What is the function of the vehicle's air system?

The vehicle's air system plays a crucial role in the operation of several systems, primarily the braking system, which is essential for safe vehicle operation. In heavy vehicles, such as those needing a Class B CDL, air brakes are commonly used due to their effectiveness and reliability. The air system is also responsible for powering other components, such as the horns and door mechanisms, ensuring that the vehicle can operate smoothly and safely in various conditions. This multifaceted function reinforces the importance of a properly maintained air system in a commercial vehicle, directly impacting overall performance and safety.

The other options, while relevant to vehicle performance, do not accurately describe the specific function of the air system. Fuel efficiency, engine performance, and temperature control pertain to different systems like the fuel management system, engine cooling system, and HVAC systems, rather than the air system itself.