Car speedos are meant to read high

摘要

Regarding the recent letters expressing concern about inaccurate speedos,the writers and the Editor are quite right about them being inaccurate but this is deliberate.As a scientific instrument maker years ago,I used to repair and calibrate civilian and police speedos.Police speedos were the only ones calibrated to read precisely(to allow them to accurately monitor road users' compliance).Every other speedo was calibrated to read about 4km high at 60kmh(or about 6% high).