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

because the radar in a cop car can only tell the difference between its self and a target car’s speed, not the actual speed.

If the cop car’s speed is not known with certainty, neither is the target car’s speed.

And you cant write a speeding ticket based on “well they may have been going to fast, that or my speedometer is wrong”