With the UK facing another heatwave later this month, drivers are being urged to think twice before using a common feature to stay cool. Keeping a car's air-conditioning running without going anywhere could prove to be an expensive mistake this summer.
The reminder about 'engine idling' comes as hot weather might encourage more Brits to cool off in their cars when parked. While it can feel like an easy fix in the heat, it may be treated as an avoidable source of pollution, meaning drivers could be told to switch off — and potentially fined if they don't comply.
Penalties and enforcement
In many places, the typical punishment is a £40 fixed penalty notice if issued by police, or an £80 penalty charge notice from a civil enforcement officer. Both can usually be cut in half if paid quickly, often within 14 days.
Most drivers won't be fined if caught breaking this rule. Enforcement officers usually ask the driver to turn the engine off first, with the fine often a last resort if the driver refuses to switch off, or if the car is left idling while unattended.
Highway Code Rule 123
The 'rule' is one that all drivers must follow under the Highway Code. Failing to switch off an engine while parked up is a direct breach of Rule 123, which states: “You must not leave a parked vehicle unattended with the engine running or leave a vehicle engine running unnecessarily while that vehicle is stationary on a public road.”
Car manufacturers are catching up with this rule and often design modern vehicles with ways to counter these behaviours. For example, cars might have automatic shut-offs built into their remote-start systems.
Warnings from motoring organisations
Almost every major automotive and breakdown company in the UK warns people about this policy that could catch drivers out when temperatures soar. Green Flag listed it as one of the "strange laws" that catch out many UK drivers.
Kwik-Fit added: "Leaving your engine idling while you’re parked or waiting is more than just bad for the environment, it can actually be illegal. Under driving law, you must not leave a vehicle running while unattended.
"Local authorities can issue on-the-spot fines if you refuse to switch off your engine when asked. Idling increases emissions and wastes fuel, so if you’re parked for more than a moment, turn the engine off. It’s better for your car, your wallet, and the planet."
Higher fines in London
Some parts of the UK take this rule seriously, going far beyond the standard punishment. In parts of London such as Islington and Westminster, motorists caught idling can face penalties of £110, with the tougher stance linked to serious air pollution concerns in those boroughs. The area has scrapped the early payment discount, highlighting just how serious the issue is locally.
