FMCSA Amends Brake Regulation on Triple Saddle Mount

The Federal Motor Carrier Safety Administration (FMCSA) has amended the Federal Motor Carrier Safety Regulations (FMCSRs) to eliminate the requirement for operational brakes on the last saddle-mounted truck or tractor in a triple saddle-mount combination, except when a full mount is present.

This is in response to a petition for rulemaking from the Automobile Carriers Conference (ACC) of the American Trucking Associations (ATA), which argued that this requirement degrades the braking performance of these combinations because the lightly loaded axle of the last vehicle tends to lock up under heavy braking.

The final rule is effective October 13.

Stopping distances are specified in the vehicle brake performance table at Sec. 393.52(d) of title 49, Code of Federal Regulations, which requires many combination vehicles, including triple saddle- mounts, to be able to stop within 40 feet or less from an initial speed of 20 mph.

The FMCSRs do not specify minimum stopping distances from higher speeds. They do, however, specify performance requirements for the emergency brakes, which deploy after the service braking system has failed. Under the emergency braking requirements in Sec. 393.52(d), triple saddle-mounts must be able to stop within 90 feet or less from a speed of 20 mph. Further, Sec. 393.71(a)(3) requires operational brakes on any wheel of a triple saddle-mount combination that is in contact with the highway.

Based on the results of braking tests performed on various triple saddle-mount combinations, ACC requested that FMCSA make two regulatory changes: (1) Amend Sec. 393.71(a)(3) to eliminate the requirement for operational brakes on the last saddle-mounted truck in a triple saddle-mount combination; and (2) amend Sec. 393.71(c)(4) to extend to triple saddle-mounts the existing requirement that a double saddle-mount with any vehicle full-mounted on it have effective brakes acting on those wheels in contact with the roadway.

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