Interpretation ID: aiam2739
Executive Secretary
Wisconsin School Bus Association
2830 No. Brookfield Road
Box 403
Brookfield
WI 53005;
Dear Mr. Rechlicz: This responds to your October 16, 1977, letter requesting again tha the National Highway Traffic Safety Administration (NHTSA) reinterpret its 20-inch measurement of occupant seat spacing in Standard No. 222, *School Bus Passenger Seating and Crash Protection*.; Mr. Levin indicated in an earlier response to your letter that sea spacing is measured at the point of greatest distance separating the seats. This measurement is used to ensure that impact forces do not exceed the forces the seat is designed to sustain or absorb. To measure as you suggest would require redesigning school bus seats to ensure their ability to sustain or absorb increased impact loads.; The NHTSA has received a number of complaints on seat spacing in schoo buses manufactured in compliance with the subject regulations. We have met with most of the major school bus manufacturers discussing production seat spacings and the Federal requirements. The agency has found that manufacturers are producing buses with seat spacings which are, in some cases, 3 inches less than the maximum specified by the regulations. These large reductions in seat spacing result principally from manufacturers' choices in designing the seats. Such seat spacing reductions are not found in all seats designed to meet the regulations.; Through its monitoring of the standard's implementation, the NHTSA ha discovered that manufacturers are not achieving the maximum seat spacing that the agency had contemplated at the time the regulation was issued. The installation of seats in school buses cannot be done with the precision that the NHTSA had anticipated. Accordingly, manufacturers in their attempts to ensure that they do not violate the 20-inch space requirement must design seat spacing as much as an inch short of the 20-inch spacing allowance. The result is seat spacing which is less than the agency contemplated. The NHTSA has taken expeditious action to alleviate this problem.; On December 20, 1977, NHTSA issued an Interim Final Rule amendin Federal Motor Vehicle Safety Standard No. 222 by increasing the maximum allowable distance from the seating reference point to the seat back from 20 to 21 inches. The agency intended that the measurement be approximately 20 inches. A seat spacing specification of 21 inches permits 20- inch spacing by taking manufacturing tolerances into account. A Notice of Proposed Rulemaking (NPRM) proposing this change in the rule was also issued on December 20, 1977.; Sincerely, Joan Claybrook