On a United Kingdom motorway, what does a red X above a lane mean?

On a United Kingdom motorway, a red X above a lane means the lane is closed.

The red X is displayed on an overhead signal, often as part of a motorway control system. Drivers must leave that lane safely at the earliest opportunity and must not continue beneath the symbol. The signal can be used for incidents, roadworks, debris, emergency access, or other hazards.

A red X differs from a temporary speed-limit display. Variable speed limits are commonly shown with a circular speed sign, while lane-control signals manage whether a particular lane may be used. The warning may be accompanied by signs, message boards, or traffic officers.

The rule matters because a closed lane may contain an obstruction or provide a protected route for emergency services. Drivers should check mirrors, signal, and move only when safe; they should never cross solid lane markings or create a new danger while responding to the signal.