Electronic speed limiters are engine control devices that interface with the engine control unit and speedometer of a vehicle and restrict engine functions once the vehicle reaches a certain predetermined speed. A speed limiter may restrict the airflow into the engine, the fuel supply of the engine or change the timing of the engine's ignition system to keep the vehicle from exceeding the predetermined speed limit imposed by the limiter.
Electronic peed limiters are common on many types of vehicles and are often mandatory equipment on large trucks and similar commercial vehicles in some jurisdictions. Laws requiring speed limiters for commercial vehicles are usually motivated by the concept that limiting the speed of these vehicles may improve highway safety. In the case of passenger cars, the motivation behind including electronic speed limiters is often to prevent the vehicle from exceeding certain design limitations in addition to safety concerns.
Electronic speed limiters are also commonly used on high-performance vehicles with powerful engines, such as the Bugatti Veyron and Dodge Hellcat Barracuda. Speed limiters on high-performance vehicles are often used to make those cars easier to handle during normal driving. It is common for the driver of one of these cars to be able to disable its speed limiter by starting the car with a special key that signals the electronic speed limiter to shut off and enable the engine's full performance.