Comment by jltsiren

This, like many other ideas combining cars and public transport, sounds like something that doesn't scale. The exact numbers vary, but the passenger capacity of a car train is usually something like 1/2 of a normal night train or 1/3 of a normal day train, assuming that the train is fully dedicated to carrying people with cars. You also need special facilities and longer stops, because cars can't just dismount at normal platforms in a couple of minutes. On popular routes, this all means that you take more cars off the road by not carrying cars on the train.