A little-known rule can give drivers a £70 fine.

The car horn is important for road communication, but using it wrongly is a problem. Rule 112 says to use it only when moving and needing to warn others. Drivers must not use their horn when stopped on the road. This means sounding the horn in traffic or to say you're arriving is against the rules.

This rule also applies to your driveway. Using the horn aggressively is not allowed, and it's forbidden in built-up areas from 11:30pm to 7am unless someone is in danger.

Penalty Charge Notices are not just for parking, but also for breaking traffic rules like using the horn wrongly. These notices cost £50-£70 in many UK areas, but can be reduced if paid within two weeks.

If a driver ignores a Penalty Charge Notice, they might go to court and pay a much bigger fine. Drivers should also check their horn is working before an MOT test, or their vehicle might fail.

There are strict rules for the sound of the horn. It cannot sound like an emergency vehicle. Only certain old cars can have different horns.