 Salt reduces the melting point of ice by freezing-point depression, causing it to melt at lower temperatures and run off to the edge of the road, while sand increases traction by increasing friction between car tires and roadways.The amount of salt dropped varies with the condition of the road; to prevent the formation of light ice, approximately is dropped, while thick snow can require up to of salt, independent of the volume of sand dropped.The grit is sometimes mixed with molasses to help adhesion to the road surface.