Effects of Interstate Speed Limits on Driving Speeds: Some New Evidence

Since the repeal of the 55 mph national maximum speed limit on US interstate highways, speed limits have been raised across the country to as high as 75 mph and more. While many studies have addressed the effects of increased speeds on accident frequency and severity, the factors that determine drivers' choice of speed in the presence of speed limits are still not well understood. This paper provides additional insight into drivers’ choice of speed by using a survey of Indiana drivers. The survey is timely since Indiana recently raised speed limits on rural interstates to 70 mph. With urban and suburban areas included, interstate speed limits in the state are now 55 mph, 65 mph and 70 mph. Using seemingly unrelated regression estimation, models of normal interstate driving speeds with low-traffic conditions are estimated for 55 mph, 65 mph and 70 mph speed limits. The results show a wide range of factors (gender, age, income, number of children, age driver is first licensed, assessment of pavement quality, and assessment of vehicle manufacturers) influence individuals' normal interstate driving speed and that the effect of these factors changes as the posted speed limit changes.


  • English

Media Info

  • Media Type: CD-ROM
  • Features: Figures; References; Tables;
  • Pagination: 14p
  • Monograph Title: TRB 86th Annual Meeting Compendium of Papers CD-ROM

Subject/Index Terms

Filing Info

  • Accession Number: 01044894
  • Record Type: Publication
  • Report/Paper Numbers: 07-0120
  • Files: BTRIS, TRIS, TRB
  • Created Date: Feb 8 2007 4:40PM