Throttle

Throttle is a control device, typically a lever or a wheel, used to set the desired power output of a motorized rail vehicle.

On diesel-hydraulic and diesel-mechanical systems, it controls the fuel injection amount to the diesel engine. On diesel-electrics it sets the electrical circuits to a desired power level, which then indirectly controls fuel injection to the diesel engine to match. On electrics, the throttle also sets the electrical circuits to a desired power level, but it then takes power directly from an electrical source.

On steam engines, the equivalent of the throttle control is called regulator. It controls the amount of steam admitted from the boiler to the cylinders.

Throttle needs to be applied gently, to prevent wheelslip or overheating the drivetrain of a vehicle.

Application of throttle is almost always made to be oriented towards the driver. This is so that, in case of emergency, the driver can push all the levers forward as a safety measure, without needing to think of each control’s individual rule.