About this Article
Written by: Bin Choi
Written on: April 30th, 2010
Tags: transportation, electrical engineering
Thumbnail by: Takeaway/Wikimedia Commons
About the Author
In 2010, Bin Choi was a 3rd year student at the University of Southern California, majoring in Public Policy, Management, and Planning with a concentration in Urban Planning.
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Volume XII Issue III > Traffic-Actuated Signals
Urban sprawl and a lack of public transportation infrastructure have led to ever increasing traffic congestion, as people commute to most of their daily activities. Traffic-actuated signals have been created to alleviate this problem by efficiently managing traffic flow. The system is capable of detecting live traffic data and assigning the appropriate light cycle (for instance, turning on green lights at a desired time). The system is composed of a detector and a controller. A detector collects live traffic data, which the controller uses to decide the traffic light cycle that drivers will respond to. With regularly scheduled maintenance, this system should be able to run for many years with no problems. Traffic-actuated signals can improve traffic congestion by responding to road conditions as problems occur.


Takeaway/Wikimedia Commons
Figure 1: Traffic congestion has become an issue for every major city.
The United States has evolved into a society of commuters due to the rate of urban sprawl or city development. Many residents have to drive every day to work or school, and getting stuck in traffic is a frustratingly common experience for most. A bigger concern may be the fact that major cities do not have public transportation systems that cover the large suburban area, forcing people to rely more heavily on their automobiles. As a result, the high usage of automobiles and other vehicles on the road causes daily traffic congestion and delays.
Traffic congestion is created by a large number of vehicles on the road at the same time. When a road reaches its maximum vehicle capacity, traffic flows inefficiently. Traffic engineers have concluded that while a reduction in the number of automobiles would alleviate the problem in the long-term, a more efficient short-term solution is necessary. Therefore, engineers have developed, implemented, and perfected a new system that operates traffic signals. These traffic-actuated control systems adapt to the volume of traffic and provide the most efficient cycle of green lights as well as adequate cycle duration.

Purpose of Traffic Signals

Initially, traffic signals were created to prevent car accidents by assigning the right of way to vehicles headed in different directions. Over time, signals were also used to provide safety for pedestrians and bicyclists. However, the number of pedestrians has decreased while the number of vehicles has increased, resulting in busy streets and highways. Thus, the purpose of traffic lights has evolved to manage the flow of vehicle traffic in an efficient manner in order to alleviate congestion, while still continuing to provide safety for pedestrians and bicyclists [3].