Cover Image

Not for Sale



View/Hide Left Panel
Click for next page ( 19


The National Academies | 500 Fifth St. N.W. | Washington, D.C. 20001
Copyright © National Academy of Sciences. All rights reserved.
Terms of Use and Privacy Statement



Below are the first 10 and last 10 pages of uncorrected machine-read text (when available) of this chapter, followed by the top 30 algorithmically extracted key phrases from the chapter as a whole.
Intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text on the opening pages of each chapter. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

Do not use for reproduction, copying, pasting, or reading; exclusively for search engines.

OCR for page 18
18 semitrailer, as seen in Figure 4, which has a single liftable axle that all quad-axle semitrailers from 2001 should have a self- ahead of a fixed tandem, was also highly damaging to roads steering single axle, as shown in Figure 18. and bridges and also had significant deficiencies in dynamic performance. Qubec therefore reduced the allowable load 2.1.11 Other Vehicle Configurations on the tri-axle group, to reduce the economic attraction of the configuration. Unfortunately, it overlooked that it allowed Stinger-steer car carriers are used principally to distribute an even higher load on a tri-axle with a 4.88-m (192-in.) spread new vehicles from car plants to terminals, and from terminals and did not reduce the allowable load on this axle group because to dealers. The United States increased the allowable length it was not being used at this time. Manufacturers quickly of a car carrier to 25 m (82 ft) by allowing the cars to over- adopted this axle group, and the intention of the change in hang a 22.86-m (75-ft) long vehicle at the front and rear. This regulation was negated. allowed more cars on a car carrier within the 4.15-m (13-ft When Ontario increased semitrailer length to 16.2 m (53 ft) 6-in.) overall height in the eastern states. The provinces did and double trailer overall length to 25 m (82 ft) in 1994, any not initially allow overhang to achieve the additional length, vehicle longer than the previous limit was subject to a strict but allowed the same number of vehicles to be carried by regulation that ensured conformity to the national M.o.U. accepting an overall height up to 4.27 m (14 ft) by special per- This was the first use of a prescriptive regulation for vehicle mit. This caused significant difficulty when a car carrier configuration in Ontario. Further, it specifically excluded use crossed the border, when an overhanging load for the United of liftable axles on any of these longer vehicles. States had to be transformed into an over-height load for Canada, or vice versa. The Task Force considered the issue, and developed a detailed vehicle specification for a car carrier 2.1.10 Phasing Out Liftable Axles that would allow it to meet the same dynamic performance In 1994, New Brunswick introduced a policy calling for a standards as a tractor-semitrailer while carrying an overhang- total phase-out of liftable axles by 2005. The six eastern provinces ing load in accordance with U.S. federal regulation. This spec- therefore began discussing their own issues of size and weight ification became the model for a standard special permit that regulations, which revolved around a transition from variable all provinces now issue for this class of vehicle. tandem axle load for variable spread through control of liftable The forestry industry in Alberta and British Columbia had axles to common enforcement strategies to ensure the same developed log trucks of many diverse configurations, with just effective rules in each jurisdiction. The principal outcomes one example shown in Figure 19. The provinces had been were a proposal to increase the tandem axle load from 17,000 allowing them to operate under permit at weights above the to 18,000 kg (37,478 to 39,682 lb), and the 3.66-m (144-in.) legal limits on certain roads and at certain times of the year. spread tridem axle load from 24,000 to 26,000 kg (52,910 to The two provinces believed that these configurations should 57,319 lb). These changes would allow a tridem semitrailer also be subject to the same principles as other legal vehicles, in to carry a payload competitive to that of the tri-axle semi- the same way that trucks and truck-trailer combinations were trailer, which would allow the tri-axle semitrailer to be phased brought into the M.o.U. A study team of government and out. Qubec and Ontario also agreed on a configuration for forestry industry representatives from each province spon- the quad-axle semitrailer. This initiative was agreed by the sored an extensive computer simulation study of these config- provinces, and was to be ratified by the Ministers of Trans- urations that identified a reasonable gross weight for each con- portation of the six provinces, as a sub-group of the Council of figuration, which effectively encouraged those configurations Ministers, at their meeting in 1995 (47). The Ontario Trucking with satisfactory dynamic performance and discouraged those Association was concerned that the measures would be dam- aging both to their members and the economy of Ontario, and persuaded Ontario's minister not to support the agreement pending further study. Two studies were commissioned, one into the economic impacts of the proposed and alternative truck size and weight options (48) and the other on the impacts of the options on roads and bridges (49). The studies, and sub- sequent review, took so long that Qubec proceeded inde- pendently to make changes to its regulations. Principally, it restricted the allowable load on a tri-axle with a 4.88-m (192-in.) spread to the same as for lesser spreads, increased its tandem and wide-spread tridem axle loads as had been previ- ously agreed upon with the other provinces, and mandated Figure 19. Western tractor tri-axle trailer log truck.

