Map-type advance trail blazer

Where you'll see it

On the left-hand side of any road where two routes join the numbered route by means of a set of one-way carriageways

What it means

To indicate that a route of equal or higher status can be entered from the road on which you are travelling. This new route consists of a pair of one-way roadways

What you must do

You need to know before hand in which direction you want to travel, e.g. North(N) or South(S)

Source: Signs manual GE11