A quiet residential street at dusk with parked cars and lit windows, a single car driving slowly past
AI-generated image, not a photograph of a real person or place.
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WHAT THE RULES SAY

A roar that could
have been avoided.

95 dB the trial's suggested noise threshold

  • Avoidable noise is not allowed
  • Exhausts must not be made louder
  • Switch off when you wait
  • Quieter streets, by the rules

Since 1986, UK road vehicle rules have banned excessive noise that the driver could avoid with reasonable care.

The same rules cover exhausts that are altered to make more noise, and engines left running while a vehicle sits still. Here is what they say, and what a government trial of roadside noise cameras found.

Updated

Check a situation

THE SHORT ANSWER

If you could avoid it,
the rules say avoid it.

Three rules do most of the work:
avoidable noise, altered exhausts, idling when stationary.

IDLING

Switch off when you wait

The Highway Code says if you are likely to be stationary for more than a couple of minutes, apply the parking brake and switch off the engine, except in traffic.

Check a situation

EXHAUSTS

No louder than built

Every exhaust and silencer must be kept in good working order and must not be altered to increase the noise of the escaping exhaust gases.

Four checks

NOISE CAMERAS

A camera with ears

A government trial paired a video camera with microphones to pinpoint excessively noisy vehicles as they passed, building evidence that could support fines.

See the trial

General information only, not legal advice. For advice on your own situation, speak to a qualified lawyer or a free advice service.

A QUICK SITUATION CHECK

What does the
rule book say?

Pick a situation to see which rule applies. The bar shows how firmly the rules come down on it.

Situation check

Choose a situation
Engine left running, nobody in the carMust not

Rule 123 says you MUST NOT leave a parked vehicle unattended with the engine running on a public road.

Exhaust altered to sound louderMust not

Regulation 54 says an exhaust system and silencer must not be altered after manufacture so as to increase the noise of the exhaust gases.

Revving hard when it is not neededNot allowed if avoidable

Regulation 97 says no motor vehicle shall be used in a way that causes excessive noise which reasonable care by the driver could have avoided.

Waiting a few minutes at the kerbSwitch off

Rule 123 says that if you are likely to stay stationary for more than a couple of minutes, you should switch off to reduce emissions and noise.

Stopped in a traffic queuePermitted

Rule 123 says it is permissible to leave the engine running when the vehicle is stationary in traffic, or for diagnosing faults.

Source: The Highway Code, rule 123; Road Vehicles (Construction and Use) Regulations 1986, regs 54, 97 and 98 (legislation.gov.uk). This is a summary, not legal advice.

From the Highway Code (rule 123) and the Road Vehicles (Construction and Use) Regulations 1986, regulations 54, 97 and 98.

TWO NUMBERS FROM THE TRIAL

Most alerts were not
the loudest offenders.

Roadside trials ran from October 2022 to February 2023
in Keighley, Bristol, Great Yarmouth and Rubery.

4% of 1,777

Camera activations attributed to excessively noisy vehicles

Of 1,777 activations recorded, about four per cent were put down to excessively noisy vehicles using the threshold the research identified. Residents and researchers also noticed a deterrent effect.

NOISE CAMERA TRIAL · DFT

95 dB LAmax at 7.5 m

Suggested noise level for roads of 50 mph or less

The outcomes support using 95 dB LAmax, measured 7.5 metres away, to help decide whether to take enforcement action against a vehicle.

THE THRESHOLD · DFT RESEARCH

The trial had £300,000 of funding. A cost-benefit assessment found at least two genuine noise camera activations a day would make a system cost neutral.

FOUR THINGS TO CHECK

Quiet by habit,
legal by default.

A roadside pole with a small camera and microphone unit beside a suburban road, cars passing below
AI-generated image, not a photograph of a real person or place.

Simple habits that line up with what the Highway Code and vehicle regulations say.

  1. Switch off when parked

    Never leave a parked vehicle unattended with the engine running on a public road.

  2. Switch off for longer stops

    If you will be stationary for more than a couple of minutes outside traffic, apply the parking brake and turn the engine off.

  3. Keep the exhaust healthy

    Exhausts and silencers must be kept in good and efficient working order, so get a blowing or damaged one looked at.

  4. Go easy on the throttle

    Noise that reasonable care could avoid, such as needless revving, is not allowed on the road.

HOW NOISE CAMERAS WORK

A picture and
a sound level.

Close-up of a car exhaust tailpipe under the rear bumper of a parked car on a residential street
AI-generated image, not a photograph of a real person or place.

The Department for Transport's trial camera takes a picture of a passing vehicle and records its noise level, creating a digital package of evidence that could be used to fine offending drivers.

Trial sites were chosen from nominations by local MPs and covered rural, suburban and urban areas known to be affected by noisy vehicles. The DfT said it planned guidance for local authorities on minimum requirements and best practice.

Questions

Questions people ask

Is it illegal to rev your engine loudly?

Regulation 97 of the Road Vehicles (Construction and Use) Regulations 1986 says no motor vehicle shall be used on a road so as to cause excessive noise that reasonable care by the driver could have avoided.

Can I make my exhaust louder?

Regulation 54 says exhaust systems and silencers must be kept in good working order and must not be altered after manufacture so as to increase the noise of the exhaust gases.

Can I leave my engine running while I wait?

The Highway Code says you must not leave an engine running unnecessarily while stationary on a public road, and should switch off if you will wait more than a couple of minutes. Running in traffic is permitted.

What are noise cameras?

Roadside units that pair a video camera with microphones. The government trialled them in four places from October 2022 to February 2023 to see whether they could automatically detect excessively noisy vehicles.

How loud counts as too loud?

The trial research supports 95 dB LAmax at 7.5 metres for roads with limits of 50 mph or less, to help decide whether enforcement action should be taken.

Sources

Where the facts come from

  1. GOV.UK: The Highway Code, rules 103 to 158 (rule 123)
  2. legislation.gov.uk: Road Vehicles (Construction and Use) Regulations 1986, regulation 97
  3. legislation.gov.uk: Road Vehicles (Construction and Use) Regulations 1986, regulation 54
  4. Department for Transport on GOV.UK: Noise camera technology, roadside trial
  5. Institute of Acoustics: Results of noise camera trials for roads published

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