Most northerners have experienced some variation on this scenario: you are driving along, temperatures are near freezing, and suddenly your vehicle is sliding. Black ice has done it again.

In larger towns and cities, this scenario can all too often result in piles of cars rammed into one another. The traditional method for making roads safer in winter is to lay on the sand and salt. But more and more places are using a high tech approach called Road Weather Information Systems, or RWIS for short.

With these automated systems, sensors are embedded in the pavement at strategic locations -- ones that are prone to icing or that are typical of roads in the area. There they gather information not only on the weather, but also on the road surface itself.

Nearby atmospheric sensors also collect weather information, and all of this data is relayed to a server at a central location where it is accessible on a dedicated web site.

Kamloops, B.C., has had RWIS systems in place for about five years, and Jim Steele with Environment Canada there can cite numerous advantages. Above all, he highlights the fact that with RWIS you can anticipate problems.

"It is proactive instead of reactive. The reactive scenario is that after it has been snowing for one or two hours, you decide to go out and plow and sand. With the proactive approach, in addition to an atmospheric forecast, you can forecast what the road temperature will be and decide what chemicals to use on the road ahead of time," he says.

A substance called Freeze Guard, which is primarily magnesium chloride, is most commonly used with the RWIS system. When spread on the road, this liquid lowers the freezing temperature of the road, reducing the possibilities of icing as the road surface cools or snow starts to fall.

"Say the roads are dry but snow is forecast. You can put the liquid chemical on the road ahead of the storm and then the road has been pretreated. Moisture from the snow starts a chemical reaction so you get a chemically wet surface instead of ice," says Steele.

The liquid is sprayed from a tank carried by a specialized truck. After it has been applied, other vehicles driving on the road help spread it even more.

At one steep ice-prone area, Kamloops is now testing an automatic spraying system. Sprinklers embedded in the pavement pop up and spray the road after the sensors have detected icing.

The Insurance Corporation of British Columbia (ICBC) is helping to fund the RWIS system in that province because of its proven ability to lower accident rates.

"The statistics show that for snow days, the accident rate has been reduced by 40 percent because road surfaces are not as sloppy. You do not get the glare ice and treacherous surfaces where people are sliding all over the place," says Steele.

Reduced maintenance costs are another advantage as once the RWIS system is in place, overall costs are four to eight times lower than with conventional methods. Less salt and sand is needed and it is easier to plow these areas after a storm.

This coating also keeps snow from bonding with the road, making it easier to plow off later. Also less sand means fewer cracked windshields and less dust after the spring melt.

Magnesium chloride is the main ingredient in the salt mixtures used on roads. Steele says that while this chemical is "not environmentally pristine, it is considerably better than throwing salt all over the roads."

"Alongside roads where lots of salt is used, you always notice the vegetation dying. This is better for it. The use of abrasives like sand is also decreased so there is less clean up to do in the spring."

British Columbia now has about 40 RWIS systems, and other provinces are expanding their existing systems. As well, they are in widespread use on roads and airport runways throughout the U.S. and Europe. So would this system be appropriate for the Yukon?

Robert Magnuson, the director of transportation and maintenance with the Yukon Department of Infrastructure, thinks it could be down the road. He says that there is a good possibility that a RWIS system could be tested in the Yukon within the next few years.

While most Yukon roads are frozen solid for many months during winter, there are areas where icing causes problems, particularly along the Alaska Highway near Whitehorse.

For more information on RWIS systems, you can check the websites of some of the companies that make them, such as Surface Systems Incorporated at www.ssiweather.com or Qualimetrics at www.qualimetrics.com.