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.