Mobile Probes

Wisconsin tries private vehicles and cell phones to monitor traffic.

by / May 31, 2007
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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

the subcontractor, Short Elliott Hendrickson in St. Paul, Minn.  

Of the approximately 90 markets where the Smart Dust Network currently operates, Schuman said it blends data from GPS probes with data from government-owned sensors in only about 20. 

"We'd like to get it from more [government sources]," he said. "Some places don't have it; some places it's not easy to get to; some places may not have high enough quality, even if they have it and make it available." 


Cell Phone Probes
In a second project, WisDOT is working with AirSage, a developer of traffic-detection technology based in Atlanta. AirSage uses cell phones in moving vehicles as traffic probes. Through agreements with wireless carriers, it collects and aggregates anonymous data from cell phones as they move along roadways. Its software uses this data to calculate traffic speeds and travel times. 

WisDOT will use the AirSage system to monitor traffic on I-94 between Milwaukee and Madison, Beekman said, explaining that the project is similar in aim to the project in the Milwaukee-Green Bay corridor, but uses a different methodology. 

The systems are expected to start operating in late summer and keep running for two years, Beekman said. 

While WisDOT uses the data in its operations, researchers at the Wisconsin Traffic Operations and Safety Lab at the University of Wisconsin-Madison will study how well the two systems work and whether WisDOT can integrate the data effectively into its traffic management activities. One test will compare traffic data obtained by Inrix and AirSage with data from other sources. 

Those sources include the WisDOT's existing in-pavement traffic sensors and some radar-based detectors that researchers can consult as needed. 

"We have autonomous devices that run on solar power and have wireless communications," said Todd Szymkowski, the lab's program manager. 

The lab will also send drivers out in GPS-equipped cars to measure their own travel speeds to compare the speeds that the two systems calculate, Szymkowski said. In addition, researchers will evaluate the methods the systems use to detect traffic incidents. 

"The Dust Network compares current speeds with historical speeds, and when it sees a large variation in what's expected, it trips an alarm," said Szymkowski, adding that AirSage monitors calls to 911 and creates an alarm when it detects a spike. "We're probably going to be working with the Wisconsin State Patrol to understand when an incident occurred and see if we can match up the alarms with the real incidents." 

WisDOT is not the only government organization turning to the private sector to supplement the traffic data it collects, said Neil Schuster, president and CEO of the Intelligent Transportation Society of America in Washington, D.C. 

Commercial vendors of traffic information are also seeking data from DOTs that can be incorporated into commercial services. 

"We're seeing more and more innovation in how you can collect data," Schuster said, "because it is available, and rapidly becoming available, from a variety of sources."

Merrill Douglas Contributing Writer