Drive systems in railways are used to transmit the torque on the traction motor or the combustion engine, usually operating with higher speeds, to the wheel set via a gearbox.
Drive systems have to be powerful, environmentally friendly, cost-effective and require very low maintenance. These requirements are much more stringent than those required of cars, for example, because the intervals between servicing are much longer. New main line locomotives are maintained frequently, but main service is done after the locomotive has logged between 1 million and 1,5 million kilometres. These locomotives operate, on average, more than 1 000 kilometres a day. Very high speed trains operate with 350 km/h and reach much higher mileages. Two major topics the AC propulsion systems and low floor mass transit vehicle designs caused fundamental changes in the drive design.