https://techcrunch.com/2017/11/16/tesla-semi-has-the-technical-capability-to-convoy-today/

Tesla founder Elon Musk revealed at the Tesla Semi unveil that the truck can work in a convoy mode, with a three-truck convoy beating not only traditional diesel trucking, but also rail transport in terms of a cost per mile price. It can do $0.85 per mile, with diesel only able to do around $1.25 per mile at today’s gas prices.

Convoying involves using a lead car to provide guidance to following vehicles that can employ autonomous features to drive in close proximity, almost like unattached rail cars on a road instead of a track. Musk said that the Tesla Semi can successfully convoy today, using existing Tesla technology – though making it actually happen on real roads will require regulator approval as well as the tech piece.