The Technology Behind Stop And Go On The Streets
Green, Yellow, And Red Technology
When we drive down a city street and approach a traffic signal, we rarely think of what it takes to make this signal operate efficiently. We usually consider it an inconvenience when we are stopped by a signal, and only consider the safety factor when we are involved in, or witness an accident at a signaled intersection. Let me say that traffic control, which includes more that signal lights; but includes stop, and yield signs, detour signs, speed limit signs, and various types of warning signs, plus much more; are put in place to allow traffic to flow as smooth as possible; and not to impede traffic.
When a car pulls up to the stop bar at an intersection and waits for a red light to change to a green light, little thought is given to the technological circuit involved in making that seemingly simple change occur. Involved in that action is a computer connection that allows a camera over head to alert a software connection that there is a vehicle in that focus area, or lane, after which the software realizing that either there is no other vehicle in the cross lane, or the time has expired for green in the cross lane, and thus gives a green light in the direction of the vehicle that pulled up to the stop bar. The time frame involved here may seem as if it takes minutes, but we are dealing with seconds. The time a traffic light stays on green and red may vary depending on the time of day, and the traffic volume; but the time it takes a traffic signal light to go from yellow to red is only 4 to 7 seconds.
The following items can clearly be seen at a signalized intersection; a traffic signal head in each direction, a span wire or mask arm on which the traffic heads are attached; two traffic signal poles located diagonally, or on each corner of the intersection,a traffic control cabinet located on a corner of the intersection, and a wire attached to the cabinet that gives electrical power to the entire signalized part of the intersection. What one does not see at that signalized intersection is; the underground wiring that allows that signal light to be synchronized with the other signals in that grid; the computer inside that traffic control cabinet; the software loaded on that computer that allows it to do vehicle detection, timed cycling, traffic monitoring. and communicate with a master program located miles away in a traffic management center.
This technology is world wide. There is an international organization called the International Municipal Signal Association that certify technicians that work in this field of technology. The standards that they use are the same in North America as they are in South America; they are the same in Europe as they are in Israel, and other Middle Eastern Nations. Therefore when we see a traffic signal malfunctioning, let us realize it is not just a problem with the signal head, but a computer problem, unless it happens to be a blown out bulb.