(a) The service brakes upon any motor vehicle or combination of vehicles shall be adequate to stop such vehicle when traveling 20 miles per hour within a distance of 30 feet when upon dry asphalt or concrete pavement surface free from loose material where the grade does not exceed 1 percent.
(b) Under the road conditions mentioned in subsection (a) of this section, the hand brake shall be adequate to stop the vehicle within a distance of 55 feet and the hand brake shall be adequate to hold such vehicle stationary on any grade upon which operated.
(c) Under the road conditions mentioned in subsection (a) of this section, the service brakes upon a motor vehicle equipped with 2-wheel brakes only shall be adequate to stop the vehicle within a distance of 40 feet and the hand brake adequate to stop the vehicle within a distance of 55 feet.