Assuming you're referring to the trailer service air supply line in an air brake equipped combination, initially, nothing - you won't have trailer brakes and you'll notice a rapid loss of air pressure in the primary system when you apply the brake pedal (if you use the Johnson bar, you'll notice a rapid loss of pressure in the secondary air system). The service (blue) line only has air going through it when the brake valve or Johnson bar is applied - it's the emergency (red) line which is continually charged to keep the spring brakes released.
The loud static radio sound while driving is usually caused by an interruption in service. It usually happens when you drive through a tunnel or a remote countryside.
The unit will be extremely hard to stop, it may not stop at all with out pulling the emergency valve.
Serious crashes.
Car needs service
The service engine soon light comes on when the engine computer has detected a malfunction and set a code. You need to have the system checked for codes to know possible causes.
It comes of by force
The security light might come on while you are driving because it has a motion detector on it and when it senses the cars movement the light comes on.
the kitty my go SPLAT! on your tires but hopefully, it never happens
You might go to jail...
Nothing. It will keep on driving. There is a safety on the gear that will not enable it to be activated while in movement. It may destroy your gear though.
If driving high you can. If driving while possessing weed you can. It pretty much comes down to if you are doing anything involving driving and marijuana you can loose it.
It would eventually get stopped up. When this happens while driving it could be really bad!