The development of relationships between safety and congestion is documented; traffic volume, speed, and crash data by 15-min periods for urban freeways in the areas of Seattle, Washington, and Minneapolis–Saint Paul, Minnesota, were used. The safety–congestion relationships were developed to provide a basis for estimating the safety effects of design treatments intended to reduce nonrecurrent congestion and increase travel time reliability. The relationships were developed with traffic volume and speed data from detectors in individual lanes for 564 urban freeway segments during study periods of up to 3 years. Traffic crash records were obtained for the same time periods as the volume and speed data. The U-shaped relationship between crash rate per million vehicle miles of travel and traffic density (the level-of-service measure for freeways) was found, with the highest crash rates at low and high traffic densities and the lowest crash rates in the middle range of traffic densities. The high crash rates at lower traffic densities represent predominantly single-vehicle crashes, whereas the high crash rates at higher traffic densities represent predominantly multiple-vehicle crashes. Quantitative safety–congestion relationships were developed for the range of traffic densities from 20 to 78 passenger cars per hour per lane, corresponding to the level-of-service range from C to F.


    Access

    Download

    Check availability in my library

    Order at Subito €


    Export, share and cite



    Title :

    Development of Relationships between Safety and Congestion for Urban Freeways


    Additional title:

    Transportation Research Record: Journal of the Transportation Research Board


    Contributors:


    Publication date :

    2013-01-01




    Type of media :

    Article (Journal)


    Type of material :

    Electronic Resource


    Language :

    English





    Relationships between Safety and Both Congestion and Number of Lanes on Urban Freeways

    Kononov, Jake / Bailey, Barbara / Allery, Bryan K. | Transportation Research Record | 2008


    Further Development of the Safety and Congestion Relationship for Urban Freeways

    Potts I. B. / Harwood D. W. / Fees C. A. et al. | NTIS | 2015


    Determining Hours of Congestion for Urban Freeways

    Wellander, C. A. / DiSarcina, A. / MacDonald, O. J. et al. | British Library Conference Proceedings | 1993