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Editor's note: This is the second of a two-part article on safety. The first portion on automatic slack adjusters appeared in our last issue.
Just as the ABS industry thought it could safely round third base and head home, NHTSA moved onto the field and play halted. Or has it?
On April 12, 1994 NHTSA threw a curve to the manufacturers of antilock braking systems. The agency came out with new technical requirements for the systems along with an accelerated application schedule for some straight trucks. The statement came as a surprise because it included design requirements that manufacturers had not anticipated.
Under the new proposal, independent wheel control on at least one axle of an ABS-equipped truck or tractor would be required. The agency had previously proposed that ABS control the wheels on the front axle and at least one rear axle. This would permit manufacturers to install systems that control brakes on both wheels simultaneously. Also under consideration is the prohibition of tandem axle ABS where no more than two wheels are controlled by one modulator valve.
ABS manufacturer reactions Paul Johnston, director of Engineering for Midland-Grau, says, "The April 12 notice took us, and I think the industry, a bit by surprise. We wee under the impression that there would be minimal changes. What we found were proposals that are design restrictive and represent some major changes. These changes are not necessarily in equipment, but rather in the way the equipment is configured on the vehicle. This means we must test and verify the performance of these new configurations before they are ready for the market."
Fleets that already have ABS likely will have to change some established practices such as technician training, stocking of service parts and so on, to accommodate the new configurations. While this is going to be costly, the cost is not really the issue. The issue for these customers is that they already have ABS systems that are very stable and provide effective stopping distances cost effectively. Specifically, these are 4S/4M (four wheel sensors and four modulating valves) ABS for truck/tractors and 2S/1M ABS for tandem control of trailers, which are proven systems but would be prohibited if the proposed changes are implemented.
Says Johnston, "We...