The Regulations and how they're enforced
In short, idling is against the traffic regulations, and drivers can be fined if they refuse to switch off when asked. But the regulations are difficult to enforce, so in reality only a handful have ever been given out. Here's why.
What the regulations say
Drivers are required to switch off engines in parked vehicles (Regulation 98 of the Road Vehicles (Construction and Use) Regulations 1986, as amended).
Local authorities in England have the power to issue a Fixed Penalty Notice (FPN) to a driver who is idling their engine unnecessarily and refuses to switch off when asked by an ‘authorised officer’, according to the Road Traffic (Vehicle Emissions) (Fixed Penalty) (England) Regulations 2002.
However, local authorities are advised by the Department for Transport (DfT) (in their Guidance on powers to require drivers to switch off engines) to only issue an FPN as a last resort; first they should try an educational approach. FPNs for idling offences are very rarely given out for several reasons. Firstly, because local authorities’ authorised persons are required to ask the driver to switch the engine off first, and only if the driver fails to comply can an FPN be issued. Secondly, because the regulations are hard to enforce - most drivers will switch off rather than get a fine.
Some local authorities have made an Experimental Traffic Order or Public Spaces Protection Order so that they can enforce idling through Penalty Charge Notices, which can provide a greater deterrent, as they have a higher fine (compared to a £20 fine for FPNs). However as with FPNs, they can only be given out if the driver refuses to switch off.
It should be noted that not all councils enforce the traffic regulations, and some only do it in certain locations where vulnerable populations are exposed, such as at schools and hospitals. You can contact your local pollution team to find out if they enforce the regulations, or run some sort of idling awareness campaign.
Exemptions
According to the DfT guidance, the circumstances where engines are permitted to be running when stationary are:
When queueing at traffic lights;
When running an engine to identify a defect of a broken-down vehicle;
Where machinery on a vehicle requires the engine to be running e.g. refrigeration equipment; and
Where a vehicle is propelled by gas produced by the functioning of plant carried on the vehicle.
The guidance also suggests that mitigating circumstances might be:
On a cold day at a taxi rank;
If the driver is elderly and running the engine to keep warm;
If the vehicle is a recovery vehicle carrying out a recovery and needing to run lights off the engine;
To help defrost a windscreen in very cold weather.
The DfT guidance advises that common sense should be applied: it might be reasonable to leave an engine running for a short time on a hot day for an air-conditioning system to have an effect; however it may not be reasonable to leave an engine running for a longer period of time to maintain a ‘pleasant environment’.
Many local authorities believe the approach of awareness-raising (speaking to drivers about what impact idling has on pollution, and why it’s better to switch off) is more effective than that of enforcement. See the how to deal with idling engines page for more information.
Who is an ‘authorised officer’
The local authority appoints ‘authorised persons’ who can enforce the regulations. Authorised persons are usually enforcement officers.
Operator licensed-vehicles
The DfT guidance also states that if a local authority becomes aware of repeated offences by the users of vehicles used by a particular heavy goods vehicle or public service vehicle operator, and where there is clear evidence of repeated offences, the local authority should inform the Traffic Commissioner who would consider action relevant to the operators Operator Licence.
Regulations and guidance referred to:
The Road Traffic (Vehicle Emissions) (Fixed Penalty) (England) Regulations 2002: https://www.legislation.gov.uk/ukdsi/2002/0110423887
The Department for Transport’s Guidance on powers to require drivers to switch off engines
https://www.stalbans.gov.uk/Images/idling%20engines%20guidance%20DfT.pdf(NB from St Albans website)
The Road Vehicles (Construction and Use) Regulations 1986 (see section 98)
http://www.legislation.gov.uk/uksi/1986/1078/regulation/98/made