Amsterdam has started the fight against noisy motorcycles and cars. On Friday, the city placed electric road signs in two places to warn road users if their vehicles are too loud. The warnings will eventually be replaced by “noise cameras,” which, like speed cameras, automatically send a fine to the offending driver, Parool reports.
This is not true. See rule 123 of the Highway Code which says it is illegal to modify your vehicle to make more noise and that the noise of a vehicle should be below 86 db.
The current issue is that enforcement is not proactive and the fines are very low. Most police departments only issue a warning for first time offenders.
See: https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/805940/roadside-vehicle-noise-measurement-phase-1-study-report-and-technology-recommendations.pdf
For an extensive review.