Road narrows on right

This warning sign means the road ahead narrows on the right, or on the left if the symbol is reversed. Slow down, check your mirrors and be ready to move over or give way to oncoming traffic where there is no longer room for two vehicles side by side.

Official Highway Code caption: “Road narrows on right (left if symbol reversed).”

Listed under “Mostly triangular” in The Highway Code: traffic signs (GOV.UK). For every sign in more detail, see the Department for Transport’s Know your traffic signs.