The 1987 Surface Transportation and Uniform Relocation Assistance Act granted states the authority to increase the speed limit on designated portions of the rural Interstate system to no more than 65 mph. The objective of this analysis was to examine the changes in fatalities that have occurred on rural Interstates on which the posted speed limit was increased to 65 mph. Of the 44,529 fatalities occurring in 1990, slightly more than 5% occurred on rural Interstates with a speed limit of 65 mph. Compared to 1989, nationwide rural Interstate fatalities in 1990 declined about 2%, an amount equal to the change experienced in total motor vehicle crash fatalities. This decline occurred in spite of increases in vehicle miles traveled (VMT) estimated at 2%. Urban Interstate fatalities were about 2% higher than in 1989. Major findings included the following: The 2,336 fatalities that occurred in 1990 on rural Interstates in those 38 states that increased their speed limits to 65 mph in 1987 is 30% greater than might have been expected based on historical trends. This variation from the estimated trend projection is the same that occurred in 1988 and 1989. This suggests the fatality effect of the 65 mph speed limit has stabilized. The 1990 fatality rate for those states with a 65 mph speed limit, which includes the effect of the additional VMT on the rural Interstate system, has returned to the 1.4 fatalities per 100 million VMT level that existed in 1986, the last year of the 55 mph speed limit. While it is evident that rural Interstate fatalities have increased with implementation of the 65 mph speed limit, the rural Interstate remains the safest component of our nation's highway system. Rural Interstate fatalities represented only 6% of total traffic fatalities for 1990, numbering 2,701 nationally. The fatality rate on the rural Interstate system in 1990 was 1.3 per 100 million VMT, compared to 2.1 for the nation as a whole. Based on speed data for 65 mph roadways, which are only available from 18 of the 40 states with increased speed limits, the average travel speed on rural Interstates is estimated to have increased from 60.6 mph in the fourth quarter of 1986 to 64.0 mph in the fourth quarter of 1990. That is, the average speed of drivers exceeded the posted 55 mph limit in 1986 by 5.6 mph, while in 1990 the average speed was one mph below the posted limit. However, the percent of vehicles exceeding 70 mph for this same time period has clearly increased from approximately 6% when the posted speed limit was 55 mph to 19% when the posted speed limit was 65 mph.


  • English

Media Info

  • Features: Figures; Tables;
  • Pagination: 23 p.

Subject/Index Terms

Filing Info

  • Accession Number: 00625521
  • Record Type: Publication
  • Source Agency: National Highway Traffic Safety Administration
  • Report/Paper Numbers: HS-807 840
  • Files: HSL, TRIS, USDOT
  • Created Date: Dec 15 1993 12:00AM