Empirical Studies on Traffic Flow in Inclement Weather

Weather causes a variety of impacts on the transportation system. While severe winter storms, hurricanes, or flooding can result in major stoppages or evacuations of transportation systems and they cost millions of dollars, day-to-day weather events such as rain, fog, snow, and freezing rain can have a serious impact on the mobility and safety of the transportation system users. These weather events can result in increased fuel consumption, delay, number of accidents, and significantly impact the performance of the transportation system. The overall goal of the research work undertaken in this study was to develop a better understanding of the impacts of weather on traffic flow. The research was intended to accomplish the following specific objectives: (1) study the impact of precipitation on macroscopic traffic flow parameters over a full range of traffic states; (2) study the impact of precipitation on macroscopic traffic flow parameters using consistent, continuous weather variables; (3) study the impact of precipitation on macroscopic traffic flow parameters on a wide range of facilities; (4) study regional differences in reaction to precipitation; and (5) study macroscopic impacts of reduced visibility. The work documented in this report was conducted in two parts: (1) literature review and development of a data collection and analysis plan, and (2) analysis and interpretation of the results. The recommended plan combined the use of macroscopic traffic data archives with archived weather data in order to meet the research goals that include achieving better understanding of the impacts of weather on macroscopic traffic flow. The results of the research conducted for this study were helpful identifying weather impacts of traffic flow in the three cities studied, Minneapolis-St. Paul, Baltimore and Seattle. No impacts were found on traffic stream jam density, but both rain and snow did impact traffic free-flow speed, speed-at-capacity and the capacity and speed parameters varied with precipitation intensity. The results of these analyses are documented in the report. This report concludes with some recommendations of future research related to weather and traffic flow. Several ideas are presented including enhancing the macroscopic analysis used in this study. Additional work is proposed related to human factors and microscopic traffic modeling.

  • Supplemental Notes:
    • This research was funded by the U.S. Department of Transportation, University Transportation Centers Program.
  • Corporate Authors:

    Virginia Polytechnic Institute and State University, Blacksburg

    Virginia Tech Transportation Institute
    3500 Transportation Research Plaza
    Blacksburg, VA  United States  24061

    Virginia Department of Transportation

    1401 East Broad Street
    Richmond, VA  United States  23219

    Mid-Atlantic Universities Transportation Center

    Pennsylvania State University
    201 Transportation Research Building
    University Park, PA  United States  16802-4710

    Federal Highway Administration

    1200 New Jersey Avenue, SE
    Washington, DC  United States  20590
  • Authors:
    • Rakha, Hesham Ahmed
    • Farzaneh, Mohamadreza
    • Arafeh, Mazen
    • Hranac, Rob C
    • Sterzin, Emily
    • Krechmer, Daniel
  • Publication Date: 2007-6


  • English

Media Info

  • Media Type: Print
  • Edition: Final Report
  • Features: Appendices; Figures; Photos; References; Tables;
  • Pagination: 114p

Subject/Index Terms

Filing Info

  • Accession Number: 01056137
  • Record Type: Publication
  • Created Date: Aug 29 2007 4:10PM