 0 1 2 0 0

Route 657 and 

Glade Drive

Route 

657 – East 

Approach

Traffic Island at Stop 

Approach 6/4/2008 2 2 3 0 0 2

Route 657 

and Clifton 

Road

Clifton 

Run – 

North 

Approach

Added Left-turn 

Lane 8/8/2007 4 1 3 1 0 0
Intersection Safety | 46

6 Summary

Fatalities at rural road intersections account for approximately 40 percent 

of the national intersection related fatalities; more than 80 percent of 

these fatalities occur at unsignalized intersections. Local administrators, 

township managers, and public works officials who maintain and operate 

local rural roads should be engaged in intersection safety to identify 

intersections with safety issues and choose countermeasures to reduce 

the number and severity of intersection crashes. 

To date, several States have completed Intersection Safety 

Implementation Plans with assistance from FHWA. These plans were 

developed to guide intersection safety implementation activities on State 

and local roads arising from the State Strategic Highway Safety Plans. The 

plans include the activities, countermeasures, strategies, deployment 

levels, implementation steps, and estimate of funds necessary to achieve 

intersection safety goals. The local road practitioners should consult 

their State’s Intersection Safety Implementation Plan, if available, before 

embarking on an improvement strategy.

When seeking to address local rural road intersection safety, the local 

practitioners should consider which implementation approach to 

use. The three main approaches are systematic, spot location, and 

comprehensive. Availability and quality of intersection crash and roadway 

data, the number of locations to be addressed, and available funding 

are factors that may play a role in the selection of an implementation 

approach.

Determining the nature of the problems and their locations will assist 

in making the most informed decisions for countermeasure selection 

and implementation in addressing intersection safety issues. When 

conducting a safety analysis, a minimum of 3 years of crash data is 

desired to obtain an accurate picture of the intersection safety issues 

within a jurisdiction, since crashes are relatively rare events and are not 

universally distributed across all intersections. Due to the possibility of 

changes in traffic patterns and the roadway itself, data more than 5 years 

old are typically not desirable for assessing safety issues. 

Analysis can range from simple “push pin” maps for identifying crash 

clusters to statistical analyses of crash rates, depending on the crash 

history and other available data. There are a number of information 

sources that can be used to identify crashes that are occurring at rural 

intersections; State and local crash databases, law enforcement crash 

reports and citations, observational information from road maintenance 

crews and law enforcement, and public notification of safety concerns. 
47 | Intersection Safety

Other variables to be considered when conducting analysis include crash 

location, date and time, crash type, crash severity, weather conditions, 

sequence of events, and contributing circumstances. In addition, roadway 

data and traffic volumes are factors to be considered when determining 

the intersection safety issues.

Regardless of the implementation approach chosen, a field review 

should be conducted at identified locations. Intersection field reviews 

have the potential to identify safety issues and solutions that cannot be 

determined by data analysis alone. Field reviews can be conducted as 

informal field assessments or as formal Road Safety Audits (RSAs). 

Decisions regarding which countermeasures to install to address a safety 

issue can be challenging. When appropriate, the local practitioner should 

seek engineering expertise from a State or local engineer or through 

the State Local Technical Assistance Program (LTAP). For a conventional 

unsignalized intersection, a typical enhancement of sign and pavement 

markings including double Stop signs, Stop Ahead signs and stop bars on 

the minor leg(s) of the intersection and intersection warning signs and 

appropriate pavement markings for the major leg(s) of the intersection 

should be considered. This installation is recommended for intersection 

locations that have experienced a high or moderate level of crashes. 

In addition, a high number of supplemental countermeasures are 

available for deployment based on crash history, location, and level of 

effectiveness. 

Countermeasure assessment after implementation is important to 

the intersection safety program. This will inform the practitioner of 

the effectiveness of the strategy and if it should be applied to other 

locations. The most common methodology for the evaluation of a 

given countermeasure is the analysis of crash data before and after its 

installation. Three years of data after the installation is ideal for evaluation, 

however, changes in traffic volume and roadway information can also 

affect the outcome and should be taken into account during assessment. 

