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Shine a light!

For quite a few months now I've been on a road trip to try to find a new car, and I've been amazed with how much automobile illumination has improved lately.

04 Apr 2010

By Dr Clive Fraser

Xenon Headlamps

For quite a few months now I've been on a road trip to try to find a new car.

It's a long journey down a rough track to find an automobile that will suit the 21st Century.

You may have noticed that, in an effort to reduce my carbon footprint, I've only been trialling the latest generation of diesel-powered vehicles.

These cars will really run on the smell of an oily rag and will still out-perform hybrids in terms of economy and performance.

But, as well as great fuel economy, I'd like some safety and creature comforts in my new car and I've been amazed with how much automobile illumination has improved lately.

I've been impressed with the longevity and visual appeal of LED bulbs, which are now becoming the norm all over the motoring world.

Though they're still an expensive option on many vehicles, I'm also totally besotted with Xenon headlights and I've discovered some interesting techno-speak about them.

For starters they don't run off the normal 12 Volts DC powering the rest of the lamps.

You see, they work off the principle of high intensity discharge (HID), whereby an 85 Volt AC electric arc ionises the noble gas (Xenon) within the bulb.

For those who can still remember their first year inorganic chemistry, noble gases such as Xenon have a full valence electron shell, meaning that they are chemically very stable and generally don't share electrons to form other compounds.

Xenon lamps produce 125% more lumens (3,500 lumens) from 30% fewer Watts (38 Watts) when compared to a halogen bulb.

And, because 24% of the electrical energy is converted into light, they are even more efficient than fluorescent tubes.

This efficiency does mean that the alternator doesn't need to work as hard and fuel economy improves, but the fuel savings are unlikely to defray the $2,500 up-front cost of the Xenon option during the life of the vehicle.

Xenon headlamps are in fact so bright that dirty lenses will dazzle on-coming vehicles and every Xenon headlight must have a lens washer because the distraction to on-coming traffic occurs without diminution of light output for the driver.

Unlike street lights which use another noble gas (Argon) to maintain the electric arc, Xenon produces a useful beam almost instantly with no delay.

And, because it is so bright, every Xenon lamp has a built-in headlight-levelling control that takes account of the vehicle's degree of squat to keep the high-intensity portion of the beam below the horizon without any action required by the driver.

This all sounds as though I'll be seeing better for longer in spite of the refractive index of my own lens changing over time (ie, I'm needing stronger glasses).

But I have just met up with another piece of technology which has left me gob-smacked.

It's called the automatic headlight dimmer.

The latest Xenon headlights use a shield behind the lens to emulate what we used to call high and low beam.

This means that there is only one bulb and the system is called bi-Xenon as the shield moves up and down masking the lamp.

Until recently, the driver needed to switch between these modes to avoid dazzling on-coming traffic, but the latest system in the car I'm looking to buy will do this for you.

Unbelievably, it can tell the difference between an on-coming vehicle or a red tail-light at 500 metres when low beam is required and a bright reflective roadside sign when I still need high beam.

It seems as though the engineers have miniaturised an auto-worker who sits inside the headlight shell flicking a switch, because the technology is incredibly intuitive and will make driving in the dark just that bit safer for us all.

It's worth remembering that 50% of accidents occur at night, but we only do 25% of our driving in the dark.

Xenon Headlamps


Whiter, brighter, better.


Expensive up-front cost and may dazzle on-coming drivers

These headlights would suit: Endoscopists who like a good light source.

Alternative practitioners: Radiologists may prefer Radon in their lamps.






85 Volts

12 Volts


400 Hz


Power consumption

38 Watts

55 Watts


3500 Lumens

1550 Lumens

Service life

2000 hours

700 hours

Safe motoring,

Dr Clive Fraser


Published: 04 Apr 2010