The salt used on roads is called white rock salt or rock salt. The grains that make up rock salt are very coarse compared to table salt that is ground. Although the same molecule, sodium chloride, table salt is ground, purified, and often has additives such as iodine and anticlumping agents. Most rock salt is mined “dry” from networks of below ground crystal salt which formed though the evaporation of ancient seas. Large machinery such as power shoveling machines are used once dynamite is placed in shafts underground. Truck or conveyers are often used to transport the remains of the salt slabs to be taken to crushing machines. When road salt is applied to pavement, it lowers the freezing point of water, making it harder for the snow to bond to the pavement. When road salt is applied, it lowers the chance of ice to accumulate on the surface. Road salt is a popular deicing method due to its ability to pretreat pavement and stop the accumulation of ice before it starts. Otherwise known as a brine layer, road salt acts as a barrier between pavement and the harsh winter elements us cold weather climate beings are accustom to. According to the American Highway Users Alliance, salting roads reduces accidents up to 93%. Whether it be salting a highway, parking lot, or sidewalk, deicing methods such as road salt allow for ice free pavement to create a safe environment for slip free surfaces.

Although there are salt mines all over the world and even in the United States such as in New York State, Kansas, and Louisiana, rock salt was first found under Detroit in 1985. Fast forward to 1914, the Detroit salt mine over 1,000 feet below the city, 1,500 acers of manmade tunnels allowed the production of 8,000 tons of rock salt every month. Transported by donkey that were lowered into the salt mine posed a dangerous problem for salt mine workers. Heavy machinery had to be lowered into the depts of the mine through narrow shafts in pieces. Once all pieces were lowered down, they were then put together underground in the mine by the miners. Road salt was first introduced to the world of transportation and vehicles safety in the 1930’s to combat snow and ice in climates that receive snowfall, low temperatures, and freezing temperatures. First introduced in New Hampshire, granular sodium chloride was introduced on an experimental basis to provide vehicle traction on roadways to reduce vehicle collisions. Prior to the experimental test in New Hampshire using granular sodium chloride, roadways relied on plows and abrasives such as sand to maintain winter roadways. By the winter of 1941-1942, a total of 5,000 tons of salt was spread on highways nationwide. After World War II ended in 1945, expanding highways was essential to the public and national economy. Fast forward about 30 years later in the 1960’s, people were commuting for both work and pleasure and more than ever using major highway systems and roadwork networks. The process of maintaining and salting roadways started out via workers shoveling salt from the pack of trucks. During the 1950’s and 1960’s, spinning disks and rollers extended the width of trucks allowed for spreading over a wide range. As advancements in the highway system were underway, methods to managing snow and ice were evolving. Highway agencies eventually learned to spread salt more effectively by withdrawing it in a narrow line to produce a concentrated brine that flowed under the iced to break the pavement ice bond.

Eventually, other methods of ice management were introduced such as the direct depositing of salt solutions from trucks equipped with a tank and nozzle with the use of prewetted salt, salt dampened with water or calcium chloride. Since prewetted salts adhere to pavement at higher rate and acts faster than standard dry salt, in turn, less deicing chemical product is required. With an increase traffic resulted in an increase in automobile accidents. In the United States alone, around 20 million tons of salt are used today, that is equivalent to about 123 pounds for every American. Deicing roadways pay for itself in just about 25 minutes after the salt is spread. During the first four hours after salt is applied, the direct road users benefits are $6.50 for every $1.00 spent on direct maintenance costs per the operation. Deicing roads and major highway systems is an essential part of winter snow and ice management in many states, whether they receive 20 inches a year or 50 inches a year. Did you know that in Minnesota, the average snowfall per winter totals about 36 inches in the southwest parts of Minnesota and stretching to 70 inches along Lake Superior, better knows as the “snow belt”. The Minnesota Department of Transportation and other highway safety effort organizations such as the American Highway User Alliance are wonderful resources that are on the lookout for the safety and well-being of those traveling on our roadways. There is no slowing down of road salt production anytime soon. With every winter brings more road salt and in turn preventing vehicle accidents and helping people return home to their family’s after every trip during our slick winter months.