Answer: Depression in Freezing Point
Explanation: When salt is kept on the icy roads, it will form a liquid layer over it thereby lowering the freezing point below the ice. Thus when this salty liquid comes into the contact with the other ice present on the road making the other ice get melt.
This keeps on decreasing the olume of the ice on the road.
Thus it is always advised to put rock salts on the roads during a snowstorm.