With improvements being made to freeways and expressways, the problem of inadequate stopping sight distance on curves accompanying installation of a concrete barrier may arise. This could also occur when lanes are added in the median of a freeway or expressway and a narrow median results. It also may become a problem on curved ramps on structures where the parapet may not be offset sufficiently from the traveled-way. One solution to the problem for freeway medians is to provide a wider shoulder (greater offset to barrier) for the traveled-way turning to the left. Where a constant median width exists, the left shoulder for the opposing direction is, of course, narrowed. When a ramp is on a structure (bridge or retaining wall) and there is a curve to the left, the traveled-way can be shifted to the right, providing a wider left shoulder for sight distance and breakdown. The right shoulder would then be narrowed, preferably to not less than 4 ft. It must be kept in mind that stopping sight distance is only one of many design and operational considerations in planning an improvement. There certainly can be trade-offs with other features and the potential influence on accident experience. Further study is needed to ascertain the optimum dimensions of all cross-sectional elements to best satisfy safety, operational, and design requirements.

Media Info

  • Features: Figures; Photos; References;
  • Pagination: p. 80-84
  • Monograph Title: Highway sight distance design issues
  • Serial:

Subject/Index Terms

Filing Info

  • Accession Number: 00490649
  • Record Type: Publication
  • ISBN: 0309048079
  • Files: TRIS, TRB, ATRI
  • Created Date: Jan 31 1990 12:00AM