Dipped headlights

Dipped headlights are the default whenever it is dark or visibility is poor. They are also worth using in dull daytime conditions — not because you cannot see, but because they make you visible to everyone else, which is the half of the problem drivers tend to forget.

Main beam throws light much further, and you use it on unlit roads when there is nobody to dazzle. The moment there is — oncoming traffic, or a vehicle you are following — you dip. On a left-hand bend an oncoming driver can be dazzled before you see them, so dip early rather than at the last moment.

If someone coming the other way fails to dip, the advice is to slow down and look towards the nearside edge of the road rather than into the lights, and not to retaliate by flicking yours to main beam. Two dazzled drivers is worse than one.