Two meteorological stations are operational and other equipment will be added as researchers from the Department of Energy's ORNL and the University of Tennessee work to develop a national resource. When complete, the instrumentation at Watt Road and Interstate 40 would create a world-class field lab devoted to answering a multitude of questions.
"We'd like to determine, for example, whether the stricter emission regulations for trucks are achieving actual benefits to the environment," said Ralph McGill, who heads the project and is a researcher in ORNL's Engineering Science and Technology Division. "In the immediate future, though, we're hoping to learn more about truck emissions during different operating conditions, all remotely so we won't interfere with traffic flow."
Large trucks are of particular interest because they are responsible for 40 percent of nitrogen oxide emissions and about 60 percent of particulate matter emissions from mobile sources. Their emissions vary according to a truck's load, speed and acceleration, yet only sparse data exist that quantify differences in emissions between the many modes of operation.
"A further complication is that engines are certified rather than particular vehicles," said Katey Lenox of ORNL's Engineering Science and Technology Division. "So we really don't know what that engine is doing under real-world conditions."
As a class of vehicle, "combination trucks," or those designed to be used in combination with one or more trailers, numbered nearly 2.1 million in 2001 and were driven an average of 62,860 miles, or, collectively, 135 billion miles. Passenger cars, light trucks and vans numbered 222 million and were driven 2.5 trillion miles for an average of 11,500 miles per vehicle per year.
The field laboratory would extend 2.5 miles eastward along the valley from the Watt Road-Interstate 40 interchange to a weigh station at the top of a ridge. This section of the interstate is one of the country's most heavily traveled highways because it is where three major interstate highways converge on a 20-mile stretch through Knoxville. The area of the field lab is also home to three large truck stops, a trucking company terminal and other trucking industry-related facilities.
In addition to the two existing meteorological towers, researchers plan to install equipment to measure nitrogen oxide and particulate matter emissions as trucks pass. Researchers envision using a stepped FM-AM lidar - LIght Detection And Ranging - technique to detect particulate matter and ultraviolet absorption to detect nitrogen oxide emissions.
While these techniques will provide concentrations of emissions from trucks, researchers will use roadside mounted panels to perform magnetic probing and sensing. This will enable them to calculate emissions for an individual truck on a gram-per-mile basis.
"By performing what's called a sound signature analysis, we'll be able to determine each truck's operating condition, including engine speed, turbine speed and the number of cylinders," Lenox said.
Faster, inexpensive instruments eventually will allow researchers to set up arrays capable of measuring more of an exhaust plume rather than just examining one slice, as will be necessary in the beginning. Later, with a suite of detectors and instruments at the site, researchers hope to attract researchers from across the country and make a major contribution to understanding truck emissions.
"This is a major undertaking, and to be successful we'll need help from the state, truck stop operators and many others," McGill said. "Ultimately, the data we're able to collect and analyze will be well worth the effort."
Funding for the project initially was provided through the Laboratory Directed Research and Development program, which is funded by DOE. Tennessee's State Partnership Program financed acquisition and installation of the two meteorological towers. Researchers are seeking additional funding to continue the project and to increase the scope of work.
ORNL is a DOE multiprogram research facility managed by UT-Battelle.
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