Winter maintenance practices often lead to debates over different methods and materials used to keep roads clear. One often-heard argument is that road authorities should go back to using sand or abrasives for winter maintenance, instead of using salt.
But how does sand compare to salt?
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. 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.
Sand does provide a temporary increase in friction. However, to supply that increase in friction, it must be located between the tires of the vehicles on the road and the snow or ice on the road. 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 can be fleeting in high-speed and high-traffic situations.
In addition, to get the friction benefits of sand, it must be applied at 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.
Some believe that there is no environmental impact from the use of sand, but when abrasives like sand settle in river beds, they choke off access of aquatic species’ eggs to oxygen, 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. The cities of Denver, Colorado, and Washoe County, Nevada, where air pollution is a concern, require that abrasives used be vacuumed up no more than 72 hours after the end of the storm. This cleanup adds to the cost of using abrasives.
This debate 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.
When properly applied at the right place, at the right time and in the right amount, road salt has been shown to be the most effective, economic and environmental way to keep roads passable and people safe in the winter.