VOSA - Testing Directive
Changes to vehicle testing: LIGHTING
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Section 1.7 – Headlamps
To keep the test up to date with modern technology, new checks have been added in respect of High Intensity Discharge (HID) and Light Emitting Diode (LED) lamps.
HID lamps use a gas discharge system and require a ballast, igniter and special high voltage circuitry. They do not use a filament in the bulb, but have two electrodes in a glass tube filled with Xenon gas and metal salts.
A high voltage is applied between the electrodes causing an arc to form which ionizes the xenon atoms, vaporises the metallic salts and creates light. A high voltage, typically up to 20,000 volts, is required to strike and maintain the arc.
Compared with halogen headlamps, HID lamps are more efficient, have a longer service life and are much brighter; up to three times brighter in fact. The benefit of this extra brightness is that it enables drivers using HID lights to see approximately 30% further up the road ahead than for a halogen system.
The downside of this extra brightness is the potential to cause excessive dazzle to oncoming traffic. To combat this, HID headlamps often have advanced electronics that control the shape of the headlamp beam to avoid dazzle when the car climbs or descends hills and likewise when the vehicle is accelerating or braking.
Dazzle can also be caused if the lamps are dirty or aimed too high due to, for example, carrying rear seat passengers and/or heavy items in the boot. Vehicles with HID headlamps are therefore required to have a headlamp washing system (a wiper is not required) and be self levelling, which may be achieved either by the use of either headlamp or suspension levelling systems.
The presence and operation of these headlamp cleaning and levelling devices has been added to the test. Therefore, if a mandatory headlamp levelling or cleaning device is missing, inoperative or otherwise obviously defective, the vehicle will fail.
This raises the question of whether these checks apply to vehicles fitted with after-market HID lighting kits. These kits convert conventional halogen headlamps to HID Xenon and they are widely sold and fitted to vehicles used on the road. The Department for Transport considers that after-market systems should be required to meet the same safety standards as that applied in respect of these lamps at vehicle Type Approval. Therefore, in order to pass the MOT test, vehicles fitted with after-market HID systems would also need to be fitted with headlamp cleaning and self-levelling systems. Some high specification estate cars are fitted with a self-levelling suspension system and this would be considered as adequate for the purpose.
It is also worthy of note that a few high performance vehicles fitted with HID headlamps that have barely any luggage space and stiff suspension do not require a self-levelling system.
HID headlamps can be easily recognised as they generally:
- take a few seconds to reach full intensity
- have a bluish tinge to the light
- have an igniter module/inverter behind the headlamp
- may also have ‘DCR’ marked on the headlamp lens.
Headlamp washing and levelling systems are mandatory for all vehicles fitted with LED headlamp systems, although these are not yet widely used and only tend to be optional fitment on some executive marques. However, as LED systems improve and because they can be arranged in almost any design configuration, they are sure to become more common.
Where headlamp levelling or cleaning devices are missing or defective, but there is doubt as to whether they are required, the benefit of the doubt should be given and an advisory notice issued.
If there is self levelling and washing then they must work (and if OEM) but don't have to be there to pass an MOT.
