Why can we make trucks like trains, run by electric motors and charged by small diesel generators?
They did make a bus on this principle ages ago, but it didn’t really catch on untill recently. The hybrid car is an example of what you describe. Lorries have to cope with a lot more friction and drag than a train, and therefore using this system would be less efficient than just plugging the wheels straight onto the engine, which is why it hasn’t been done yet.
