Tracking cell phone signals could be a way to reduce highway congestion.

Current Traffic Tracking

The next time you are driving to work, take a minute to look at the technology in place to keep traffic flowing. Over the past two decades, state departments of transportation have installed billions of dollars' worth of electronics to keep an eye on and manage traffic.

Here are the three basic devices used in managing traffic today:

Loop detectors are wires embedded in the road that detect small changes in electrical voltage caused by a passing vehicle. Traffic speed can be determined by detecting how quickly cars pass between two sets of loop detectors. Volume and speed data is transmitted to a central computer, which is monitored by local transportation departments.

Notice the loop detectors placed in the road. As cars pass over the loops, the detectors are able to detect speed and movement.

Photo courtesy Arizona Department of Transportation

If the detectors sense a slowdown or an increased quantity in traffic, workers can use video cameras to get a better understanding of what's causing it. Meanwhile, messages can be displayed on electronic signs to warn motorists of congestion ahead and to advise of alternate routes.

"The traditional loops in the road and cameras up on poles and guys sitting behind desks looking at monitors is too expensive to extend as far as people would like," Marshall said. Installing these detectors, cameras and signs has been a long process to complete, and is costing billions of dollars for state and federal governments to implement. Transportation officials are now searching for cheaper alternatives for managing traffic.

In the next section, we will learn how a new traffic-management system will utilize communication devices already in place to ease traffic flow.