The point, which has been mis-understood by various people is that if it is fully dark, many drivers tend to be that bit more careful, look a bit more, and remember to turn their lights on. When it's half light, lots of people just assume it's the same as full light, and don't take any extra care.

Personally, I think it's six of one and half a dozen of the other. We could do with less idiots on the road either way though