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Engine idling: Why it’s so harmful

Engine idling is when you leave your car stationary with the engine running.

When you leave your car idle, you pump out exhaust fumes. These emissions kill about 4,000 people each year, the Guardian reports. To try and reduce this, councils have been targeting idling cars and their drivers.

Drivers who don't cut their engines aren't just wasting fuel and damaging the environment, they're breaking the law and risk being fined.

A car with fumes while stationary

Idling engines 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.

If drivers stopped idling for 3 minutes every day of the year, carbon dioxide emissions would reduce by 1.4 million tonnes annually. That’s the equivalent of taking 320,000 cars off the road. This is according to new research by University College Cork.

What are the rules on car 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.”

This applies even if you’re waiting for someone. Switch your engine off and wait. If it’s a hot day, try to keep your wait time to a minimum. You should also turn your engine off while:

  • Loading and unloading your vehicle
  • Waiting at car parks and lay-bys
  • Parking in set-down and pick-up points

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. This could rise to £40 if unpaid within the required timeframe. You only get this if you refuse to turn off your engine though.

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

A 2022 article by the Guardian revealed more than 70,000 idling drivers were reported in Westminster through the council's 'report it' tool since 2017.

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

Nickie Aiken, the MP for Westminster, asked the government to increase the £80 fine. She stated that £80 isn't an effective deterrent for people to turn off their engines:

“Tackling air quality is a major priority for my constituents – and therefore me.

"From my experience, when I introduced the ‘don’t be idle’ campaign as council leader, the vast majority of drivers who are asked to turn off their engines do so. Perhaps that is why we have very few fines given out. For those who refuse, £80 doesn’t seem to cease their behaviour. Perhaps a larger fine will focus their minds.”

Other councils in the UK support action on engine idling. In a survey, over 50% of Central Bedfordshire residents said that engine idling has negatively affected their health.

But, their local Counsellor Tracey Wye, executive member for sustainability and climate resilience, is choosing to raise awareness rather than taking enforcement action:

“It was clear from last year’s survey that people want to see us raise awareness of the issues around engine idling before taking any enforcement action. That’s why we have begun this campaign with a message that ‘Every Minute Counts’, reminding people how much damage they are doing to the environment – and to their finances – by not switching off when they are stationary.”

Wales has introduced a fixed penalty notice for idling. According to Torfaen Council, a fine is only issued if the driver refuses to turn off their engine if they're told to do so by an authorised officer.

The council also said it wouldn't penalise drivers if they were idling their engine to de-ice their windscreen or cool their vehicle on a hot day.

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.

You can leave your car idling in your drive if you’re:

  • Defrosting the windscreen
  • Cooling your car down with your air conditioning

You should try and keep idling to a minimum though, as you’re still emitting toxic fumes into the air.

Never leave your car unattended if you’re doing this. Your car is at risk of being stolen if the engine is running. If it does get stolen, your insurer might not pay out for the claim in full. This could also increase your car insurance price in future by around 60%*.

Yes, engine idling can be bad for your car. This is because when your engine is idling, the engine isn't operating as efficiently as it should. The fuel doesn’t combust properly and can leave behind a residue that could harm your exhaust over time.

No. It’s a common misconception that turning your engine off and on again uses more fuel than leaving your car idling.

But if you drive an older car, it’s wise to plan ahead rather than turning your engine on and off. This could affect the battery, especially if it’s more than 5 years old.

If you have a new car, it might have ‘stop-start’ technology. This means that the engine stops when the car does, and only comes back on when you next apply the clutch.

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

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