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17 The maximum hitch offset was standardized at 1.8 m (71 in.) The minimum track width for a trailer axle fitted with wide for all configurations; single tires was reduced to 2.3 m (90.5 in.) for trailers built The minimum wheelbase for a semitrailer, pony trailer or in 2007 or earlier, but remained at 2.5 m (98.4 in.) for all full trailer was standardized at 6.25 m (246 in.); axles on trailers built in 2008 or later; An inter-axle spacing less than 3.0 m (118 in.) between the An aerodynamic device installed at the rear of a truck, lead trailer and an A- or C-dolly was allowed, subject to a trailer or semitrailer was excluded from measurement of weight restriction on the two axle groups; overall length, trailer length, semitrailer length, box length The fifth wheel on the lead trailer of a B-train was restricted and effective rear overhang; and to no more than 0.3 m (12 in.) behind the center of the A clarification was added to exclude from measurements rearmost axle of the lead semitrailer. This was because of overall width: existing semitrailers in some provinces were being modi- Auxiliary equipment and/or devices not designed or fied with a low-mounted fifth wheel behind their rearmost used to carry cargo that do not extend more than 10 cm axle, which towed a pony trailer fitted with a kingpin. This beyond each side of the vehicle, and combination met the dimensional limits for a B-train, but Rearview mirrors that do not extend more than 30 cm the significant hitch offset of the lead trailer fifth wheel beyond each side of the vehicle. resulted in poor dynamic performance for the pony trailer; The allowable weight on the steer axle of a straight truck was increased to 7,250 kg (15,983 lb); 2.1.9 Qubec and Ontario Size The caps on the weight of the second trailer of A- and C-train and Weight Changes doubles were replaced by a requirement that the combined In the mid 1980s, Qubec began allowing multi-axle semi- weight of the tractor drive axles and the lead trailer axles trailers from Ontario to operate into Qubec at Ontario weights must be greater than the weight of the second trailer; by special permit. Qubec began to realize that many of these A clarification was added that a vehicle fitted with any vehicles, with one or two liftable axles, could operate with liftable axles was recognized as meeting the "national stan- their liftable axles raised and produce excessive loads on both dards," provided that when the liftable axles were raised, all roads and bridges. The permit program rapidly became very other requirements were met; and popular and also became difficult to administer. A computer A clarification was added that each jurisdiction continued simulation study identified significant dynamic performance to retain authority to allow more liberal weights and dimen- deficiencies with many of these configurations (45). Qubec sions, or different vehicle configurations, for trucking oper- therefore rewrote its regulations in 1991 and made a first step ations within their jurisdiction. In addition, when trucking to categorize its configurations and reduced the allowable operations took place between adjacent jurisdictions with loads on those considered less desirable from the point of compatible weight and dimension regulations, which are more liberal than those specified in the M.o.U., the local view of roadway impacts and stability and control. It elimi- regulations can prevail. nated the permit program for Ontario multi-axle semitrailers and defined a quad-axle semitrailer with a single axle and a The fourth amendment to the M.o.U. was made in Sep- fixed tridem axle, as seen in Figure 18, as the preferred semi- tember 2004, as follows: trailer configuration for high payloads by penalizing the allowable load on all other arrangements of four or more The box length of an A-train double was increased to 20 m axles on a semitrailer (46). Qubec recognized that the tri-axle (65 ft 7 in.); The kingpin setback of the second semitrailer of a B-train double was limited to the same 2.0-m (79-in.) radius as other semitrailers; and The intercity bus category was amended to include a recre- ational vehicle on a bus chassis, allowing the recreational vehicle an overall length of 14 m (46 ft). Finally, a fifth amendment to the M.o.U. was made in April 2008, as follows: An axle fitted with two wide single tires, each 445 mm or wider, was allowed 7,700 kg (16,975 lb) on a single axle, or Figure 18. Ontario and Qubec self-steer quad 15,400 kg (33,950 lb) on a tandem axle; semitrailer.