Different types of headlight

• We explain what the various headlight types are 
• Know your halogen from your xenon

There used to be a time when you bought a car, it had headlights, and that was pretty much the end of any lighting chat. Those headlights were probably as effective as a candle in a high wind, but at least car buyers knew what they were getting.

Now there is more than one type of headlight with some cars combining several different technologies. But what’s the difference between these various sorts of headlight? Is xenon better than halogen? Where does LED fit into the picture? And are laser lights even legal?

What is a halogen bulb?

Halogen is the oldest type of headlight bulb that’s used in cars. It’s the same technology that used to be lighting up our living rooms. Bulbs use a tungsten filament which produces light and heat when a current is passed through it. Halogen gas protects the filament, hence the name.

Like our household bulbs (which have now been banned and replaced with LEDs), halogens use a lot of energy because so much heat is generated in producing light. They’re also quite easy to replace by simply unscrewing one and installing its replacement. And they’re relatively fragile – which isn’t such a good thing when you have to cope with bumpy roads.

What’s the difference between halogen and xenon headlights?

Xenon bulbs work in a completely different way to halogens. Rather than using a filament, they produce light from an arc that’s created by passing a current between two electrodes. They get their name from the xenon gas that helps to create the electric arc at low temperatures.

They make great headlights because the light is bright, with a bluey look to it. Xenon lights are also called High Intensity Discharge or HID lights. As the name suggests, they’re much brighter than their halogen rivals. They last a lot longer too, up to 10 years because less heat is generated.

The big difference is xenon lights are more complex than halogens which is why HID lights are so expensive to replace. As your car gets older, the likelihood of HID bulbs wearing out increases. And while they’re more energy efficient than halogens, they’re not as good as LEDs.

What are LED lights?

LED stands for Light Emitting Diode. It works by flowing a current between a cathode and anode via a semi-conducting material. This emits light.

The big advantage of LEDs is that they generate very little heat and draw very little current from the car’s battery. In turn that means they use very little fuel.

They are also much more compact than traditional bulbs and their light is much brighter. That car lets designers make much slimmer headlights for more modern looking motors.

How much are LED lights used?

It’s almost impossible to say what cars have LED headlights because an increasing number of car makers are using them for their design and fuel efficiency benefits. And if they’re not employing them for the main lighting, they’re using LED running lights.

Daytime Running Lights (DRLs) have been a fixture on new cars since February 2011, because they’ve been shown to improve road safety.

As these are turned on all the time, many car makers have chosen to make them using LEDs to reduce energy consumption. An added benefit is different car firms can make their DRLs into cool, recognisable shapes such as Seat’s and Peugeot’s.

LED lights don’t have much to go wrong either and they’re predicted to last far longer than 10 years, which should see them outlast most of the cars they’re fitted too. But the big downside is cost. When they do go wrong, you don’t just change a bulb, you often need a whole new unit. And that can be eye-wateringly expensive.

What are matrix LED lights?

Increasingly, car makers are using adaptive lighting. This is where the range and direction of headlamps is automatically adjusted to suit road conditions. Although adaptive lighting doesn’t have to use LEDs, it’s easy if it does.

Matrix LED lighting is a step further than simple adaptive lighting. It uses a collection of LED modules – usually around 15 per light – plus mirrors. These are then linked to sensors and cameras that read the road ahead and adjust the lights accordingly.

If they see a corner coming up, matrix LED lights can point towards the corner to light it up. If they detect oncoming traffic, they can switch off some of the modules so they don’t blind other road users. The real benefit is the driver always has the best lighting possible for the road conditions they’re facing. And there’s no more flicking the stalk to switch between main beam and dipped lights.

What are laser lights?

While LEDs are gradually becoming more widely used, laser lights are just at the start of their journey. Top of the range BMWs feature them today but as time goes by, they’ll be fitted to ever-more affordable cars.

Laser lights work by firing a laser at phosphorous. This produces light which is filtered through a lens so as not to blind other road users and spread out by mirrors. There are hundreds of these adjustable reflectors which can be switched on and off depending on what the car’s lighting computer decides.

For the driver, the big advantage is similar to matrix LED lighting: the road is lit up as much as it possibly can be. But laser lights have a much further reach than LEDs making illumination even better.

See also:

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Best cars with a seven-year warranty

Best self-driving cars