... all the V2V and V2X telematics that the experts have promised? Oh, that's right. This stuff won't work unless 100% of the traffic adopts the protocols. Poor people, say goodby to your 10 year old sedan*.
Seriously, it's just a matter of installing Opticom receivers on autonomous vehicles. Or a radar detector receiver that can handle SWS (Safety Warning System) messages. And then put transmitters in emergency vehicles.
*Basing traffic safety on V2V/V2X communications is a lost cause. Because bicycles won't have them. And homeless bums wandering aimlessly through traffic won't either. But I'm repeating myself.