Navigation lights for ships were first regulated in the United Kingdom by a statute introduced in 1848 and revised four years later, since when there have been few changes. Originally the regulations referred to oil-burning lamps fitted to vessels rarely in excess of 400 tons and rarely sailing much above 10 knots. The sheer increase in average size and in speed of typical modern ships, particularly marked over the last four decades, raises the question as to how effective the regulation lights actually are in practice. This question is made more pertinent in view of the other great change in ships, namely their general arrangement: the superstructure may be forward, midships or astern, masts and derricks vary in number, complexity and size. Although the regulations for the positioning of lights are reasonably comprehensive they inevitably leave considerable freedom to the designer because of the variety of superstructure configurations.