...personal vehicles do this too.
The scenario works like this:
You get in your car (or *a* car), and tell it where you want to go. Let's say it's a 50+ km journey using a motorway. Along the way, it's extremely likely that someone else, in another vehicle will be sharing a significant portion of your journey (that's why there's so much traffic on the motorways). So, each vehicle needs only to advertise its intended course, along the way, at regular intervals, then other cars join in - driving close enough to benefit from decreased wind resistance. In fact this benefits the lead car too, since such a configuration reduces the lead cars drag. When each car in the "train" needs to depart the train, it only needs to emit a warning signal a few seconds before hand, then maneuvers out of the train, whereupon the train reforms without that car in.
This has all kind of benefits for the passengers. Reduced cost, and nose. Increased safety. Probably faster journeys too.