The INDOT Intelligent Highway System Web interface
When it comes to traffic gridlock, Indiana is not the first state to come to mind.
by James Careless
"OK, so we do have relatively low congestion compared to other jurisdictions, but there are some areas on our interstates that really back up," said Indiana Department of Transportation spokesman Will Wingfield. "In particular, the I-80/I-94 from Gary to Chicago, on the south shore of Lake Michigan, acts as a funnel into the Windy City. Traffic can become very heavy there, and on the I-65, I-69 and I-465 in Indianapolis. These are the two areas we have to keep a close eye on."
To do this effectively, INDOT has deployed an Intelligent Highway System (ITS). This is an integrated network of pan/tilt/zoom video cameras, highway speed sensors and programmable electronic signs.
ITS IN ACTION
INDOT's ITS has remote-controlled pan/tilt/zoom cameras (various makes and models) and traffic sensors deployed along 190 miles of state highway. The cameras are spaced anywhere from a half-mile to a mile apart, depending on the obstacles within their field of view. The road sensors are embedded at various distances, based on perceived congestion and available money, to provide a comprehensive picture of traffic flow.
The data collected by these systems is analyzed by Traffic Management Centers (TMCs) in Gary and Indianapolis. INDOT staff use this real-time data to detect trouble, send help, and redirect traffic on the fly to clearer routes. Redirection information is sent to programmable electronic overhead signs mounted over the highways.
From one desk, dispatchers have access to traffic cameras, dynamic message signs and the Hoosier Helpers freeway service patrol. INDOT's live camera feeds and traffic flow data are made available to public safety organizations, news departments and the general populace online at Web pages dedicated to the northwest part of the state and the Indianapolis area. Both sites feature interactive "zoomable" maps that access camera feeds in real-time, data on actual traffic speeds, "active incidents" (accidents), detour routes, road closures and local access restrictions. Trouble spots are highlighted using pulsing pink squares; mouse over one of them and the site tells you precisely what is happening there.
"All lanes of eastbound I-80/94 are moving very slowly near Grant St. due to heavy traffic," said one recent warning from the northwest Indiana region. "Expect delays as you travel eastbound on I-80/94 near mile 8.5."
Clearly, the INDOT ITS is very capable. But it does have a weakness: The original ITS network relies solely on fiber-optic links and licensed microwave radios to backhaul the video and traffic data back to Gary and Indianapolis.
Unfortunately, this system was not very adaptive either for quick deployments to new trouble spots or repairs to existing equipment that had been damaged; for instance, a truck that burned underneath an overpass destroyed a local camera position. As well, fiber-optic cable is expensive and slow to deploy. The same is true for licensed microwave connections, due to equipment fees and authorizations.
The 600 solar-powered vehicle detection cabinets don't attract too much attention. This is why INDOT decided to use unlicensed WiMAX microwave to connect new ITS cameras and traffic sensors a few years ago. The wireless technology it selected was made by Proxim Wireless Corp. of Milpitas, Calif. Proxim has supplied similar WiMAX products to the California Department of Transportation (CALTRANS).
THE WIMAX SOLUTION
WiMAX (Worldwide Interoperability for Microwave Access) is a broadband microwave radio standard that supports data transmission at rates up to 30 Mbps. Basically, WiMAX is WiFi, but without the 300-foot distance limits that hamper WiFi for outdoor use.
WiMAX can be transmitted as radio signals in either the licensed or unlicensed bands. "Operating in a licensed band requires gaining FCC approval—a potentially expensive and time-consuming process—but provides the user with exclusive use of the assigned spectrum," says Robb Henshaw, Proxim Wireless' vice president of Marketing and Channels. "Using the unlicensed bands avoids the FCC approval process, but runs the risk of interference from other unlicensed users accessing the same space."
In INDOT's case, using the unlicensed bands made the most sense. "We wanted to be able to set up cameras in places where construction is underway, to expand our coverage in areas where congestion is starting to be a problem, and to replace cameras and sensors that have been damaged," Wingfield says. "We also wanted to avoid the time and expense associated with the licensed band."
INDOT has deployed some 600 solar-powered Proxim Tsunami MP.11 5054 unlicensed radios, all operating in the 5 GHz frequency range. They pump out video and data readings in real-time, with no need for external electrical or communications wiring. The data is picked up by ITS TMC receivers and radios mounted on programmable message signs. The system can even be set to automatically update the traffic signs with changes in traffic flow speed as it happens, without direct human intervention.
"WiMAX has saved us millions of dollars in network deployment costs," says Wingfield. "But the great part is the speed with which we can deploy new equipment as needed. This keeps our ITS current and up-to-date. It also motivates people to check our feeds before they leave home, thus enlisting their help in improving traffic patterns."
As for security concerns? It is possible to encrypt the video and data feeds on the ITS WiMAX network, but why bother? "The more eyeballs we get on our information, the better t e roads will run," Wingfield says. "So if people want to look at our feeds—assuming they have to equipment to do so—that's okay with us." Meanwhile, Proxim's equipment automatically searches for the most interference-free frequencies to use, switching channels when required by other traffic.