What should you do?
Switch on dipped headlights, remove sunglasses, keep a safe gap and follow any lane or speed signs inside the tunnel.
How to recognise it
Yellow diamond with a black arched tunnel entrance outlined in stonework.
Common confusion
It warns of a tunnel, not a low bridge; look for a separate safe height plate if headroom is limited.
Explanation written by the My Driving Test editorial team using the Department of Transport Traffic Signs Manual conventions and the RSA Rules of the Road.
