Field observations (on several grades) to obtain information on downhill truck speeds for use in calculating user costs for economic studies and for use in capacity analysis for determining lane requirements, failed to produce standard curves for use in any situation. However several conclusions were drawn: downhill truck speeds depend on the behavior of the driver as affected by the length of the grade, sight distance ahead, and other variables; there appears to be a difference in the behavior of trucks on long downgrades (over 4 miles) as compared to shorter downgrades. In shorter grades of less than 4 percent, the average speeds are generally equal to or faster than truck speed on level highways. For steeper grades, the speeds are slower near the summit but incrase uniformly down the grade. Sustained speeds observed on long grades are tabulated. The results of field data are included. The speed curves presented here can be used as guides in selecting speeds for estimating travel time for trucks. It is emplasized that averaging speeds directly and multiplying by the distances will result in erroneous travel time. the correct procedure would be to average the reciprocal of the speeds and multiply by the intervening distance to obtain the time.

Media Info

  • Features: Figures; Tables;
  • Pagination: 16 p.

Subject/Index Terms

Filing Info

  • Accession Number: 00152995
  • Record Type: Publication
  • Source Agency: National Safety Council Safety Research Info Serv
  • Report/Paper Numbers: Traffic Bull No. 1
  • Created Date: May 31 1977 12:00AM