(a) The service brakes upon any motor truck, truck, and tractor or combination of vehicles shall be adequate to stop such vehicle or vehicles 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 one percent.
(b) Under the conditions contained in subsection (a) of this section, the hand brake shall be adequate to hold such vehicle or vehicles stationary on any grade upon which it is operated.
(c) All braking distances specified in this section shall apply to all vehicles mentioned, whether such vehicles are not loaded or are loaded to the maximum capacity permitted.
(d) All brakes shall be maintained in good working order and shall be so adjusted as to operate as equally as practicable with respect to the wheels on opposite sides of the vehicle.