Local highway agencies have unique responsibilities and challenges 

related to the safety of the intersections on their roadway system. By 

beginning any traffic safety effort using a data-supported approach, 

those agencies will be in a better position to address their highway 

safety needs. While the challenge to decrease the number of intersection 

crashes on local rural roads can be challenging due to limited resources, 

there are a number of low-cost proven countermeasures that can be 

installed to improve intersection safety on local roads and many can be 

installed within a short timeframe.
Intersection Safety | A-1

Appendix A – Resources and References

This section contains references to further information on the types 

of countermeasures available, studies and technical reports on local 

rural roads and intersections, and guidelines used for countermeasure 

installation. 

Selected Technical Resources

Federal Highway Administration, Intersection Safety website. Available at 

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

Federal Highway Administration, Rural Intersection Safety website. 

Available at http://safety.fhwa.dot.gov/intersection/rural

Federal Highway Administration, Unsignalized Intersection Safety 

website. Available at http://safety.fhwa.dot.gov/intersection/unsignalized/

Federal Highway Administration, “Low-Cost Safety Enhancements 

for Stop-Controlled and Signalized Intersections,” FHWA-SA-09-020. 

(Washington, DC: 2009). Available at 

http://safety.fhwa.dot.gov/intersection/resources/fhwasa09020/

Federal Highway Administration, “Objectives and Strategies for 

Improving Safety at Unsignalized and Signalized Intersections,” 

(Washington, DC: 2008). Available at 

http://safety.fhwa.dot.gov/intersection/resources/intsafestratbro/inter_guide_

key.cfm

Federal Highway Administration, “Intersection Safety Strategies 

Brochure,” FHWA-SA-08-008 (Washington, DC: 2008). Available at 

http://safety.fhwa.dot.gov/intersection/resources/intsafestratbro/#ue

American Traffic Safety Services Association, National Association of County 

Engineers, “Low Cost Local Road Safety Solutions,” 2006. Available at 

http://safety.fhwa.dot.gov/intersection/resources/fhwasa09027/resources/

Low%20Cost%20Local%20Road%20Safety%20Solutions.pdf

Federal Highway Administration, “Guidance Memorandum on 

Consideration and Implementation of Proven Safety Countermeasures.” 

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

Neuman, T.R., et al. A Guide for Addressing Unsignalized Intersection 

Collisions, NCHRP Report 500, Vol. 5. TRB, National Research Council, 

Washington, DC. 2003. Available at: 

http://onlinepubs.trb.org/onlinepubs/nchrp/nchrp_rpt_500v5.pdf
A-2 | Intersection Safety

Federal Highway Administration, Road Safety Audits website.

Available at http://safety.fhwa.dot.gov/rsa/

Federal Highway Administration, Manual on Uniform Traffic Control 

Devices (Washington, DC: 2009). Available at http://mutcd.fhwa.dot.gov/

Federal Highway Administration, “Vegetation Control for Safety: A Guide 

for Local Highway and Street Maintenance Personnel” FHWA-SA-07-018 

http://safety.fhwa.dot.gov/local_rural/training/fhwasa07018/

McNinch, T.L. and Colling, T.K., “Traffic Safety Education for 

Nonengineers.” U.S. Department of Transportation, Federal Highway 

Administration, pp. 32-38, Public Roads, May/June 2009. Available at 

http://www.fhwa.dot.gov/publications/publicroads/09june/05.cfm

Resources Related to Program Development and Coordination

Local Technical Assistance Program (LTAP)

The web page below summarizes the roles and functions of the LTAP 

program and provides links, by State, for local points of contact who may 

help identify data, resources, and offer assistance. 

http://www.ltapt2.org/nltapa

Strategic Highway Safety Plans (SHSP)

