Minimum geometric conditions must exist to provide an ample amount of preview sight distance (PVSD) for comfortable and safe traffic operations. The PVSD concept is based on the assumption that the driver views or previews the roadway surface and other cues that lie ahead to obtain the information needed for vehicular control and guidance. The driver needs a minimum PVSD to perceive and respond to upcoming alignment cues; the roadway geometry affects how much PVSD is available for the driver. A roadway designed with geometric features adequate to the design speed would in many cases provide ample PVSD, but a roadway with constrained design features could have inadequate PVSD. The paper includes a derivation of equations to calculate the available preview sight distance on a crest vertical curve and discusses two applications of the PVSD concept to sharp horizontal curves. When a geometric analysis finds that inadequate PVSD exists, upgraded signing or pavement marking to provide drivers with extra positive guidance may be considered as a means of compensating for inadequate PVSD.


  • English

Media Info

  • Features: Figures; References; Tables;
  • Pagination: p. 139-145
  • Monograph Title: Geometric design, roadside safety features, roadside hardware monitoring, and scenic loop tours
  • Serial:

Subject/Index Terms

Filing Info

  • Accession Number: 00715001
  • Record Type: Publication
  • Files: TRIS, TRB
  • Created Date: Dec 26 1995 12:00AM