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Sizing It Up

Ministers of transport across Canada are considering a number of vehicle weights and dimensions policies and their decisions will prove crucial to the trucking industry. Following is an update of the most important issues under consideration.


Ministers of transport across Canada are considering a number of vehicle weights and dimensions policies and their decisions will prove crucial to the trucking industry. Following is an update of the most important issues under consideration.

Tridem-Drive Tractors

The use of three drive axles on a tractor was pioneered by the Forest Engineering Research Institute of Canada (FERIC). The forestry industry needed something to haul heavy loads, over difficult roads – often with soft surfaces – and tridem-drive tractors proved successful. They have been operating under permit in British Columbia and Alberta since the mid-1990s and, more recently, a few permits have been issued in Saskatchewan. B.C. has now amended its regulations so that anyone can operate tridem-drive tractors (no permit needed). Tridem-drive tractors are also legal under Ontario’s regulations governing trucks outside the national agreement.

As tridem-drive tractors gained popularity in the western forest industry, the trucking industry has been asking the National Task Force on Vehicle Weights and Dimensions Policy to consider putting these configurations into the national agreement. If the provinces could agree on standards, then it might be possible to develop uniformity in the spec’s of tridem-drive tractors across the country – for example, on the minimum/maximum wheelbases, on the axle spreads of the tridem and on the loads allowed on both the steering axles and the drive tridems. The advantage of the tridem-drive tractor is that it is relatively simple (just another drive axle on a tractor), not too expensive (about $12,000- to-$15,000 more than a tandem-drive tractor) and it increases the payload considerably without adding more articulation points to the configuration. There are two hurdles to overcome for other provinces to agree on including them in the national agreement: the current limit on tractor wheelbase lengths (6.2 metres) and the current limit on tire loads (3000 kg). To make tridem-drive tractors work in B.C. and Alberta, wheelbases had to be extended to 6.8 metres and steering axle loads to 7300 kg (3650 kg per tire).

Tractor Wheelbase

The 1988 agreement set the maximum wheelbase for a tractor at 6.2 metres (244 inches). This was to limit the amount of off-tracking the rear axle did in a tight turn. But there has always been a controversy about this, particularly by drivers of American tractors entering Canada with tractors having wheelbases longer than 244 inches. The debate has heated up with the introduction of tridem-drive tractors. These have wheelbases as long as 7.7 metres (303 inches) in Ontario, although B.C. and Alberta limit the wheelbase to 6.8 metres (268 inches). Some within industry want the Task Force to re-visit the need to limit tractor wheelbases to 244 inches.

Wide-Base Tires

The 1988 national agreement set a limit of 3000 kg per tire because research suggested that, for a given load, a wide-base tire did more pavement damage than a set of dual tires. Since then, manufacturers have developed new ways of making very wide tires (over 17 inches) that are pavement friendly. Michelin’s X-One series and Bridgestone’s Greatec tires are examples.

While these tires are selling in the United States on the grounds that they save fuel and decrease tare weights, they have run into a road block in Canada. At 3000 kilograms per tire, a tandem only carries 12,000 kg, far below the legal limit of 17,000 kg in western Canada or 18,000 kg in eastern Canada. So two years ago Michelin sponsored research at the Virginia Tech Transportation Institute that showed that the new X-One tires were roughly equivalent to a set of dual tires in terms of pavement wear.

The provinces responded by producing their own research. Research by the Ontario Ministry of Transportation concluded that, while it might be safe to raise the tire-load limit in Canada to the 4000 kg range, pavement wear from wide-base tires would be much more than from dual tires above this limit. Ontario already allows some single tires as much as 4500 kg under its regulations governing trucks outside the national agreement. And that’s too much, according to Ontario’s latest research. Another report from the Qubec Ministre des Transports also shows that wide-base tires are more damaging to pavements than duals at equivalent heavy loads.

Why the discrepancy between the U.S. research and the two Canadian reports? For one thing, the Virginia study only considered tandem axle loads of up to 15,422 kg (34,000 lbs – the U.S. federal limit) and these are considerably lighter than Canadian tandems. Second, the Virginia study used a very strong test section of pavement. This might represent pavements on the U.S. Interstates but Canadian officials pointed out that many provinces have many kilometres of thin-pavement roads to worry about.

Eliminating Lift Axles in Ontario

Ontario’s old regulations governing trucks that are not under the national agreement allow any number of axles, in any position and have no prohibition on lift axles. The new regulations (Reg 32/94) for trucks under the national agreement apply to tractor-semitrailers with trailers longer than 48 feet and doubles with an overall length greater than 75 feet (23 metres). Many trucks in Ontario still operate under the old regulations and Ontario has grown increasingly concerned about what all the lift axles are doing to pavements and bridges. As a result of these concerns, Ontario began a program to eliminate lift axles in 2001. Phase 1 and 2 have now been completed. Phase 1 dealt with 3-axle semitrailers (“tri-axles” or a lift plus a tandem) and Phase 2 dealt with end-dump and open-top hopper-bottom trailers. Lift axles are being phased out for semitrailers under both Phases 1 and 2. Phase 3 of the program is now underway and it will attempt to deal with semitrailers with four or more axles. There already is an acceptable model for 4-axle semitrailers-commonly known as the “Qubec quad” with a self-steering axle replacing the lift axle in front of a tridem. Ontario and Qubec agreed to this arrangement at the time they began to allow 53-foot trailers with four axles.

In the category of “more than four axles,” common trailers include the “five leggers” (lift+tridem+lift) used to haul steel products or the “five leggers” (lift+lift+tridem) used in the forestry industry. These will be difficult to replace and preliminary analysis suggests there are no replacement vehicles that meet all the performance standards such as off-tracking and stability originally established by the National Task force in the mid-1980s. One configuration that comes close to meeting the performance standards is a tridem-drive tractor with a 4-axle semitrailer. At 61,300 kg, this might be a suitable replacement for some of the 5+ axle semitrailers now gracing Ontario roads. However, Ontario is a long way from making a decision on this. The next step is to do some actual testing of real vehicle configurations.

Qubec: Spring Thaw Axle Weights

A recent study supports Qubec’s decision to reduce axle loads on main highways during spring thaw. Qubec is the only province to do this. Other provinces lower weights on secondary roads during spring thaw, but not on main highways. According to Qubec, there is a $40 million cost to the trucking industry when it has to operate with reduced payloads during the approximately two month spring thaw period every year. But there would be an approximate $50 million cost to repairing pavements if the trucks were allowed to operate at normal axle loads when pavements are weak because of the thaw conditions. According to Denis St-Laurent of the Qubec Ministre des Transports, the removal of spring thaw axle load reductions would reduce pavement lives by 8% on main highways and as much as 15% on collector roads.

Ralph Boyd of the Atlantic Provinces Trucking Association is not happy with Qubec’s numbers. According to Boyd, his members only use Qubec as a corridor between Atlantic Canada and central Canada. Boyd pointed out that Qubec’s number of $40 million in extra trucking costs only includes travel within the province – it doesn’t consider the extra cost of travelling at reduced weights in New Brunswick and Ontario for truckers using Qubec as a corridor.


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1 Comment » for Sizing It Up
  1. Alphonse Gosselin says:

    Are they looking at the possibility of having straight truck with tridem axles. We have trucks with a pulp loader on the back (Prentice Loader) with a pup trailer. When we haul wood and the land is kind of swampy we can leave the pup at the main road and still go get a load of wood, top off the pup and go get another load.

    Thanks

    .

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