It is no surprise that in the winter we see many articles about how our roads get plowed and treated. Nor is it particularly surprising that winter maintenance practices often lead to debates over different methods and materials used to keep roads clear. One often-heard rebuke is that road authorities should go back to using sand or abrasives for winter maintenance, instead of using salt. Unfortunately, that would be very counterproductive for many reasons.
Sand alone does not melt any snow or ice. Any time melting has been associated with sand, it is because a small amount of salt (about 10 percent or less) is typically included in the stockpile to stop the sand from freezing solid. It is sometimes said that some melting occurs because the color of the sand creates excess solar heating, but that is minimal compared to the normal solar heating occurring on roads anyway.
This matters because we need roads to be free of snow and ice in the winter. A study by Global Insights indicated that when roads are impassable because of snow or ice, a state can lose between $300 million and $700 million in economic activity per day. A study from Marquette University has shown that a safe and sustainable snowfighting program that uses road salt in an appropriate manner will reduce accidents by up to 88 percent.
Sand does provide a temporary increase in friction. However, to supply that increase in friction, it has to be located between the tires of the vehicles on the road and the snow or ice on the road. But the sand does not stay where it is needed for very long, especially at highway speeds. Studies have found that the friction increase due to sand disappears after 10 to 20 vehicles have driven over it at highway speeds. So the benefits of sand in terms of increasing friction are very fleeting in high-speed and high-traffic situations.
In addition, to get the friction benefits of sand, it has to be applied at much higher rates than salt. This means that trucks must be refilled more often, and when a truck is in the yard being refilled, it is not out on the road system plowing and applying materials appropriately.
Some believe that there is no environmental impact from the use of sand, but this is not the case. When abrasives like sand settle in river beds, they choke off access of aquatic species’ eggs to oxygen, thus reducing their value as spawning grounds, potentially putting the breeding of certain fish species at risk. The other danger is to air quality. As cars drive over the sand and other abrasives, these get ground up and become dust. Both the city of Denver, Colorado, and Washoe County, Nevada, where air pollution is a particular concern, require that any abrasives used be vacuumed up no more than 72 hours after the end of the storm. This cleanup adds significantly to the cost of using abrasives.
When properly applied at the right place, at the right time and in the right amount, road salt is the single most effective, economic and environmental way to keep our roads passable and people safe in the winter.