Michigan's Extra Heavy Trucks

Michigan's allowance for trucks up to 164,000 pounds elected gross vehicle weight has caused considerable concern. Most states allow just 80,000 pound maximum. However, many engineers believe that Michigan's super heavy trucks actually impose less damage than the lighter trucks in other states. Michigan's 164,000-pound trucks must spread their weight over 11 axles, compared to just five axles on conventional 80,000-pound trucks. In Michigan, the 11-axle trucks are allowed a maximum weight per axle of 13,000 pounds, compared to 18,000 pounds per axle on 80,000-pound trucks. Axle weight determines damage, not total gross weight.

Blanchard Administration MDOT Director Jim Pitz offered testimony on truck weights and damage before the House Transportation Committee's Subcommittee on Truck Weights on November 27, 1990.19 Mr. Pitz indicated that based on American Association of State Highway and Transportation Officials (AASHTO) tests, a truck with two 13,000-pound axle loads would exert 62% less stress on the road than an axle loading of 18,000 pounds. Other outside academic experts made the same point.

Opponents of 164,000-pound trucks who concede this point about axle weights often point out that bridges must absorb the entire weight of the truck and that this would cause damage to the state's bridges. However, during the same hearings MDOT testified that all state trunkline system bridges built since 1973, and all bridges reconstructed since that date, have been designed and built to withstand these higher weights. There are just 10 of 4,500 bridges in the state that could not accommodate 164,000-pound trucks without an adverse impact on bridge life as of 1990. Mr. Pitz further testified that "an additional 4% cost is incurred for each bridge built to Michigan specifications, with the 4% resulting in an average expenditure of $16,000 per bridge at today's [1990] average bridge costs." These additional costs are more than made up for by the average $2,304 in various registration fees for a 164,000-pound truck in Michigan, compared to the average 80,000-pound registration fee of $1,306.

Heavy 164,000-trucks have provided a significant competitive advantage for Michigan manufacturers. Without them, an additional 17,000 trucks would be necessary, according to testimony to the 1990 Subcommittee on Truck Weights by Sullivan and Leavit, P.C. One of the major impacts of elimination of such trucks would be an increase in highway construction costs. For instance, according to testimony to the Subcommittee, the I-696 project in Detroit would have required an additional 115,500 truck-trips over four years if 164,000-pound trucks had not been available. The Michigan Trucking Association has estimated that an 80,000-pound truck weight limit would result in a need for 21,500 additional trucks, with a first year acquisition cost of $2.15 billion and an annual operating cost increase of $.77 billion, assuming 2,000 hours per year at $45 per hour .20