From eating and sleeping to having a dirty number plate, find out what can land you in trouble while at the wheel

If you exceed the speed limit or drive through a red light, then you can probably expect a fine.

But there are some lesser known rules that could end up costing you if you don’t know them. Here are scenarios where it pays to know the law:

1. Flashing your lights to give way

We’ve all been there. We’re sat at a junction praying for a gap in the traffic when a friendly driver slows and flashes their lights to allow us to pull out in front of them.

Although it’s a common practice, this Good Samaritan act could technically be considered a driving offence if an accident resulted from it.

The Highway Code states: “Only flash your headlights to let other road users know that you are there. Do not flash your headlights to convey any other message.”

Flashing your headlights to warn other drivers of a speed trap on the road ahead could also attract fines of up to £1,000 if caught by police.

2. Eating while driving

While it’s not illegal to be snacking at the wheel, it is frowned upon and could leave you in hot water if you’re distracted enough to present a significant danger to yourself or others.

The police could prosecute you for careless driving if they consider you were not in proper control of the vehicle.

3.Using your phone as a sat nav

Sat navs have to be in a fixed position, either on your windscreen or your dashboard and the same applies if you are using your phone to give you directions.

Using a hand-held mobile phone while driving is illegal, punishable by six points on your licence and a £200 fine. But it is fine to use it as a sat nav as long as long as you keep it in a fixed position and you do not touch it while driving.

4.Using Apple Pay at a drive-thru

It’s is a convenient app which acts as a digital wallet allowing contactless payment to be made with an iPhone or other Apple device.

But if you are using it instead of cash while ordering your McDonald’s or Costa Coffee then take care to ensure you are not flouting the law.

The only legal way to use it is to ensure your engine is off and you are fully parked with the handbrake on. But if your engine is still running then you are breaking the law and could be fined and given six points.

5. Having a dirty number plate

Keeping your number plate clean is a must. Dirty and unreadable number plates could leave you with a fine of up to £1,000. They should also show your vehicle registration number correctly. You can’t rearrange letters or numbers, or alter them so that they’re hard to read.

Your car will fail its MOT test if you drive with incorrectly displayed number plates.

6. Sleeping in your car when drunk

You may think that ‘sleeping it off’ in your car is perfectly legal but it comes with a risk of being convicted of drunk in charge of a vehicle.

This does not incur as serious penalties as drink driving but can still involve a hefty fine and points. However if you prove that you never had any intention of driving -- for example, you’ve left your keys elsewhere – then you may just receive a caution.

7. Splashing pedestrians with rainwater

If you drive through a puddle and soak someone walking on the pavement then you could be fined. It is considered driving without ‘reasonable consideration’ for other people.

Drivers can be punished with a fine of up to £5,000 but you are more likely to be be issued with a £100 fixed penalty notice and three penalty points if you are caught.

8. Sounding your horn in anger

You may not like the way the motorist in front of you is driving but think before bleeping your horn. It is actually illegal to use the car horn, except to avoid a potential dangerous situation. It is believed that unnecessary use of the horn can distract other drivers, potentially leading to accidents. Police have the power to issue motorists a £30 fine for the illegal use of car horns. This fine could rise to up to £1,000 if the matter ends up going to court.

9. Middle-lane hogging on the motorway

Motorists who just stay put in the middle lane are considered by some to be one of the biggest nuisances on the motorway. But anyone caught refusing to budge could be handed an on the spot fine of £100 by police.

The middle-lane should just be used for overtaking with the Highway Code stating that all drivers must keep to the left-hand lane when not passing other motorists.

10. Overtaking at a pedestrian crossing

It can be tempting to zip past a stationary car at a crossing on a multi-lane road as soon as the lights turn to green but this is actually illegal because of the danger it poses to pedestrians, who may still be walking across.

Caught and you could be handed a £100 fine and three penalty points.