How do traffic signals work?
Phase- A phase is a numbered designation used to define the direction of travel. For example, east bound direction of travel is phase 2, south bound phase 4, west bound phase 6, and north bound phase 8. Cycle- A cycle is the length of time designated by an engineer for the completion of all phases. Example: 60 second cycle or 120 second cycle. There are three types of signal operation in Houston: fixed-time, semi-actuated, and fully-activated… Fixed-time operation is a predetermined amount of time is given to all directions or phases of an intersection. There are some cases where the traffic lights can be set to change to different cycle length during peak traffic hours. Fixed-time operations can be found in downtown, where traffic movements are fairly predictable and pedestrian walk lights are automatic. Currently less the hundred are in operation. Semi-actuated operation uses vehicle detection devises to move between signal phases according to the amount of traffic detected. Detector
When installed under conditions that justify its use, a traffic signal, is a valuable device for traffic control. However, an ill-advised or poorly designed signal is not only annoying, but can be dangerous to pedestrians, cyclists and drivers. Therefore, it is essential that, before traffic signals are installed, engineering studies be made by qualified personnel. A traffic signal provides alternate right-of-way for different traffic movements at an intersection. It provides a degree of control that is second only to physical barriers. A good general guide is to use the least traffic control required to provide for the safe and efficient movement of vehicles and pedestrians. Specifications for signals and their placement as well as warrants for their use in the County of Riverside are based on two publications entitled “Manual on Uniform Traffic Control Devices” published by the U.S. Department of Transportation, and the “Traffic Manual” published by the State of California, Business,
