Fog Lights
Created | Updated Jan 28, 2002
Fog lights are special lights fitted to cars to improve their visiblity and forward vision in very poor weather.
In the UK drivers are bound by The Highway Code. It has this to say about fog lights:
You MUST use headlights when visibility is seriously reduced, generally when you cannot see for more than 100 metres (328 feet). You may also use front or rear fog lights but you MUST switch them off when visibility improves
The reality is of course somewhat different.
Rear fog lights
Rear fog lights are red and very bright. They are usually 21W, compared to 6W or 10W for ordinary rear lights. Some cars have two, one each side - this is now frowned on as it makes them harder to distinguish from brake lights, which are the same brightness.
You will see rear fog lights used on motorways in perfectly clear conditions at night (they have even been called "motorway lights" by some mis-informed people). This has the effect of dazzling drivers behind so they can't see past the car with fog lights.
You will also see them left on for several months after a light mist, because (a) people are too brain-dead to notice the large orange light in the instrument panel which informs them their fog lights are on and (b) manufacturers are, for the most part, too miserly to incorporate the incredibly simple device needed to cancel the fog lights when the headlights are switched off.
Front fog lights
Front fog-lights are usually mounted low down. They have a broad, flat beam and are designed to pick out the kerb and road surface. Fog and snow share the effect that your headlights reflect back at you. Fog lights use a flatter beam, below your line of vision, to avoid this problem. In real fog you are likely to want to switch your headlights off altogether and use dimmed headlights or sidelights, in combination with foglights. You will, of course, drive extremely slowly in these conditions.
Front fog lights are as misused as rear ones. Some of this is due to supidity on the part of manufacturers. Often you can't switch the rear fog lights on without the front ones. How do you switch the fronts off to avoid dazzling oncoming motorists without losing rear visibility? Good question.
Some people use front fog lights in light mist, and switch their main beam headlights on as well. In the words of the immortal Bart, "Doh!" If your main beam lights can be used without turning the world into one giant white blob six feet in front of the car, then you have no business using front fog lights. It's not what they are for!
Some people use front fog lights round town. This is because they have the BMX Turbo Nutter B*****d version of the Repmobile, and this has fog lights as standard. Clearly they must be switched on to ensure that lesser mortals know they should give way.
But of course the leading use of front fog lights is to enable you to continue driving at speed when visibility is down to ten feet.
Conclusion
Fog lights are a useful safety feature which, in most places, you can legitimately use about three times per year. The rest of the time, do the world a favour and turn them off. And if you do need fog lights, you should be driving slowly. Always always drive within the distance you can see to be clear - do not assume that because you can see a dim red glow from the car in front's fog lights there is a clear road in between you. And remember - if he stops or crashes and you go into the back of him, it's your fault. If you hit a tree it's your fault. If you knock over a pedestrian it's your fault. Drive too fast in fog and you can wave your insurance bonus goodbye.
