Every motor vehicle and combination of vehicles, at all times and under all conditions of loading, upon application of the service brakes, shall be capable of:
(1) Developing a braking force that is not less than the percentage of its gross weight tabulated herein for its classification,
(2) Decelerating to a stop from not more than twenty miles per hour at not less than the feet per second per second tabulated herein for its classification, and
(3) Stopping from a speed of twenty miles per hour in not more than the distance tabulated herein for its classification, such distance to be measured from the point at which movement of the service brake pedal or control begins.
Tests for deceleration and stopping distance shall be made on a substantially level (not to exceed plus or minus one percent grade), dry, smooth, hard surface that is free from loose material.