How many tons can a single unit pull on strait and level track?
At least 13,876 tons.
but not much faster than a walk.
According to a book I have, most locomotives, it used a GP40 for an example, can pull that. Yeah it won’t be fast, and the main thing is it has to be able to start it first.
While diging for info I found out tests at the Transportation Test Center at Pueblo, Colo., indicated what the SD70MAC could do. A single unit, working on a 1% grade and a 1.5-degree curve pulled (at 40% adhesion) and restarted (at 45% adhesion) a 7,000-ton train under various rail conditions that included continuous water spray, intermittent oil and soap application, and the heavy rain that occasionally hits Pueblo. On dry rail, one SD70MAC pulled (at 42% adhesion) and restarted (at 45% adhesion) a 7,600-ton train.