Studying Characteristics of Operating Speed for Proper Speed Limit: An Age-Old Subject with New Evidence from a Developing Country

Using design speed as a primary consideration factor in selecting a freeway speed limit has been a common practice since the opening of the first freeway in China about 20 years ago. This practice has been questioned and challenged in recent years on many freeways mainly because of the definition of design speed for a freeway. The speed limits solely based on the somewhat vaguely defined design speed in many newly completed freeways have been under intensive public scrutiny, particularly at locations where the operating speeds are much higher or lower than the speed limits. One key consideration in establishing speed limit is operating speed that, among other things, is closely related to driver behavior. Driver behaviors vary greatly by a host of factors including cultural background and stage of the economic development. Undoubtedly the different social, economic and cultural environments contribute to significant variation in driver behaviors. The methods used by developed countries in speed limit selection may not be suitable or at least not entirely applicable to situations in developing countries. Thus, as the part of a project sponsored by the Chinese Ministry of Communication on speed, the goal of this study is to investigate relationship between speed limit and operating speed under different highway environments. The principal findings from the study are: (a) operating speed is only loosely associated with speed limit, (b) for a given speed limit, the average speed varies greatly depending on the location characteristics, (c) freeway speed variation is much bigger than that in a typical freeway in developed countries, and (d) there are huge speed gap between small and large vehicles. The wide spread operating speed represents a big safety problem for freeway transportation. The coexistence of speeding and slow running vehicles on freeways significantly lowers freeway capacity. The unique speed characteristics observed by this study prompts a few suggestions on speed limit and speed management.


  • English

Media Info

  • Media Type: DVD
  • Features: Figures; References; Tables;
  • Pagination: 14p
  • Monograph Title: TRB 89th Annual Meeting Compendium of Papers DVD

Subject/Index Terms

Filing Info

  • Accession Number: 01154424
  • Record Type: Publication
  • Report/Paper Numbers: 10-1911
  • Files: TRIS, TRB
  • Created Date: Jan 25 2010 10:53AM