On the other side, with the Air brake system, there is air that is under pressure. That pressure is around 125 p.s.i. and is in the tractor and the trailer.
With this pressure you can apply brakes available only a few feet away from the brakes. When the air supply is close to the wheels, next thing you need to apply the brakes is a “signal” pressure from the brake pedal.
When you have an Air brake system on your vehicle the failure mode is brake application. So, if you have a massive leak in the system, you won’t have a brake failure. Instead, your vehicle will stop and not move until you replace, repair or bypass the system.
Totally different scenario happen if you have hydraulic system, because a failure mode there mean no brakes and you can end up risking your life as well as other people lives. Best case scenario, you can end up damaging property, but again, I don’t even want to imagine the worst case scenario!
