Mr. Nasser Zamani, Senior Manager
Compliance and Regulatory Affairs
Daimler Trucks North America LLC
4747 N. Channel Ave.
Portland, OR 97217-7699
Dear Mr. Zamani:
This responds to your request for assurance that we will apply a tolerance when measuring the width of flexible occupant seats, in testing school buses for compliance with Federal Motor Vehicle Safety Standard (FMVSS) No. 222, School bus passenger seating and crash protection. We regret to inform you that this letter is unable to provide a tolerance.
You ask about a flexible occupancy seat, which is defined in S4 of FMVSS No. 222 as:
a bench seat equipped with Type 2 seat belts that can be reconfigured so that the number of seating positions on the seat can change. The seat has a minimum occupancy configuration and a maximum occupancy configuration, and the number of passengers capable of being carried in the minimum occupancy configuration must differ from the number of passengers capable of being carried in the maximum occupancy configuration.
S4.1 of FMVSS No. 222 specifies how the National Highway Traffic Safety Administration (NHTSA) will determine the number of seating positions and seat belt positions on a bench seat, including flexible occupancy seats.
Except as provided in S4.1(d), the number of Type 2 seat belt positions on a flexible occupant seatis expressed by the symbol Y, and calculated as the seat bench width in millimeters [(mm)] divided by 380 and rounded to the next lowest whole number. See Table 1 [of the standard] for an illustration.
A flexible occupancy seat meeting the requirements of S4.1(c) may also have a maximum occupancy configuration with Y +1 Type 2 seat belt positions, if the minimum seat bench width for this configuration is Y +1 times 330 mm. See Table 1 [of the standard] for an illustration. (Emphasis added.)
Request for Tolerances
You indicate that your flexible occupancy seat has an occupancy configuration of two Type 2 seat belt positions large enough for mid-size adult males under S4.1(c) and an occupancy configuration of three seat belt positions for smaller passengers under S4.1(d).
Under S4.1(d), the minimum seat width for the maximum occupancy configuration is 990 mm (3 x 330 mm). You would like the seat width to be permitted to be slightly less than 990 mm wide.
You state that since it is difficult to control the tolerance of cushions, the average seat bench width would have to be greater than 990 mm in order to ensure the cushions produced never measured less than 990 mm. You are worried that if the seat bench width is greater than 990 mm, the bus aisle width would be less than 305 mm, which might not meet some State and local requirements. To avoid the difficulties of manufacturing soft goods, you ask if we apply tolerances to the measurement of seat bench width. You suggest that, Tolerances on soft good of this nature are typically +/- 13 mm.
We regret to inform you that we cannot issue an interpretation along the line you suggest. NHTSA cannot provide variations from the explicit requirements of the FMVSSs through our interpretation letters. This is because under the National Traffic and Motor Vehicle Safety Act (49 U.S.C. Chapter 301; the Safety Act), NHTSA must establish by order appropriate safety standards. The Administrative Procedure Act (APA) applies to all orders establishing, amending, or revoking a safety standard. The APA generally requires agencies to publish a notice setting forth the proposed change to a safety standard, and allow the public to comment thereon, before the agency can adopt any change to the established safety standard.
Our interpretation letters are not subject to the requirements for public notice and comment, because interpretations do not add, delete, or change any requirements established in a safety standard. Instead, our interpretations explain how the requirements established in safety standards or the Safety Act apply to particular vehicles or equipment, or otherwise clarify the meaning of the established requirements.
In this case, S4.1s language is clear. Under S4.1(d), a flexible occupancy seat (bench seat) may have a maximum occupancy configuration with Y +1 Type 2 seat belt positions, if the minimum seat bench width for this configuration is Y +1 times 330 mm. Thus, under the standard, the minimum seat bench width for your flexible occupancy seat is 990 mm (3 x 330 mm=990 mm). We cannot interpret this language to include a tolerance of +/- 13 mm for the bench. Your letter suggests a change to the requirements of FMVSS No. 222, not a clarification of those requirements. We cannot change those requirements without initiating rulemaking and giving the public notice of and the opportunity to comment on the change.
We also note that interpreting the standard to include a tolerance would confuse the meaning of Table 1 of the standard. Table 1 illustrates the number of seating positions as a function of seat bench width. The table shows that a seat bench with a width of 990-1139 mm would have a minimum of two seating positions (fixed occupancy seats or flexible occupancy seats), and for flexible occupancy seats, a maximum occupancy configuration of three seating positions. The table also shows that a seat bench with a width of 760-989 mm would have a minimum of two seating positions (fixed occupancy seats or flexible occupancy seats), and a maximum occupancy configuration of two seating positions. If we applied a tolerance of +/- 13 mm as you suggest, a bench seat of 760-989 mm nominal width could have a maximum occupancy of two or three seating positions. An interpretation that 990 mm means some lesser value would render the values in Table 1 confusing.
For the above reasons, we cannot interpret FMVSS No. 222 to provide the tolerance you seek.
O. Kevin Vincent
Ref: Std. No. 222
 We assume you meant +/- 13 mm for the entire 990 mm bench and not per 330 mm seating position, but it is unclear from your letter.