TWR, much as it may surprise you, I've driven for a living for many years and the simple answer to the question you probably meant to ask is... you stay well back from what's in front of you and you always look as far ahead of you as you can see
seeing brake lights come on several miles ahead should be a warning to anyone, but in the spirit of the question, far too many people don't look that far ahead and realise it will mean they'll have to brake soon.
Now this is really annoying me! I've just paid £4 to use the M6 toll road and I didn't see anything unforeseen! I saw lots of things which i expected to see but that's no fun, is it?
I was going to write to my MP but, since I've recently become an anarchist (and, by recent, I mean in the last thirty seconds) I'm going to write to the lead singer of Echo and the Bunnymen...
From some of the answers thats been put on I gather a lot of you do not drive at night? have you never come across animals, cars with no lights broken down, retreads off HGVs, Timber, Wheels that have come off HGVS, Flat bed Trailer sheets, Loading straps & restrainers. these are the types of things you DO NOT SEE AT NIGHT UNTILL YOU HIT THEM.