Junctions and dual carriageways
Dual carriageways are roads with two or more lanes of traffic travelling in each direction. The outer or right-hand lane in each direction is the lane nearest to the centre of the dual carriageway.
You must normally drive in the left-hand lane of a dual carriageway. You may use the outer lane of a two-lane or three-lane dual carriageway only: for overtaking; and when intending to turn right a short distance ahead.
Turning left onto a dual carriageway
Drive as close as you safely can to the left-hand edge of the approach road.
Watch for oncoming traffic.
Take the turn when it is safe to do so.
Keep to the left-hand lane on the dual carriageway and build up your
speed to that of the normal flow of traffic, subject to the speed limits and road conditions.