Lane ends

TW214

Where: On any road with more than one traffic lane in the direction you are travelling.
Purpose: To warn that the double-lane road you are driving on narrows by a full lane from the left (W215 or TW215) or from the right-hand side (W214 or TW 214).
Action: Depending on which sign is displayed, change in good time to the lane that carries on.

Manual on Road Traffic Signs, page 27.