The days of the old, pure tungsten-filament headlamp are long gone, and the modern headlamp market offers a wide variety of models, types and price points. If you're purchasing a new car, or fitting aftermarket headlamps to a vehicle you already own, you'll want to be aware of the advantages and disadvantages of the type of headlights you'll be purchasing — not just for reasons of safety or efficiency, but because government legislation on how a headlight should perform is very strict, and steep fines are levied for non-compliance.
Modern headlamp types can be sorted into three basic categories, based on the mechanism they use to create light: halogen, LED and HID.
The oldest variety of headlight still in common usage, halogen headlights are essentially a more modern refinement of the pure tungsten light. They still contain a tungsten filament, which heats up to create light, but the longevity of the filament is increased with the addition of halogen gas, which is encased within the airtight bulb. This halogen gas produces a chemical reaction that causes evaporated tungsten to be deposited back onto the filament once the bulb is switched off, greatly increasing the filament's usable lifespan.
Halogen headlights may not be particularly sophisticated, but they provide adequate light for most eventualities. Some brands of halogen bulb are marketed as 'extra-bright' if you'd prefer a more intense beam, but be aware that these bulbs still have to conform to legal standards regarding glare. The greatest advantage of halogen bulbs is their cost; they are almost always the cheapest option on the market, and their ubiquity lets you shop around extensively for the best deal. They are also easy to replace yourself, requiring no professional assistance.
Unfortunately, halogen bulbs are a fragile option and may be broken by bumps or sudden knocks — and unlike LED headlights, once they fail, they fail utterly, essentially leaving you with one headlight until you can make repairs. They also waste energy because of the excessive heat they produce, and while energy-saving varieties are available, these may not produce enough light for you to see absolutely clearly at night.
A relatively new, and very fashionable, addition to the headlight market, LED headlights generate light with a series of light-emitting diodes, small semiconductors that generate light when subjected to electrical current. You'll find these fitted to a wide variety of modern cars.
The main advantage of using LED headlights is their remarkable energy efficiency, and a car running with LED lights will use less fuel and emit less pollution. It also reduces drain on your car's battery, extending its life. The light they produce is much closer to natural light than that produced by other bulbs, which reduces glare for oncoming drivers and allows your eyes to adjust more quickly in the dead of night.
It all sounds great, but if you haven't bought a car with LED lights fitted in the factory, you're out of luck. While aftermarket models can be fitted to some cars, as of yet this is not legal under Australian highway law, as these lights have not passed the requisite inspections.
HID stands for High Intensity Discharge, and the name is apropos. These lamps emit a powerful light by creating an arc of high-voltage electrical current. They are often sold as 'xenon' or 'bi-xenon' lamps and should not be confused with halogen lights containing xenon.
When it comes to sheer power, HID headlights are unmatched, and a pair of well-adjusted HID lamps can provide great visual clarity even when dipped. Despite this power, they are actually more energy efficient than halogen bulbs, since they don't have to contend with the electrical resistance of a tungsten filament. They are also relatively inexpensive to fit as an aftermarket option, and many car manufacturers offer them as an optional extra.
If you're thinking of fitting HID lights, you'd better think hard. Very few aftermarket options have been approved for legal use by Australian highway authorities, and the ones that have must be fitted very carefully — improperly adjusted HID lamps can easily dazzle other drivers — and you'll eat some big fines if you're caught with badly fitted HIDs. You should also be careful that the light these lamps produce is white, as some produce a light that is tinged blue. This will also get you fined. HID lamp conversions are illegal in Queensland.
If you need spare car parts, check out the stock of a business like Q.A.H. Auto Spares to find what you need.