ORONO, Maine — The Maine Department of Transportation began its current program of winter-weather road maintenance in 1995. Since then, the number of fatalities on the roads the Maine DOT maintains during ice, snow and slush conditions has declined.
However, fatalities and serious crashes in winter conditions have not declined on roads not maintained by the DOT.
The difference between Maine DOT’s roads and many local municipalities? Maine DOT uses a salt brine solution before storms as a preventive measure known as anti-icing. Most municipalities use rock salt and sand during and after storms, which is known as de-icing.
Although a new report from the University of Maine’s Margaret Chase Smith Policy Center is not ready to link anti-icing maintenance with fewer fatalities — as well as the potential for eventually reducing the amount of salt in the environment and lower corrosion rates — the report’s author said it’s a fact anti-icing speeds up the clearing of winter weather messes on the roads.
“The anti-icing leads to a quicker return to a bare road, we know that,” said University of Maine professor Jonathan Rubin, who was the lead author on “Maine Winter Roads: Salt, Safety, Environment, Cost,” which was released Friday.
“We can’t say definitively that the anti-icing has led to a decrease in fatalities because there are other things that have occurred as well, such as increased safety [awareness],” Rubin added. “But we have not observed the decrease in fatalities on the roads DOT does not maintain. So that’s why we think there’s an effect, but we can’t be sure.”
In addition to the School of Economics and Margaret Chase Smith center, the yearlong study also included researchers from UMaine’s engineering departments along with the university’s Sen. George J. Mitchell Center for Environmental and Watershed Research. Other sources included the Maine Department of Transportation, AAA Northern New England and the Maine Turnpike Authority.
The study cost about $80,000, Rubin said, and was funded through a cooperative agreement with the Maine DOT.
Maine spends an estimated $98 million a year — including the purchase of an estimated 490,000 pounds of rock salt — on winter road snow and ice control. Maine DOT maintains 18 percent of those roads, Rubin said, and it’s those roadways where the decline in fatalities was noted during a period from 1989 to 2008, Rubin said.
The rest of Maine’s total 23,450 miles of roads are maintained by municipalities, counties and reservations (81 percent) and the Maine Turnpike Authority (1 percent). Fatalities were not shown to have dropped in the same time period on town roads and state-aid highways, according to the survey.
Data were not available to determine the level of vehicle traffic during winter storm events, but according to the report the number of vehicle miles traveled has increased during 1989-2008 with the exception of the last two years.
Winter-weather crashes overall were not shown to have dropped on any of Maine’s roadways, according to the report.
The DOT uses an anti-icing maintenance program, which involves spreading calcium chloride brine on roads in anticipation of winter weather. De-icing is the spreading of a combination of sodium chloride, known as rock salt, and sand after a storm. The methods have comparable expenses, but Rubin said anti-icing is more effective.
“If you just put rock salt on a road, it doesn’t necessarily do anything until it starts to melt. It’s that melting that is what melts the ice,” he said. “In solid form [rock salt] doesn’t do anything. The brine is very effective, and in fact if you pre-wet your rock salt, which is recommended practice, it helps speed up the process.”
Some municipalities, such as Bangor, have switched to anti-icing with brine. Rubin said in the interest of using less salt overall, municipalities and other road-clearing entities should consider doing whatever they can to reduce usage including identifying high- or low-priority roads and salting less frequently during a winter weather event.
“When you go to an anti-icing policy, you can decrease the amount of sand which saves money and time,” Rubin said. “You’re probably using a little more salt, but you’re using salt more efficiently. It’s a matter of cost and effectiveness. [Municipalities] need to use these salts, but they should work to reduce salt use through smarter use, paying more attention to the weather and also levels of service.”
One fact that came out of the study may not be related to the anti-icing versus de-icing issue.
According to “Maine Winter Roads,” young drivers were found to be more likely than their older counterparts to have crashes on winter roads. Drivers ages 16-17 are involved in 9 percent more winter-condition crashes than their share of crashes during other road conditions. Drivers in the 18-34 age group also have higher accident rates in snow, ice and slush, but not as high as the youngest drivers.
Drivers ages 65-74 have a smaller share of crashes during winter conditions than crashes under dry conditions.
Rubin said the age profile of drivers on the road during a storm is unknown, however.
“What we do know is when you look at the crash statistics, the younger drivers are significantly overrepresented,” he said. “It’s either they just don’t know how to drive in the snow, or they don’t heed the warnings and drive when they shouldn’t. We also know the older drivers are underrepresented, and we don’t know if it’s because they’re skilled, or, if it’s what we think it is — they just don’t drive in the snow.”
Regardless of what kind of maintenance or preventive measures are taken, salt is known as a corrosive agent. There are no firm data on this, Rubin said, but anyone can observe how quickly vehicles rust in places that spread some form of salt on the road.
“We tried to get quantitative estimates, and we just couldn’t do it,” he said. “The problem is, it’s really hard to say that corrosion is caused by salt as opposed to just workmanship or some other cause. We know it’s a big issue, but we couldn’t actually say this is the dollar cost of corrosion.”
Rubin said corrosion may occur faster now than before the chemical compound hexavalent chromium, a corrosion inhibitor which was used in several industries related to automobiles, was found to be carcinogenic when inhaled.
The report found several environmental effects of winter roadway maintenance. All of the chemicals used on roads end up in soil and water, according to the report, and salt-contaminated groundwater wells continue to be found near Maine’s roads.
“We need to use less salt,” Rubin said. “We know the salt in groundwater is increasing. It’s not an immediate problem, but over decades it is a problem and we need to figure out what to do.”
To read the report, go to www.umaine.edu/files/2010/02/Winter-Road-Maint-Final.pdf