First of all, the road train wouldn't be going 100MPH on the highway. It'll basically do the speed limit, maybe less, about 55MPH, since that is about when cars are most fuel efficient. (some tests showed 40)Second, cars that can participate in the road train will need a specific system installed. Which would require that the car be maintained on a regular basis. Otherwise the computer will simply not allow the car to join the road train... (DENIED)Third, laws will be passed regarding the road train, for example if they're all making a turn at an intersection, cars should allow the lead vehicle and all its followers to pass, and not do a 1x1 cross passing. This is ofcourse assuming the road train will get off main highways, which is avoidable since they have specific routes. Also assuming that there is some indicator as to the last car in line to the road train, otherwise people might take advantage.All in all, I see it as a great concept, and yes as some have mentioned earlier, we might still be a decade away from seeing it implemented. Hopefully we get to see some real road tests.But ofcourse now car manufacturers will be like.. "Now Road Train compatible." yet you'll still pay an arm and a leg to get the "compatible" systems installed. Which in turn uses more electricity and takes up more of the MPG.