How to keep a constant speed

[e-paw]

Hmmm. :? That's a good question. I would have to guess that the biggest problem in that scenario would be the start up from a dead stop. Once the train is moving I don't think one more empty would cause all that much more drag to effect train speed. The wheel sleep system, voltage regulator, and act of the loco making transition should help to even out the train speed under load. I think that the change in track elevation on hills probably gives the engineer more work to do as far as throttle goes, but I'm sure his left hand is kept busy because of several factors on any run. But remember, I'm an electrician not am engineer I really only have a rail fans experience on such things.. 8-)