I am aware of your subcommittee's efforts to develop recommendations for presentation to the AASHTO Joint Committee on Domestic Freight Policy. Since I was unable to attend your subcommittee meeting of January 6-8, 1993, I feel it is appropriate to provide you with information which is important to your subcommittee's charge.

Idaho, like several western states, has been operating a permit program for Longer Combination Vehicles (LCV's) for over twenty years. That program has been very successful and has created very positive benefits for both industry and government. Transportation Research Board Publication SPECIAL REPORT 225, TRUCK WEIGHT LIMITS: ISSUES AND OPTIONSprovides a good reference on some of those benefits.

It is my conclusion that, in Idaho, LCV's have reduced the number of trucks on our highways with the result being less pavement and bridge wear as compared to conventional STAA truck configurations. That result comes not only from fewer truck trips but more importantly from reduced average axle loadings and reduced equivalent single axle loads per ton of freight as compared to 80,000 GVW combinations (the 18 wheel industry standard and the twin 28' trailers). My perception of the excuse by Congress for the current ISTEA-91 LCV freeze is that LCV's are huge, unsafe truck combinations. That has not been our experience in Idaho.

Although our current accident reporting system and vehicle classification system does not allow us to separately evaluate the accident experience of all LCV configurations operating in Idaho, it does allow us to evaluate triple trailer combinations (triples). Triples, too, are probably the most visible LCV configuration which operates in Idaho. Their accident rate is phenomenally low as compared to the rest of the commercial vehicle combinations. In 1991, triples accident rate was about 24% of single trailer combinations and about 21% of double trailer combinations. I believe that the superior safety record for triples in Idaho is due to Idaho's strict permit system. Other western states which operate LCV permit systems, I believe, can produce similar comparisons.

Clayton L. Sullivan, P.E.
Maintenance Engineer

  • Idaho Trucking Association
  • 3405 East Overland Road, Suite 175
  • Meridian, ID 83642
  • Local: (208) 342-3521
  • Fax: (208) 343-8397
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