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July-August 2015

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Virginia's Smart Road: Where Researchers Make the Extreme Weather

Located a couple of miles from the Virginia Tech campus in the mountains of rural southwest Virginia, the Virginia Smart Road stands as a 2.2-mile-long thoroughfare that actually goes nowhere, at least for now. The result of a grand plan conceived back in the 1980s, the road is a unique, state-of-the-art, closed test-bed research facility managed by the Virginia Tech Transportation Institute (VTTI) and owned and maintained by the Virginia Department of Transportation (VDOT).

Today, it offers researchers and product developers a laboratory for testing new transportation technologies. Eventually, it will be extended to also provide the motoring public a direct route between Interstate-81 and Blacksburg to facilitate a link between Roanoke, 25 miles east, and Virginia Tech.

But perhaps the most intriguing feature of this road is a half-mile section that sports towers, much like you see at a ski resort, sprouting 25 feet above the road that spew rain, fog, and snow to create extreme weather conditions for testing vehicles. The Smart Road can actually create its own weather!

Operating a system like this has its rewards, according to Jared Bryson, Smart Road Mechanical Systems Group Leader in VTTI's Center for Technology Development: “It's fun to go out there and crank the system wide open and see what we can do as far as snowmaking. It always makes a nice cool winter day that much more fun when you can make a foot of snow.”

Tom Dingus, director of VTTI and a professor in the Civil and Environmental Engineering Department at Virginia Tech, says in 2013, the Smart Road logged the highest number of paid hours of research since its inception. “It's getting more and more popular,” he reports. Over two dozen major non-proprietary research projects use the Smart Road for testing in a given year. Participating organizations include car manufacturers, the Department of Transportation, the National Highway Traffic Safety Administration, and the Federal Highway Administration Research and Innovative Technology Administration.

The weather-making section of the road consists of 75 towers mounted on the side of the road and extending over it that can create snow, fog, freezing rain, and heavy downpours. A 500,000-gallon water tank lies on the ground below the road, and a 400-horsepower pump pressurizes the water to feed the towers. They use city water, and the large tank allows for filling at off-peak times so they don't stress the system. Two 700-horsepower, three-stage centrifugal air compressors generate compressed air for the fog- and snow-making applications. Water and air pipelines run the entire length of the weather testing section.

VTTI developed rain- and fog-making setups in-house. For rain, this includes a reconfigurable nozzle that attaches to the tower, allowing them to generate an inch to two and a half inches of rain per hour. For fog, Bryson says, “We have that nice cyclic high humidity every morning, and if we inject a small amount of super-atomized water into the air, we actually cause the natural humidity to cascade out, which amplifies the effect, and we create a large, thick bank of fog. It makes anywhere from well over 100-foot visibility fog to a pea soup where you can barely see 10 feet in front of you.”

For snow, they use off-the-shelf water nozzles made for snowmaking. Compressed air mixes with the water at the nozzle to atomize it, and this turns to snow as it falls to the ground. They can make up to four inches an hour in suitable weather conditions.

As Bryson tells it, the weather-making system creates quite a stir when it comes to life. As the fog or snow starts, a whistle fills the air, and when the water reaches the nozzles, the towers rear back. Because the road is cut into a mountain in this stretch, the sloped banks shield the towers on both sides, so as the fog runs, it settles and fills this valley, slowly flowing down the road like a river. Snow arcs from the towers and drifts to the roadway, dusting all the surroundings on a cold night. Since the rain system doesn't use compressed air, the towers run quietly, but when water reaches the nozzles, they flex and buck. Then they quickly settle down and produce a shower of large droplets. On a sunny day, a rainbow often accompanies the rain. With electric motors driving the compressors, they sound like a jet turbine winding up as they start, and emit a loud, distinct whine.

According to Steve Keighton, science and operations officer with the NWS in Blacksburg, the weather around in the area is conducive to making weather and testing vehicles under extreme weather conditions. “We have a typical mid-latitude climate with a wide variety of weather types and a full flavor of all four seasons.” Snow and ice are common in winter months in the Appalachian Mountains at an elevation of about 2,000 feet. Fog is common in the late summer and fall but can occur at any time of year. Heavy rain from thunderstorms can occur frequently as well. A rare topical system can bring remnants into the Appalachians with extreme rainfall and wind.

“The two conditions that seem to generate the most challenges for drivers around here are snow and ice on the roads and dense fog,” Keighton says. “With a lot of truck traffic on interstates with varying up- and downhill grades in these parts, even rain on the roads can cause issues.” He envisions winter testing with varying road surface temperatures, as well as different forms of frozen precipitation, such as dry snow, wet snow, sleet, and ice from freezing rain to determine effects on road slickness and vehicle stopping capabilities, and then the sort of vehicles, tires, and road treatments that can best deal with these. He posits, “As far as fog, or even low visibilities with heavy snow or rain, what are appropriate speeds and stopping distances for various types of vehicles given a specific visibility threshold?”

