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.
You need to know beforehand in which direction you want to travel, e.g. north (N) or south (S).
Where to expect 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.
