depends on the power you have... most loco's have a slow speed control system... it is like cruise control for low speeds [below 15mph i believe]
when i am moving power around the shop tracks, you just jockey the throttle between the notches to maintain a speed. with no train in tow [single locomotive] N1 will give you about 7mph N2 will give you 13-15mph or so. if i am spotting a unit or coupling to something, i will drag the brakes... on most 6 axle power around 20psi brake cylinder pressure [independent brakes] and N1 power you will just creep along. N3 power will give enough power down to start to overcome 80psi brake cylinder pressure. hit N4 and you will start moving with 80psi brakes [unless you are trying to drag something with brakes on... i got 1500amps on a dash9 that was not loading in a consist, but on it's own it would hit 1500A before you got wheelslip and power drop...

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