Regulations and Standards Technician
Drummondville, Qubec J2B 6V4
Dear Ms. Fortin:
This responds to your request for an interpretation of 49 CFR 571.10(b)(1) and (2). Those paragraphs include formulas for determining the required number of designated seating positions (DSPs) in a seating surface area. In your letter, you cite an example of four adjacent seats in a line with a total width of 1778 mm. You observe that, using the calculation procedure set forth in section 571.10(b)(2), the seating surface would have three DSPs. You ask whether the regulations would allow you to designate four DSPs for that seating surface area instead of the result of the calculation. The issues raised by your letter are addressed below.
By way of background, for the purpose of the Federal Motor Vehicle Safety Standards, NHTSA has defined a designated seating position as a location capable of accommodating a person at least as large as a 5th percentile adult female. On June 22, 2005, NHTSA published a notice of proposed rulemaking for a revised definition of designated seating position that would be more objective. NHTSA had identified a problem of three people occupying a seat with only two DSPs. It was believed that providing a more objective definition of designated seating position would help alleviate this problem.
In the October 2008 final rule, NHTSA amended the definition of designated seating position for vehicles manufactured on or after September 1, 2011. The new definition states that a seat location that has a seating surface width of at least 330 mm is a designated seating position. The final rule also established a procedure, codified in section 571.10, for measuring seating surface width and calculating the number of DSPs at a seat location. For seat locations with a seating surface width of less than 1400 mm, the number of DSPs required is equal to the seating surface width divided by 350, rounded
down to the nearest whole number. For seat locations with a seating surface width of 1400 mm or greater, the number of DSPs required is equal to the seating surface width divided by 450, rounded down to the nearest whole number.
In your letter, you put forth a scenario where four seats are placed adjacent to each other, each one having a width of 444.5 mm, such that the total width of the seating surface area, as calculated under section 571.10(c)(2), is 1778 mm. You observe that, under the formula used to calculate the number of DSPs for a seating surface width of at least 1400 mm, there would be three DSPs at the seating area. You ask whether you may, under the new DSP definition set forth in the October 2008 final rule, consider the actual designated capacity (represented by the defined seating positions) instead of the result of the calculation in section 571.10(c)(2). You stated that you believe the goal of the new regulation is to prevent the possibility of having more occupants on a seat than the allowed capacity of the vehicle without reducing the actual capacity of the vehicle.
As indicated above, we changed the definition of designated seating position because of a concern that, in certain situations, more people were occupying a seating surface area than the number of DSPs. You put forward a scenario in the opposite direction, where a manufacturer wants to designate more DSPs than the number required by the formulas in section 571.10(b), and also where the seating area is specifically designed for that greater number of occupants. However, the definition of designated seating position was also revised to be more objective. NHTSA developed a procedure, set forth in section 571.10(b)(1) and (b)(2) to calculate the number of DSPs for a seating location.
Our rulemaking was not intended to limit manufacturers from designating more DSPs than specified by the formulas or to permit manufacturers to designate a smaller number of designated seating positions than the number they actually intend to be used by occupants. In light of the issue you have raised, we will consider clarifying the language of section 571.10(b) in a future rulemaking or in the responses to petitions for reconsideration of the new DSP definition. Nothing in this letter should be construed as a response to any of the petitions for reconsideration.
I hope this information is helpful. If you have any further questions, please feel free to contact David Jasinski of my office at (202) 366-2992.
O. Kevin Vincent
Ref: Std. 571
 On December 23, 2009, NHTSA issued a partial response to petitions for reconsideration of the new DSP definition in which we allowed one year of additional lead time before the new DSP definition is applicable. See 74 FR 68185.