Each State is required to develop an SHSP to promote best practices and 

strategies that are designed to have a substantial impact on reducing 

fatal and injury crashes. There is no central site for all State plans; to 

review your State’s plan, you will need to search using your State and 

“strategic highway safety plan” as search terms in order to access and 

review your State’s plan. The FHWA has resources available to help States’ 

in their development and implementation efforts. 

http://safety.fhwa.dot.gov/hsip/shsp/

Resources Related to Data Analysis and Evaluation

Federal Highway Administration, Highway Safety Facts and Statistics 

website. Available at http://safety.fhwa.dot.gov/facts_stats/

National Highway Traffic Safety Administration, Center for Statistics and 

Analysis, Fatality Analysis Reporting System (FARS). Available at

http://www-fars.nhtsa.dot.gov/Main/index.aspx
Intersection Safety | A-3

Green, E.R. and Agent, K.R., Crash Rates at Intersections, University of 

Kentucky College of Engineering, Kentucky Transportation Center. 

Research Report KTC-03-21/SPR258-03-2I (2003). Available at 

http://www.ktc.uky.edu/Reports/KTC_03_21_SPR258_03_2I.pdf

Gross, F. and Yunk, K. U.S. “Using CRFs to Improve Highway Safety.” 

Department of Transportation, Federal Highway Administration, Public 

Roads, May/June 2009, pp. 26-31. Available at 

http://www.fhwa.dot.gov/publications/publicroads/09june/04.cfm

Federal Highway Administration, “Issue Brief: Toolbox of 

Countermeasures and Their Potential Effectiveness for Intersection 

Crashes.” (Washington, DC: 2009). Available at 

http://safety.fhwa.dot.gov/intersection/resources/fhwasa10005/brief_8.cfm

Federal Highway Administration, “Desktop Reference for Crash Reduction 

Factors.” (Washington, DC: 2007). Available at 

http://www.ite.org/safety/issuebriefs/Desktop%20Reference%20Complete.pdf 

Federal Highway Administration, Crash Reduction Factors website. Available at 

http://safety.fhwa.dot.gov/tools/crf/

Federal Highway Administration, Crash Modifications Factors 

Clearinghouse website. Available at http://www.cmfclearinghouse.org/

Examples of State Programs and Initiatives

Federal Highway Administration, “Making the Case for Transportation 

Safety – Ideas for Decision Makers” (Washington, DC: 2008) Available at 

http://tsp.trb.org/assets/briefing%20book%20hi-res.pdf

Iowa Department of Transportation, “Crash Analysis.” Available at 

http://www.intrans.iastate.edu/pubs/traffichandbook/5CrashAnalysis.pdf

Minnesota Department of Transportation and Minnesota Local 

Road Research Board, Safety Impacts of Street Lighting at Isolated Rural 

Intersections, 2004. Available at 

http://www.ctre.iastate.edu/reports/rural_lighting.pdf

Federal Highway Administration, Wyoming Technical Transfer Center, 

Kansas LTAP, “Field Guide for Unpaved Rural Roads.” (2004) 

http://www.t2.unh.edu/pubs/field_guide.pdf 
B-1 | Intersection Safety

Appendix B – MUTCD Compliance Issues at Rural, 

Two-Way Stop-Controlled Intersections

All Signs

Retroreflectivity (MUTCD Table 2A-3)

The MUTCD provides suggestions for methods to be used:

A.Visual Nighttime Inspection—The retroreflectivity of an existing sign 

is assessed by a trained sign inspector conducting a visual inspection 

from a moving vehicle during nighttime conditions. Signs that are visually 

identified by the inspector to have retroreflectivity below the minimum 

acceptable level should be replaced. 

B.Measured Sign Retroreflectivity—Sign retroreflectivity is measured 

using a retroreflectometer. Signs with retroreflectivity below the minimum 

acceptable level should be replaced.

