A hi-tech device will be used to spy on some government workers in a blitz on lazy staff.
A computerised device will be installed in the 25 Urban Services Department street-cleaning or drainage clearing vehicles to record every movement and detail of its operations.
Similar to the black box installed in an aeroplane, the device can record the time of the movements of the vehicle, speed, and the pieces of equipment used.
A pilot scheme is expected to be launched in the middle of this year.
The move comes amid a disciplinary probe into claims some overnight workers were playing cards during office hours.
The controversy broke after provisional urban councillors conducted a surprise blitz last month at the department's Mongkok depot.
The councillors said they saw some overnight-shift drain cleaners playing cards or sleeping after clearing a drain outside their office.