While 2, 4, 8, 16, or however many cars are waiting for a light to change on a minor street, 16, 32, 64, or more cars might move along the major street. Signals are usually programmed so that each intersection is "timed" to work with other intersections. When traffic in opposing directions is light, a couple of minutes' waiting can certainly seem like ten! Traffic engineers attempt to move the greatest volume of traffic in the shortest amount of time. A full cycle at a given intersection might take several minutes. Consider left turns, straight traffic, and yellow signal timing for each direction. Each direction might get 60 seconds (or more) of GREEN time. Major streets come together at some intersections. While waiting for the light to change on a side street, remember that most traffic is moving on main streets. This new video-based system uses the same size zones as the signal loops. When the background changes due to a vehicle's pulling into the detection zone, a signal is sent to the traffic signal controller, which causes the light to change eventually. We are also deploying a relatively new technology, video detection, in which detection zones are drawn on the background of the static video of an approach to an intersection. Your browser does not support the video tag. They start at the stop bar on each approach as depicted in purple in the above drawing. Typically, left turn loops are 60 feet long and those in through lanes are 20 feet long. Where is the detection zone? Vehicle sensors are "loops" of wire embedded in the pavement. Law requires that the bumper or most forward part of the vehicle be behind the stop bar. Vehicles with a RED light (such as the one just above the crosswalk in the diagram) are usually permitted to turn "right on red." However, vehicle traffic must always yield to pedestrians! Here in Tallahassee. Vehicles with a GREEN light (such as those at the left and right sides of the intersection) might turn left or right into the crosswalk. As seen in the diagram at the right, with the crosswalk shown at the top of the intersection, cars may turn into a crosswalk from three directions, even though pedestrians have the right-of-way. ![]() While WALK is on for pedestrians, vehicle traffic also may have a green light. ![]() Planning, Blueprint, Minority Business, Economic VitalityĪbout Traffic Lights First, remember: You're sharing the road with pedestrians.
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