Evaluating the Safety of Signalized Intersections

Transportation safety has been, and continues to be, a critical component emphasized by the United States Department of Transportation (USDOT). The number of deaths on highways in the United States remained steady for the 15 year period from 1990-2005 at approximately 40,000 fatalities per year. Since 2005 the number of deaths has declined steadily to 30,797 fatalities in 2009 (NHTSA 2011a). The fatality rate has continued to drop during the entire 20 year period from 1990-2009 due to an increase in the total number of vehicle miles traveled (VMT) in the nation. The rate has dropped from 2.08 fatalities per 100 million VMT in 1990 to 1.13 fatalities per 100 million VMT in 2009 (NHTSA 2011a). Even with this decline in traffic fatalities, there is still room for improvement in all areas of transportation safety. The Utah Department of Transportation (UDOT) has placed transportation safety at the forefront of their priorities over the past several years. One of the more active programs in the state is the "Zero Fatalities: A Goal We Can All Live With™" campaign. Since the inception of the campaign, awareness of the dangers of traffic safety has increased, while traffic fatalities in the state have dropped 37 percent since 2000 (UDOT 2011). While great strides have been made in transportation and traffic safety, there are continual improvements to be made. One area to consider for improvement in terms of transportation safety is that of signalized intersections. Each year the Utah Department of Transportation (UDOT) makes improvements to signalized intersections in an effort to improve safety (particularly to reduce right-angle crashes). These improvements include signalization of a non-signalized intersection, left-turn phasing, dilemma zone detection, improved roadway lighting, and others. Nationwide approximately 8 percent of all fatal crashes, 26 percent of all injury crashes, and 23 percent of all crashes occur at traffic signals (NHTSA 2011b). As such there is a need to address the safety benefits of signal improvements in an effort to identify those practices that have the highest benefit for safety reduction at signalized intersections. The primary objective of this research is to determine the safety effects of signal improvements at intersections as a function of crash reduction. The results of the research will be used to determine benefit/cost ratios for various signal improvements to help in allocating safety funds. Specifically the objectives of the research are to: 1) estimate safety benefits of signal improvements; 2) utilize UDOT databases (crash data, traffic studies, warrant reviews, etc.) to collect data on signalized intersection locations throughout the state that have had intersection improvements made to determine the safety benefits of such improvements; 3) develop crash modification factors for each improvement with a focus on specific crash types (generally high severity crashes); and 4) determine cost/benefit ratios for use in evaluating the effectiveness of signal improvements. UDOT will benefit from this project by better understanding the effectiveness of specific signal improvements in terms of overall safety and performance. The goal of UDOT Traffic & Safety is to reduce right angle crashes (and other severe crashes) at intersections, and ultimately to save lives, while effectively utilizing available funding. This research is important to help meet these goals. The measures developed will help UDOT Traffic & Safety determine the most efficient use of program funding. UDOT will benefit not only through Traffic & Safety, all citizens of the state will benefit through the safety improvements that will move the state closer to ZERO FATALITIES.


    • English


    • Status: Active
    • Contract Numbers:



    • Sponsor Organizations:

      Utah Department of Transportation

      4501 South 2700 West
      Project Development
      Salt Lake City, UT  USA  84114-8380
    • Project Managers:

      Nichol, Kevin

    • Performing Organizations:

      Brigham Young University

      Provo, UT  USA  84602-4081
    • Principal Investigators:

      Schultz, Grant

    • Start Date: 20111001
    • Actual Completion Date: 20130901
    • Source Data: RiP Project 33618

    Subject/Index Terms

    Filing Info

    • Accession Number: 01472090
    • Record Type: Research project
    • Source Agency: Utah Department of Transportation
    • Contract Numbers: 12-9109, UT11.303
    • Files: RiP
    • Created Date: Feb 13 2013 1:00AM