This SAE Recommended Practice establishes a method of testing the structural integrity of the brake system of all new trucks, buses, and combination vehicles designed for roadway use and falling in the following classifications:a. Trucks and Bus Over 4500 kg (10 000 lb) GVWRb. Combination of vehicleÂTowing vehicle over 4500 kg 10 000 lb) GVWRThe test consists of two parts: a Structural EnduranceTest followed by a Structural Ultimate Strength Test.