Vehicles may not pass the temporary traffic signals when the red light is shown

The board that marks where to stop at temporary signals. At road works there is usually no stop line painted on the road, so this sign marks the point instead: when the portable signals show red you MUST NOT go past this board - wait at it, not beyond it. The red often holds far longer than you'd expect because it's protecting a long single-lane stretch, so sit and wait. Never edge past or follow the car ahead through.