Motorists seeking relief from the ongoing heatwave by sitting in their parked cars with the engine running and air conditioning on may be breaking the law and could face fines of up to £110, according to the RAC.
What Does the Law Say?
Rule 123 of the Highway Code 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." It adds that if a vehicle is stationary and likely to remain so for more than a couple of minutes, drivers should apply the parking brake and switch off the engine to reduce emissions and noise pollution. This rule does not apply when stationary due to traffic queues.
The RAC warns that "drivers seeking to cool down by sitting in stationary vehicles with their air-con are running the risk of a fine for breaking vehicle emissions laws." It states: "Remaining in a vehicle with its engine idling causes air pollution and is punishable with a fine of up to £110 for people who refuse to switch off after being asked."
Penalties Vary Across the UK
The standard penalty for engine idling across the UK is a fixed penalty notice ranging from £40 to £80, with fines typically halved if settled promptly. However, certain councils, including the London boroughs of Islington and Westminster, have exercised powers to impose steeper fines of up to £110.
In Wales, the Welsh Government is increasing the current £20 fixed penalty fine to a higher penalty range of £75 to £150 from 30 September 2026. It states: "Many people are not aware that stationary idling is an offence. We are working to address this by raising awareness and encouraging drivers to switch off, when stationary." It specifically lists "operating heating/cooling systems for comfort" as an unacceptable reason for idling.
Why Is Idling Harmful?
The Welsh Government explains that idling "creates air and noise pollution which is harmful to public health," "contributes to a range of problems including heart and lung diseases," and that "children, young people and people with existing health conditions are particularly vulnerable."
RAC senior policy officer Rod Dennis said: "Air conditioning is a game-changer in modern vehicles, making otherwise uncomfortable journeys by road a genuinely pleasant experience. We even advise those driving vehicles without air-con to consider delaying any non-essential trips this week until the heatwave passes. But while we're all desperate to stay cool, just sitting in the car with the engine and air conditioning running and going nowhere isn't advisable. Due to the air pollution this causes, you risk a fine from a police or civil enforcement officer."
Leniency Possible During Heatwave?
Given the exceptional conditions currently being experienced across much of the UK, police officers and enforcement officials may opt to exercise a degree of leniency. However, the RAC advises drivers to switch off their engines if stationary for more than a couple of minutes to avoid the risk of a fine.
