How to silence car-alarms and horns

All cars shall have a legally mandated device that disables the vehicle for one day should its driver lay on the horn for too long. The length of horn-time that disables the car is somewhat random.
Less than one second: you're safe. One to three seconds: you're taking your chances. More than three seconds will definitely disable the vehicle. To be safe, the car wouldn't stop right away, but rather would refuse to run on the next attempt to start it.



Car alarms would have a similar device. After an alarm lasting more than a few seconds, the car would refuse to run (How better to prevent its being stolen?).



This last idea is a compromise from what I'd really like to see; namely, that any car whose alarm sounds for more than ten seconds should blow up.



Exploding car



Of course, the explosive charge only needs to be strong enough to crack the engine block. Shrapnel should be kept to a minimum. I'm sure it would be perfectly safe, considering that passers by would have a loud ten-second warning -- plenty of time to run for cover.
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