Final answer:
Air brakes are supplemented by engine braking in heavy vehicles during descents to manage heat buildup and prevent brake failure. Hybrid and electric vehicles use regenerative braking, transforming energy into electricity rather than heat, enhancing efficiency and reducing wear.
Step-by-step explanation:
The use of air brakes on a long or steep downgrade, under normal conditions, is primarily a supplement to the engine braking system. Air brakes help to control the speed of a vehicle by converting gravitational potential energy into heat in the brake material, which prevents it from being converted into kinetic energy. However, truck brakes alone are not sufficient for this task due to the likelihood of a rapid temperature increase in the brake material, leading to brake failure. This is why engine braking is preferred; it uses the engine's resistance to slow the vehicle down, significantly lessening the burden on the air brake system and reducing the risk of overheating.
Additionally, modern vehicles like hybrid and electric cars employ regenerative braking, which converts mechanical energy into electrical energy stored in the car's batteries. This technology provides an efficient alternative to traditional braking systems and contributes to the reduction in wear and tear on the brake material.