That can be done more reliably with lidar. Adding BT and other wireless dependencies to critical control systems opens up new vulnerabilities and attack vectors. Sociopath hackers would use it to fake an imminent collision and cause crashes.
The most efficient path forward is higher density cities, less low density sprawl, and free mass transit (trains, light rail, and buses) to remove the dependency on private cars, then gradually upgrading to driverless only lanes and roadways as private vehicle traffic is reduced over time; much more realistic than waiting for tech companies and politicians to solve complex technical and regulatory problems that could take many decades.
The government should also be directing investment and subsidies to smaller single-person “pod” transport options too, as it’d be cheaper, easier, and more efficient overall if we could accommodate the majority of traffic in both directions within a single car lane, freeing up space for future transition work — after-all, most road traffic is a single person in a 5+ seater car.