By Mike Antich

The National Highway Traffic Safety Administration (NHTSA) is proposing to amend its air brake standard to improve the stopping distance performance of commercial trucks. Based on current safety trend data and brake system technologies, NHTSA is proposing to reduce the required stopping distance for tractors by 20 to 30 percent. The proposed rule would cover all truck tractors equipped with air brakes.  The proposed rule does not include single unit trucks, buses, or trailers.

"The proposed rule was issued not because of an increase in accidents, but more in an effort to further reduce accidents between trucks and cars because of the disparity in braking distances," said Thomas Bray, transportation editor for J. J. Keller & Associates, Inc., in Neenah, Wis.

The current stopping distance requirements under Federal Motor Vehicle Safety Standard (FMVSS) No. 121, Air brake systems, as established under the 1995 final rule, are determined according to vehicle type. Under the loaded 60-mph stopping distance requirements of FMVSS No. 121, air-braked tractors must comply with a stopping distance requirement of 355 feet when loaded to GVWR using an unbraked, single-axle test trailer. Under the unloaded 60-mph stopping distance requirements of FMVSS No. 121, air-braked single-unit trucks and air-braked truck tractors must comply with stopping distance requirements of 335 feet.

Since announcement of the proposed rule in 2005, truck fleets have been concerned whether they will be mandated to retrofit existing units to meet the new stopping distance requirements. However, this doesn't appear to be the intent of NHTSA.

"There is no retrofit requirement, so long as existing vehicles meet the FMVSS No. 121 standard in place when they were built," said Bray.

Since NHTSA established the stability control and stopping distance requirements for heavy vehicles almost 13 years ago, data indicates the involvement of large trucks in fatal and injury-producing crashes has slightly declined, even though vehicle-miles-traveled have increased. However, because the number of registered large trucks has increased, the total number of crashes continues to remain high. NHTSA's position is that reductions in stopping distances, in most cases, will result in a reduction in the impact velocity, and, as a result, the severity of a crash. In some cases, reduced stopping distances will actually prevent a crash from occurring, said NHTSA..

NHTSA proposes to reduce the stopping distance requirements for loaded and unloaded service brake distances and emergency brake distances for tractors by 20 to 30 percent. NHTSA says data indicates most tractors could comply with a reduction in this range through use of larger drum brakes. Also, NHTSA said its testing did not include other vehicle modifications that may further optimize a vehicle's braking capabilities. NHTSA has tentatively determined this data justifies the proposed range of reduced distances and requested comments on the feasibility of truck tractors to comply with this proposal.

"However, NHTSA will not require specific brake component requirements," said Bray. "What NHTSA is saying is that this technology is out there, we should be using it."


Cost Impact of Proposed Braking Regulation

NHTSA's preliminary regulatory impact analysis shows enhanced brake system specifications will have net cost savings for truck fleets after considering property damage savings. However, NHTSA said truck fleets do not have this cost-saving information and only a few are purchasing the improved brake systems. As a result, NHTSA said progress towards improved brake systems is impeded because truck fleets are cost-sensitive to the initial purchase price and reluctant to add different types and sizes of brake components to their specifications. Although truck manufacturers offer improved drum brakes and are introducing air disc brakes, very few fleets are purchasing them.

However, truck fleets are bracing themselves for higher expenses to comply with the proposed rule once it becomes final. "The new trucks and trailers will become more expensive due to the improved braking systems," said Bray. "Downstream you'll get increased maintenance costs associated with enhanced drum brakes or brake-by-wire systems. This will result in additional maintenance costs and training of technicians to inspect and service the newer braking systems."

NHTSA proposes a two-year lead time after the final rule is issued in the Federal Register for OEM compliance. NHTSA wrote two years would be adequate lead time for manufacturers to comply with a reduction in stopping distances in the proposed range.  However, the actual implementation date still remains undetermined." The rule hasn't been published yet in the Federal Register, so we don't know the exact trigger date," said Bray.

Let me know what you think.

Originally posted on Automotive Fleet

About the author
Mike Antich

Mike Antich

Editor and Associate Publisher

Mike Antich has covered fleet management and remarketing for more than 20 years and was inducted in the Fleet Hall of Fame in 2010.

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