Every year thousands of families or friends take their vacations together, many of them take their cars and go for a walk or adventure. While driving their cars, many cannot communicate with each other unless they have bluethoth service or park to do so.
The idea that I have would allow communication between these families or friends who go on vacation together in their cars to remain connected, if they wish, throughout the duration of their trip.

Nowadays all automobiles come with radio and sound equipment included, what I propose is that these equipments be modified so that they become radio receivers and transmitters.

Each automobile would use its registration number as a communication channel and would have the power to accept or reject calls.