How Intelligent Highways Will Work

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.

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.

You are in a shrinking minority of the American population if you don't own at least one electronic communications device. There are more than 119 million cell-phone users in the United States as of July 2001. Each day, thousands more sign up. Millions more have two-way pagers. The radio signals emitted from these devices can reveal our location at anytime. This ability to locate cell-phone users will become a vital component of future traffic-management systems.

On a short stretch of highway in Calgary, Alberta, Cell-Loc is testing out its new cell-phone tracking technology. In July 2001, the company sent a known vehicle down a 1.25-mile (2-kilometer) section of a major highway, through the heart of the town, to test the accuracy of its system. The truck carried a GPS receiver onboard to compare the system's accuracy.

"We collected data from both the GPS receiver in the vehicle, and from our system that was monitoring the cell phone remotely, and we compared the two and found them to be, not identical, but close enough for our applications we're talking about," Andrew Hillson, Cell-Loc's director of service technology, said.

Here's how the Cellocate system will work, according to Hillson and company documents:

"Hyperbolic multilateration" is just a fancy way of saying triangulation, Hillson said. A position is determined by locating the intersection of the hyperbolas from the radio waves detected by the listening posts. By analyzing how long it takes the radio wave to reach the listening post from the cell phone, a computer can calculate almost precisely where someone is located on the highway. If the person's location on the map is shown as off the highway, the computer corrects for this and snaps the location to the road. The entire process of detecting a person's position occurs in seconds.

Hillson said that Cellocate meets the FCC's mandate and is accurate within 330 feet (100 meters) 67 percent of the time. Within 990 feet (300 meters), the system is accurate 95 percent of the time. It supports AMPS (Advanced Mobile Phone System) and CDMA (Code Division Multiple Access) air interfaces. Cell-Loc is pursuing partnerships with cell-phone service providers. The service, which would allow cell-phone users to receive instant, personalized traffic warnings, will likely be available in a year or two and cost about $4 or $5 per month.

To supplement cell-phone tracking systems like Cellocate, transportation agencies are also installing additional electronic toll tag readers along major highways. In some cities where toll booths are common, radio-frequency tags are attached to cars. As cars pass the reader, it detects the tag and subtracts a set amount of money from a prepaid account. (See How E-ZPass Works for information on this type of system.)

These radio tags, or transponders, can be used to time vehicles between points in a freeway system. Unlike with a toll booth, drivers would not have to slow down for the reading device. They would merely drive past it. By analyzing a particular car's time between two points, a computer can determine the car's location and speed.

These tags and the cell-phone tracking systems will make it almost impossible for someone to travel undetected, which has raised privacy concerns about this new technology. Cell-Loc has said that it would not sell information about motorists' locations to advertisers. Other companies have said that they are considering selling the information.

Once information is detected from cell phones, it has to be disseminated to motorists. In order for drivers to be routed around traffic, they must be informed of how fast the traffic is flowing, if it's clogged or if there is an incident blocking traffic altogether. This is where the cell-phone service provider comes into the picture. The provider would send this information out to customers.

There are three ways to transmit information to motorists:

By getting information to the customers more quickly, developers believe that commuters will have enough time to react to these warnings and find another way around the congested areas. This would be an advance compared to how information is released today, which is primarily through radio or television news reports. By the time the radio and TV report an incident, it's typically too late for most commuters to act on the information.

Cell phones and other digital devices are as commonplace as cars, so why not combine the two to solve the problem of congested highways? In the next few years, we will learn for ourselves whether these new technologies will make our commute to work easier or if our only hope is to find a way to stay home.

For more information on intelligent highways and related topics, check out the links on the next page.