Captain Jones has indicated that the navigator needs improved technical assistance in avoiding collisions during conditions of inadequate visibility. When the aided eye fails to distinguish the aspect of a vessel until it is much closer than the optimum distance at which a risk of collision ought to be recognized, then visibility is inadequate. For large ships a warning can be required before the distance closes to three miles, for example, whereas a visibility limited to three miles is commonly experienced. However, more guidance on this point is still needed from navigators.