A Recent Admiralty Notice to Mariners (No. 1555/1968) advises that a vessel trading the southern North Sea and the English Channel has been fitted with experimental direction indication lights in order to indicate to an approaching vessel the direction in which she is altering course and the duration of the alteration. The positioning of these lights are 10·5 ft. higher than the after masthead light and 4 ft. outboard on each side of the centre line, and they are coloured red to port and green to starboard. When altering course the appropriate light flashes until the vessel is steadied up on her new course.