Science for snow battles

Sensors: Maryland's high-tech data system helps highway crews keep up with clearing roads.

January 21, 2000|By Marcia Myers | Marcia Myers,SUN STAFF

Behind the scenes of the season's first snowfall yesterday, state road crews embarked on a 21st century-style battle against highway snow and ice.

In its pursuit of bare pavement, Maryland is leading the nation with a sophisticated network of road sensors and weather stations that relay the tiniest details to highway crews every 20 seconds.

It means early warnings of dangerous conditions. And fixing them before they do harm. The precision of the data helps eliminate the guesswork and misjudgments that can conspire to strand motorists and cost the state millions.

"Now, even before we start our rounds, we have a better idea of what we're up against," said Eric Lincoln of Hereford, a plow driver for 12 years. Efficiency is another benefit. "We've cut back on fuel use, truck use, and we're managing our manpower and resources much better."

Road crews used to stand by for hours, watching and waiting for the first flakes to fall. Problem spots on the roads were frequently discovered by accident, literally. As a last resort, one could curse the roads.

These days, the roads do the talking.

More than 170 sensors embedded in the pavement of major roads around the state report the temperature of the road and the ground underneath it, the amount of moisture on the road and the levels of salinity from salt or of chemicals already applied. With this knowledge, engineers can decide what materials to use on the roads and when to apply them.

The sensors are placed near weather towers -- the state has 51 -- which relay additional data, including precipitation, air temperatures, wind gusts and cloud cover. Partnered with this information, radar data show the speed and intensity of a storm on color-coded maps and announces its arrival time. A "pavement contour map" highlights areas in danger of frost or black ice.

The state installed most of this equipment in 1995, although the system didn't win instant credibility among road crews.

"People wondered, `Is it accurate? Is it dependable? Am I able to take what this computer is telling me and hang my job on it?' " said David Rossbach, who oversees the system. "That takes awhile."

Over time, the crews became more convinced -- though a shortage of storms in the past three years left the system largely untested. Until this week.

One fact can alter plans significantly. "If I see that the pavement is above freezing, I don't necessarily have to react as quickly," Rossbach said. That alone can save thousands of man-hours spent salting prematurely.

David Ramsey began his snow attack plan early Wednesday -- a full 18 hours before the storm was to hit the parts of Baltimore and Harford counties that make up District 4, where he is the State Highway Administration's assistant district engineer.

The sensors gave him welcome but not unexpected news -- temperatures on roads were holding well below zero. That would permit his crew to experiment with a snow control system using liquid magnesium chloride that has met with great success in Colorado and elsewhere.

Snow control system

Applied before a storm, the chemical adheres to the road like a glaze and melts snow and ice as it lands. The substance can work for up to 12 hours and reduce the need for plowing and salting.

In Boulder, Colo., the system has reduced the cost of snow control from $5,200 per mile of lane to $2,500. The catch: If the road surface is not cold enough, the chemical becomes gel-like and forms an oily slick.

Without the sensor data, Ramsey says, he might hesitate to apply the chemical. "It would make us a lot more susceptible to the risk of it not being effective, or even problematic."

A click on his computer displays a precipitation timing map, with wide blue bands that show the storm is expected in Baltimore about 2 a.m. and it will deposit 2 to 4 inches of snow.

"Without the timing map, you know it's coming, you just don't know when it's coming," Ramsey said. If he didn't have it available, he said, "I would err on the cautious side and bring people in early. I'm not going to risk putting the system in jeopardy, I'm going to keep people on the clock."

Slippery alert

But Wednesday, he and his managers were confident enough in the predictions to cut their crews loose about 4 p.m. so they could go home, have dinner and report back at midnight well rested. Their trucks had been loaded with appropriate chemicals and ready to go by midafternoon.

Throughout the early-morning hours yesterday, the system informed Ramsey of possible trouble. A sensor at Interstate 83 and the Beltway called for a snow and ice watch at 2: 25 a.m. A slippery spot was identified on the U.S. 1 bridge over Little Gunpowder Falls a short time later. Ramsey sent crews to check the conditions of each.

Meanwhile, as the region's roads were salted and de-iced, one by one the corresponding sensors sent a yellow signal with the message "chemical wet," meaning de-icing materials were taking effect -- and a sign that the job was getting done.

Analyzing reports

Highway officials say the system will continue to help them once a storm is over because the detailed reports can be analyzed to find what worked and what didn't.

"In the past, our records were kept on paper, mainly for inventory, not for determining how well we performed," Rossbach said. "We weren't thinking that far ahead.

"Now we're fine-tuning and trying to get out front of the storm instead of being reactive."

Sandra Dobson, a spokeswoman for the Maryland State Highway Administration, said officials had not yet had a chance to critique their overall response to the storm.

"But we had very, very successful rush hours from our standpoint," she said. "The roads were clear early. We had just about reached bare pavement by 10: 30 a.m."

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