Drivers in Glasgow who leave their engines running when parked could be fined if the city council accepts a recommendation to take a "firmer line".
The council wants to cut exhaust emissions
The council's environment officials want it to ditch the "soft approach" and start to hit drivers of idling vehicles "in the pocket".
The plan to issue £20 fixed penalty fines will be considered by a council committee on Thursday.
The move is an attempt to cut exhaust emissions in the city centre.
The council has had the power to give out the fines since 2004, but has not issued any penalties for "idling" offences.
Enforcement officers previously warned drivers about idling and if the engine was switched off or the vehicle driven away then no ticket was issued.
After seeking legal advice, council officials want to take a harder line, especially in city centre "hot spots".
Bus and taxi operators were being sent letters alerting them to the change in enforcement of the legislation.
Robert O'Neill, the council's director of environmental protection services, said: "It was very frustrating knowing that people would wait until we moved away, then turned the engine on again.
"They are doing nothing to help clean up the air in the city.
"We'll now start hitting then in their pockets."