When it comes to road treatments, Dingus says they're already on this: “Surface properties of pavements is a big research area. There's a lot of tradeoff in pavement design, like noise versus traction versus wear. We do a lot of surface properties kind of work on the Smart Road.”

VTTI also has a project titled Prediction of Roadway Surface Conditions Using Onboard Vehicle Sensors, sponsored by the U.S. Department of Transportation (DOT), under research on the Smart Road. This proposes a method for predicting compromised roadway conditions in which the differential rotational displacement of driven versus free-rolling wheels of a vehicle is used to predict the relative coefficient of friction between tire and pavement. This can indicate diminished tire traction before thresholds are attained for activating safety systems such as antilock brakes.

Another weather-related project is Safety and Human Factors of Adaptive Stop/Yield Signs Using Connected-Vehicle Infrastructure, also sponsored by the DOT. Traffic professionals have proposed adaptable, or changeable, stop and yield signs to improve travel time, reduce air pollution, increase fuel economy, and adjust to different traffic conditions, such as peak hours, weather, or emergency vehicles. With the advent of connected-vehicle technology, the ability exists to change these signs based on vehicle-to-infrastructure and vehicle-to-vehicle communications.

Bryson says VTTI does a lot of testing with its lighting evaluation group and points out one area where weather testing can play a role in this: “If we run a typical incandescent light and shine that through a fog or snow event we're creating, light is fairly limited passing through that. Specialized lighting such as ultraviolet lighting may not help you see any better ahead, but it would cause things like clothing to fluoresce and actually increase the visibility of, say, a pedestrian.”

The Smart Road features two paved lanes and three bridges, one of which ranks as the tallest state-maintained bridge in Virginia at 175 feet. It also has a signalized intersection; in-pavement sensors for moisture, temperature, strain, vibration, and weighing-in-motion; a lighting test bed; an on-site data acquisition system; a high-bandwidth fiber network; and a differential GPS base station. Zac Doerzaph, director of the Center for Advanced Automotive Research at VTTI, says, “The Smart Road provides a unique facility for testing transportation systems because it is limited to access for research yet is built to the standards of an actual interstate.” To operate the Smart Road, VTTI employs a team of multidisciplinary researchers, engineers, technicians, support staff, and students. They recruit Virginia Tech electrical and mechanical engineering students as graduate research assistants to serve as employees.

VTTI offices house the Smart Road Control Room used to schedule and oversee on-road research, and dispatchers monitor the road from here. Researchers can observe highway traffic and driver performance using surveillance cameras. Engineers can also control the lighting and weather on the road from here.

Having been in operation for 20 years, the Smart Road has accrued a list of accomplishments that have made their way into today's production vehicles. Doerzaph says, “We have influenced technologies such as forward collision warnings, backing cameras, and crash imminent braking, wherein the vehicle will automatically apply the brakes to avoid a crash.” Dingus adds, “If you look at the new Cadillacs that came out last year, they have half a dozen of these active safety systems, all of which were tested on the Smart Road before they were deployed. That's a way we have a pretty big impact.”

Bryson points out another technology pioneered on the Smart Road: adaptive cruise control. This uses forward-looking radar to detect the speed and distance of the vehicle ahead of it. It maintains the vehicle's preset speed but automatically adjusts the speed to maintain a proper distance between vehicles in the same lane.

A couple of notable technologies are being developed now that should follow this same path. Connected vehicles are equipped with radios and GPS so they can communicate with each other as well as the infrastructure. If a car is in a collision, it can broadcast that it just experienced a crash or incident, and all the vehicles around it would know. The computer on every vehicle would figure out if it's in the path and what action the vehicle should take, such as alerting the driver or applying the brakes and stopping the vehicle.

As another emerging technology, Dingus says active safety systems serve as subsystems that will lead to automated cars: “The next generation is working on lane-centering systems, where you can actually drive hands off the wheel, and if the car sees an obstacle in front, it will brake to avoid a crash. Those are coming out very soon; in the next few years, they'll be in production.”

Planning for the Smart Road actually began as far back as 1985. In early 1992, the Virginia Department of Transportation began designing it, working closely with the Federal Highway Administration and Virginia Tech's Center for Transportation Research. Groundbreaking took place in 1997, and construction on the first 1.7-mile segment of the road in a four-lane right-of-way was completed in 1999. The second phase of construction, including the tall bridge, was completed in 2002, making it 2.2 miles.

Where will the Virginia Smart Road go from here? The timetable for extending the road to become part of the public transportation system will depend on growing traffic demands on the Route 460 Bypass and state and federal transportation funding. It will eventually become 5.7 miles of four-lane road designed and built in a series of test beds with the ability to shut down two lanes in off-peak hours for testing.

As it continues to play out, this unique public/private/academic project should continue to advance transportation technology for years to come, thanks in large part to its multifaceted weather-making system.

Based in Milton, Pennsylvania, TOM GIBSON, P.E. is a consulting mechanical engineer specializing in machine design and green building and a freelance writer specializing in engineering, technology, and sustainability. He pubishes Progressive Engineer, an online magazine and information source (       

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