Transport Canada’s rules on anti-lock brakes-outlined in proposed amendments to CMVSS 121 (governing air brakes) and 105 (hydraulic and electric brakes) published Feb. 6 in the Canada Gazette-would require most new medium and heavy trucks and trailers to be equipped with ABS as of Dec. 1. The changes would, in most cases, harmonize Canada’s braking regulations with those in the United States, which come under the U.S. National Highway Traffic Safety Administration’s Stability and Control Requirements for Medium and Heavy Vehicles, FMVSS 121 and 105. Instead of phasing in the requirements over several years like the U.S. did, Transport Canada plans to cover all air-braked trucks, trailers, and buses and all hydraulically braked trucks and buses in one fell swoop.

ABS is defined as a portion of a service brake system that automatically controls the degree of rotational wheel slip during braking by: 1) sensing the rate of angular rotation of the wheels; 2) transmitting signals regarding the rate of wheel rotation to one or more devices, which interpret these signals and generate responsive controlling output signals; and 3) transmitting those signals to one or more devices which adjust braking forces in response to the signals.

For straight trucks, tractors, and full trailers, ABS would be required to directly control the wheels of at least one front axle and the wheels of at least one rear axle of the vehicle. A tractor would also be required to have the wheels on at least one axle controlled independently by the ABS, and to have no more than three wheels controlled by one system modulator. For semi-trailers and dollies, ABS would have to control the wheels of at least one axle on the vehicle. For all vehicles, wheels on other axles could be indirectly controlled by the ABS.

Also contained in the Transport Canada rule:

* After March 1, 2001, all tractors must have in-cab warning lights and trailers capable of sending a signal to the tractor should the trailer ABS malfunction. To be in harmony with the U.S., the amendment would require full-time ABS power to the trailer, but not a separate dedicated circuit. This means the auxiliary circuit (No. 7 blue wire) can be used for ABS power and other things such as interior trailer lights. The stoplight circuit is the backup if the other circuit fails. A separate ground circuit is not required; you could still use the common ground (No. 1 white wire).

A word of warning for operators who use the auxiliary circuit for powering other devices: all new tractors now come with the auxiliary pin wired hot and you may have to do some rewiring to prevent trailer equipment from activating unintentionally.

* There are no specific voltage/amp requirements for trailer ABS. Manufacturers are expected to follow SAE recommended practices, which spell out minimum requirements.

* New trailers and converter dollies made before March 1, 2010, would need an exterior ABS malfunction warning lamp. Transport Canada wants the light because a new trailer or dolly may be towed by a vehicle that does not have an ABS malfunction warning lamp. The regulation presumes that all vehicles will be equipped with ABS-and thus a warning lamp-by 2010.