Intersection Safety

Short Version

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Photo of a multi-vehicle crash at a signalized intersection with EMS and police responders on the scene.


Downloadable Version
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slide notes:

This is an approximately 30-minute presentation on the topic of safety at intersections. The presentation is intended to relay safety issues at intersections (including the typical types of crashes) along with some techniques to address these issues. Specific topics covered include:

  • National and state statistics concerning fatalities at intersections.
  • Various resources that are available to help states increase safety and reduce fatalities at intersections.
  • Basic techniques for improving intersection safety.

This presentation is a summary on intersection safety and is one of a series of five presentations on intersection safety issues. The other presentations address in particular:

  • Red light running
  • Signalized intersections
  • Unsignalized intersections
  • Roundabouts

More details, including countermeasure effectiveness information, can be found in these four presentations.

A longer 60-minute version of this presentation is also available that includes more information on national data statistics and FHWA research efforts.


slide 2


Intersections

Traffic photo of a ninety degree collision between two vehicles in an intersection.

  • Among the most hazardous components of the highway system for all users (planned points of conflict)
  • Complex speed-distance judgments under time constraints
  • Interstates (full access control) have fatality rates less than half of other highway types

slide notes:

Major Points to Make:

  • Intersections are complex features of our transportation system. They are planned points of conflict that include ALL users. And each user group has their own particular needs when it comes to navigating through an intersection. And oftentimes these needs conflict with the needs of each other.
  • It has been estimated that there are at least 3 million intersections in the U.S. of which some 300,000 (or more) are signalized.


slide 3


National Statistics

Stacked bar chart shows that total highway fatalities has remained fairly steady over the past 11 years.

slide notes:

Major points to make:

  • This graph shows the number of total fatalities on the highway system (not just intersections) for the past 11 years.
  • Overall, there has been very little change in the number of fatal crashes in the past decade. However, when vehicle-miles of travel are factored, the fatality rate has dropped from 1.64 (in 1997) to 1.36 (in 2007) fatalities per million vehicle-miles travelled (source: FARS database).
  • Further the percentage of fatal crashes occurring at intersections essentially remained unchanged at 22-23% (see data in table below).
  • The past 3 years of data indicate a downward trend in total fatal crashes, but it is too soon to tell if this is just normal fluctuation (randomness) in crash data, or if, indeed, there is an improvement in safety due to recent emphasis and investment in safety projects.


slide 4


National Statistics

  • There were 41,059 highway fatalities in 2007. Where did they occur?
  • About half of all crashes and half of all injury crashes occur at intersections.

Pie chart shows that 79 percent of fatalities occur at non-intersections and 21 percent occur at intersections.


slide notes:

Major points to make:

  • This slide represents the most recent published crash data in the FARS database. Includes only FARS elements of "intersection" and "intersection-related" fatalities.
  • A little more than half of all crashes occur at intersection locations.


slide 5


Intersection Fatalities

  • There were 8,657 intersection fatalities in 2007.
  • Where did they occur?

Image indicates that 39 persent of intersection fatalities occur in rural areas and 61 percent occur in urban areas.  Chart breaks down total fatalities by arterial road (5,232), collector (1,472), local road (1,739), and unknown (214).


slide notes:

Major points to make:

  • Looking at just intersection fatalities, we see that well over 1/2 occur in urban areas and the majority occur on arterial facilities.
  • 60% of intersection fatalities occur on arterial streets.
  • For rural intersection fatalities, approximately 90% occur at unsignalized intersections and 10% at signalized intersections
  • For urban intersection fatalities, approximately 60% occur at unsignalized intersections and 40% at signalized intersections.
  • Fatalities at unsignalized intersections constitute about 3/4 of the total number of intersection fatalities while about 1/4 occur at signalized intersections.
  • Source: FARS database


slide 6


State Statistics

Map indicates the number of fatal crashes (not individual fatalities) that occurred in each state that were classified as either 'intersection' or 'intersection-related' in the 2007 FARS database.

slide notes:

Major points to make:

  • This map indicates the number of fatal crashes (not individual fatalities) that occurred in each state that were classified as either "intersection" or "intersection-related" in the 2007 FARS database.
  • Darker shades indicate higher numbers of crashes, lighter shades indicate fewer crashes.


slide 7


Red Light Running

Fatalities Attributed to Red Light Running
Chart shows fatalities attributed to red-light running over the period 2000 to 2007. The trend has remained generally consistent during the period, with fatalities remaining in the 800 to 1000 range, although there is a notable dip in fatalities in 2005 to below 800.


slide notes:

Major points to make:

  • This chart shows the number of fatalities that are attributed to red light running crashes (according to the FARS database) for the years 2000-2007.


