Interpretation ID: aiam1807
Jr.
Executive Director
Truck Equipment & Body Distributors Association
602 Main Street
Cincinnati
OH 45202;
Dear Mr. Pieratt: This responds to the Truck Equipment and Body Distributors Associatio February 6, 1975, petition to amend Standard No. 121, *Air brake systems*, by exempting completed vehicles permanently from S5.3.1 of the standard (stopping distance) and until March 1, 1976, from S5.3.3 and S5.3.4 (actuation and release), if they have been 'certified' to these requirements as incomplete vehicles. You base this request on the commercial desirability of modifying the standard brake system on incomplete vehicles to accommodate additional axles, modification of the wheelbase, or installation of accessories. You conclude that testing of each modified vehicle would be involved in certification to the standard, and that such a burden is unreasonable.; We do not believe that a delay in the application of S5.3.1, S5.3.3 and S5.3.4 of Standard No. 121 to multi-stage vehicles would be advisable. As you know, the agency did consider postponing the standard in December, and decided against it based partly on information indicating that such a last-minute delay would be disruptive and wasteful. The conclusion would be even more valid today. Since the standard applies only to completed vehicles, it could not be suspended for completed vehicles as you suggest with the chassis still required to comply. Even if this were possible, it might cause anomalous and even hazardous results, since the final-stage manufacturers could disregard any design cautions of the chassis manufacturers, and could remove or disable portions of the chassis brake systems. Furthermore, even a complete delay in the standard with respect to the classes of vehicles with which you are concerned would probably not accomplish your purpose, since the chassis manufacturers could not be expected to produce chassis conforming to the standard with accompanying documentation, during the period of delay.; With regard to testing, your assumption that each vehicle must b road-tested following modification of the braking system may not be correct. For example, your members could establish categories of models which share a common brake system modification, and certify them all on the basis of tests on the most adverse configuration in the category. Alternatively, joint testing might be undertaken with a major supplier of brake and axle components. In the case of standard models, your members might be able to rely on the supplier's warranty of his products' capacities.; Neither of these methods would require road testing of each vehicl manufactured, nor would every model have to be road tested. A manufacturer must simply satisfy himself in the exercise of due care that the vehicle is capable of meeting the stopping performance requirements if it were tested by the NHTSA. What constitutes due care in a particular case depends on all relevant facts, including such things as the time to elapse before a new effective date, the availability of test equipment to small manufacturers, the limitations of current technology, and above all the diligence evidenced by the manufacturer.; Accordingly, your petition for delay of Standard No. 121 is denied. Yo and your members may be assured that, within the limits of the law, this agency will be understanding in its approach to problems experienced by intermediate and final-stage manufacturers as they bring their vehicles into conformity with the new standard.; Sincerely, James B. Gregory, Administrator