TRAFFIC CONTROL
 
TRAFFIC CONTROL

Jul 1, 2001 12:00 PM
By MICHAEL FICKES

The county positions traffic surveillance cameras at signalized intersections, at highway interchanges, and along the highway, focusing on sites where accidents tend to occur.

It was a Friday afternoon in June when a traffic engineer in the Montgomery County, Md., Transportation Management Center (TMC) noticed the beginning of a traffic backup on Old Georgetown Road, a major surface road connecting Washington, D.C., with the Maryland suburbs to the north.

A network of 1,000 devices called inductive loop detectors embedded in roadways across Montgomery County provided the first indication of a developing problem. The inductive loop detectors sense pressure on the road surface, and a computer system converts that information to numbers of vehicles.

When the detection system sends word of an impending traffic tie-up, a traffic engineer can call up video from one or more surveillance cameras monitoring roadway conditions in the area of possible congestion.

In this case, three cameras could see what had created the trouble: a car accident near the intersection of Old Georgetown Road and Interstate 270, the highway running from the Capital Beltway north. The accident blocked two of four lanes on Old Georgetown Road. In just minutes, cars had begun to pour onto Interstate 270 at the Old Georgetown ramp, threatening to congest the interstate at the beginning of rush hour. In addition, traffic was backed up for two miles on Old Georgetown itself.

Ten years ago, it would have been the beginning of a bad afternoon. In June of 2001, it took a few minutes to solve the problem.

"We adjusted five traffic signals, using controls in the Traffic Management Center," says Michael Kinney, an engineer with the transportation systems management section of the Montgomery county department of public works and transportation. "Within 15 minutes, only one camera showed any back-up, and that was less than a quarter of a mile."

Traffic jams frequently fray the nerves of Montgomery County drivers. According to the Texas Transportation Institute, a group that studies traffic across the United States, the roads running from Washington, D.C., through Montgomery County to Baltimore rank second only to southern California in traffic congestion. No new roads will be built to ameliorate the problem, and the region must rely solely on technology to deal with traffic congestion.

Montgomery County has responded to the problem by creating an advanced traffic management system, one of the most sophisticated in the world. "Visitors from all over the world come here to study our methods of traffic management," Kinney says.

One of the keys to the success of the Montgomery County traffic system lies in its video surveillance capabilities. More than 100 black and white cameras, manufactured by Ultrak Inc., Lewisville, Texas, watch approximately 300 miles of the county's 5,000-mile road network.

The TMC not only watches video, it shares the pictures with the local media and the police and fire departments by way of fiber-optic and coaxial cable connections to remote monitors.

The county began using cameras to watch its roads in the early 1990s. In 1994, county engineers discovered the benefits of modern pan-tilt-zoom domes and switched to Diamond Smart Scan II cameras. In 1995, Ultrak acquired Diamond Electronics and has been providing about 20 cameras a year to the expanding Montgomery County system.

According to Kinney, the county positions traffic surveillance cameras at signalized intersections, at highway interchanges, and along the highway, focusing on sites where accidents tend to occur as well as along the routes where tie-ups tend to build. About half of the cameras are mounted on poles or mast arms supporting traffic signals.

A camera installation includes a cabinet that houses an Ultrak control board containing a power supply, a surge suppressor, a video port that accepts the signal from the camera, and a data port for pan-tilt-zoom control.

Coaxial cable connects the control board to a fiber-optic cable modem made by Optelecom, Gaithersburg, Md. The modem digitizes the analog video signal. The modem stream, with video traveling from the camera and control data traveling to the camera, rides on fiber-optic cable between the cabinet and one of 11 hub sites situated throughout the county. The county uses fiber-optic cable supplied by Chromatic Technologies, Franklin, Mass., and Hitachi Manchester, Manchester, N.H.

"Our hubs are unmanned facilities, usually freestanding precast concrete structures," Kinney says. "The hubs house the transmitters for the fiber-optic system. Each transmitter can terminate up to 16 cameras."

