I was watching this video of a live chicken trapped on a moving truck and thought it was strange that it’s not possible to say anything to them even when circumstances might warrant it. All we got is honking and waving. There could be a touchscreen interface with a map of nearby vehicles. It could be voice controllable or the passenger could do it for safety.
Yeah my friend has a cb radio and he says when traffic is bad people are just yelling at each other. Although that’s anonymous, if the messages showed you were X person from C vehicle it would probably be a bit more civil