Saving Money and the Environment
A new approach to winter maintenance keeps Oregon roads clear of ice and sand.
The winter of 1992-1993 was unusually severe in Oregon, forcing the Oregon Department of Transportation (DOT) to use more sand than usual to keep roads safe. This intensified public concerns about the environmental effects of sand use.
Sand improves safety on icy roads, but it is of limited value on icy roads and is not good for the environment. An Oregon DOT study found that 50 percent to 90 percent of sand applied to pavements remains in the environment after cleanup. The Oregon Department of Environmental Quality says that dust from road sanding operations may contribute to air pollution, while the U.S. Forest Service says sediment in streams and rivers is bad for salmon.
To reduce its use of sand, Oregon DOT decided to try using anti-icing strategies, which reduce sand use without impairing travel safety or incurring unreasonable costs. Anti-icing strategies, which had been evaluated under the Strategic Highway Research Program (SHRP), rely on the fact that it is easier to prevent ice from bonding to pavement than it is to break that bond by plowing or to reduce the hazard by applying sand to icy roads.
To use an anti-icing strategy, Oregon DOT winter maintenance managers closely monitor information collected on pavement and weather conditions. When those conditions indicate that ice will soon form on roads, crews head out to apply chemicals to the pavement that will prevent ice from bonding to the road. When freezing rain or snow begins to fall, the pavement is already coated with materials that will prevent ice from forming and packed snow from sticking to the road.
Putting the Technology to the Test
In the winter of 1993-1994, Oregon DOT evaluated an anti-icing strategy at 21 sites in 9 districts across the State. Test sites included city streets, mountain passes, low-volume rural roads, and other locations in most of the State's many climates. Two liquid chemicals were tested. The study continued through the next winter.
Oregon DOT found that the anti-icing strategy offered significant environmental benefits by dramatically reducing the amount and cost of materials used. The chemicals used in the test required far fewer applications than was the case with sand. The test showed that Oregon DOT could significantly reduce the environmental problems associated with sand use by adopting an anti-icing strategy.
The anti-icing strategy also has financial advantages. Because sand requires more applications per storm, it has high costs for materials, labor, and equipment. In addition, for environmental and safety reasons, Oregon DOT is required to clean up the sand left behind on the pavement, in catch basins, and other locations, adding to the expense.
For example, in storms that brought freezing rain, Oregon DOT had to make only two applications of liquid magnesium chloride to the roads, for a total cost of $15 per lane-km ($24 per lane-mi). In contrast, sand had to be applied three times, for a total cost of $59 per lane-km ($96 per lane-mi).
By keeping roads clear of ice rather than trying to make icy roads passable, Oregon DOT's anti-icing strategy also improves safety for motorists. Although it is difficult to quantify, anti-icing had clear safety benefits. "The State Police told us, 'You guys are doing a great job,'" says Dick Parker, a consultant to Oregon DOT.
In Portland, managers can retrieve real-time information on pavement and weather conditions from a road weather information system (RWIS), a technology also being implemented in other Oregon cities. Although an RWIS makes the job easier, it's not necessary, says Parker. "With good crews and a good sense of how chemicals work, you can still do a good job even if you don't have an RWIS," Parker says. "Some of the most impressive savings were in areas with no RWIS and where crews were using homemade chemical spreaders."
The Oregon DOT and local highway agencies agree that the anti-icing strategy is a success. The State highway agency is working with Portland and other city and county governments to expand anti-icing strategies.
By adopting an anti-icing strategy, Oregon DOT has
- Improved safety on the State's roads.
- Saved money on materials.
- Reduced the environmental impact of winter maintenance.