Why do police cars have certified speedometers, while civilian cars do not?

Question

Why do police cars have certified speedometers, while civilian cars do not?

In: Engineering

Answer 1

If the police is going to use their speedometer as evidence, then it needs to be checked periodically to make sure it’s still providing valid evidence.

You don’t use your speedometer as a legal documentation device.

Another example are scales, your bathroom scale doesn’t need to be rechecked, but a truck scale on the side of the road does.