Differences in Gap Acceptance of Elderly Drivers and the Impact on Traffic Simulation Modeling

As the population of the US ages, so does the driving population. This is a potential problem for microscopic traffic simulation models, which depend heavily on assumptions about driver behavior. This project proposes to investigate the possibility that elderly drivers (65 years or older) exhibit different gap acceptance behavior when making unprotected left turns across oncoming traffic, and whether or not accounting for this different behavior improves the fidelity of micro-simulation models. Elderly and other drivers will be observed turning left at unsignalized intersections both with and without left turn lanes and when crossing either a single or two lanes of oncoming traffic on roads with different speed limits, and considering other relevant factors. Statistical analysis will be used to identify whether or not older drivers choose different gaps for turning left, and under which conditions these differences are most significant. Finally, traffic simulations of the observed conditions will be run with both default gap acceptance distributions and those observed to determine how sensitive the simulation program output is to this basic parameter. We expect the results to provide valuable information about how to more accurately account for the effect of growing numbers of seniors in the driving population as well as how to improve the safety and confidence of senior drivers as they become a more dominant element of the population. The objectives of this project are to conduct field studies of driving behavior classified by age category to identify differences in gap acceptance decisions between elderly and other drivers. This study will focus on left turns at unsignalized intersections, where drivers must evaluate gaps in oncoming traffic and decide whether or not it is safe and comfortable to execute a left turn maneuver through each gap. Our approach will be to observe the operation at unsignalized intersections where there are a substantial number of left turning vehicles and after classifying drivers by age range, note the lengths of all gaps each declines and uses, and from this information determine the critical gap for each driver. We will control for physical characteristics of intersections, including presence and absence of left turn lanes, number of oncoming traffic lanes, urban, suburban or rural setting, speed of oncoming traffic and traffic volume. We will study not only the "average" critical gap, but also the frequency of accepted gaps that are significantly shorter than the typically accepted gap (causing conflicts and potential crashes) and the frequency of rejected gaps that are significantly longer than the typically accepted gap (causing undue delays). We will then incorporate the resulting gap distributions in simulations of the intersections studied to confirm that accounting for the actual gap acceptance behavior of the drivers improves the fidelity of the simulation. We will also note the conditions under which any differences in gap acceptance behavior are greatest, to provide information about how best to improve intersections to help make this maneuver less dangerous and more comfortable for senior drivers, and thus, for the general population as well.


    • English


    • Status: Completed
    • Contract Numbers:



    • Sponsor Organizations:

      Research and Innovative Technology Administration

      Department of Transportation
      1200 New Jersey Avneue, SE
      Washington, DC  United States  20590
    • Performing Organizations:

      UVM Transportation Center

      University of Vermont
      210 Colchester Avenue
      Burlington, VT  United States  05405

      University of Maine, Orono

      Department of Civil and Environmental Engineering.
      5717 Corbett Hall
      Orono, ME  United States  04469-5711

      Center for Transportation and Urban Planning

      University of Connecticut, Storrs
      179 Middle Turnpike Unit 5202
      Storrs, CT  United States  06268-5202
    • Principal Investigators:

      Sadek, Adel

      Garder, Per

      Ivan, John

    • Start Date: 20060901
    • Expected Completion Date: 0
    • Actual Completion Date: 20080831
    • Source Data: RiP Project 19612

    Subject/Index Terms

    Filing Info

    • Accession Number: 01466327
    • Record Type: Research project
    • Source Agency: New England University Transportation Center
    • Contract Numbers: DTRS99-G-0001, UCNR`9-`0
    • Files: UTC, RiP, USDOT
    • Created Date: Jan 3 2013 3:14PM