Vehicles emitting excessive dark smoke may be reported by trained accredited spotters. The Environmental Protection Department (EPD) investigates and screens the reports, and then asks vehicle owners to bring their vehicles for smoke test. Non-attendance at the test or failure to pass the test within the specified period can result in the vehicle licence being cancelled. If dark smoke emission complaints from the public are received, the EPD checks the information and issues advisory letters to the vehicle owners drawing their attention to rectify the problem.
The numbers of smoky vehicle reports received and smoky vehicles tested saw a decrease in 2014.