sTraffic lights, also known as traffic signals, traffic lamps, signal lights, robots in South Africa and, in the past, semaphores, are signalling devices positioned at road intersections, pedestrian crossings and other locations to control competing flows of traffic. Traffic lights were first installed in 1868 in London and are now used all over the world. Traffic lights alternate the right of way accorded to road users by displaying lights of a standard color (red, yellow/amber, and green) following a universal color code. In the typical sequence of color phases: * the green light allows traffic to proceed in the direction denoted, if it is safe to do so * the yellow/amber light denoting prepare to stop short of the intersection, if it is safe to do so * the red signal prohibits any traffic from proceeding
Failure to obey traffic lights is a crime everywhere.
The simplest traffic light comprises either a single or a pair of colored aspects that warns any user of the shared right of way of a possible conflict or danger. Dual aspects
These are often seen at railway crossings and at intersections of streets. They flash yellow when cross traffic is not expected, and turn red to stop traffic when cross traffic occurs. They are also used on ramp metering, where motorists enter a freeway in heavy traffic. Only one driver per lane goes per green. Three or more aspects
The standard is the red light above the green, with yellow between. (And railroad signals are intentionally the opposite: with green on top and red on the bottom so that the two types can't be confused.) When sideways, the arrangement depends on the rule of the road. In right-lane countries, the green light is on the right, and in left-lane countries, the left. Sounds
In some jurisdictions such as Australia and Ireland pedestrian lights are associated with a sound device, for the benefit of blind and visually impaired pedestrians. These make a slow beeping sound when the pedestrian lights are red and a continuous buzzing sound when the lights are green. In the Australian territories of New South Wales, Victoria and Western Australia, the sound is produced in the same unit as the push buttons. This system ofassistive technology is also widely used at busy intersections in Canadian cities. Australia
In Australia, the light sequence is:
* Green man: Cross the intersection
* Flashing red man: Finish crossing
* Red man: Do not cross
Some traffic lights in Melbourne have countdown timers for pedestrian crossing lights, usually they countdown from 30 when the red flashing man appears. This however was a trial and was removed as it resulted in large amounts of jaywalking. Some traffic-light controlled junctions have a light sequence that stops all vehicular traffic at the junction at the same time, and gives pedestrians exclusive access to the intersection so that they can cross in any direction (including diagonally). This is known as a pedestrian scramble in some places. European Standard
The European approach to a signalized crossing is use dual or more rarely, a triple aspect with a blackened out lens of a Pictogram pedestrian. For cyclist, the same approach is used with the lens blackened out for a bicycle frame. It is not uncommon to see lenses with both symbols on them. Most of European countries use orange instead of yellow for the middle light. The light sequence is:
* Green: Cross.
* Yellow/Orange: Continue to cross only if unable to stop safely. * Flashing Yellow/Orange: Cross with caution (usually used when lights are out of order or shut down). * Red: Do not cross.
In Germany, a combination of Red and Orange lights is used just before to switch back to Green. It allows drivers to stop their engine during the red light. The light sequence is as follows: * Green: Cross.
* Orange: Continue to...
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