Final answer:
The 'Merge ahead' sign is used to notify drivers about an upcoming reduction in the number of traffic lanes, instructing them to merge safely.
Step-by-step explanation:
The sign that provides advance notice of a reduction in the number of lanes of pavement ahead is known as the Merge ahead sign. This sign alerts drivers that they should be prepared to merge with traffic in the lane next to them due to their current lane ending soon. It is critical for safety as it helps manage the flow of traffic and prevents congestion and accidents that may occur when lanes are reduced unexpectedly.