NTSB Number: HSS-72/05
NTIS Number: PB-214061

Requirements for the deceleration performance of passenger cars are proposed in NHTSA Docket 70-27. Commercial-vehicle stopping requirements are prescribed in Motor Vehicle Safety Standard (MVSS) 121, which will become effective in September 1974. However, even if Docket 70-27 culminates in a standard which will substantially reduce the differences in stopping distances between passenger car models, MVSS 121 will continue to permit much longer stopping distances for commercial motor vehicles than for passenger cars (at given speeds) and thus will tend to perpetuate this dangerous incompatibility.

The most significant feature of MVSS 121 is the requirement for antilock systems. This requirement should improve panic or "spike" type (momentary) stops as well as vehicle control under adverse road-surface conditions. However, MVSS 121 does not require the improvement in overall braking performance which is possible with available technology.
Reluctance of manufacturers and carriers to accept major changes in brake systems appears to be based principally on the cost/benefit factor and the problem of maintaining interchangeability between tractors and trailers. However, such changes would increase highway safety in the foreseeable future. As the Interstate Highway System nears completion, the average speed of all motor vehicle traffic has been increasing. Heavier truck payloads and an increasing use of double (and, in some States, triple) vehicle combinations point up the need for an immediate and concerted effort by all concerned to improve the braking performance of commercial vehicles.

The recommendations in this study are intended to encourage regulatory agencies, manufacturers, suppliers, and the motor carrier industry to use more advanced technology to reduce the differences in braking performances of passenger cars and commercial vehicles. The study proposes that Federal funds be made available to design, build, and test an Experimental Safety Vehicle-Truck Brake (ESV-TB) incorporating new technology for advanced braking systems. An ESV-TB program would define the technically feasible performance parameters of commercial vehicles, provide a firmer basis for voluntary and mandatory advances, and propose practical solutions to the vehicle interchange problem.

RECOMMENDATIONS

The National Transportation Safety Board recommends that the Bureau of Motor Carrier Safetv (Federal Highwav Administration) and the National Highway Traffic Safety Administration of the Department of Transportation, cooperatively;

Initiate a research and development program to reduce substantially the incompatibility of braking performances of passenger cars and commercial motor vehicles, and to eliminate other braking inadequacies in commercial vehicles. (Recommendation No. H-72-60)

Make Federal funds available to design, construct, and test an Experimental Safety Vehicle-Truck Brake (ESV-TB), which will incorporate the best available braking technology in art integrated system. The results of this work should be published periodically to guide voluntary changes as well as timely changes in existing standards. (Recommendation No. H-72-61)

Form a technical advisory committee for the ESV-TB program which will include not only the technical viewpoint of the commercial vehicle industry and its suppliers, but also the viewpoint of brake suppliers for the aerospace industry and passenger car suspension technologists, as well as a technically qualified representative of the interests of passenger car occupants. (Recommendation No. H-72-62)