The amount of salt put down is a function of the nature of the storm event. In some cases, when air or surface temperatures allow, little salt may be required. In other cases, especially in icing/sleeting situations or protracted snowstorms, salt may be continuously spread to keep the roads passable. In most case a white residual will be evident after remnants of snow and ice melt and roads are dry. Department personnel have no interest in applying too little or too much salt. If drivers apply too little salt, the roads will not clear. Too much salt translates into unnecessary expense.