No matter how great your eyesight or competent behind the wheel you may be, night-time driving can be a stress – especially when you’re tired or when the weather’s taken a turn for the worse.
There are few features of a car that can inspire greater confidence at this time than a good set of headlights. Being able to clearly see the road ahead makes it easier to spot potential hazards much sooner, vastly reducing the risk of road accidents.
One of the increasingly common systems employed by manufacturers these days are xenon headlights. Also referred to as High Intensity Discharge (or HID) headlights, they offer a crisp whitish-blue light that illuminates the road far ahead. But how do they work? And are they worth the extra cost to add them to your new car?
The Sciencey bit
Xenon is a chemical element categorised as a noble gas – a group of six chemical elements which are generally clear, odourless and very stable under the typical atmospheric temperatures and pressures we consider acceptable here on earth.
Unlike a traditional halogen light – which emits light due to a huge electrical resistance caused by passing a current through a narrow wire (a filament) – the light in a xenon unit is produced by an electrical arc jumping from one contact to another. The xenon gas fills the chamber in which the contacts sit, and amplifies the brightness of the light, helping it to quickly reach the temperature necessary to emit an intense beam.
In a filament bulb, the constant change in temperature (caused by the lights switching on and off) will gradually cause the thin wire to become more fragile, and eventually fail (that’s what happens when a lightbulb ‘blows’). The lack of a filament in HIDs light means that they generally last far longer than traditional bulbs. The light they provide is more intense too, and offers a consistent, clearly defined beam.
Due to their intensity, they can be known to dazzle oncoming traffic, so manufacturers employ self-levelling systems to prevent the beam pointing too high. This is particularly a problem in estate cars, when the back of the car might be weighed down with people and luggage. In many xenon-equipped cars you’ll notice the headlight beam dancing about when you first turn the ignition on at night – this is a calibration pattern to make sure they level correctly.
Many cheaper cars still make use of the typical halogen systems, with xenon headlights available on higher spec trim levels. On pricier cars, xenon units are now being replaced with LED lights, which are not only able to light the road ahead more effectively, but with greater accuracy, reducing glare.
The limited-run Audi R8 LMX was the first production car to be offered with laser headlights, just pipping the BMW i8 to the throne. Laser headlights offer an even greater intensity of light with even better accuracy in preventing glare for oncoming traffic, and we expect them to become commonplace over the next five years or so.
Good. Now head over to the homepage and configure a new car – just be sure to pick the headlights you want!