This study provides data on 31,883 fatal and injury accidents occurring in California during the latter half of 1972. The accident frequency and experience of doubles, defined as two semitrailers coupled by a converter dolly and drawn by a truck-tractor, are compared to the accident frequency and experience of each of the following vehicles: tractor-semitrailer combinations, other trucks excluding pickups and panels, commercial buses and all other motor vehicles. Principal findings are: 1. Doubles are under represented in accidents when compared to their portion of all motorized vehicles on California's State maintained roadway system. They are approximately 1.5% of the motor vehicles but were involved in only 1.1% of fatal and injury accidents. 2. The number of accidents per million miles of travel was very low for both double and tractor- semitrailers, (0.5). Only the commercial bus has a lower rate, (0.4). 3. Accidents involving doubles are no more severe than those of other vehicles when considering persons killed and injured per accident, but are slightly more severe when considering the number of vehicles involved. 4. The distribution of "violation charged" was very similar to that of "primary cause". In both, drunk driving was relatively low and equipment violations, especially defective brakes, were relatively high among doubles. Each distribution supported the inference that doubles are less of a passing hazard than tractor-semitrailers. 5. Analysis of "collision type" and "type of involvement" revealed that relative to all other vehicles, the portion of doubles' accidents which were single vehicle accidents such as "hit fixed object" was small. This implies a lack of handling difficulties among doubles. 6. A 65 foot double was found to have a smaller required "track width" in a 60 foot radius turn than a 60 foot tractor-semitrailer. 7. The double met State and Federal braking requirements and was not found, according to the U.S. Department of Commerce, to be more of a passing haxard than any large truck or bus. It appears from the data gathered, that doubles are at least as safe as tractor-semitrailers in terms of accident frequency, and are a more maneuverable vehicle than the tractor- semitrailer.

  • Corporate Authors:

    California Highway Patrol

    Planning and Analysis Division, P.O. Box 942898
    Sacramento, CA  United States  94298-0001
  • Authors:
    • Zeiszler, R
  • Publication Date: 1973-4

Media Info

  • Features: References; Tables;
  • Pagination: 43 p.

Subject/Index Terms

Filing Info

  • Accession Number: 00080609
  • Record Type: Publication
  • Source Agency: National Safety Council Safety Research Info Serv
  • Files: TRIS
  • Created Date: Mar 6 1975 12:00AM