When should you flash your headlights at other road users? And four other headlight rules

Looking out for other road users is one of the fundamental rules of driving. 

And beyond safety measures, it’s not uncommon to see drivers waving at each other on the road. Whether that’s to acknowledge someone they know, waving at someone with the same car, or thanking someone for giving way—for the most part, drivers are pretty friendly to each other. 

However, our team at Dick Lovett has warned that there are some friendly gestures on the road that could land you in a bit of hot water. Namely: flashing your headlights.

When should you flash your headlights at other road users?

Drivers flash their headlights for a variety of reasons but what does it mean when someone flashes their lights at you? 

Acting as a visual form of communication, drivers use their headlights to alert other road users of many things, from thanking them, to letting them know they’ve not put their headlights on or as a hazard warning to tell others of dangers on the road. 

However, if drivers are caught doing one ‘friendly’ headlight flashing gesture they could get into some trouble, as it’s illegal. 

With over 9 million drivers caught speeding in the past 5 years, it’s no surprise some drivers like to warn others of speed cameras and mobile police speed check vans on the road, with flashing headlights being a very common way to do this. 

However, if drivers are caught doing this, drivers could face fines of up to £1,000, as legally, this would classify as ‘obstructing police duties’ under section 89 of the Police Act 1997. 

And while it might feel nice to help and look out for a fellow driver, it could lead to more reckless drivers on the road if they’re not caught by police and fined accordingly. Remember, speed limits are there to keep everyone, including you, safe.

So, is it illegal to flash your headlights? According to the Highway Code, drivers should only ever flash their headlights to warn other road users of their presence—this is the only legally permitted scenario for doing so. 

This technically means that even flashing your headlights to thank another driver for letting you pass is illegal.

In most cars, you can flash your headlights by quickly and repeatedly pulling the indicator dial towards you. This turns your high beam lights on and off quickly, leading to a flashing motion.

Four other headlight rules to be aware of 

1. Dipped headlight rules 

What are dipped highlights? Dipped headlights are essentially the ‘standard’ headlights that drivers use the most. They refer to the standard, low-beam headlights that drivers use in the dark or in low visibility, as opposed to full beam headlights that angle upwards. 

So, when should you use dipped headlights? As per the Highway Code, you should use dipped headlights when visibility is reduced—or when you’re able to see less than 100 metres (328 feet) ahead of your vehicle. Basically, any time you’re driving at night or during bad weather. 

Failure to turn on your headlights when you don’t have this kind of visibility could land you with a £100 fine if caught by the police, and if you are caught with the issue again unfixed, this can rise to £1,000. 

However, if the conditions are serious enough, the police officer could charge you with dangerous driving, which carries a minimum 12-month driving ban. 

Drivers with automatic headlights should not always rely on their vehicle to determine the right conditions to put their dipped headlights on, as these systems might not always activate in certain conditions like heavy rain, fog or snow.

2. Full beam headlight rules 

What are full beam headlights? Full beam headlights are the brightest type of headlights on normal vehicles. Unlike dipped headlights, our full beam headlights are angled upwards to allow drivers to see more of the road ahead. 

They usually work from the same switch as your other lights and usually come on when you push the light stalk forward. However, you may need to consult your vehicle's user manual if your car works differently from this. 

Is it illegal to drive with your full beam on in the UK? While there aren’t any specific laws in the UK against using full beam headlights, the Highway Code states that “you MUST NOT use any lights in a way which would dazzle or cause discomfort to other road users”. 

If you are found to be causing issues for other drivers because of driving with full beam headlights on, then you could be charged with inconsiderate driving or ‘driving without due care and attention’. 

This is an offense under section 3 of the Road Traffic Act 1998 and could see you get a fine of £100 and three points, but the most serious examples could go to court where offenders can face much higher penalties of up to £5,000 plus 9 points or a ban.

If you’re confused about when to use full beam headlights, it’s best to only use them on unlit stretches of road at night. When road users start coming in the oncoming direction (including both pedestrians and cyclists) then you must turn off your full beam to avoid dazzling other road users and potentially causing accidents as a result.

If you’re struggling with the brightness of other driver’s headlights, take a look at our top safety tips for driving in the dark.

3. Hazard light rules 

What are hazard warning lights? Hazard warning lights are flashing indicator lights that warn other road users of your presence or alert them of potential hazards ahead. 

When turned on, both the front and back indicators of a vehicle will flash intermittently at the same time to alert other drivers of hazards. They use the same bulbs as your normal indicators do, giving them an orange or amber colour.

When may you use hazard warning lights? According to the Highway Code, you should only use hazard warning lights when your own car presents a hazard to other road users—for example if you have broken down—or if you’re alerting other drivers of another hazard on the road. 

Is there an illegal use of hazard lights? Hazard warning lights are sometimes used as another mode of communication for other drivers—but not necessarily in a situation that warrants their use. 

For example, many drivers may use their hazard warnings when they’re ‘parked’ somewhere they probably shouldn’t be to let other drivers know that they’re still in their vehicle. However, the Highway Code states: “Never use them as an excuse for dangerous or illegal parking”. 

Illegal parking can lead to fines but prices vary as they are usually determined by the local authority.

Another common misuse of hazard warning lights is putting them on and off quickly to thank other drivers. However, using hazards incorrectly could see you charged with ‘driving without due care and attention’.

4. Headlight cleaning rules 

As we get out of the winter, drivers will naturally be using their headlights less. 

However, with the summer solstice (the longest day of the year) not occurring until late June, Brits still have plenty of commuting hours in the dark. 

Over the winter, our headlights can become foggy or cloudy looking. This is primarily caused by a combination of dirt and buildup from salt on the road. Cloudy headlights can seriously reduce our visibility, not to mention create glare for other drivers, so headlight cleaning is essential. 

In fact, driving with cloudy headlights is illegal. If caught, you could be charged with ‘driving without due care and attention’.

After all, the Highway Code states “lights, indicators, reflectors and number plates MUST be kept clean and clear”. 

Having cloudy headlights could also cause you to fail your MOT.