ABSTRACT
The control of traffic at intersections by lights dates back to 1913 in Cleveland, Ohio, although the current format of three lamps showing red, yellow and green is believed to date back to 1918 in Detroit and New York.1 , 2 In the UK, the first manually operated signals were installed in 1925 in London and the first automatic system was installed in 1926 in Wolverhampton. Since then, traffic signals have become all pervasive, successfully regulating traffic in all major cities round the world.
