Signals situated on the central reservation apply to all lanes. On very busy stretches, signals may be overhead with a separate signal for each lane.
257. Motorways - Motorway signals
Amber flashing lights. These warn of a hazard ahead. The signal may show a temporary maximum speed limit, lanes that are closed or a message such as'Fog'. Adjust your speed and look out for the danger until you pass a signal which is not flashing or one that gives the'All clear'sign and you are sure it is safe to increase your speed.
258. Motorways - Motorway signals
Red flashing lights. If red lights on the overhead signals flash above your lane and a red'X'is showing, you MUST NOT go beyond the signal in that lane. If red lights flash on a signal in the central reservation or at the side of the road, you MUST NOT go beyond the signal in any lane.