WINNIPEG — Manitoba is the next western jurisdiction to increase its allowable axle weight threshold for new generation, single wide-base tires.

The Manitoba Department of Infrastructure and Transportation, which also announced new length rules for aerodynamic devices, has joined B.C. in increasing the wide-base tire weight threshold on certain routes from the standard 6,000 kg to over 7,000 kg per axle.

Like B.C., which last year upped its threshold to 7,700 kg, the change allows carriers to spec single tires primarily for U.S.-destined loads, where the maximum load is 17,000 lb (7,700 kg per axle).

Quebec is the only province where single tires enjoy a 9,100 kg per axle maximum, allowing (by special permit) full parity between single tires and a set of duals. Coming close is Ontario, where the limit is generally 8,000 kg per axle.

Manitoba hikes single tire limits, but more research
needed before allowing them on weaker pavements.

Other provinces still follow the Memorandum of Understanding (MOU) on Interprovincial Vehicle Weights and Dimensions, which caps single tires at 6,000 kg (two tires per axle).

Until the Vehicle Weights and Dimensions on Classes of Highways Regulation (MR 575/88) can be amended, the current oversize/overweight permit policy will be changed to allow permits for carriers wishing to take advantage of the new single tire weight rules, which are as follows:

RTAC Routes:

A information notice distributed by Manitoba Transportation states that weight limits for axles fitted with single tires with a width of 445 mm or greater are being increased on RTAC Routes to 7,700 kg; and to 15,400 kg (from 12,000 kg) for tandem axle groups.

Class A1 and Class B1 Highways:

For Class A1 routes, the weight limit for single axles fitted jumps only to 7,280 kg, and 12,800 kg for tandem axle groups.

On Class B1 highways, the weight allowance is marginal. Up to 6,560 on a single axle. On tandem groups, the cap remains unchanged at 12,000 kg.

Manitoba Transportation says that more research is required before any further increased loading can be considered on these lesser strength pavements.

Additionally, to support an orderly transition to use of wide single tires, “while preserving desirable vehicle stability and control characteristics,” the minimum track width on axles fitted with single tires will be reduced to 2.3 m (from 2.5 m) for vehicles built in 2007 or earlier. The minimum track width for all axles on vehicles built in 2008 or later will be maintained at 2.5 m.

Meanwhile, aerodynamic devices installed at the rear of trucks, trailers and semi trailers — referred to at times as boat tails — will not be included in the measurement of overall length, trailer length, semitrailer length, box length and effective rear overhang.

This applies only when no portion of the device more than 1.9 metres above the ground protrudes more than 0.61 metres beyond the rear of the vehicle; and, no portion of the device within 1.9 metres of the ground protrudes more than 0.305 metres beyond the rear of the vehicle.