Research on Choice of Design Parameters for Vertical Alignment Based on Vehicles' Operating Performance on Highway Downgrade Segments

Steep and consecutive downgrade segments of the highways in mountainous areas are considered hazardous to vehicles, especially to heavy trucks. Drivers frequently applying brakes on those segments often induce overheated brakes and weaken brake efficiency, which can consequently lead to an out-of-control vehicle. Crash rates on those downgrade segments are generally higher than those on the other segments. Most downgrade segments are identified as hazardous locations with high crash frequency. In China, over half of the crashes on those segments are caused by brake failure. Due to many other restrictions, sometimes it is impossible to avoid long downgrade segments in mountainous terrain. Therefore, development of the critical design standard that controls the maximum vertical grade and corresponding length is crucial. But how to determine parameter values for the consecutive downgrade segments perplexes geometric design engineers all the time. The objective of this study was to provide research results to support the revising of the design standards in the Chinese Technical Standard of Highway Engineering (TSHE). The paper analyzes truck driver behavior on the downgrade segments and investigates the relationship between braking distance and vertical grade, and between temperature of brakes and vertical length. Based on the investigation, the paper proposes the maximum vertical grades for various design scenarios, which can be used along with other parameter values (such as horizontal and cross-sectional design features, construction costs, and/or design consistency) to determine the maximum vertical grades for the new TSHE to maximize the highway safety.


  • English

Media Info

  • Media Type: CD-ROM
  • Features: Figures; Photos; References; Tables;
  • Pagination: 18p
  • Monograph Title: 3rd International Symposium on Highway Geometric Design, June 29-July 1, 2005, Chicago, Illinois: Compendium of Papers CD-ROM

Subject/Index Terms

Filing Info

  • Accession Number: 01004383
  • Record Type: Publication
  • Files: TRIS, TRB
  • Created Date: Sep 28 2005 10:41AM