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45 43,500 to 49,500 kg (95,900 to 109,127 lb), depending on the load restrictions would need to be applied to Canadian vehi- tridem spread and whether it operates in western or eastern cles. If, however, the vehicles were reconfigured to maximize Canada, and 6-axle A- or B-train doubles are suitable for their weight in accordance with the capacity of U.S. bridges, freight of moderate density. The 7-axle B-train, with an allow- then the vehicles would have only a slightly diminished capac- able gross weight of 56,500 kg (124,560 lb) in the four western ity compared to the Canadian vehicles. provinces, and 59,500 kg (131,173 lb) in the six eastern When Ontario and Qubec allowed 16.2-m (53-ft) semi- provinces, and the self-steer quad 7-axle tractor-semitrailer, trailers in 1994, 5 years after the effective date of the original with an allowable gross weight of 57,500 kg (126,764 lb) in M.o.U., they allowed only those semitrailers longer than the Ontario and Qubec, are suitable for higher density freight. prevailing length of 14.65 m (48 ft) if they met the exact re- Seven-axle doubles are not common, but the self-steer quad is quirements of the M.o.U., so they were only allowing a tan- very significant because it has had greater range in Qubec dem or tridem axle group. Semitrailers with other axle groups than the 8-axle B-train. The 8-axle B-train, 8- and 9-axle were restricted to 14.65 m (48 ft), which quickly limited their tractor-semitrailers, and other doubles in Ontario, all with an utility. Many carriers use a van semitrailer as a general-purpose allowable gross weight from 62,500 to 63,500 kg (137,787 to vehicle, regardless of its number of axles. So, a tridem semi- 139,992 lb), move dense and heavy freight. The truck size and trailer will take a load that uses all or a substantial part of the weight regulations in Canada therefore provide a range of pay- weight capacity of the vehicle. However, a similar load may load weight bands that allow shippers and carriers to optimize not be available for the return trip, so the vehicle will take a truck configuration for a payload. a load that could otherwise go in a tandem semitrailer. This In the United States, the same light freight moves in 5-axle improves the utilization of the tridem and diminishes the tractor-semitrailers as in Canada, at the same gross weights. need for tandem semitrailers. However, this was not possible The 5-axle tractor-semitrailer also moves medium and heavy at a time when tandem loads were increasingly being pack- freight, both locally and between states, usually at a gross weight aged for 16.20-m (53-ft) semitrailers, so the utilization of van close to 36,287 kg (80,000 lb). Medium and heavy freight also semitrailers that were not of an M.o.U. configuration was less moves locally in diverse other configurations that operate under than ideal. Ontario and Qubec subsequently realized the grandfather or LCV rights, principally within one state, or pos- necessity to allow all semitrailer configurations in regulation sibly by permit into neighboring states. Michigan is really the and with a secure future length of 16.20 m (53 ft), so that a only state that has a range of configurations that address a range carrier could optimize the utilization of all vehicles in its fleet. of freight like Canada, though most of these would not be con- templated as candidates for the M.o.U. in Canada. 3.4.2 The Need for Uniform Definitions In Canada, about 60% of trips are made by trucks that carry light freight, such as the 5-axle tractor-semitrailer with It cannot reasonably be expected that a desired outcome a typical actual gross weight up to 36,287 kg (80,000 lb). will be achieved if terms in which vehicles are described have About 13% of trips are made by 6-axle tractor-semitrailers different meanings in the regulations of different jurisdic- with an allowable gross weight of up to 49,500 kg (109,127 lb). tions. The terms include those for vehicle configurations, axle About 7% of trips are made by 7-axle tractor-semitrailers groups and axle arrangements, dimensions, components, and and doubles with an allowable gross weight up to 59,500 kg anything else relevant to description of a vehicle. (131,173 lb). About 15% of trips are made with vehicles that The M.o.U. included a set of definitions of terms, and all can carry heavy freight, such as the 8-axle B-train, with an al- provinces have adopted these. If the U.S. federal government lowable gross weight from 62,500 to 63,500 kg (137,787 to would set further truck size and weight regulations, these would 139,992 lb). The remaining 5% or so of trips are made by be interpreted uniformly if it also required states to adopt all the trucks of diverse configuration, and many of them are made definitions in the federal regulations, in the same manner as the with a special permit, either for an LCV, such as a turnpike STAA. If a group of states agrees to harmonize aspects of their double, or to carry an indivisible large or heavy load. regulations, then this should also include an agreement to adopt Canada has a greater proportion of dense freight and heavy definitions of terms, in a similar manner to the M.o.U. loads because its economy is proportionately more depen- dent on natural resources than the United States. Nevertheless, 3.4.3 The Need for a Complete if the distribution of freight density would be the same in Vehicle Specification the United States as in Canada, and the United States would adopt the M.o.U. configurations and weights, then it would When Ontario introduced regulation by its bridge formula require about 15% fewer trucks to move the freight that in 1970, it was intended that the provincial economy should moves in vehicles with 6 or more axles in Canada. This calcu- benefit from the substantial increase in allowable gross lation is a very rough estimate. U.S. bridge analysis suggests weight. It was expected that new configurations would arise