Sampling Qualcomm's C-V2X tech in an Audi Q8 at CES 2019
https://www.cnet.com/roadshow/news/qualcomm-c-v2x-tech-audi-q8/
In the Q8, an on-screen prompt warns the driver when they're approaching an intersection and advises them to stop. Then, behind the scenes, the C-V2X tech communicates with other vehicles to negotiate which car goes first. For instance, if two opposing cars are both going straight, they can drive away immediately -- whereas someone turning left would be prompted to stop. That will ease traffic congestion with human-driven cars and, of course, would be a boon for autonomous cars.
There are also safety applications. When the rider of a Ducati motorcycle (deliberately) blows the stop sign, the Audi Q8 displays a warning about oncoming traffic. That could prevent accidents before in-car sensors detect a hazard. There's also functionality to warn if a car ahead is braking hard. Even if the car is ahead of a truck, for instance, the following car would receive a warning of the impending stop. Qualcomm's demo even has a setup to keep people safer when they're not in a car. A crosswalk sign transmits a warning over the C-V2X network, prompting the Audi to warn of a pedestrian ahead.