One major complaint often heard from motorists is about LED headlights and the blinding glare they can cause to oncoming drivers.

Most new cars now have LED headlights installed as standard. These lights are designed not to glare and dazzle other drivers; they may look brighter, but they don’t cause more of a problem than traditional halogen headlights.

While it may be tempting to buy and install aftermarket LED headlamp bulbs for your car (especially during dark winter months), that might not be the best idea.

How do LED headlights work?

The average car on the road has halogen headlight bulbs. These type of bulbs produce light and heat by passing an electrical current through a filament of tungsten that is surrounded by halogen gas.

There are two main types of headlights: the xenon or High Intensity Discharge (HID) bulb, and the Light Emitting Diode (LED).

The HID bulb works by heating up xenon gas to produce light. LED headlights work in a totally different way – they use an electrical current to illuminate a semiconductor, which then emits photons. This produces a clear, bright light that illuminates the road ahead.

LED bulbs are far more efficient than halogen or HID bulbs, as they use less energy.

Generally speaking, LED headlights are sealed units. This means that motorists can’t replace burnt-out bulbs themselves. However, they do last much longer. So if they’ve been manufactured well, they should last for the life of the car at least.

The technology in automotive applications is still relatively young so it remains to be seen how LED headlights will fare long-term. But one major downside is that if something does go wrong with an LED headlight unit, it could prove quite expensive to replace!

Aftermarket LED headlight bulbs come in the same sizes as halogen bulbs and so can replace traditional bulbs, which offers much better illumination. Even though they’re unlikely to be as sophisticated or effective as factory-fitted LED units, there’s a bigger problem for drivers to consider before fitting them to their car.

What’s the problem with aftermarket LED headlight bulbs?

A headlight unit contains a reflector or projector that focuses the light from its bulbs or LEDs. Halogen headlight bulbs are omnidirectional, which means their light is widely dispersed unless it’s directed by a reflector. This prevents them from effectively illuminating the road ahead.

LEDs are not omnidirectional, meaning that they require a lens to focus the light being produced.

What this means is that, if an aftermarket — or “retrofit” — LED bulb is used in a headlight unit that wasn’t designed for LED bulbs, the light will not only be much brighter than a standard halogen bulb, but will likely be glaring to other drivers and possibly won’t be very effective from an illumination point of view.

There’s also a chance (the same as with a halogen bulbs) that an aftermarket LED bulb may not be fitted correctly and that the level of the beam may not be set correctly, further exacerbating the problem of dazzling other drivers.

All of that said, none of these things are the biggest issue when it comes to aftermarket LED headlight bulbs…

Are aftermarket LED headlight bulbs legal?

No, they’re totally illegal in the UK and other markets for a wide variety of reasons, not least their aforementioned problems.

The Road Vehicles Lighting Regulations 1989 states that all headlight bulbs must carry either a European E mark or a British Standards mark to ensure their quality.

At present, no technical legislation exists surrounding the use of LED bulbs in headlamp units designed for halogen ones, which means that aftermarket LED bulbs cannot receive a European E mark, or a British Standards mark, and so cannot be certified for road use in the UK.