Motorists could face £20 spot fines if they leave their engines running while stuck in traffic.
Traffic wardens will be able to issue the penalties - after a warning - in a bid to cut down on pollution.
A pilot scheme is due to be launched in January in Shoreham-by-Sea, West Sussex, and will be expanded if it proves successful. West Sussex Council said it would target areas where exhaust emissions build up unnecessarily, such as rail crossings and town centres.
But drivers branded the plans yet another round of the war on the motorist. The AA pointed out that to switch off an engine and start up again within a minute actually uses more fuel than letting it idle.
Cabbie Roger Turner, 30, said he was disgusted with the idea,
adding: 'Who gave them the right to tell us to switch off our engines?
'It's not like we try to waste fuel, but can you imagine what would happen if everyone starts shutting off their engines?
'The ones I feel sorry for are the old dears, who won't know what's going on and could end with a £20 fine for not turning off the engine in their Fiat Panda. It's another example of the nanny state.'
West Sussex Council has already set up two Air Quality Management Areas in Shoreham, many of whose 20,000 residents are elderly.
A spokesman said: 'We want to get people out of the habit of leaving their cars ticking over out of convenience.
'We would stress that this is just an investigation at this stage. If it were ever introduced the fixed penalty would probably be £20, but we would hope the vast majority of motorists would be willing to cooperate. Air pollution is a particularly important issue for our residents, particularly those with asthma, lung and heart conditions.'
Signs have been put up at level crossings, telling drivers to switch off when the barriers are down.
AA spokesman Paul Watters said: 'We hope councils will not adopt a heavy-handed attitude with this. There is a huge difference between running the engine for less than a minute at the traffic lights and idling for a quarter of an hour.
'If you are stuck in a traffic jam and a warden slaps a ticket on your windscreen, that is ridiculous. The danger of everyone switching off in a jam is that some may not start up again. And then there's gridlock.'
Mr Watters added: 'The legislation allowing councils to impose such fines has been on the statute books for a few years, but few drivers are aware of it.'
The Department for Transport said it had issued guidance to councils stressing that they should not issue a £20 penalty notice without first giving drivers a warning.
Rule 123 of the Highway Code says: 'If the vehicle is stationary and likely to remain so for more than a couple of minutes, you should switch off the engine to reduce emissions and oil pollution.
'However, it is permissible to leave the engine running if the vehicle is stationary in traffic.'
Why turning the engine off in traffic might not be that green after all...
A car engine is at its most inefficient when it is idling, the AA said last night, but turning off the engine is not necessarily an improvement.
A spokesman explained: 'In terms of emissions, the catalytic converter only works properly when it's hot, and it cools down when idling.
'This means emission levels of gases and hydrocarbons will rise.
'Our own fuel consumption tests showed that a car uses somewhere between
0.36 and 0.78 litres an hour when idling - so that's no miles per litre, but plenty of carbon dioxide and more toxic emissions.'An hour of idling can produce around 2.36kg of carbon dioxide - the 'greenhouse gas' blamed by scientists for global warming.
But switching an engine off is not necessarily a better option, the AA warns.
A burst of fuel is needed to start an engine, so switching it off and then on again seconds later actually uses more fuel than idling and produces more emissions.
The AA said: 'For less than a minute it is not fuel efficient to switch off because you will use more fuel starting up than you will save. It only becomes fuel efficient to switch off if you are going to be stopped for a minute or more.'