If the service air line comes apart while driving a combination vehicle, what is likely to happen immediately?

When the service air line disconnects while driving a combination vehicle, the immediate consequence is that there will be no effect until the brakes are actually applied. The service air line is responsible for supplying air pressure to the brakes, and if it is severed, the braking system will not receive that air pressure unless the driver attempts to engage the brakes.

At that moment, if no braking action is taken, the vehicle will continue to move normally since there is no immediate change to the vehicle's speed or operation. It's only when the driver applies the brakes that the lack of air pressure in the system will lead to a failure in the braking action, which could result in a loss of control of the vehicle. This understanding is critical for drivers operating combination vehicles to ensure they are aware of the potential risks associated with air line issues and the importance of timely repairs or precautions.