The Usage Law: When You Must Dip

Equipment law says your lights can dip; the handbook supplies the when, in metres:

Dip within 150 m of an oncoming vehicle.
Dip when following within 60 m.
In rural driving, dip on the approach to curves and hilltops — so you can see oncoming glow before oncoming drivers see your glare — and return to high beam when no lights are visible.
In fog: low beams, never high — high beam reflects off the moisture back into your own eyes.

The defensive half, for when the other driver hasn't read this: look up, beyond, and slightly to the left of oncoming lights, holding your lane by the left road edge rather than surrendering your night vision to their beam.

Key takeaways

Dip within 150 m of oncoming, within 60 m when following, and on rural curves and crests; in fog, low beams only (high beam bounces back at you)
Against others' glare: eyes up, beyond, and slightly left — hold your lane by your own edge, don't surrender your night vision to their beam

Quick check

Night, rural road, high beams on; an oncoming vehicle's lights appear ahead at distance. When must you dip, and what do you do with your eyes as you pass?

A) Dip within 60 m; look straight at their lights to judge distance

B) Dip within 150 m of the oncoming vehicle; as you pass, look up, beyond, and slightly left to protect your night vision and hold your lane by the left edge

C) Dip only if they dip first; look right, toward the centre line

D) Keep high beam so they can see you; look down at your bonnet