Specifications include, but are not limited to: 3.2.3.1 Passenger Comfort Needs. Motor coach buses must afford passenger comfort needs as follows:3.2.3.1.1 Seat Specifications. Passenger seats must be of such design as to afford optimum comfort during movement, and include the following: Be upholstered with foam rubber or other material providing equivalent comfort which will prevent contact with structural parts of the seat bottom or back. Seats with shifted or excessively worn cushioning will not be acceptable, even if they otherwise meet the requirements herein.Be equipped with two padded arm rests of such density as will provide adequate vibration insulation and prevent the feel of any arm cap protuberance through the padding. Be of minimum width of 37 ½ inchesfor double seats (2 passengers) and 16 ½ inches for single seats. (Equipment presently configured at 34 inches for double seats and 16 ½ inches for single seats remain acceptable.)Be capable of reclining to 30 degrees, except that seats immediatelyahead of lavatories or those in the extreme rear of the coach need not conform to this requirement. The degree will be measured from a line perpendicularto the floor to a line tangent to the front surface of the seat back fully reclined. The seat adjustmentlever for each passenger will be located conveniently for the use of the seated passenger and designed so it will not present a hazard to the occupant when seated or when entering or leaving the seat.3.2.3.1.2 SeatSpacing. Measured parallel to the floor, seat spacing will not be less than 35 inches center to center. (Equipment presently configured at 34 inches will remain acceptable.) Where passenger seats face a bulkhead, tire well, or other obstruction, a seatcushion to the base of the obstructionmust be provided.3.2.3.1.3 Aisles. Aisles must allow unobstructed passage to lavatory, doorways, and other passenger accessible positions. They must be at least 12 inches wide measured parallel to the floor at all levels up to and including the armrest, and at least 17 inches wide above the armrest level. Aisle widths will be measured as the shortest distance between lines paralleling the longitudinal axis of the bus through the inboard edge of any seat or obstruction. Minor variances (not to exceed 1 inch) may be authorized where not more than two aisle seats in successive rows per coach prevent compliance.