Several times in these freezing conditions I have encountered the following:
I am driving at night on an unlit ungritted B road, keeping a steady 40-45 mph, watching the road very carefully for ice or compacted frost.
Someone comes up behind me, and tailgates impatiently for a few minutes. After a while he overtakes, but instead of disappearing off into the distance he finds that he too can only do my speed, so he sticks at about 100 yards ahead.
I dipped my headlamps as he passed and pulled ahead, but now I cannot see the road surface so well. At what distance behind him would it be acceptable to turn the lights back to full beam?
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The correct answer is of, course, when he is no longer visible, or so far ahead that his lights are barely visisble. In the interim, drive within the limits of your visibilty and subsequent stopping distance, which may mean reducing your speed. But you knew all this ;-)
There's no real answer. If you have xenon HID lamps, then he'll need to be a good bit further ahead than 100 yards before you use the main beam. If they are standard bulbs, without any upgrade, then perhaps 100 yards is fine. In any event, you'll risk some sort of road rage if you are blinding him.
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If someone did that to me, it would be about 15 yards. Just far enough in front so he gets his eyeballs fried.
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>> There's no real answer.
I agree. Personally, if a car behind me had main beam on I would just dip my rear view mirror. I might, just might, in addition wink my rear fog lights a couple of times. However, all in all I wouldn't be overly bothered.
Last edited by: L'escargot on Thu 9 Dec 10 at 09:21
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>> Personally, if a car behind me had main beam on I would just
>> dip my rear view mirror. I might, just might, in addition wink my rear fog
>> lights a couple of times. However, all in all I wouldn't be overly bothered.
>>
I usually dip the interior mirror and adjust the door mirrors outwards so that he/she gets the reflection from his main beams.
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I agree with "when he's out of (line of) sight", but perhaps 1/4 mile might be OK. 100 yards is too much too close.
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>> I dipped my headlamps as he passed and pulled ahead, but now I cannot see
>> the road surface so well.
www.agingeye.net/visionbasics/theagingeye.php
The light adapted eye of a 20 year old receives six times more light than that of an 80 year old. In dark adapted conditions, the 20 year old eye receives about 16 times more light. In comparison to younger people, it is as though older persons were wearing medium-density sunglasses in bright light and extremely dark glasses in dim light.
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John H, no, I didn't mean I couldn't see the road so well because of my age, I meant because previously I was on full beam but now out of courtesy to the car that has just overtaken, I am only on dip beam.
So the "correct answer" seems to be that whereas previously I was able to maintain a speed consistent with the visibility available on full beam, now because he has placed himself ahead of me I am obliged to slow down so as not to dazzle him while he slowly pulls to 1/4 mile ahead?
Then of course more cars will catch up, and I shall be obliged to work my way to the back of the queue.
There's something wrong here. Perhaps I should just stay on full beam, and let anyone who wants to deliberately drive into it do so at their own risk.
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Mike H's first paragraph is the correct answer, and - for me - the only answer. 'Retaliatory' measures are, at best, selfish and childish - at worst, provocative and dangerous.
It's a bit like someone pulling out suddenly from an inside lane and occupying your safe following distance. It is always best to pull back again to that safe following distance (no matter how often it occurs), rather than tailgating to 'make a point'.
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Just slow down a bit more, let him move forward further, and then continue on your full beam.
It is quite daring for someone to overtake in that situation though.
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>> It is quite daring for someone to overtake in that situation though.
I can think of alternative words to "daring" .......
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>> At what distance behind him would it be acceptable to
>> turn the lights back to full beam?
>>
Happens to me occasionally. I think I am a little less caring than you, reasoning that if the overtaker hasn't got a dipping mirror, hard luck.
The answer is that your vision requirements are paramount. When I was doing stuff with small boats ISTR one of the rules of overtaking was "the overtaking vessel keeps clear". If anything happens, it's the fault of the faster boat. We could do with something along those lines in the HC perhaps.
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Just remember your own safety is more important than courtesy.
If you can't see properly, then it is a great risk.
If you glare the driver in front, he can always set his mirror in night mode (most modern cars have this option).
Having said so, I find that having a car just in front of me (not tailgainting though) in bad road (ice/fog etc.) is often a good thing. He needs to do most of the judgement instead of me doing :)
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On the road in question with the possibility of black ice etc i'd be quite happy to follow someone else travelling at about my speed...should they encounter that nasty sheet of ice then you have an early warning and can cruise gingerly by giving them a wave of thanks.
I like having a wake to follow in fog too.
There's another benefit to following, if some chump is leathering the other way too fast and brakes when they see your trail blazer and loses control you have an extended front bumper.
It's all about surviving in this weather.
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I don't trust the judgement of other drivers in front enough to follow them to my death. This is one of the reasons motorway pile-ups happen, people following the driver in front, using them as a guide as to what speed to travel. The domino effect creates less and less braking distance the further back you are in the queue. The example of the chump mentioned above, coming the other way, is probably more likely to swerve and miss the lead car and fishtail into someone further down the line. I'd rather create my own space in front.
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>> I don't trust the judgement of other drivers in front enough to follow them to
>> my death.
I don't agree, the traffic or car ahead of you is a good indicator of what is happening ahead of them. For example there is a speed camera van location around a curve near me, if cars brake as they go round the bend it's a safe bet that the van is present. This is all part of reading the road and being aware of what is going on around you. If you see brake lights ahead of you don't you slow down? Or if the car ahead is unstable in cold conditions might this be an indication of ice?
Last edited by: Old Navy on Fri 10 Dec 10 at 11:10
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I think the two points of view are still compatible. The behaviour of the car in front is essential information for any driver - it extends your own vision to the range of view of the driver in front.
But you still have to have time to act on this information. Take heavy rain as an example: spray means you can't see far, but experience tells you there will be big puddles on the nearside. By keeping the car in front close to the limit of your own vision, you can get the maximum warning of the puddles, and even judge whether they can be driven round or have to be driven through. If you're too close, you'll get no warning at all - no sooner does the car in front encounter the puddle than it's your turn.
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>> the traffic or car ahead of you is a good indicator of
>> what is happening ahead of them
A good and useful indicator. However, you *must* leave enough room to stop (and consider what's behind you as well). Anyone whio doesn't is an idiot.
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I'd agree with you there, FT.
A car hitting deep standing water can stop at a frightening rate. Relying on the 'lead' driver to spot it in time is to court disaster!
I always aim to be able to stop safely within the distance I can see to be clear - not what I assume to be clear.
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>> A good and useful indicator. However, you *must* leave enough room to stop (and consider
>> what's behind you as well). Anyone who doesn't is an idiot.
>>
Agreed FT, it is using all the information available to you to decide what "you" are going to in response to that information. I does not relieve you of any responsibility for your actions.
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one of the other factors is how your dip beam is currently set up.
I see plenty where the lights are pointing down too much - presumably set for fully loaded - with only a few yards illuminated in front of the car.
My dip, when "fully up" gives sufficient visibilty on a flat surface to stop without drama from around 60 mph on a dry surface. (I'd guess around the 200 ft mark)
Main beam is antisocial if I can still see their tail lights.
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I often drive in unlit rural areas, and often find myself behind a car being driven slowly on dipped headlights for no apparent reason. Maybe they dont know how to switch on main beams, (or rear fog lights off).
Last edited by: Old Navy on Fri 10 Dec 10 at 16:44
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Full beam minimum distance? - Mike H
