Assuming a world where there were no steam engines available, would it be possible for large passenger or cargo trains to exist?
Would it be possible to use horse-engines to power a locomotive?
If the railway planners knew that they had a more limited source of power and had to rely almost entirely on momentum to carry the trains across big distances, and therefore managed to engineer tracks which were extremely flat, even flatter than real tracks, would that help? Or is it really feasible that railroad tracks could get much flatter due to the difficulty of building bridges and blasting rocks? Small hills I'm sure could be moved or dug through, but maybe it just wouldn't be feasible?
If horse-engines couldn't do it, would there be another potential way? What if the train cars were specially built to be very light-- would there be a way to make them lighter than real train cars?