https://www.cnet.com/roadshow/news/bmw-eu-cellular-v2x-wifi-connected-cars/

The road to connected cars, and eventually self-driving cars, will be paved with radio waves. (That's a metaphor, obviously; radio waves aren't solid.)

The other standard ignores cellular networks entirely. ITS-G5, otherwise known as dedicated short-range communications (DSRC), relies on the 5.9-gigahertz radio spectrum (802.11p, if you speak in IEEE standards) to send communications between vehicles and local infrastructure. Volkswagen backs DSRC for connected cars, as does Toyota, which hopes to deploy DSRC-equipped cars in the US starting in 2021.