C. Expected Sign Life—When signs are installed, the installation date is 

labeled or recorded so that the age of a sign is known. The age of the sign 

is compared to the expected sign life. The expected sign life is based on 

the experience of sign retroreflectivity degradation in a geographic area 

compared to the minimum acceptable level. Signs older than the expected 

life should be replaced.

D.Blanket Replacement—All signs in an area/corridor, or of a given type, 

should be replaced at specified intervals. This eliminates the need to assess 

retroreflectivity or track the life of individual signs. The replacement interval 

is based on the expected sign life compared to the minimum levels for the 

shortest-life material used on the affected signs.

E. Control Signs—Replacement of signs in the field is based on the 

performance of a sample of control signs. The control signs might be a 

small sample located in a maintenance yard or a sample of signs in the field. 

The control signs are monitored to determine the end of retroreflective life 

for the associated signs. All field signs represented by the control sample 

should be replaced before the retroreflectivity levels of the control sample 

reach the minimum acceptable level.

F. Other Methods—Other methods developed based on engineering studies 

can be used.
Intersection Safety | B-2

Roadside Placement (MUTCD, Figure 2A-2)

For a typical rural road with no shoulder, the sign should be placed 

on the right side of the roadway, 12 feet laterally from the edge of the 

traveled way. In terms of vertical height, the bottom of the sign should 

be installed 5 feet above the ground elevation at the edge of pavement.

Enhancing Sign Conspicuity Cost Effectively (MUTCD Figure 2A-1)

In a situation where it is desirable to enhance a sign’s conspicuity, any of 

the following methods may be used:

•	 Increasing the size of the sign; 

•	 Doubling-up by adding a second identical sign on the left hand side of the 

roadway; or

•	 Adding a strip of retroreflective material to the sign support.

Regulatory Signs and Markings

Stop Sign (R1-1)

Sign Size

The minimum size for a STOP sign shall be 30” x 30” for a typical rural, 

two-lane facility.

Stop Bars

Design

Stop bars shall be a solid white line.

Stop bars should be 12-24” wide.

Placement

The stop line should be placed at the desired stopping or yielding point, 

but should not be placed more than 30 feet or less than 4 feet from the 

nearest edge of the intersecting traveled way.

Pavement Markings

Design

Markings should be visible at night by use of retroreflectivity or ambient 

illumination (Section 3A.03).

The MUTCD specifies allowable colors for pavement markings and the 

function of each color. (Section 3A.05).

Placement

To avoid confusion to the road user, pavement markings should be 

placed according to the MUTCD, and pavement markings which are no 

longer applicable should be removed (Section 3A.02)
B-3 | Intersection Safety

Warning Signs

All Signs

When to use

The use of warning signs shall be based on an engineering study or on 

engineering judgment.

Placement

Warning signs should be installed in advanced of the intersection in 

accordance with Table 2C-4, which provides placement distances based 

on speed.

Stop Ahead (W3-1)

Sign Size: 30” x 30” minimum

These signs shall be installed on an approach to a STOP sign that is not 

visible for a sufficient distance to permit the road user to respond to the 

device.

To be used only on the “side road” that must come to a stop.

Intersection Ahead (W2-1, W2-2, W2-3, W2-4)

Sign Size: 30” x 30” minimum

The Intersection Warning sign should illustrate and depict the general 

configuration of the intersecting roadway, such as cross road, side road, 

T-intersection, or Y-intersection. 

Advisory Speed Plaque (W13-1P)

Sign Size: 18” x 18”

Roadside Placement

The sign height changes when a speed plaque is added. See Figure 2A-2, 

Page 38, for details.

Two-Direction Large Arrow (W1-7)

Sign Size: 48” x 24”

The two-direction large arrow shall be installed on the far side of a 

T-Intersection in line with, and at approximately a right angle to, traffic 

approaching from the stem of the T-intersection.
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For More Information

Office of Safety

Federal Highway Administration

1200 New Jersey Ave, SE

Washington, DC 20590-9898

http://safety.fhwa.dot.gov

FHWA-SA-11-08