Drivers who leave their engines running when their vehicles are parked in Inverness can be fined for adding to pollution.
The council wants to cut exhaust emissions
New powers to levy a £20 fixed penalty have been agreed by Highland Council.
The authority has brought in the legislation in an effort to cut exhaust emissions in the city centre.
A report to councillors said that the measure was targeted at bus companies whose vehicles were often seen idling at bus stops in the city.
But bus drivers insisted they needed to have their engines running to keep vehicles warm for elderly passengers.
They also argued that it was more efficient to idle for a few minutes than keep switching the engine on and off.
Legislation came into force earlier this year giving local authorities the option of introducing the fines for drivers.
Officials from Highland Council recommended that members of its transport and environment committee backed fixed penalty notices of £20.
Officials said the fines would act as a deterrent and predicted that very few fixed penalty notices should need to be issued.
The report argued that action was needed because Inverness city centre risks exceeding Scottish air quality objectives.
It also noted that other parts of the Highlands were unlikely to face the same threat from traffic fumes.