I've been learning about trackmobiles lately. They seem like such a good idea being that they don't need tracks, can borrow weight from the car it's pulling for tractive effort and use little fuel. It makes me wonder why railroads like the Grafton and Upton which hauls 1 or 2 cars at a time don't use them? You know how a lot of shortlines don't like some of the newer heavier cars because it's so hard on the track? why don't they just have a trackmobile at each end to lighten the cars? Is this idea unrealistic?