Interpretation ID: aiam1898
Manager - Central Engineering
Trailmobile Technical Center
5570 Creek Road
Cincinnati
OH 45242;
Dear Mr. Hammond: This is in response to your letter of April 14, 1975, in which yo described two factors that you see as problems in the completion of air-braked trucks in accordance with Standard 121, by final-stage manufacturers.; The first problem you cited was that without knowing how this agenc will require air-braked trucks to be loaded for test purposes, specifically whether we will load them according to the chassis manufacturer's specifications, the final-stage manufacturer does not have a basis for certification. The answer to this implied question is that the NHTSA will use the chassis manufacturer's loading limitations for purposes of determining compliance. We agree that in many cases there is no practicable way for a final- stage manufacturer to ensure compliance other than relying on the chassis manufacturer's statements in the Part 568 document, and these statements are contingent on the loading conditions.; Secondly, you argued that 'If a tested and certified vehicle cannot b stopped in actual use in the required distance because the real load has a center of gravity higher than an unrealistic test load, an unsafe vehicle has been created, even though it complies to the safety standard.'; We completely disagree with that position, and know of no facts t support its validity. We have no reason to believe that vehicles that conform to Standard 121 will be unsafe when loaded the same as comparable pre-121 vehicles. In fact, we have much reason to believe they will be safer than pre-121 vehicles, with stronger, better modulated brakes, and in many cases stronger front suspensions to carry the forces imposed by high-CG loads in a braking situation. The required stopping distances are part of a large and complex package of test requirements, whose conditions and procedures must be precisely specified to meet statutory requirements of objectivity. They are designed to give rise to vehicles whose braking systems use the best of modern technology to provide excellent braking performance under a wide range of loading and environmental conditions. There is no implication from the standard that a vehicle that, under certain loading conditions, does not stop in the specified distance is necessarily unsafe. If the NHTSA discovers vehicles that are truly unsafe when normally loaded, because of unusual handling difficulties, for example, it will proceed against them under its safety-related defect jurisdiction.; Sincerely, James C. Schultz, Chief Counsel