Highway geometric design has usually been considered in separate two-dimensional (2-D) projections of horizontal and vertical alignments. Such a practice was followed mainly because three-dimensional (3-D) analysis of combined highway alignments was expected to be difficult. As a result, the effect of ignoring the 3-D nature of the highway alignment could not be quantified. With the long-term objective of developing 3-D design practice, a framework for 3-D highway geometric design was developed and 3-D sight distance was extensively studied as the first design basis. The status of sight distance in current design policies and previous research is summarized, and mainly 2-D analysis was considered. The five main tasks performed to cover the 3-D highway sight distance are presented. ( a) As a preliminary step, the 2-D sight distance on complex separate horizontal and vertical alignments was modeled, and the finite element method was used for the first time in the highway geometric design. ( b) The 2-D models were then expanded to cover the daytime and nighttime sight distances on 3-D combined alignments. ( c) The analytical models were coded into computer software that can determine the available sight distance on actual highway segments. ( d) The models were applied in 3-D design of combined horizontal and vertical curves in cut-and-fill sections, and preliminary design aids were derived. ( e) Finally, a new concept of red zones was suggested to mark the locations on alignments designed according to current practices where the available sight distance will drop below that required. A comprehensive work on 3-D sight distance analysis has been compiled that should be of great importance for highway researchers and professionals.


    Access

    Download

    Check availability in my library

    Order at Subito €


    Export, share and cite



    Title :

    Highway Alignment: Three-Dimensional Problem and Three-Dimensional Solution


    Additional title:

    Transportation Research Record


    Contributors:


    Publication date :

    1998-01-01




    Type of media :

    Article (Journal)


    Type of material :

    Electronic Resource


    Language :

    English





    Model for Three-Dimensional Highway Alignment

    Cheng, J.-F. / Lee, Y. | British Library Online Contents | 2006


    Model for Three-Dimensional Highway Alignment

    Cheng, Juey-Fu | Online Contents | 2006


    Three-Dimensional, Probabilistic Highway Design

    Sarhan, Mohamed / Hassan, Yasser | Transportation Research Record | 2008