Gear ratio and its effect on traction motors

The mechanical power delivered by the motors of electrically propelled vehicles is almost always transmitted through gears to axles. The few exceptions are some gearless electric locomotives designed many years ago. Although the top speeds of vehicles and locomotives have increased materially since the inception of electric drive, the very nature of the service requires high tractive efforts in starting from standstill and at low speeds. In the case of transit vehicles, frequent stops require operation at relatively low speeds a large percentage of the time.