CCOR Comlux, now owned by Force Inc., Christiansburg, Va., manufactured the transmitters as well as the receivers at the other end of the system.

A single-mode fiber-optic cable connects to the TMC, which may require a cable run as long as 10 miles.

While such fiber runs may seem lengthy to security directors who consider 1,500 feet a long distance, 10 miles is a short run for the kind of fiber-optic cable used in the system. "We use single-mode fiber," Kinney says. "This is the kind of fiber that communications companies use for long-distance connections covering miles and miles."

At the TMC, fiber-optic receivers break out the individual signals from the digitized video stream and connect to a matrix switcher.

"Currently we have two switches, each with 64 camera inputs," Kinney says. "They are basically full, because we have a few other video sources in addition to the surveillance cameras."

Kinney is replacing one of those switchers with a MAX-1000 Ultrak matrix switcher with 196 inputs. The county plans to keep the other switcher made by Iris Technologies, Greensburg, Pa. This broadcast television switcher enables the TMC to feed audio reports on traffic conditions through the fiber-optic network to AM radio transmitters.

The switching system sends video to 18 monitors in the TMC. The monitors range in size from 5 to 36 inches.

Monitor suppliers include Mitsubishi Digital Electronics America Inc., Irvine Calif., Panasonic Security Systems Group, Secaucus, N.J., and Sony Electronics Inc., Pine Ridge, N.J.

Currently, TMC system operators call up cameras based on information supplied by the separate inductive loop detection system. "We use the cameras to verify delays and investigate the cause," Kinney says.

The TMC plans to make a software connection between the two systems. Once installed, the inductive loop detectors would notify the CCTV system of a problem and switch video to a designated monitor. According to Kinney, the technical development has been done, and the system will come online as soon as the budget permits.

In addition to developing this alarm capability, the county plans to expand its surveillance range with another 100 cameras in the years to come.

"Cameras make us less reliant on other people telling us what's happening on the street," Kinney says. "When three people pass an accident, they tell three different stories. Thanks to the cameras, we can see where the backups are and how far they extend. That enables us to change the traffic signal timing, which often reduces the delays. There is just nothing better than seeing the situation with your own eyes."
Finding locations for traffic cameras

Like corporate security operations, Montgomery County struggles to find acceptable positions for its exterior cameras. "When we decide we would like to place a camera in a general area, we have to find a view that isn't blocked by trees," says Michael Kinney, an engineer with the Montgomery county department of public works and transportation. "Initially, we installed cameras on 40-foot poles along the side of the road. But this generally forced us back into the trees, most of which are higher than 40 feet."

The county has found two ways around this problem.

The first solution comes from a company called (MG)2 Inc., Birmingham, Ala. (MG)2 provides 70-foot poles that can position cameras far above trees. To facilitate service of cameras positioned so high, the poles offer mounting systems that allow the cameras to be cranked down on a steel cable. "We just crank the camera down to work on it and crank it back up when we're done," Kinney says.

The second solution is an adapted street light device with two arms. Montgomery County adapted the device to clamp onto a traffic signal pole. The arms extend 20 feet and can support a domed camera over an intersection. Kinney has also placed these adapted arms on poles set among trees on the side of the road. The arms jut out of the trees and allow a clear view to the camera.
Preventive maintenance for cameras

Unlike many corporate security directors who often put off maintenance until a camera stops working, Montgomery County has developed a regular preventive maintenance schedule for its cameras. "We try to do maintenance of each of our cameras twice a year," says Michael Kinney, an engineer with the Montgomery county department of public works and transportation.

The preventive maintenance schedule calls for technicians to clean the camera domes and lenses with a commercial product. Next, the technicians inspect the inside of the camera looking for water damage and other obvious problems. They check the heater, to make sure it is working properly. They also test the power supply, surge suppressor, and cable connections. Finally, they change the filter on the fan that vents the equipment cabinet.

"Preventive maintenance is a good technical policy to maintain any electronic equipment used in the field," Kinney says.


 
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