[pmontra]

> setting the cruise control to 50 when in a 50km/h zone will have you driving 45 in reality as evidenced by speed measuring displays I drove by. At 100km/h you'll probably be going 90.

This is very common and it's probably a deliberate choice of the manufacturer.

I know that my old car in the 90s reported 10 km/h more than the real speed and most other cars did the same, especially at low speeds. My current car is not as bad but I have to set 52 to go 50, 72 to go 70.

Furthermore some speed displays are calibrated differently. Some of them report me at 50, 47, 53 at different towns on the same route. I know I'm OK at 52 because I never got a fine.

I'm more conservative on roads that I'm not familiar with (eg: on a vacation in another country.) The general rule has always been to go at the same speed of the other cars.