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Engine idling law: is idling illegal in the UK?

Idling car engines are annoying and unhealthy - pumping out exhaust fumes while you're walking along the pavement or sitting outside a cafe. But drivers who don't cut their engines when waiting aren't just wasting fuel and damaging the environment. They're breaking the law and risk being fined.

A car with fumes while stationary


What is idling?

Idling is the act of sitting in a stationary car with your engine running while it churns out noxious emissions.

These emissions kill about 4,000 people each year, the Guardian reports. To try and reduce this, councils have been targeting drivers who idle. 

There are some times when idling can’t be avoided, for example when you’re in traffic or stuck in a queue. But you should always switch your engine off if you can. This would include being in gridlocked traffic, stopping outside school or picking up a passenger.

You might also think there’s no harm leaving your car idling your drive. However, this could also have an impact on your car insurance, as you’re making your vehicle susceptible to thieves if you leave it unattended. 


What is wrong with idling?

Idling engines can cause significant air pollution.

An idling engine can produce up to twice the emissions of a car in motion. It pumps out unnecessary sulphur dioxide, particulate matter and nitrogen oxide into the atmosphere.

These chemicals all have a negative effect on air quality and contribute to asthma, heart disease and lung cancer.


How much pollution does an idling car create?

Research has found that an idling car causes enough emissions to fill 150 balloons with harmful pollutants – every minute.

It’s a common misconception that turning your engine off and on again uses more fuel than leaving your car idling. Unless your car has ‘stop-start’ technology you should switch your engine off, so long as it’s safe to do so.

However if you drive an older car, it’s wise to plan ahead rather than turning your engine on and off.

Doing so could affect the battery, especially if it’s more than five years old.


Engine idling law: what are the rules?

To reduce the impact of harmful pollutants, there are laws to discourage drivers from idling.

Stationary idling is an offence under Section 42 of the Road Traffic Act 1988.

The act enforces Rule 123 of the Highway Code, that states: "You must not leave a vehicle’s engine running unnecessarily while that vehicle is stationary on a public road." 


Can I get a fine for car idling?

If you’re caught idling you could be hit with a £20 fixed-penalty fine under the Road Traffic (Vehicle Emissions) Regulations 2002, rising to £40 if unpaid within the required timeframe.

Fines can be as high as £80 in certain areas of London where there are additional measures to cut emissions.

Islington Council mounted what's thought to be the first crackdown of its kind on vehicles churning out ‘unnecessary pollution’ in 2014 and then again in 2016.

In 2018, Westminster Council launched its #DontBeIdle campaign in an effort to curb idling in the city.

A report by the Guardian in 2022 revealed more than 70,000 idling drivers have been reported since 2017 in Westminster. They were reported through the council's "report it" website.

Only 63 fines of £80 were issued though, and only half of these were paid.

In 2021, Nickie Aiken, the council leader and now MP for Westminster at the time asked the government to increase the £80.

Aiken said it was not an effective deterrent for people to turn of their engines.

Wales has also introduced fines for idling, and its rules extend to drivers leaving their engines running in stationary traffic.

The Welsh government is also proposing Low Emission Zones and fines for drivers with high-polluting vehicles as part of the Clean Air Bill.

Along with the laws on idling, the government has also introduced other measures in an effort to improve the air quality in the UK. This includes cutting speed limits on motorways

A higher tax on diesel cars was introduced in an attempt to reduce nitrogen oxide, and in 2030 sales of new petrol and diesel cars will be banned

It’s thought that speed bumps also contribute to emissions, so new forms of traffic calming are now being considered.


I have a stop-start car, do I need to worry about idling?

No. Increasingly, manufacturers are building new cars with stop-start technology. This means that the engine stops when the car does, and only comes back on when you next apply the clutch.

The car uses a computer to detect when the car has come to a standstill, stopping fuel delivery and spark to the engine.

This technology saves drivers fuel, reduces emissions and could stop you from getting a fine for idling.


Is it illegal to leave your car running in your drive?

The rules over vehicle idling apply to public roads only, so you aren’t breaking the law if you idle in your drive, or in a supermarket car park, for example.

However, just because it’s not illegal doesn’t mean it’s the right thing to do. You’re still chucking just as many toxic fumes into the air regardless of whose land you’re on.


Should I leave my car idling when I’m waiting for someone? 

You shouldn't leave your car idling even if you're waiting for someone, it's illegal if you're on a public road.

If you’re waiting for someone, it’s best to switch the engine off.

Turning your engine off while loading and unloading your vehicle, waiting at car parks, lay-bys or set-down and pick-up points also help tackle emissions.


Can I keep my engine idling in hot or cold weather?

On the rare occasion where you might be in a heatwave, keeping the air-conditioning on can seem like a sensible reason for idling. 

Usually you can keep the air conditioning running by leaving the ignition on but not the engine.

If there’s no choice but to leave the motor running you should try to keep waiting down to a minimum.


Can I keep my engine running  to defrost my windscreen?

The rules on idling still apply if you are on a public road, even if you’re de-icing your windscreen.

If you leave the engine running while you get out to scrape your windscreen, you could be penalised for not being in control of your vehicle while the engine is running. 

And never leave your car unattended when your engine is idle, even if you're leaving it to de-ice your windscreen or letting your blower get rid of condensation

It's a perfect opportunity for thieves to steal your car, resulting in a car insurance claim.

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Is idling bad for my car?

Vehicle idling isn’t just bad for the environment, it can be bad for your car too. This is because when your engine is running but your car is stationary, the engine won’t be operating as efficiently as it should. The fuel may not combust properly, leaving behind a residue that could, in time, harm your exhaust.