United States Department of TransportationInterpretation ID: 11391MLV
Compliance Engineer
Western Star Trucks, Inc.
2076 Enterprise Way
Kelowna, British Columbia
Canada V1Y6H8
Dear Ms. Fichtner:
This responds to your fax of November 21, 1995, in which you asked how many seat belts would be required on a box base seat. You stated that the seat had the following dimensions:
Box width - 29.71 inches Width of flat area between foam bolsters on seat back - 24 inches Overall width at the widest part of the foam - 31 inches
Federal Motor Vehicle Safety Standard No. 208, Occupant Crash Protection, specifies occupant protection requirements (seat belts or air bags) based on vehicle type and seating position within the vehicle. The requirements apply to "designated seating positions," defined at 49 CFR 571.3 as:
any plan view location capable of accommodating a person at least as large as a fifth percentile adult female, if the overall seat configuration and design is such that the position is likely to be used as a seating position while the vehicle is in motion, except for auxiliary seating accommodations such as temporary or folding jump seats. Any bench or split-bench seat ... having greater than 50 inches of hip room ... shall have not less than three designated seating positions... In a May 22, 1978, notification to vehicle manufacturers, the agency stated that manufacturers are responsible for determining the number of seating positions that are in the vehicle. The agency also stated:
This does not mean, however, that the manufacturer's designation will be accepted by the agency if there are additional, obvious seating positions that are likely to be used by occupants while the vehicle is in motion. The agency unquestionably intends to require protection for all vehicle occupants.
Thus, while it is your responsibility to determine the number of seat belts required, we can provide some guidance to help you determine whether more than one belt would be required on this seat.
The agency has previously stated that the definition of "designated seating position" should not be read to mean that vehicles with less than 50 inches of hip room are never required to have three seat belts, but rather that this amount is "conclusive evidence that there should be at least three designated seating positions." On seats with slightly less than 50 inches, the agency said "the seat design should be such that it is obviously to be used by only two persons if the manufacturer only designates two positions." Your seat has significantly less than 50 inches of hip room, and therefore, you would not have to designate three positions.
The definition of designated seating position does not include an amount that is conclusive evidence that there should be at least two designated seating positions. The information you provided indicates that the seat would have 31 inches of hip room. The sitting hip breadth of a 5th percentile adult female is 12.8 inches. Because your seat has more than 25.6 inches of hip room, it could be possible for more than one 5th percentile adult female to use the seat. However, we also note that the amount that is conclusive evidence of three positions is greater than 38.4 inches (the amount of hip room of three 5th percentile females). Therefore, we believe that this situation is analogous to the situation of a seat with slightly less than 50 inches of hip room, and would look to see whether the seat design is such that it is obvious that the seat is only for one person.
The seat appears in the drawings to be generally flat, similar to a bench seat that would be used for more than one occupant. Therefore, if you wish to designate only one seating position, you should modify the seat design to make it clear that the seat is intended for one occupant. For example, you could sculpt the foam similar to bucket seats or captain's chairs.
I hope this information has been helpful. If you have other questions or need some additional information, please contact Mary Versailles of my staff at this address or by phone at (202) 366-2992.
Sincerely,
Samuel J. Dubbin Chief Counsel
ref:571 d:3/4/96
On January 16, 1996, you faxed additional drawings to our office. Those drawings indicate that, except for some narrowing at the upper corners of the seat back, the seat bottom and seat back are 31 inches wide. 43 FR 21893. 44 FR 23229, 23232. 44 FR 23229, 23232.