slide 8


Pedestrians

2007 Pedestrian Fatalities at Intersections
Chart indicates total pedestrian fatalities for 2007 was 1,152. The age groups with the highest fatalities were the 45-54 and over 74 groups, with the second highest fatalities occurring in the 35-44, 55-65, and 65-74 age groups; and the third most fatalities occurring in the 25-34 age group.


slide notes:

Major points to make:

  • This chart shows the age distribution of pedestrian fatalities at intersections in the US for 2007 (according to the FARS database). Obviously older pedestrians are at much greater risk when negotiating intersections.


slide 9


Crash Type Distribution

Pie chart shows that 45 percent of crashes are right angle-crashes, 17 percent are pedestrian/bicycle crashes, 13 percent are single vehicle (object) crashes, 14 percent are opposite direction crashes, 6 percent are rear-end crashes, 3 percent are sideswipe crashes, and 2 percent are other crashes.


slide notes:

Major points to make:

  • This pie chart looks at the categories slightly different from the previous slide. This shows the distribution of crash types for intersection crashes involving at least one FATALITY. This data is for all intersections combined. The FARS database does not identify crash categories exactly like the previous slide. The main point is, however, that right-angle collisions certainly account for the largest piece of the pie.


slide 10


Crash Reduction Factors

Image of the cover of the 'Desktop Reference for Crash Reduction Factors.'   Cover shot of the FHWA document 'Toolbox of Countermeasures and Their Potential Effectiveness to Make Intersections Safer.' and a link to the FHWA Report Center at report.center@dot.gov


slide notes:

Major points to make:

  • The Desktop Reference for Crash Reduction Factors is a an extensive list of countermeasures and their effectiveness at reducing crashes. Some CRFs are based on very robust research studies. Others are based on smaller sample sizes and may not be statistically significant. Notes are included to indicate this.
  • Crash reduction factors for the many countermeasures shown in subsequent slides in this presentation are included in the desktop reference and in Issue Brief #8. 


slide 11


Techniques for Improving Safety

  • Increase visibility of intersections and traffic control devices
  • Increase awareness of intersections
  • Improve the design of intersections to reduce conflicts
  • Improve driver comprehension to reduce confusion
  • Improve the operations of intersections
  • Improve sight distance at intersections
  • Improve driver compliance with traffic control devices

slide notes:

Major points to make:

  • This slide simply lists the major categories for improving safety for ALL USERS at intersections (as outlined in the NCHRP Series 500 Reports on Signalized Intersections and Unsignalized Intersections). There are other categories that are not covered in this presentation but this list covers the vast majority of techniques. Far more detail on safety techniques can be found in the presentations on "Safety at Signalized Intersections" and "Safety at Unsignalized Intersections" and in the NCHRP Series 500 Reports (Volumes 5 and 12), the accompanying guide sheets, and brochure.
  • The following slides will give a few examples of each technique. However, they do not represent all of the ways to implement the technique.


slide 12


Increasing Visibility

Collage of images including a photo of an intersection featuring one signal head per lane, a photo of a 12 inch lens on a signal head, signal heads with back plates, and the covers of NCHRP Report 500 and an FHWA publication on low-cost safety enhancements for intersections.


slide notes:

Major points to make:

  • Lack of visibility of traffic control devices may contribute to crash experience at intersections. Visibility of traffic signals and signs at intersections may be obstructed by physical objects (such as signs or other vehicles) or may be obscured by weather conditions, such as fog or bright sunlight. Also, drivers' attention may be focused on other objects at the intersection, such as extraneous signs. Poor visibility of signs and signals may result in vehicles not being able to stop in time for a signal change or otherwise violating the intended message of a regulatory or directional sign. Providing adequate visibility of signs and signals also aids in drivers' advance perception of the upcoming intersection.
  • Note: The photo on the bottom is of a traffic signal that was undergoing an upgrade that very day. When the photograph was taken, only the leftmost signal head had a backplate installed. By the end of the day, all three signal heads had backplates. The photo clearly shows how much of an improvement backplates can have on visibility.
  • Document(s) shown:
    • NCHRP Report 500, Volume 12: A Guide for Reducing Collisions at Signalized Intersections (HTML and free PDF download at AASHTO's web site). This report covers a vast array of countermeasures at signalized intersections (not just increasing visibility).
    • Signalized Intersection Safety Guide Sheets (HTML and free PDF download at FHWA Office of Safety web site). There are 77 Safety Guide Sheets that cover various strategies for improving safety at intersections. 28 of them relate to signalized intersections, 49 are applicable to unsignalized intersections.


slide 13


Increasing Visibility

Collage of images including a photo of oversized Stop signs at a multi-lane highway crossing, supplemental streetlights on a rural roadway, and the covers of NCHRP Report 500 and an FHWA publication on low-cost safety enhancements for intersections.


