Smarter Roads Mean Safer Roads

Each year, approximately 300 Canadians are killed and 11 000 injured in road accidents in which snow and ice are a major cause—more than the annual total for all accidents involving all other modes of transportation. While the 4.7 million tonnes of road salt used on our highways each winter makes driving safer, a recent study by Environment Canada shows that it has numerous harmful impacts on freshwater systems and biota.

The need to improve public safety and reduce the environmental effects of chemical road treatment is prompting many provinces and municipalities to install hi-tech Road Weather Information Systems (RWIS)—automatic weather stations that are located adjacent to roadways and have sensors in the surface and substrate of the pavement. These systems record atmospheric conditions, such as air temperature, relative humidity and wind speed, as well as the temperature and wetness of the roads themselves.

Using its own heat-balance model, Environment Canada's Meteorological Service of Canada (MSC) combines RWIS data with atmospheric information to forecast the road-surface temperature and road conditions over the next 24 hours. Knowing in advance when black ice or other slippery conditions are on the horizon allows maintenance crews to apply salt before ice and snow bond with the pavement—the condition responsible for reducing the grip between rubber and road. This proactive approach to winter road maintenance is known as "anti-icing".

Since dry salt won't adhere to dry pavement, it has to be dampened before it is spread. In Sweden, the United Kingdom, and parts of the United States, where road-condition forecasts and anti-icing techniques have been in regular use for more than a decade, maintenance crews apply a thin film of brine solution. Studies have shown that pre-treating a road with brine requires up to four times less salt than applying dry salt to eat through accumulated snow and ice.

Anti-icing has enabled many road authorities in Europe and the US to reduce salt usage by 20-30 per cent while reducing accidents by 10-15 per cent. In fact, anti-icing has demonstrated sufficient savings in labour, equipment, supplies and fuel, to pay for the cost of RWIS and pavement forecasts twice over. Indirect benefits from reduced accidents, legal fees, and salt damage to roads, structures and the environment, and the more efficient use of existing roads are estimated to be 11 times the cost.

Canada currently has about 80 RWIS sites across the country, most of which are located in Ontario and British Columbia. However, major new RWIS installations are planned over the next five years that will boost that number significantly, and the federal government, provinces, territories and other partners are currently discussing the creation of a nationally integrated road weather system.

Since even several thousand sensors would fall short of providing coverage for the nearly one million kilometres of roadway across Canada, MSC hopes to use three-dimensional numerical weather prediction models and to work closely with the private sector to fill in the blanks. MSC's high-resolution supercomputer in Dorval, Quebec, would use data from the national RWIS network to produce road forecasts for all model grid-points coinciding with roadways-even those where no RWIS exists.

A nationally integrated RWIS network would result in a national highway system that is safer, more environmentally sustainable, and more efficient. Information obtained from the sites could be further enhanced by adding other equipment—such as visibility sensors, air-quality monitors, or traffic counters. Some regions are already planning to use RWIS data in the off-season for such purposes as determining the best time for planting and harvesting crops in nearby fields, and identifying conditions that could lead to forest fires.

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