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Intersection safety is and has been a major program at the Federal Highway Administration (FHWA). Within intersections, vehicle-vehicle and vehicle-pedestrian conflicts occur as drivers, bicyclists, and pedestrians need to cross the path of other vehicles. Not surprisingly, the intersection, whether or not it is under traffic signal control, can be a hazardous location as evidenced by various motor vehicle crash statistics.
Utilizing the year 2002 crash database maintained as part of the National Accident Sampling System, there were an estimated 2.7 million motor vehicle crashes at intersections in the United States in 2002. Approximately 1.4 million crashes were reported at unsignalized intersections and 1.3 million were crashes reported at signalized intersections. An estimated 925,000 people were injured in the crashes at intersections. Approximately 445,000 people were injured in crashes at signalized intersections and nearly 480,000 were injured in crashes at unsignalized intersections. In terms of fatalities based on the Fatality Analysis Reporting System, a total of 9,117 people died in 2004 as a direct result of crashes for which the relation to junction was classified as at intersection (non-interchange) or intersection-related (non-interchange).
Drawing upon information in a recent 2001 paper by Harwood, et al., entitled "Overview of Current Intersection Safety Conditions"(1) and a compilation of crash statistics, the following statements further describe the crash experience at intersections in the United States:
As these crash statistics demonstrate, intersection safety is a significant problem in the United States. Achieving a higher level of intersection safety has become a priority of the safety community as evidenced by the following:
In May 2002, a scanning study of signalized intersection safety in Europe was sponsored by the FHWA and AASHTO. With the goal of improving signalized intersection safety, the focus of the scanning study was on innovative signalized intersection safety practices in Europe. In December 2003, the FHWA published Signalized Intersection Safety in Europe(2) as part of FHWA's International Technology Exchange Program. A copy of the cover is presented in figure 1. Given the relative success of that European scan and feedback on the report, FHWA decided that a scanning study should be conducted of select areas in the United States. It was hoped that a Domestic Scan would also produce tangible benefits through identifying, and making highway agencies aware of, innovative treatments and practices that have been successfully implemented in the United States.
Figure 1. FHWA's Report on Signalized Intersection Safety in Europe.
The goal of this Domestic Intersection Safety Scan was to reduce fatalities, personal injuries and crashes at intersections in the United States by documenting and subsequently promoting innovative intersection treatments and comprehensive intersection safety processes that have been implemented in this country.
One of the primary objectives was to identify and document selected innovative intersection treatments that have been implemented at intersections in the United States and have demonstrated, or have the potential to improve safety at intersections. Another objective was to identify and document selected comprehensive safety processes and procedures that have been implemented by transportation agencies specifically to improve intersection safety.
The range of treatments to be considered within the scan included treatments that addressed and/or contained the following elements:
During the scan, a secondary objective was to gain knowledge about and document the processes and procedures that were employed to gain agency management's approval for successful implementation and deployment. To the extent that the treatments had been evaluated by local agencies, the scan endeavored to gain knowledge about the safety effectiveness of these treatments and comprehensive approaches to intersection safety.
Because of limited resources, the scan team was limited to visiting five areas of the country. A search was conducted to identify areas where innovative intersection treatments and comprehensive safety processes have been implemented and the local agencies were recognized for their prominence in selected areas and expressed a willingness to participate and share their knowledge, time, and experiences. Additional weight was given to areas that were in states that are participating with FHWA on strategic safety programs. The areas that were ultimately selected are presented in figure 2, including the following:
Figure 2. Areas Visited.
The rationale for the selection of these areas is summarized below:
The cities of Detroit and Grand Rapids, Michigan, and the counties of Oakland, Kent and Livingston, Michigan. Several years ago, the American Automobile Association (AAA) Michigan, in concert with several agencies, conducted safety studies of target intersections selected based on crash severity. Improvements were designed and implemented, and a post-implementation evaluation study was performed. Since the AAA Michigan studies were so well documented, the focus for this scanning study was on the process that the local agencies subsequently incorporated into their practices.
Another notable program in Michigan is their intersection safety action plan, which was developed by the Governor's Traffic Safety Advisory Commission (GTSAC). The plan was developed by a diverse group of agencies involved in a variety of aspects that affect intersection safety. The multi-agency group developed a plan that included actions for each group and have continued to work together to foster improved intersection safety. For the purposes of this scanning study, the level of success achieved through interagency coordination was another primary reason for selecting Michigan.
While in Michigan, the scan team visited two transportation organizations. The Southeast Michigan Council of Governments (SEMCOG) developed a Web-accessible crash records system. The SEMCOG also participated in several other projects that had a high relevance to intersection safety, including the development of a very thorough traffic safety manual. The Oakland County Traffic Improvement Association (TIA) has been involved in the capture and distribution of crash reports for Oakland County, Michigan, since the late 1960s. It also has a long history of involvement in intersection safety improvement projects and programs in Oakland County. A joint meeting was held with the Road Commission for Oakland County (RCOC) and the Oakland County TIA.
The city of Richardson, Texas, and the Greater Dallas/Ft. Worth Metropolitan Area. The city of Richardson, Texas, has been involved with progressive red light running enforcement. Of particular interest was an experimental dynamic Red Light Hold (RLH) system that had been tested in the city. Conceptually, the red clearance interval is extended if a vehicle approaching at a relatively high rate of speed is predicted to enter the intersection when the signal indication was red. The RLH system alerts the controller and applies a "stop time" during the timing of the red clearance interval to permit safe passage of a red light runner. In addition, Richardson has been heavily involved with the use of the so-called "rat light" or "enforcement light," which is a light wired to the signal that illuminates when the traffic signal section displays a red indication. A police officer can observe the intersection and the "rat light" from a position downstream of the intersection and can determine when a vehicle runs a red light.
