Analysis of Heavy-Truck and Automobile Speed Distributions for Uniform and Differential Speed Limit Configurations on Rural Interstate Highways

The topic of differential speed limits for heavy trucks and automobiles on rural interstate highways is an issue currently facing many state legislatures and commercial trucking organizations. There has been a significant amount of research on the topic; however, the results and conclusions are often conflicting or do not provide definitive conclusions. One of the reasons for the inconsistency of the results is that the research does not address the separate distributions of truck and automobile speeds. In addition to lower posted speed limits in some states, truck speed is often limited by company policies. Most commercial fleets use speed limiters on their trucks’ engines to restrict the maximum speed. Therefore, even in states that do not have a posted speed limit differential, there is actually a “virtual” differential due to truck speed limiters that are set below the posted speed limits. The objective of this paper is to present the results of a research effort that analyzed the distributions of truck and automobile speeds under four different speed limit configurations. Two of the sites that were investigated had uniform speed limits (70 mph and 75 mph) and two had speed differentials (70/65 and 65/55 mph). The empirical speed distributions for the different configurations are presented in the context of both absolute truck and automobile speed and speed variances. In addition, a computer simulation was used to evaluate the number of vehicle interactions (passing and being passed) under the different speed limit configurations.


  • English

Media Info

  • Media Type: CD-ROM
  • Features: Figures; References; Tables;
  • Pagination: 15p
  • Monograph Title: TRB 86th Annual Meeting Compendium of Papers CD-ROM

Subject/Index Terms

Filing Info

  • Accession Number: 01046266
  • Record Type: Publication
  • Report/Paper Numbers: 07-2949
  • Files: TRIS, TRB
  • Created Date: Feb 8 2007 7:40PM