Each entrance to a bus must be securely fitted with steps that meet the following requirements:

(a) the height of the tread of the lowest step from the ground must not be more than 410 millimetres or less than 250 millimetres;

(b) the height of any step in relation to an adjacent step must not be more than 300 millimetres;

(c) the transverse depth of the tread of each step in a small bus must not be less than 180 millimetres;

(d) the transverse depth of the tread of each step in a large bus must not be less than 225 millimetres;

(e) the width of the tread of the lowest step must not be less than the width of the entrance;

(f) the width of each step, other than the lowest step, must not be less than 450 millimetres;

(g) each step must be fitted with skid-resistant tread;

(h) step treads and risers must be directly illuminated, except in the case of an external access step to a single row of seats for a small bus having a seating capacity of not more than 15 adults, including the driver.