slide notes:

Major points to make:

  • Other examples of increasing visibility.
  • Document(s) shown:
    • NCHRP Report 500, Volume 5: A Guide for Addressing Unsignalized Intersection Collisions (HTML and free PDF download at AASHTO's web site). This report covers a vast array of countermeasures at unsignalized intersections (not just increasing visibility).
    • Unsignalized Intersection Safety Guide Sheets (HTML and free PDF download at FHWA Office of Safety web site). There are 77 Safety Guide Sheets that cover various strategies for improving safety at intersections. 28 of them relate to signalized intersections, 49 are applicable to unsignalized intersections.


slide 14


Increasing Awareness

Collage of photos including an advance signal ahead warning sign, a splitter island at the approach to a T intersection, Stop Ahead pavement markings, and the a screenshot of a new FHWA document on low-cost improvements for stop-controlled and signalized intersections.


slide notes:

Major points to make:

  • Some intersection-related collisions occur because one or more drivers approaching an intersection are unaware of the intersection until it is too late to avoid a collision. This is a particular problem for high-speed uncontrolled approaches. Improving signing and delineation and installing lighting can help warn drivers of the intersection.
  • Document(s) shown:
    • Low Cost Safety Enhancements for Stop-Controlled and Signalized Intersections (available soon on the FHWA Office of Safety web site). This document covers numerous improvements beyond just increasing awareness of intersections to improve safety. The NHCRP Series 500 reports and Safety Guide Sheets (shown on previous 2 slides) are also excellent sources of information.


slide 15


Improving Design

Collage of photos depicting a roundabout, a roadway redesigned to reduce skew, and pavement remarking to create dedicated turn lanes on a rural road. Image also contains screenshots of two publications on roundabouts.


slide notes:

Major points to make:

  • Reducing the frequency and severity of vehicle-vehicle conflicts at intersections can reduce the frequency and severity of intersection crashes. This can be accomplished by separating through and turning movements at the intersection, minimizing the skew angle of intersecting roads, providing acceleration lanes, closing or relocating intersections, or constructing roundabouts (which can significantly reduce the number of fatal and major injuries crashes).
  • Document(s) shown:
    • Roundabouts: An Informational Guide (HTML and free PDF download at FHWA Office of Safety web site) – in process of being updated, new version expected in late 2009 or early 2010 (as of June 2009)
    • Roundabouts: A Safer Choice (HTML and free PDF download at FHWA Office of Safety web site)
    • Other design improvement countermeasures are covered in the Series 500 Reports on signalized and unsignalized intersections and the accompanying guide sheets.


slide 16


Improving Design

Photos of a channelized turn lane and a closed driveway near an intersection as well as an image of a CD labeled 'Access Management Manual.'


slide notes:

Major points to make:

  • Design of intersections can also be improved by implementing an access management program/policy. For more information on this topic, visit the TRB Access Management Committee's web page at: http://www.accessmanagement.info/
  • Document(s) shown:
    • Access Management Manual (available for purchase from TRB)
    • Various access management techniques are also discussed in the Series 500 Reports on signalized and unsignalized intersections and the accompanying guide sheets.


slide 17


Improving Comprehension

Two photos, one in which overhead signs guide drivers to the correct lane for the route they wish to take, one of an aerial photo of a complex intersection featuring turn markings on the pavement to guide turning vehicles through the intersection and into the correct lane.


slide notes:

Major points to make:

  • Complex intersections can provide challenges to unfamiliar drivers. By improving signing and marking, drivers can more easily navigate such intersections. In the left photo, overhead signing is used to give drivers advance notice of which lane they need to be in. The photo on the right shows turn markings (sometimes called "cat" tracks, "chicken" tracks, etc.) to assist drivers making left turns at a large intersection.


slide 18


Improving Operations

Collage of images indicating improved operations through light phasing (improved signal timing), modified change intervals, and signal coordination. Collage also includes a screenshot of the new FHWA Signal Timing Manual.

slide notes:

Major points to make:

  • Improvements to the method of assigning ROW at intersections can reduce the potential for conflicts. For signalized intersections, this can be accomplished by modifying signal phasing, improving coordination, providing additional traffic control devices and pavement markings, and restricting turn movements. Improvements to traffic control can also benefit traffic operations and reduce emergency response time.
  • Document(s) shown:


slide 19


Improving Operations

Collage of images including a pedestrian countdown signal head, a sign next to a signal head warning of turn restrictions, a worker removing a signal, and a screenshot of the cover of an FHWA signalized intersection informational guide.


slide notes:

Major points to make:

