actually I want to prevent collision between vehicles so, distance we can say when two vehicles come near to each other.
Have you a $50m driverless car budget like Google, GM, Volkswagen etc ? (Or is it $500m each?)
Driverless cars will, in the first instance, be able to do what you say without any data coming from the car in front.
Even assuming there was a reliable wireless system, what data could you transfer that would help?
How would a vehicle know which vehicle the data had come from?
And building a reliable wireless system that could be used in a life-threatening application is a whole other ball game.