Traffic lights, traffic signals, stoplights or robots (as they are known in South Africa) are signalling devices positioned at road intersections, pedestrian crossings, and other locations to control flows of traffic. The world's first traffic light was a manually operated gas-lit signal installed in London in December 1868. It exploded less than a month after it was implemented, injuring its policeman operator. Earnest Sirrine from Chicago patented the first automated traffic control system in 1910. It used the words 'STOP' and 'PROCEED', although neither word was illuminated. Traffic lights follow a universal colour code which alternates the right of way accorded to users with a sequence of illuminating lamps or LEDs of three standard colours:Green lightAllows traffic to proceed in the direction denoted, if it is safe to do so and there is room on the other side of the intersection. Red lightProhibits any traffic from proceeding. A flashing red indication requires traffic to stop and then proceed when safe (equivalent to a stop sign). Amber light (also known as 'orange light' or 'yellow light')Warns that the signal is about to change to red, with some jurisdictions requiring drivers to stop if it is safe to do so, and others allowing drivers to go through the intersection if safe to do so. In some European countries (such as the UK), red and amber is displayed together, indicating that the signal is about to change to green. A flashing amber indication is a warning signal. In the United Kingdom and Ireland, a flashing amber light is used only at pelican crossings, in place of the combined redamber signal, and indicates that drivers may pass if no pedestrians are on the crossing.