Drivers in the oncoming lane flashing their lights will often warn you of an approaching speed trap.

This forced me to pull out into the oncoming lane — a most disconcerting feeling when you can't see behind you.

Snowplows are dangerous to overtake; often, the oncoming lane may not be completely free of snow.

Passing on the left means that the overtaking vehicle must enter the oncoming lane.

Truck drivers also use flashing headlights to warn drivers in the oncoming lane(s) of a police patrol down the road.