That’s an idea being pushed for by the current Secretary of Transportation.
The man has lost all sense of reason, and is overreaching his authority. Hearing the description, it is easy to think that the man has delusions of grandeur, thinking he can somehow control the nation, from his little corner of the world.
Stating that he is on a (self-described) rampage to end distracted driving, he has not stopped to think that cars are frequently occupied by more than a driver and putting some sort of jamming equipment into cars is insane on more than one level.
Not only can non-drivers operate a cell phone while a driver is driving without any problems, the Secretary of Transportation apparently has no clue about how radio transmission, and therefore blocking, works. There will be no neat little field that will only affect those within the car, and there is also the problem of the bandwidth affected by the jamming. Putting something in a vehicle to jam cellular communication would involve some sophisticated circuitry, that would need to be set to only affect very narrow areas of the RF spectrum.
The cost would not be trivial, nor would the changes needed for proper operation in every type of car, as they all present different problems to radio reception and interference.
But all that is truly pointless if a little thought is given, because there are so many other things that can distract, and cause problems. Radios, CD players, children, other adult passengers…where do we stop? After all those things are removed, then there is the boredom of having nothing to listen to, and letting the mind wander.
If that is not enough, there will be a cottage industry springing up for those who are not willing to put up with this in their cars. It will become the first stop off the showroom floor for many, getting the jamming device removed and returning the car to the way it should have been delivered. Civil disobedience on a grand scale, for all the people who believe that their car is their own.