What are main beam lights and when should you use them?

June 24, 2024 by

Knowing when to use main beam headlights and when to choose dipped headlights instead is important to keep you and other road users safe at night and in low light conditions.

It’s not too complicated, but some drivers do get it wrong. This carwow guide should clear up any confusion.

What are main beam lights?

Main beam lights are bright headlights that help you see well ahead of your car. They’re also known as full beam headlights or high beam headlights. Drivers can switch between main beam and dipped beam depending on the type of road, the weather, the time of day, and whether there are other road users around.

Depending on the make and model of car you’re driving, main beam lights could use halogen, LED, or xenon light bulbs. Halogen lights have been around for decades, but many modern cars now come with brighter LED or xenon headlights.

What is the main beam light symbol?

The main beam light symbol shows a bulb with horizontal lines coming from it to represent the light projecting from the headlight. The bulb symbol looks a bit like a capital letter ‘D’.

Don’t confuse the main beam light symbol with the one for dipped beam. This uses the same ‘D’ shape to represent a bulb, but with the horizontal lines slanting downwards.

When to use main beam lights

Here’s when you should use main beam lights:

  • In the dark
  • On unlit roads
  • When there are no other road users just ahead or travelling in the opposite direction

There’s no benefit to main beam when you are driving on a well-lit road, and if there are other road users around then main beam may dazzle them.

In the daytime, especially in clear visibility, you can rely on daytime running lights to help other road users to notice your car. You can use parking lights (also known as sidelights) in low visibility or while parked in a road or lay-by.

How to turn on main beam lights

You can usually find the switch to turn on headlights on the left-hand stalk or on the dashboard to the right of the steering wheel. Twist the stalk or turn the switch so the line on the control points to the headlight symbol. You’ll usually have to turn the control past the setting for side lights before the headlights switch on.

Dipped headlights will be the default setting. To switch from dipped beam to main beam, push the stalk away from you. When you want to return to dipped beam, pull back on the stalk.

If you are in any doubt which type of headlight is switched on, look for the main beam or dipped beam symbol which should be illuminated on the driver’s display.

Many modern cars now have automatic headlights. So long as the switch is in the ‘automatic’ position, the lights will come on without the driver needing to do anything.

Some models go one better with adaptive headlights. These adjust the beam pattern to suit different road conditions and to avoid dazzling other road users. With this type of light, you don’t have to switch between dipped and main beam lights – the car does it for you.

Main beam lights vs dipped lights

Most cars have two types of headlight – main beam and dipped beam.

Main beam is best for seeing with. The light shines a long way into the distance, giving you a clear view up ahead. Main beam is ideal for driving on an unlit road at night, when you need all the help you can get to see where you are going.

Dipped beam headlights don’t reach as far into the distance, as they’re angled downwards. This is so that dipped beam lights don’t dazzle other road users. If you’ve ever driven towards another car at night whose driver has forgotten to dip their headlights, you’ll know how disorientating this can be.

It’s worth switching to dipped beam when it’s foggy, even if there’s no other traffic around. This is because the fog reflects the light back at you, making it harder to see.

If visibility is very bad (less than 100 metres) then turn on fog lights as well as dipped beam.

Main beam headlight FAQs

Are main beam lights and fog lights the same?

No. In fact, you should never use fog lights and main beam headlights at the same time.

You might think you want to use your brightest headlights when fog restricts visibility, but in thick fog full beam does more harm than good. That’s because the light from the headlights reflects back off the fog and makes it harder to see.

Front fog lights are very bright but they are mounted low down, so they won’t reflect back off the fog as brightly as main beam lights. They will help you to see and – just as importantly – be seen by other road users.

Rear fog lights are also very bright and should only be used in very bad visibility when you can see no more than 100 metres.

Can a light bar be used as main beam?

A light bar is a form of daytime running light (DRL) that stretches across the front of the car. It’s not a substitute for using main beam.

As a type of DRL, a light bar makes it easier for other road users to spot your car. Light bars aren’t designed to illuminate the road ahead to any meaningful degree, so you really mustn’t rely on a light bar or any other type of DRL at night.

Can I drive with one main beam and one side light?

No, you can’t rely on one main beam and one side light. This combination won’t light the road ahead properly.

Using main beam – even on one side of the car if the other bulb has failed – could dazzle other road users. Highway Code Rule 114 says drivers must not “use any lights in a way which would dazzle or cause discomfort to other road users”.

If a headlight bulb fails you should replace it as soon as possible.

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