Western Australia has removed compulsory testing but retains referral by doctors, as well as referral by family or friends, to the licencing authority to withdraw licences on the basis of evidence, including eyesight checks. In Korea, car drivers from 70 years onwards are subject to a driving ability test every five years. Currently, no regulation is in place for commercial car drivers in Korea, however mandatory driving ability tests for bus drivers are being discussed. In Korea many professional drivers are self-employed and as such are not subject to corporate legislation.