It works remarkably efficient for locomotives. I do not know for sure, but its efficiency gains may come as weight increases. Think trucks hauling loads, vehicles pulling trailers and MINIVANS. There is your hint.
...................
Too bad this could not be installed in minivans. My brother drives Amish around in 16 people step vans. Lower fuel costs are always helpful. But this would be too cost prohibitive and hard to maintain for an installation.
No, it will debut in minivans.