I think that's what he meant. But he will have been able to see their headlights from a much greater distance than they will have seen his stoplights. They ran into him, I figure they should have seen his lights far enough away to stop. Personally I wouldn't dream of doing less than the speed limit on a motorway even if it's pitch dark (excluding fog, rain, snow or ice) and I just have my headlights. I frequently drive quite slowly on normal roads though when I can't see very far. I think the calculated risk of hitting something on the motorway is just too low to worry. 1) There are multiple lanes to go across, even if I can't see far enough to stop I can see far enough to safely go round an object. Depends on the traffic - you don't want to sideswipe something as that, or even just a sudden lane change, can cause a loss of control. Even if there is a vehicle alongside that you don't hit, it restricts your chance of getting into another lane. 2) If a motorway is so dark that the above is necessary I can be 99% sure I won't be driving dangerously for other road users. Depends on the situation, as I said previously, if you're following another vehicle, you would probably get an indication from it if there was something on the road - unless it dropped something. If the road is clear, you can probably use high beam. 3) If an accident blocks all lanes then it's going to be big enough to be lit (hazard lights, headlights, stoplights from multiple vehicles) from a long way. Depends how soon after an accident you come across it - often there will be no, or little, lighting initially - a single unbroken taillight can be deceptive and by the time you realise it's stationary, it's probably too late. It could be debris, as I said, or a broken down vehicle with a failed battery - you may pick up the reflection from it's rear reflectors if you're lucky. There are also a lot of other hazards that would not be lit up, like stock and spillages. The risk of all three of those factors failing isn't great enough for me to do 40mph on a motorway.