By Dan Friedell
A public high-speed wireless mesh network helped traffic engineers in Tennessee gain remote control over 200 signals as Volkswagen and Amazon set up shop in their city.
February 11, 2014—When a 7,000-acre parcel of land north of Chattanooga that housed a World War II-era dynamite plant—dormant since the end of the Vietnam War—was earmarked for development a decade ago, city traffic engineers knew they had to consider advanced solutions to manage the coming traffic boom and encourage efficient travel through the southern part of Tennessee.
Roads leading to new employment centers in Chattanooga have become crowded, especially during employee shift changes. So the city recently implemented an innovative wireless communications system that makes use of high-speed fiber-optic Internet capabilities to help traffic engineers control more than half of the city’s 360 traffic signals. City of Chattanooga
As both Volkswagen of America's Passat assembly plant and an Amazon fulfillment center opened in 2011, the former Volunteer Army Ammunition Plant, which had mostly been turned into parkland and hiking trails, was overrun by as many as 7,000 employees during the busiest days of the year. Traffic on the roads leading to the new employment centers—Bonny Oaks Drive and Volkswagen Drive, adjacent to Interstate 75—made for crowded commutes, especially during shift changes. More than 18,000 vehicles hit the roads each day in 2012.
New highway interchanges were built and roads were widened in anticipation of the development, but city traffic engineer John Van Winkle, P.E., and his team knew that the efforts to manage this explosive growth could not stop there. The city lacks a ring road, forcing traffic to flow through the center of the city, and Chattanooga is located in the heart of the busiest truck corridor in the United States. The plans by Volkswagen and Amazon meant time was at a premium.
So when Chattanooga's power company, EPB, launched a regionwide high-speed fiber-optic network program in 2009, the engineers took advantage of the newfound bandwidth to upgrade a traffic management system that had previously relied on phone lines and twisted pairs of wires. Instead of burying cable throughout the city as other municipalities have done to gain control over traffic signals, the city launched a wireless mesh network that enabled a gigabit Internet signal to be broadcast using radio transmitters and receivers. Receiving nodes could then communicate with antennae on top of traffic signal cabinets. Called InSync, the intelligent transportation system, produced by Rhythm Engineering, of Lenexa, Kansas, was installed to help the engineers control more than half of the city's 360 signals. Eventually all of the city's signals, as well as dozens more in nearby jurisdictions, will be linked and centrally managed. While this pales in comparison to the City of Los Angeles, which recently announced it has central control over 4,400 signals, it's a significant accomplishment to use only wireless technology within such a short period of time. (Read "Los Angeles Completes Long-term Traffic System," on Civil Engineeringonline.)
"As far as signals, just like other cities around the country, we're trying to take advantage of the new technologies which are becoming available to us," says Van Winkle. "It's not to say that they're cheap, but they're something that's doable."
Funding for the project, which included upgrading cabinets and signals within the central business district, came from the American Reinvestment and Recovery Act, the federal Surface Transportation Program, and the FHWA's Congestion Mitigation and Air Quality Improvement Program. "There's only so much [in] tax dollars," says Van Winkle. "There were these programs available, and we decided to get into the game. Fortunately we were successful."
Chattanooga is one of only three cities in the United States with this type of high-speed network, the others being Kansas City, Missouri and Provo, Utah. All use a fiber service provided by Mountain View, California-based Google.
Van Winkle points out that Chattanooga's proximity to the Oak Ridge National Laboratory (ORNL) creates the possibility of a partnership between the city and the research facility. Jan-Mou Li, Ph.D., a researcher at ORNL who specializes in traffic studies and optimization, says ORNL is interested. "You can imagine, with this ultra-high-bandwidth, we can do something that's never happened [before]. It could have excellent applications in the future," He says. "That's why we're interested in what is happening in Chattanooga."
He adds that the move from the legacy system to the wireless network was a big step. "There is a significant cost savings inherent in being able to remotely control the system compared to sending an engineer out to open a cabinet and make an adjustment," he points out. There's still plenty of work to be done in Chattanooga, says Van Winkle, so the prospect of a research partnership with ORNL is intriguing, even though discussions are still in a preliminary stage. Access to funding and new technology will be important if Chattanooga wants to meet its goals of connecting satellite communities and providing travelers on surface roads with not only the kind of instant travel-time information one sees on interstate highway message boards, but also directions to alternate roads that are prepared to receive the rerouted traffic.
Van Winkle would also like to see video surveillance added into the system. And one earlier idea that has yet to take shape is testing a device that measures pollution at individual intersections.
Van Winkle knows that technology can take a city only so far. Multiple elements need to work in concert to enable drivers to be able to move more efficiently. "Governments will see [that] we can't keep building [our] way out of congestion," he says. "There's a trend [of] people living closer to work so they can ride a bike or walk, [but] we [still] need to make the best use of the roadways we have."
Consequently, wide-reaching broadband networks like the one in Chattanooga, and even the city's plan to build more roundabouts, which can smooth traffic flow, are probably the wave of the future for midsized cities.
And that makes sense to observer Douglas Noble, P.E., PTOE, a program manager for the National Transportation Operations Coalition, an initiative of the Federal Highway Administration and the Institute of Transportation Engineers that is dedicated to improving the management and operation of the nation's transportation system. Noble says that systems like the one in Chattanooga can be great in theory, with their ability to loop more signals into a network controlled by a central location, but the key to getting the most out of such a new investments is a smart traffic management strategy. "That's where the real bang for the buck is going to be."
For his part, Van Winkle is happy to share his experiences. "It's still a work in progress, but a lot of people have expressed an interest in what we're doing," he says. "I think it's helpful to share our stories and lessons learned."