A British light emitting diode(LED)traffic light(Siemens Helios)in Portsmouth,United Kingdom
Traffic lights,which may also be known as stoplights,traffic lamps.traffc signals,stop-and-go lights,robots or semaphore,are signaling devices positioned at road intersections,pedestrian crossings and other locations to control competing flows of traffic.Traffic lights have been installed in most cities around the world.They assign the right of way to road users by the use of lights in standard colours(Red-Amber-Green),using a universal colour code(and a precise sequence,for those who are colour blind).The most common traffic lights consist a set of three lights:red,yellow and green.When illuminated,the red light indicates for vehicles facing the light to stop;the amber indicates caution,either because light are about to turn green or because lights are about to turn red(depending on the region of the world you are in);and the green light to proceed(if it is safe to do so).There are some variations in the use and legislation of traffic lights,depending on the customs of a country and the special needs of a particular intersection.There may,for example,be special lights for pedestrians,bicycles,buses,trams,etc.and there may be special rules or sets of lights for traffic turning in a particular direction.Complex intersections may use any combinations of these.
