Why do trucks use air brakes?

Air brakes are used on heavy trucks for many reasons. As already written, air brakes are much more practical when a vehicle has to be repeatedly coupled and uncoupled from a trailer. No need to bleed brake fluid of air since the fluid is air. read more

Air brake systems are much more tolerant to leaks. If there is a leak the governor reloads the compressor and the reservoirs are refilled. They are proven, been in use on the big vehicles since the 1920s. There is a fail safe system. If you run out of air the spring brakes apply or dynamite and the vehicle stops. read more

Air brakes are installed in the trucks and most of the heavy duty vehicles in the form of emergency brakes. Considering the length and structure of the trucks and other heavy duty vehicles, the brake lines are significantly long as compared to cars and vans. read more

While parking brakes on trucks are spring-actuated (fail "on") the normal driving/operating brakes work just like hydraulic brakes. The parking brakes will actuate either by switching them on (when parking the truck) or when the brake system air pressure drops below a lower limit. read more