Highlights ► Adverse-weather crashes on mountainous freeway section are 82% higher than in dry-weather season. ► Segments with steep downgrades are more crash prone. ► Segments with steep downgrades found to be more dangerous during snow season. ► Small radii, wider medians and more number of lanes found to be associated with lower crash rate. ► Ranking of sites confirmed the above-mentioned results and helped to identify sites with promise.

    Abstract While rural freeways generally have lower crash rates, interactions between driver behavior, traffic and geometric characteristics, and adverse weather conditions may increase the crash risk along some freeway sections. This paper examines the safety effects of roadway geometrics on crash occurrence along a freeway section that features mountainous terrain and adverse weather. Starting from preliminary exploration using Poisson models, Bayesian hierarchical models with spatial and random effects were developed to efficiently model the crash frequencies on road segments on the 20-mile freeway section of study. Crash data for 6 years (2000–2005), roadway geometry, traffic characteristics and weather information in addition to the effect of steep slopes and adverse weather of snow and dry seasons, were used in the investigation. Estimation of the model coefficients indicates that roadway geometry is significantly associated with crash risk; segments with steep downgrades were found to drastically increase the crash risk. Moreover, this crash risk could be significantly increased during snow season compared to dry season as a confounding effect between grades and pavement condition. Moreover, sites with higher degree of curvature, wider medians and an increase of the number of lanes appear to be associated with lower crash rate. Finally, a Bayesian ranking technique was implemented to rank the hazard levels of the roadway segments; the results confirmed that segments with steep downgrades are more crash prone along the study section.


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    Titel :

    Exploring a Bayesian hierarchical approach for developing safety performance functions for a mountainous freeway


    Beteiligte:
    Ahmed, Mohamed (Autor:in) / Huang, Helai (Autor:in) / Abdel-Aty, Mohamed (Autor:in) / Guevara, Bernardo (Autor:in)

    Erschienen in:

    Erscheinungsdatum :

    2011-03-22


    Format / Umfang :

    9 pages




    Medientyp :

    Aufsatz (Zeitschrift)


    Format :

    Elektronische Ressource


    Sprache :

    Englisch