Sentence:  The red cross means no stopping, not even to pick up or set down passengers. The sign is used to indicate a 24-hour <WSD>clearway</WSD> (usually on a rural road) or may be incorporated into other signs with the words “No stopping” (e.g. the “no stopping except local buses” sign at bus stops. On a 24-hour <WSD>clearway</WSD>, the prohibition of stopping applies only to the main carriageway. You may stop in a lay-by unless there are signs to say otherwise. A 24-hour <WSD>clearway</WSD> does not have any special road markings, but there should be smaller repeater signs at approximately one mile intervals. 
Meaning of the word marked with <WSD> tags:  A road or other path that is kept free of obstructions, or on which stopping is strictly regulated, in order to maintain free flow of movement.