How do companies limit the speed of a car?

Most modern cars are equipped with an Engine Control Unit (ECU) which can adjust fuel suply when the vehicle reaches the maximum speed. There is a function called " Speed Governor / Limiter" within the ECU where this speed can be set by the " Homolocation team " of the Car maker . read more

There's a sensor on the wheel that tells you the speed the car is going. Once it hits 155mph, the ECU limits the flow of fuel to the engine. In some cases the speed limit can be removed -- see the article on Wikipedia: Speed limiter. read more

In most cases, speed changes, whether local or state, are the result of a study. A public agency conducts a spot speed study (also known as a speed zoning study) to document individual vehicle speeds along a specific road. read more

Large sections on the Autobahn (80%) do not have a general speed limit, having some kind of vmax (on public roads) seems quite reasonable. The voluntary limit of 250kmh (155mph) for regular cars in Germany was a reaction of manufacturers ca 1987 to avoid the imposition of government regulation. read more