From the Highway Code:
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 (see Rule 236).
[Law RVLR regs 25 & 27]
You MUST NOT use front or rear fog lights unless visibility is seriously reduced (see Rule 226) as they dazzle other road users and can obscure your brake lights. You MUST switch them off when visibility improves.
[Law RVLR regs 25 & 27]
As the years go on I find myself getting more and more disturbed by how few people there are on the roads who understand the use of fog lights, and more and more narked by the idiots who clearly don’t bother to read the Highway Code where it tells you the rules (see above) on their use. If you’re not au fait with the Highway Code then you may not know that, where MUST or MUST NOT is specified then the rule is based on statute and a reference to it is supplied at the end of the paragraph. Both of the rules above are of that type, so I’ve provided links to the relevant acts of parliament that provide the legal definition. As such, these rules are more than just guidelines that can be used to support a prosecution, they are rules that, if broken, can result directly in prosecution (normally a fine).
Unfortunately though the number of prosecutions that occur based on those laws are minimal and, in my opinion, should be much higher.
The other day I travelled around 100 miles in fairly misty conditions down mainly motorways. Now, on motorways, it is extremely easy to work out whether you can see 100m or more; not only are there little markers by the side of the motorway set at 100m intervals (the little white posts with blue and red bits on them), but the countdown markers at the approach to junctions are 100m ahead.
At no point during the time I was on the motoway that day was the visibility reduced to less than about 400m, yet the number of people using fog lights was massive! Not only that, much of the journey was lit by streetlights which helps to improve the long distance visibility in conditions like those.
What amazes me the most is the lack of brain use that seems to happen when these people are driving. I always thought that it was quite important to put your brain in to gear as well as your car, but I think I must be in a minority. Why would anyone possibly imagine, as they’re driving along in a queue of traffic x metres behind a car without fog lights on (and they can see it perfectly clearly), that the driver following x metres behind them is incapable of seeing them without their fog lights being on! It absolutely defines logic.
Then you’ve got the people who suddenly decide that it’s so foggy they need to put their fog lights on despite the fact they’ve been being followed fairly closely for some distance! Do they think the driver behind will somehow think they’ll have disappeared all of a sudden?
Interestingly the AA publishes a book that provides a list of hundreds of driving test theory questions. Question numbers 690 through to 710 cover the use of fog lights, and nearly all of them have answers that reinforce the fact that using your fog lights inappropriately is dangerous as it can dazzle following drivers and can cause confusion due to masking your brake lights.
So, if you are someone who likes to use fog lights, please switch your brain on before you go out and, while you’re driving think about the following points:
- If you’re on a motorway and the visibility is reduced, check the distance markers at the side of the motorway. If you reach one and can see the next one then visibility is NOT less than 100m so you should not be using fog lights.
- Try to remember how far 100m is so that, when you haven’t got the motorway markers to help you, you can still roughly estimate whether visibility is less than 100m or not.
- On any road, if you can clearly see the headlights of the vehicle behind you in your mirror then, unless they’ve just appeared, it’s highly likely they know you’re there so you probably don’t need to switch on your fog lights (or, if you already have them on, you can switch them off in order to avoid dazzling the driver)
- If you can clearly see the tail lights of the car in front of you even without that vehicle having fog lights on then, if there’s a vehicle around the same distance behind you, they probably know you’re there and can see you without your fog lights on so don’t switch them on (or switch them off if you’ve already got them on)
- If the road is empty as far as you can see behind you then, if visibility is less than 100m, feel free to switch your fog lights on. However remember that they’re on and that you need to switch them off if the situation changes (i.e. if visibility improves or if there’s a vehicle fairly close behind you)
- If someone behind you is flashing their headlights then it may be because your fog lights are dazzling them. If they’re on, switch them off and see if their flashing stops
- Don’t automatically switch your fog lights on just because it gets a little bit more foggy, or because a roadside sign says “Fog”; think about all of the above first – it may not be appropriate to use fog lights at that time
One final question you should ask yourself, and this is aimed mostly at BMW drivers as they seem to be the worst culprits in my experience, is “if I think visibility is bad enough to warrant switching my fog lights on, should I really be travelling 10m from the car in front of me at 90mph?”.