Traffic Lights |  | | Uploaded by suryachalla 3 years ago.
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A traffic light, also known as traffic signal, stop light, or semaphore, is a signalling device positioned at a road intersection, pedestrian crossing, or other location in order to indicate when it is safe to drive, ride, or walk using a universal color code.
In most countries, the sequence is red (stop), green (go), amber (prepare to stop).
Traffic signals must be instructed when to change phase. Traffic signal phase changes are based on one of three systems: pre-timed, semi-actuated, and fully-actuated. The simplest control system uses a timer in which each phase of the signal lasts for a specific duration before the next phase occurs. This pattern repeats itself regardless of traffic. Many older traffic light installations still use timers. | |
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