There is an increasing interest in crossing situations. This has been stimulated by the success of traffic separation schemes to generally reduce the level of risk of collision from ships approaching in opposing directions. There have recently been crossing collisions in the Dover Strait which have occurred during conditions of poor visibility. These might have been avoided if the officers in charge of the vessels had allowed more time to manoeuvre. They bear witness to the fact that, in fog, a vessel can travel a considerable distance before its course alteration is detected on another ship's radar and appropriate collision-avoidance action taken by that other vessel.