10. The side walls of the body of a school bus shall be provided with 2 outside rub rails attached horizontally, one at the level of the seat cushions and the other at the floorline. The rub rail at the level of the seat cushions shall make a complete circuit around the passenger compartment without interfering with the wheel housing, and the other rub rail shall not block the rear door.
The rub rails shall be
(1) of 16-gauge sectional or triangular steel, or of any other metal having the same structural features as such steel;
(2) at least 100 mm wide; and
(3) attached to each post of the passenger compartment.
To avoid permanent distortion resulting from a collision with a snow bank, a bus of more than 4,536 kg shall also be provided, on the lower part of its skirt, with a strengthening rail complying with subparagraph 1 of the second paragraph.