What does this motorway sign mean?

Explanation: Look out for signs above your lane or on the central reservation. These will give you important information or warnings about the road ahead. To allow for the high speed of motorway traffic, these signs may light up some distance from any hazard. Don't ignore the signs just because the road looks clear to you.

Category: Road and traffic signs

References: The Official DVSA Guide to Driving: Section 6, Highway Code: Page 102, Know Your Traffic Signs: Page 91