Why do people leave their cars running?

Attention drivers! Turn off your idling engines

Reducing vehicle idling will cut air pollution and save you money

Report published: February 2009

Idling is when a driver leaves the engine running and the vehicle parked. Every day in the U.S., millions of cars and trucks idle needlessly — sometimes for hours — and an idling car can release as much pollution as a moving car.

You may not be able to avoid keeping your engine running when you’re stopped at a traffic signal or stuck in slow-moving traffic. But other times idling is unnecessary.

Four ways to be idle-free

Turn off your ignition if you’re waiting more than 10 seconds. Contrary to popular belief, restarting your car does not burn more fuel than leaving it idling. In fact, idling for just 10 seconds wastes more gas than restarting the engine.
Warm up your engine by driving it, not by idling. Today’s electronic engines do not need to warm up, even in winter. The best way to warm the engine is by easing into your drive and avoiding excessive engine revving. After just a few seconds, your vehicle is safe to drive. The vehicle’s engine warms twice as quickly when driven.
Warm up the cabin interior by driving, not idling. Easing into your drive is also the best way to get your vehicle’s heating system delivering warmer air faster. Sitting in an idling car means you are breathing in more of the dirty exhaust that leaks into the car cabin. Any warmth you may get from a car heater is not worth the damage to your health. If parked and waiting, it is healthier to get out of your car and go inside a store or building.
Protect your car engine by idling less. Frequent restarts are no longer hard on a car’s engine and battery. The added wear (which amounts to no more than $10 a year) is much less costly than the cost of wasted fuel (which can add up to $70-650 a year, depending on fuel prices, idling habits and vehicle type). Idling actually increases overall engine wear by causing the car to operate for longer than necessary.

Reasons to stop idling

A simple turn of your key can keep the air cleaner and save money and fuel. Every time you turn off your car engine in place of idling, you’ll:

Make the air healthier by cutting down on hazardous pollution in your town or community. Idling tailpipes spew out the same pollutants as moving cars. These pollutants have been linked to serious human illnesses including asthma, heart disease, chronic bronchitis, and cancer.
Help the environment. For every 10 minutes your engine is off, you’ll prevent one pound of carbon dioxide from being released (carbon dioxide is the primary contributor to global warming) . An EDF report shows that in New York City alone, idling cars and trucks produce 130,000 tons of carbon dioxide each year. To offset this amount of global warming pollution, we would need to plant an area the size of Manhattan with trees every single year.
Keep money in your wallet and save fuel. An idling car uses between 1/5 to 7/10 of a gallon of fuel an hour. An idling diesel truck burns approximately one gallon of fuel an hour. With average U.S. prices for diesel fuel topping $2 a gallon 1 , that’s about $2 an hour wasted.

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.

What is idling?

Idling is when a stationary car is left with its engine running. The car isn’t moving, and all the 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 you can’t avoid idling, for example when you’re in traffic or stuck in a queue. But you should always switch your engine off if you can. This includes being in gridlocked traffic, stopping outside school or picking up a passenger.

You might also think there’s no harm leaving your car idling in 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.

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What is wrong with idling?

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.

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.

But 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 5 years old.

Engine idling law: what are the rules?

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.

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

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

In 2021, 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 of 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.”

Wales has also introduced a fixed penalty notice for idling. According to Torfean 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.

What else has the government done to cut emissions?

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.

Cities across the UK are also launching Low Emission Zones that fine drivers with high-polluting vehicles. This is part of the Clean Air Bill.

A higher tax on diesel cars was introduced in an attempt to reduce nitrogen oxide, and in 2030 the government will ban the sales of new petrol and diesel cars.

Speed bumps might also contribute to emissions, so governments and local councils are considering new forms of traffic calming measures.

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

No. More 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. 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 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?

You can leave your engine on to de-ice your windscreen but it should only be for a few minutes and you shouldn’t leave your vehicle while the engine is running. If you get out to scrape your windscreen or leave your vehicle entirely, you could be penalised for not being in control of your vehicle while the engine is running.

There are a couple of ways you can de-ice your windscreen and avoid this. You could scrape the ice off with an ice scraper and de-icer or another home made solution if you need it. Once you’ve done this you can sit in your car and turn on your heating to melt away any stubborn icy areas.

Or you can sit in your car with the heat on to loosen the ice. Once it’s defrosted a bit, turn off the engine and then de-ice your windscreen with your usual tools.

Whatever you do, 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.

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 isn’t operating as efficiently as it should. The fuel may not combust properly, leaving behind a residue that could, in time, harm your exhaust.

What to do if you see a dog in a parked car

Leaving pets locked in cars is never safe. But when the weather gets warmer, it can be deadly. High temperatures can cause irreparable organ damage and even death. Protecting animals from an unnecessary death is a problem we can all agree to prevent.

How to help a dog or cat left in a hot car

Take down the car’s make, model and license plate number.
If there are businesses nearby, notify their managers or security guards and ask them to make an announcement to find the car’s owner. Many people are unaware of the danger of leaving pets in hot cars and will quickly return to their vehicle once they are alerted to the situation.
If the owner can’t be found, call the non-emergency number of the local police or animal control and wait by the car for them to arrive. In several states, good Samaritans can legally remove animals from cars under certain circumstances, so be sure to know the laws in your area and follow any steps required.

Rolling the down windows has been shown to have little effect on the temperature inside a car.
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Other ways to help

Get informed: Learn your town’s and state’s laws about leaving pets in hot cars. An increasing amount of states prohibit leaving pets in hot cars, and some grant immunity to good Samaritans who must rescue pets in visible distress.
Be ready to call for help: Gather essential telephone numbers and have them on hand. You’ll want to have your local animal control agency’s number and the police department’s non-emergency number so you can quickly report the situation. Keep these numbers in your purse, your car’s glove compartment or programmed into your phone.
Spread the word: Distribute the Humane Society of the United States’ hot car flyer [PDF], which spells out the dangers of leaving pets in parked cars. Also share guidelines with your local law enforcement officials for how to investigate hot car-related deaths [PDF].
Get involved: Ask local store managers, shopping malls, restaurants and other businesses to post signs asking customers not to leave their pets in their cars while shopping or dining. A huge part of the solution to this problem is raising awareness.
Speak up: If your town or state doesn’t have a law prohibiting leaving pets in parked cars, contact your local representatives or attend a town hall meeting to start lobbying for one.

Cool outside doesn’t mean cool in the car

It doesn’t have to be that warm outside for a car to become dangerously hot inside.

When it’s 72 degrees Fahrenheit outside, the temperature inside your car can heat up to 116 degrees Fahrenheit within an hour.
When it’s 80 degrees Fahrenheit outside, the temperature inside your car can heat up to 99 degrees Fahrenheit within 10 minutes.
Rolling down the windows has been shown to have little effect on the temperature inside a car.

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