City keeps an eye on traffic with video technology
Last fall, Chandler, Ariz., opened a new traffic management center that is equipped with computer, communications and display technology that helps the city monitor traffic conditions. Through the use of the technology, the city plans to cut commute times by 10 percent.
Immediately southeast of Phoenix, Chandler is a 70-square-mile city with 743 miles of streets and 125 intersections. In recent years, the city has seen an increase in both population and traffic congestion.
The city’s previous traffic management center, which was housed in the city’s maintenance building, used loop detectors in the pavement and 10-year-old traffic signal software to monitor the congestion. However, the technology was not keeping up with the demands of the engineers who worked to reduce traffic.
To improve its ability to monitor congestion and to adjust signal timing, the city upgraded its traffic signal software, installed cameras at 12 major intersections and contracted with Phoenix-based Audio Video Resources to construct a wall of large-scale video displays. The center employees wanted to be able to see everything from the status of a single traffic signal to live video depicting the number of vehicles traveling along a 20-block stretch of a major arterial.
The company installed six display units by Wilsonville, Ore.-based Clarity Visual Systems, a video wall processor by San Leandro, Calif.-based Jupiter Systems and a matrix switcher from Richardson, Texas-based AMX. The processor controls what is shown on the display screens, and the switcher controls the video wall itself as well as all of its information sources. The displays are 52-inch, rear-projection units designed for digital wall applications.
Located on the second floor of the city’s public works building, the new traffic management center occupies a 20-foot-by-20-foot room. The data wall measures 12 feet wide by 6 feet high, and the displays sit on a pedestal, which can be adjusted up or down. In front of the displays, traffic engineers man a two-pod monitoring station, containing PC and AMX system screens.
The data wall shows a variety of digital and video images from intersections with cameras and nearby freeways. It also shows traffic signal status information, including the number of vehicles that have made turns in particular intersections and when signals have been switched to allow fire trucks to pass through.
Typically, center engineers monitor nearly 20 images simultaneously. Those include feeds from still cameras; full-motion cameras with pan, tilt and zoom capability; and local and cable television stations. Alternatively, they can call up a full-wall image that shows 20 intersections and tracks up to 100 vehicles. “I can see what speeds are, how many lights cars are catching and where a problem is developing,” says Benjamin McCawley, traffic analyst. “And because I’m looking at it all in real time, I can make signal changes that will quickly relieve a backup or keep one from happening.”
Using information on the data wall, engineers can conduct traffic signal simulations, which means they can make a traffic signal change to see how it affects the entire system. “Previously, we could only do this by putting people out in the field, who relayed traffic status information in by radio, and then we could only view it on a 21-inch monitor,” McCawley says. “Now, even if we just assign it to one display cube, the 52-inch image gives us a much better picture of what’s going on.”
The city plans to install 36 more cameras at intersections this year, and it plans to share its traffic information with surrounding cities, and county and state agencies. “We’re working on getting all of these images on to a server so people can look at them on an intranet, and then down the road onto the Internet,” McCawley says.
