A locomotive or trainset designed to operate using three different power sources, typically overhead electric catenary, an onboard diesel engine, and a battery bank. This configuration allows a single train to run at high speeds on electrified main lines, switch to diesel on un-electrified branches, and use battery power in enclosed stations or emissions-restricted zones.
The new tri-mode units will let's run straight through the tunnel on battery before firing up the diesel for the branch line.
Related terms
Bi-mode
A locomotive or trainset equipped to draw power from an external electrical supply or generate its own electricity with a diesel engine.
Electric locomotive
A locomotive that draws its propulsion power from an external electrical source.
Diesel locomotive
A motive power unit that uses a diesel engine to generate electricity for electric traction motors.