The second agency visited was the city of Dallas, which has been involved in many innovative intersection projects, especially in the area of traffic signal control. Dallas had implemented a software routine to the traffic signal controllers that allows pedestrians to depress the pedestrian push button for five seconds, triggering a longer flashing "DON'T WALK" interval. Consequently, a longer time to cross the street is provided to a pedestrian with reduced mobility capabilities. The process that Dallas has used includes meeting with elderly pedestrians at the intersections and walking with them.
The scan team also visited in the Fort Worth-Dalla area, the North Central Texas Council of Governments (NCTCOG). The NCTCOG is involved in several areas related to intersection safety and its leadership is very knowledgeable and progressive in promoting intersection safety within the region.
The city of Portland, Oregon. Several innovative intersection treatments geared toward pedestrians and bicyclists at intersections were identified in the city of Portland. Notably, the city's efforts to improve intersection safety have included the deployment of technologies for sensing pedestrians as they cross the street and lengthening the pedestrian clearance interval as needed. Portland also has a comprehensive traffic-calming program at intersections, and has implemented and evaluated several innovative safety treatments to enhance bicyclists' safety at locations where they cross-vehicular traffic paths.
The city of Charlotte, North Carolina. The city of Charlotte was recently selected by the FHWA to become an urban center for the Highway Safety Information System (HSIS). This decision was made because Charlotte has and maintains many unique data sets such as roadway inventory data that includes driveway density and curb types, turn movement counts with pedestrian crossing volumes, crash records for crashes reported on all streets in the city except Interstates (responsibility of State Patrol), traffic calming inventory data, sidewalk data, bike lane data, and transit bus stop data, among others. In terms of innovative treatments, Charlotte has an extensive amount of speed humps, speed tables, and unique pedestrian crossings. Charlotte was recognized by ITE for their programs in pedestrian safety.
The city of West Palm Beach and Florida DOT District 4 (Office: Fort Lauderdale) A location with innovative geometric intersection treatments was desired for the scanning study. One area identified was the city of West Palm Beach. The city has been known for innovation in traffic safety, notably being one of the first police forces to provide laptops to their officers for the automated preparation of police crash reports. It has recently been involved in new urbanism for street design. West Palm Beach redesigned and reconstructed a corridor in its downtown, specifically Clematis/Narcissus Street, as one of the first traffic calming/redevelopment projects for the city. The street was narrowed and shifted laterally, with trees, landscaping and storefront improvements. At the intersections, curb extensions slowed turning traffic and offered improved pedestrian crossings. Since the successful implementation of that project, the city developed a downtown master plan that featured similar intersection geometric projects.
While looking for other agencies in the West Palm Beach area, a very interesting project was initiated in the Fort Lauderdale area by the Florida Department of Transportation, District 4. The project was developed in an attempt to reduce the speed of drivers on a freeway off-ramp that terminated in a very sharp right turn onto a state highway. The system consisted of a series of activated in-pavement lights that flashed in a sequential manner if vehicles entering the ramp were detected to be traveling above 50 mph. It is important to note that while the junction of the ramp with the state highway was technically a ramp terminal, the potential for application to at-grade intersections was very appealing.
The participants on the scan team were selected to bring a different perspective to the team. They were selected to represent broad constituencies in city, county and State government and in the research field. Each invited participant had over 30 years of directly relevant experience in a wide range of areas related to intersection safety. These participants devoted 13 consecutive days to participating on the scan, and provided a wealth of knowledge and input to the development of this report. The team members included the following:
In addition to these individuals named above, Warren E. Hughes, P.E. and Jennifer Weigle of Vanasse-Hangen-Brustlin, Inc. served as scan team facilitator and scan logistics coordinator, respectively. Debra Chappell and Shyuan-Ren (Clayton) Chen, Ph.D., P.E., members of the FHWA Office of Safety Intersection Team, served as observers of the scan, and collaborators to this report.
Figure 3. Scan Team (From left: Gene Calvert, Loren Hill, Stan Polanis, Clayton Chen, Doug Harwood, Jen Weigle, and Warren Hughes). Not pictured: Debra Chappell.
The report is organized in the following manner:
Chapter 1 covers the scan background, goals and objectives, scope, team and organization.
Chapter 2 presents information on comprehensive safety management systems and processes that have the potential to positively improve intersection safety.
Chapter 3 covers innovative treatments involving traffic control devices for motorists.
Chapter 4 describes innovative traffic control and other devices for pedestrians and bicyclists at intersections.
Chapter 5 presents items related to traffic operations and not tied to specific traffic control device hardware.
Chapter 6 covers intersection geometric treatments.
Chapter 7 presents a concise discussion of selected enforcement and educational programs uncovered during the scan. Although the scan focus was not on enforcement or education, several items elated to enforcement and education were identified and discussed during the scan by the host agency.
Chapter 8 presents the scan team's conclusions.
Appendix A presents information about the scan team members, their affiliations, and brief biographies.
Appendix B contains a list of the agencies and their personnel who participated in the scanning tour and provided significant contributions.
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