The randomness of freeway capacity has been analyzed in a large number of studies. In contrast, relatively little attention has been paid to the critical density at capacity and its relationship to breakdown occurrence, although density is used as a quality of service criterion for freeways. In the paper, distributions of freeway capacity and critical density are estimated and compared based on traffic data samples from 38 freeway bottleneck sections in the U.S. and Germany. It is shown that the well-established methods for stochastic capacity analysis can be applied to estimate critical density distributions by replacing volume with density in the corresponding mathematical models. Comparison of the estimated capacity and critical density distribution functions reveals that the relative variability of the capacity is lower than the variability of the critical density. This suggests that traffic volume is the more appropriate parameter to represent the trigger of traffic breakdowns than traffic density. The empirical results also show that the rather smooth traffic flow on U.S. freeways leads to a smaller variance of both the capacity and the critical density distribution compared with German freeways, whereas the average capacity per lane is roughly the same.


    Access

    Download

    Check availability in my library

    Order at Subito €


    Export, share and cite



    Title :

    Comparison of Stochastic Estimates of Capacity and Critical Density for U.S. and German Freeways


    Additional title:

    Transportation Research Record: Journal of the Transportation Research Board


    Contributors:


    Publication date :

    2019-04-04




    Type of media :

    Article (Journal)


    Type of material :

    Electronic Resource


    Language :

    English



    Optimum Capacity of Freeways: A Stochastic Approach

    Sohrabi, Soheil / Ermagun, Alireza | ASCE | 2018


    Freeways

    Halprin, Lawrence | TIBKAT | 1966


    Freeways

    Elefteriadou, Lily | Springer Verlag | 2013


    Traffic Capacity Through Work Zones on Urban Freeways

    C. L. Dudek / S. H. Richards | NTIS | 1981


    Freight-Freeways

    Simaey, S.Van | Online Contents | 1997