Work out train traction power instantly with clear inputs, formula shown and shareable results.
Rim power is tractive effort times speed, and input power is that divided by transmission efficiency. The second check is adhesion: tractive effort cannot exceed the coefficient of friction times the weight on driven axles, which is why locomotives are built heavy and why wheelslip control matters.
Traction power
P = tractive effort x speed / efficiency; adhesion required = TE / (driven mass x g)
Rail results are planning estimates only. Verify against the infrastructure manager's rule book, approved braking curves and applicable railway safety regulations.
About 0.30-0.35 on dry rail with modern slip control, dropping to 0.15 or less on wet, greasy or leaf-contaminated rail.
Below a base speed the effort is limited by adhesion and motor current; above it, power is capped, so effort falls inversely with speed.