Mobile Probes

A delivery van rumbling toward Green Bay, Wis., could become a new tool for dealing with traffic congestion. So could a car full of students on a road trip from Milwaukee to the University of Wisconsin-Madison.

Lacking the infrastructure to monitor congestion on intercity roads, Wisconsin's Department of Transportation (WisDOT) is launching two projects, using private-industry technology, to test the use of mobile probes for traffic detection. 

One project combines GPS information captured from private fleet vehicles with data from public sources to get updates on the traffic flow. The other uses data from cell phones to calculate similar information. 

In the Milwaukee metropolitan area and other urban regions around the state, WisDOT installed in-pavement detectors to capture traffic data and networks to move that data to WisDOT's Statewide Traffic Operations Center (TOC) in Milwaukee. The TOC uses the information to manage traffic and inform the public about road conditions -- employing changeable message signs to notify drivers and using Highway Advisory Radio and TV station and radio reports. 

In addition, WisDOT deployed approximately 100 video cameras on the Milwaukee freeway system to help monitor traffic and provide TV news images. Video from about 30 of those cameras is also available on the Web. 

"The challenge for us is capturing travel speeds and traffic data in more rural areas," said Dean Beekman, intelligent transportation systems and traffic engineer at the Statewide TOC. 

Enough vehicles travel Interstate 43 and U.S. 41 between Milwaukee and Green Bay, for example, to make it desirable to monitor traffic in that corridor. But that's no simple proposition. 

"It becomes cost-prohibitive, almost, to try to put traffic detectors from here to Green Bay, where we don't have a communications system in place," Beekman said. With no fiber-optic cable installed along that corridor, WisDOT had no easy way to get data from fixed traffic detectors back to the TOC. 

The Smart Dust Network, a system developed by Inrix of Kirkland, Wash., offers an alternative.

AVL Data
Inrix, a Microsoft spinoff, gets its GPS probe data from anonymous motor vehicle fleets, including long- and short-haul trucking companies, taxi and limousine services, utility companies and others. 

Inrix forges agreements with third-party companies that provide fleet owners with automatic vehicle location (AVL) and fleet management systems or, in some cases, makes agreements with fleet operators themselves. 

As the fleet operators or their technology vendors collect data from GPS devices on their vehicles, they share that information -- including latitude and longitude coordinates, vehicle speed and direction -- with Inrix. When traffic data is available from other sources, such as WisDOT's traffic operations center, Inrix adds the information to the mix. 

The company's proprietary software aggregates the data from these sources and processes it to calculate current and future traffic speeds. 

The "dust" in Inrix's Smart Dust Network refers to the numerous data points that go into the calculations, which make up a "dust cloud" of information, according to Inrix.  

Inrix collects data from 250 sources across the United States, said Rick Schuman, the company's public-sector vice president. It offers its customers historical, real-time and predictive traffic speeds for both limited-access highways and surface roads. 

"What this contract with Wisconsin DOT has asked for is real-time data," he said, adding that the contract covers only I-43 and U.S. 41, not the secondary roads in the corridor. 

In the past, Inrix has sold its services to businesses that provide traffic information to end-users via cell phones, portable navigation systems, radio broadcast services and other channels. Inrix just started marketing the service to public entities last summer, Schuman said, and this is its first contract with a government customer. 

Inrix is providing the service to WisDOT through