RFID in vehicles

We are a relatively new Service & Solutions Integrator for IT & Personal Security Solutions, providing both HW & SW.

We want to add RFID to our catalog. The first application of RFID that we are contemplating is one for a vehicles traffic registration, control and security solution, using RFID in all vehicles. We expect to present the solution to several regional authorities in which the amount of car may vary from 400k to a million.

I have been searching on the web, but have found so far, literature that does not seem to be updated. Could you provide me with some information or tips, on this topic.