Free-flow speed variation of passenger vehicles along a road segment is one of the most used factors in road safety studies, as a surrogate measure to evaluate road design consistency. Free-flow speed may be measured when a road segment is already built but must be estimated during the design phase. Several studies have been carried out to calibrate models to estimate free-flow speed, with geometric features as explanatory variables. Currently, most free-flow speed models focus only on mean speed or speed in particular percentiles, such as the 85th or 95th. Moreover, most studies have assumed normality in the free-flow speed distribution without checking this hypothesis. The main objective of this study was to analyze the free-flow speed distribution on two-lane rural road curves and tangents. The research focused on two main issues: determining whether speed data were normally distributed at a specific site and analyzing the behavior of the mean and standard deviation of speed on curves and tangents. The study was based on continuous operating speed profiles, which were obtained from a database of more than 16,000 vehicles/km. A total of 63 horizontal curves and 78 tangents were analyzed. According to the results, the normal distribution is not the best distribution in most cases for describing free-flow speeds. In 46 of the curves and 64 of the tangents, free-flow speed cannot be assumed to be normally distributed. Therefore, some other distributions should be tested in further research.


    Zugriff

    Download

    Verfügbarkeit in meiner Bibliothek prüfen

    Bestellung bei Subito €


    Exportieren, teilen und zitieren



    Titel :

    Examination of the Free-Flow Speed Distribution on Two-Lane Rural Roads


    Weitere Titelangaben:

    Transportation Research Record




    Erscheinungsdatum :

    2016-01-01




    Medientyp :

    Aufsatz (Zeitschrift)


    Format :

    Elektronische Ressource


    Sprache :

    Englisch



    An Investigation of the Speed-Flow Relationship in Two-Lane Rural Roads

    Karlaftis, Matthew G. / Golias, John C. | ASCE | 2002



    An Investigation of the Speed-Flow Relationship in Two-Lane Rural Roads

    Karlaftis, M. G. / Golias, J. C. / American Society of Civil Engineers | British Library Conference Proceedings | 2002


    Modeling Operating Speed and Speed Differential on Two-Lane Rural Roads

    Misaghi, P. / Hassan, Y. | British Library Online Contents | 2005