OCR for page 18
19 with poor dynamic performance (50). This work still contin- ues, where the industry supports development of new config- urations and enhancement of others to improve productivity and dynamic performance. This has provided a sound techni- cal basis for the provinces to set permit conditions. In the same time period, it became clear that as the gross weight of log trucks operating on mountain roads in winter conditions in British Columbia and Alberta increased, drive traction was becoming a significant issue. A study assessed drive options for tractors and recommended use of a tandem drive tractor with a liftable pusher axle. The provinces would Figure 21. Ontario self-steer tri-axle semitrailer. not countenance use of a liftable axle, so industry elected to develop a tridem drive tractor for forestry uses. The tractor Phase 1 introduced the self-steer tri-axle semitrailer, as shown was subject to extensive testing, and computer simulations in Figure 21, and the self-steer quad semitrailer, as shown in were conducted to determine appropriate trailer combina- Figure 18, where the single axle on the semitrailer was required tions for use with a tridem drive tractor (51). The tridem to be self-steering with a lift mechanism that could not be drive tractor was adopted into regulation in British Colum- operated by the driver from the cab. It included an agreement bia, operates widely under special permit for forestry and with Qubec that each would issue permits to accommodate other purposes in Alberta, and is also in limited use in other the various configurations of quad and self-steer quad that provinces under permit. It was recently also adopted into reg- were possible under the regulations of the other province. ulation in Ontario (52). The tridem drive tractor has substan- Phase 2 extended the Phase 1 weight reductions to end-dump tially addressed the traction issues that caused its development. semitrailers with liftable axles. Phase 3 dealt with multi-axle It is shown in Figure 20. trailers. An extensive simulation study was used to define fea- The Road and Bridge Study conducted in Ontario after sible configurations for use within Ontario, and as a compro- 1995 became the basis for a projection that use of liftable axles mise between the regulations of Ontario and Michigan (53), on trucks and trailers combined with allowances and require- two vehicles with different arrangements of two self-steering ments for different weight on different axles was necessitat- axles and a fixed tridem axle group, as shown in Figure 22 and ing Can$300 million in road and bridge maintenance and Figure 23, were built and tested (54). These configurations repairs that would not occur if the freight would be moved in were embodied in a new regulation that extended the format vehicles without liftable axles. The Ontario Ministry of Trans- of the M.o.U. to a new range of "Safe, Productive and Infra- portation defined a four-phase program to eliminate the use structure-Friendly" (SPIF) configurations (52). Phase 3 became of rigid liftable axles. Phase 1 dealt with tri-axle semitrailers, effective in 2006. It reduced the allowable gross weight for any and became effective in 2001. It reduced the gross weight for new non-SPIF multi-axle semitrailer built in 2006 or there- any new tri-axle semitrailer, and reduced the allowable gross after by 4,500 kg (9,920 lb), or 9,000 kg (19,841 lb) for a semi- weight for existing tri-axle semitrailers by 3,000 kg (6,613 lb) trailer with two or more liftable axles. The same weight reduc- from 2006, and 4,500 kg (9,920 lb) from 2011. End-dump tions apply after 2016 to any non-SPIF multi-axle semitrailer trailers were excluded, and tank and cryogenic trailers had built before 2006. Phase 4, now under way, addresses straight longer periods before the gross weight reductions took effect. trucks and truck-trailer combinations, as well as other con- figurations not covered in Phases 1 through 3. Figure 20. Tridem drive tractor. Figure 22. Ontario 113 SPIF 5-axle semitrailer.