Pavement has no privacy from their relentless scrutiny. Foster and Weller take the ARAN for exactly the same drives every year. When they return, they hand over hard drives. The data, about a gigabyte per mile, will reveal detailed images of the roads’ bumps and grooves, along with electronic measurements of every flaw.
This 10,000-mile tapestry goes on display for the engineers and planners who share in deciding what roads to fix next and how to fix them. The data help guide roadwork that is two or maybe three years away, said John Andrews, the assistant chief of the State Highway Administration’s Field Exploration Division, home base for the roving ARAN.
For the state of Maryland, asphalt is an asset, one that gets more valuable as the cost of road resurfacing goes up. If highway officials have better information about the state of the asphalt, it should help them decide where to allocate their resources. That preserves an asset — and it makes driving safer.
Andrews and William Adzimahe, the chief of the division, sound like road geologists as they describe the natural and man-made forces that can destroy pavement.
The sun’s heat can make pavement brittle, and cracking can result.
Look where the tire tracks go to see signs of pavement fatigue.
Or there might be an old highway underneath the pavement, so traffic loads may impose different stresses on different sections of the roadway.
A newer surface of asphalt may cover concrete slabs. Movement at the joints may be reflected up through the asphalt. The asphalt layers, put down lane by lane, may not be joined up adequately at the seams, and cracking could develop along those lines.
What ARAN does
Engineers and other highway staffers could go out and make up their own road report cards to document all that. The ARAN vehicle is designed to save time and resources while offering an objective, uniform view of the statewide network.
That view comes in several forms. High-definition cameras mounted behind a window above the cab provide a virtual tour of the state’s roadways that tops anything available in a Google Street View. But the engineers aren’t looking at the scenery. They might want to catch a glimpse of what Andrews called the “roadside furniture,” anything along the roadways that might suggest a cause for pavement damage, or show the results of it.
The vehicle’s positioning systems allow viewers to pinpoint the locations of any such issues.
But the prime mission of the cameras and sensors mounted in front and back of the vehicle is to look down rather than ahead. The instruments “look at surface distresses,” Andrews said. The ARAN can’t see below the pavement, but the experts on pavement condition who review the results can use the surface condition to diagnose the underlying cause.
The instruments also can measure the bounciness of the road. That’s not just for driver comfort. “Rough road is hard on itself,” Andrews said. A rough roadway can become its own worst enemy, as the bouncing of vehicles causes further damage.
The first of Maryland’s ARANs hit the road in 1996 and now has more than 300,000 miles on it. The second, added in 2008, has more sophisticated equipment, and it runs a lot better, too. The Field Explorations Division would like to buy a new one and retire the first ARAN.
The crew’s challenge
Weller doesn’t drive like the rest of us. He needs to be gentle with the vehicle, leave enough room front and back and compensate for the driving skills of others. He needs to look well forward into traffic, to see rumble strips or a big steel plate coming up.
“There’s a lot to watch,” he said.
The person in the passenger’s seat is anything but a passenger. Sitting in front of his frequently changing computer screens while the ARAN rolls along, Foster seems more like the systems officer on a fighter jet, though the officer probably doesn’t have to climb out of the cockpit and squeegee the camera window to remove the squashed bugs.
Foster monitors the software to maintain the quality of the data and looks ahead so he can tell the systems some things they need to know to help with their measurements.
Weller and Foster can’t just start at Route 1 each year and work their way up the numbers on state-maintained roads. The ARAN needs to move at least 25 mph to take some of its readings. The forward-looking cameras need to have a clear view of the road ahead, and the road surface needs to be clear for the measurements. Tailgaters can also be a problem for the sensitive measurements.
So they tour Maryland’s coastal areas before the beach traffic builds up. Then they’re out to western Maryland, but they want to be done with that before mid-June, when the cabins and hotels will be fully occupied and there won’t be a lot of room for smooth operations on a limited road network.
After the schools close, traffic drops about 10 percent in the state’s most congested areas. That’s a good time to tour Montgomery and Prince George’s counties.
They wrap up in October, before the leaf fall gets heavy and makes it difficult to closely measure the road surfaces.