Is it just me or does this seem like it could be abused? Like, could you just stand on a bridge on a freeway and send ‘I’m max braking’ signals to all the cars

Is it just me or does this seem like it could be abused? Like, could you just stand on a bridge on a freeway and send ‘I’m max braking’ signals to all the cars and then they all react to that and stop? Bearing in mind the incredibly poor tech of most cars - like the keyless entry that you can just boost the signal while the keys are in a house and open the car - I don’t have much faith in car companies to do a good job. I don’t mind my car reacting to real events actually happening before I know about them, but reacting to signals scares me a bit. Is there some clever way that they’ll avoid this?