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12 in Canada. The Roads and Transportation Association of Canada (RTAC) coordinated highway engineering standards, and the provincial highway departments were the principal sponsors of the association. RTAC therefore formed a Vehi- cle Weights and Dimensions Committee, with a charge to rationalize truck configurations, and their sizes and weights, across Canada (8). The committee quickly established that enough was known to upgrade roads for heavier axle loads, and a highway strengthening program was undertaken in the Prairie and Atlantic Provinces, with significant federal fund- ing. It also found that the live-load capacity of bridges was Figure 9. Prairie 7-axle A-train double from the late unclear, particularly with respect to overload permits. This 1970s. resulted in a national study of bridge capacity (8), which showed that despite considerable apparent diversity in provin- and allowable weights. British Columbia introduced a limited cial weight and dimension regulations, the consequent vehi- number of configurations similar to some in Ontario, but cles were generally compatible with bridges in all provinces (9). required a liftable axle to be self-steering. The three Prairie This was to be expected as the provinces generally designed Provinces (Alberta, Saskatchewan, Manitoba) allowed double their bridges to AASHTO (10) or Canadian Standards Asso- trailer combinations, and 7- or 8-axle A-trains, as shown in ciation (CSA) codes (11), which resulted in bridges of roughly Figure 7 and Figure 9, respectively, and a 7-axle B-train, shown equivalent capacity. The provinces were able to identify a in Figure 10, became the heavy-haul vehicles of choice. The small number of bridges which needed strengthening, and 8-axle A-train was particularly favored, as it fared better under these were upgraded or replaced, relatively quickly, again spring weight restrictions than the 7-axle B-train, even though with some federal funding. the latter had a higher allowable gross weight outside the thaw By 1981, highway and bridge strengthening programs on period. The vehicle of choice in Qubec and the Atlantic the primary highway systems of the provinces had allowed an Provinces (Newfoundland and Labrador, New Brunswick, increase in axle loads and gross weights in other provinces to Nova Scotia, Prince Edward Island) became the tri-axle semi- 80% to 90% of Ontario's, with British Columbia and Yukon trailer, as shown in Figure 4, and the 7-axle B-train, as shown matching Ontario's 63,500 kg (139,992 lb). Overall lengths in Figure 10, also became common in Qubec. The three Prairie reached 21 to 23 m (69 to 75 ft 6 in.), and double trailer com- Provinces as a group, and the four Atlantic Provinces, also binations became much more popular, particularly in west- as a group, each developed their regulations to provide con- ern Canada. siderable regional uniformity in format and allowable size, axle group weights and gross weights, though significant dif- 2.1.4 Canadian Council of Motor Transport ferences remained between these two regions and the other Administrators/RTAC Vehicle Weights three provinces. and Dimensions Study, 19811986 These changes tended to increase, rather than decrease, the diversity in size and weight. The 1973 oil crisis brought into By 1981, improvements to highways and bridges across focus a need to increase the efficiency of truck transportation Canada allowed travel coast-to-coast for vehicles with a gross weight of 60,000 kg (132,276 lb) or more. However, there were two significant impediments. First, other provinces and territories (except Yukon) were not prepared to adopt the same form of regulation as Ontario, nor were they prepared to accept many of the truck configurations or axle arrange- ments commonly used in Ontario to generate these weights, particularly those with liftable axles. Second, a tridem axle group (three equally spaced axles) would be required for an increase in allowable gross weight, and this axle group was not recognized in a number of provinces, especially in the Prairie Provinces. The Canadian Council of Motor Transport Administrators Figure 10. Prairie Provinces 7-axle B-train double (CCMTA)/RTAC Vehicle Weights and Dimensions Com- from the late 1970s. mittee developed the Vehicle Weights and Dimensions Study