What does this sign mean?

Explanation: You should change lanes as directed by the sign. Here, the right-hand lane is closed but the left-hand and centre lanes are available. Merging in turn is recommended when it's safe and traffic is going slowly; for example, at roadworks or a road traffic incident. When vehicles are travelling at speed, this isn't advisable and you should move into the appropriate lane in good time.

Category: Road and traffic signs

References: The Official DVSA Guide to Driving: Section 6, Highway Code: Page 102, Know Your Traffic Signs: Page 90