I am curious why the speedometer in most passenger cars almost always uses the highest wheel speed, even if the rest of the wheels are stationary. Is this intended to be a safety feature of some sort?

I would think that the reference vehicle speed would be calculated per the following patent Vehicle speed calculation system for four wheel drive vehicle and the method thereof

Is this speed internally calculated but not displayed on the speedometer? Based on this kind of algorithm, a car stuck in a ditch would accurately display a vehicle speed of 0 rather than the speed of a spinning wheel.

  • $\begingroup$ In the UK, the law says any errors in the speedometer readout must be high. In other words if the readout says you are travelling at the speed limit, you are not going to be above the limit. $\endgroup$ – alephzero Jul 17 at 1:41

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