Road Trains
A "Road Train" is a group of vehicles driving down the road in unison, very close together, similar to how a train on tracks is a group of vehicles driving down the track in unison. We often think of traditional trains as a single vehicle on the tracks, but it's really a chain of vehicles but they're bolted together. This is in part so they can easily go around curves, partly so there can be one engine in the lead unit of the train, and partly for aerodynamics.
A Road Train is a train-like chain of vehicles operating on a regular highway rather than on steel tracks.
Hoped-for gains are better utilization of the road surface, and better fuel efficiency from aerodynamic gains.
