WASHINGTON — The U.S. National Highway Traffic Safety Administration has issued a proposal for more stringent stopping distance requirements for heavy trucks.

The agency intends to amend the air brake standard in order to improve the stopping distance performance of truck tractors.

After performing an extensive series of stopping distance tests with two trucks at various weights and stopping distances at its Vehicle Research and Test Center in East Liberty, Ohio, the NHTS has determined that stopping distances for tractors can be reduced by 20 to 30 percent from current standards.

Furthermore, because of new developments in air disc brakes, enhanced larger-capacity drum brakes, electronically controlled brake systems (ECBS), and advanced ABS, the NHTS concludes that tractors can achieve these new conditions with existing available technology, with modifications only to the foundation brake systems.

Tests show trucks can achieve 30 percent
better stopping distances with existing technology

The NHTS is also researching and requesting comment concerning improving the braking performance of other types of heavy vehicles, such as trailers, straight trucks, and buses. The agency says it may address improved braking performance for these other vehicles in a future rulemaking.

The current stopping-distance requirements under the Federal Motor Vehicle Safety Standard are determined according to vehicle type. Under the loaded, 60-mph stopping-distance requirements, air-braked single-unit trucks must comply with a stopping distance of 310 feet, and air-braked truck tractors must comply with a stopping distance requirement of 355 feet.

Unloaded at 60 mph, air-braked trucks and air-braked truck tractors must comply with a stopping distance requirement of 335 feet. Under the emergency-brake,60-mph stopping requirements, air-braked single-unit trucks must comply with a stopping distance of 613 feet, and air-braked truck tractors must comply with a
stopping distance requirement of 720 feet.

With disc brakes at all wheel positions, both test vehicles at gross vehicle weight rating conditions traveling at 60 mph were able to exceed a 30 percent stopping distance reduction — stopping in at least 249 feet — from the current requirements.

Both test vehicles were also able to exceed the 20 percent reduction — 284 feet — using a hybrid braking system.

Even though crash rates have gone down in recent years (The U.S. Department of Transportation reported last week a 30-year low at 1.96 fatal crashes per 100 million vehicle-miles-traveled), the NHTS says that overall incidents still remain high, mainly because the number of trucks on the road has increased.

To read the full report and testing results go to: http://edocket.access.gpo.gov/2005/05-24070.htm

Comments can be submitted at the Federal eRulemaking Portal: at www.regulations.gov.