  • Other examples of improving operational characteristics of intersections.
  • Document(s) shown:
    • Signalized Intersections: Informational Guide (HTML and free PDF download at FHWA Office of Safety web site)
    • NCHRP 500 Volume 12 is also an excellent source for countermeasures related to signal operations.


slide 20


Improving Sight Distance

Collage of images depicting an intersection where overgrown shrubbery on the corner prevents adequate sight distance to stopped or turning vehicles, an offset turn lane, and a screenshot of the cover of an FHWA publication on intersection safety and design.


slide notes:

Major points to make:

  • Some collisions at intersections occur because of limited sight distance for drivers who are approaching the intersection or who are stopped on an intersection approach. Provision of clear sight triangles in each quadrant of an intersection can minimize the possibility of crashes related to sight obstructions.
  • Providing offset turn lanes can help safety by allowing left turning drivers to see oncoming through vehicles by slightly shifting the left turning vehicles to the left.
  • Document(s) shown:
    • Toolbox of Countermeasures and Their Potential Effectiveness to make Intersections Safer (part of a series of Intersection Safety Briefs available from the ITE web site). This document includes many crash reduction factors that can be used to estimate potential safety benefits of many of the countermeasures.
    • Toolbox on Intersection Safety and Design (available for purchase from ITE)
    • Improving sight distance techniques are also discussed in the Series 500 Reports on signalized and unsignalized intersections and the accompanying guide sheets.


slide 21


Improving Compliance

Collage of images including enforcement lights, a sign warning of automated photo enforcement at a signal ahead, a police officer writing a ticket, and the cover of an FHWA publication on making intersections safer.


slide notes:

Major points to make:

  • Many crashes are caused by noncompliance with traffic control devices or traffic laws at intersections. The use of enforcement (both traditional and automated) has been shown to be an effective measure in reducing traffic-law violations and, consequently, in improving safety at intersections.
  • Document(s) shown:
    • Making Intersections Safer: A Toolbox of Engineering Countermeasures to Reduce Red-Light Running (HTML and free PDF download at FHWA Office of Safety web site)
    • Various techniques for improving compliance are also discussed in the Series 500 Reports on signalized and unsignalized intersections and the accompanying guide sheets.


slide 22


Information and Education

Collage of images depicting web sites, printed material, and a speed trailer. Other educational opportunities exist in school programs, radio and TV, and community outreach.

slide notes:

Major points to make:

  • Information and education can be geared towards reducing crashes of ALL TYPES. However, it is presented here because of the fairly easy way to target pedestrians and bicyclists in schools and other civic organizations.
  • Providing targeted public information and education (PI&E) on safety problems at intersections is a preventive measure that can help improve driver compliance with traffic control devices and traffic laws. PI&E programs generally add effectiveness to targeted enforcement programs as well.
  • Another option is to develop public information campaigns aimed at specific drivers who violate regulations at intersections, even though it is often difficult to identify and focus upon a subset of the driving population using a specific intersection. Therefore, an area-wide program is often the preferred approach.
  • Data on the effectiveness of this strategy for this specific application are not known, but it is expected that providing information to drivers will help improve safety at intersections. It may not be possible to identify or reach the entire audience that would benefit from a PI&E campaign.


slide 23


Training Opportunities

National Highway Institute logo.  http://nhi.fhwa.dot.gov/

  • Signalized Intersection Guidebook Workshop
  • Intersection Safety Workshop
  • Designing and Operating Intersections for Safety
  • Interactive Highway Safety Design Model
  • Roundabout Workshop
  • Low-Cost Safety Improvements Workshop
  • Low-Cost Safety Improvements (Blended Approach)
  • Planning and Designing for Pedestrian Safety
  • Application of Crash Reduction Factors (CRF)
  • Science of Crash Reduction Factors

slide notes:

Major points to make:

  • This slide lists just some of the current training opportunities offered by NHI related to intersections and intersection safety. Visit the NHI web site for course details and to find out when and where they are being offered. Other organizations offer various training opportunities related to intersections and safety such as ITE (http://www.ite.org/) and ASCE (www.asce.org).


slide 24


For More Information


slide notes:

Major points to make:

  • These web sites can be accessed for further information on the material contained in this presentation.

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Program Contact

Ed Rice

202-366-9064

Jeffrey Shaw

708-283-3524

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FHWA's Intersection Resources Library CD-ROM

Highlights

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Mini-Roundabouts Technical Summary

Access Management in the Vicinity of Intersections Technical Summary

Intersection Safety Case Studies

Intersection Safety Technologies

Presentation: Intersection Safety

Example Intersection Safety Implementation Plan

Intersection Safety Implementation Plan Workshop

Example Data Analysis Package and Straw Man Outline