ADOT's Role
Magnesium Chloride: Just the facts
Why do workers spray liquid onto the roadways before a big storm arrives? If you live in Northern Arizona you've probably asked yourself that question. It may seem dangerous to add liquid to a road that might freeze but that liquid can be your best friend when winter driving conditions are at their worst. That liquid, known as magnesium chloride solution, can prevent snow from sticking to the road and prevent frost or black ice. It's one of the newest weapons against icy roads. Thanks to magnesium chloride, winter driving can be a safer experience.
Definition and uses of Magnesium Chloride
Magnesium chloride works like anti-freeze by lowering the freezing temperature of water and preventing ice from forming a strong bond to the road. It helps keep roads from becoming slick, improves safety and reduces accidents.
Anti-icing: a light application of the liquid is made to a road before a storm to prevent a hard bond of ice, reduce snow buildup and speed snow and ice breakup after a storm.
De-icing: a liquid or solid is applied to remove a thin layer of snowpack or ice already on the road. It can be very effective for melting black ice and freezing rain.
Pre-wetting: wetting the traditional cinder material with anti-icing or de-icing chemicals to cause cinders to stick to snowpack better. Keeping cinders on the road is nearly impossible in some circumstances, especially in very cold weather and in cases where there's traffic at highway speeds. Magnesium chloride can keep cinders from blowing to the shoulder of the road.
Safety
Less toxic than baking soda or salt, the use of anti-icing chemicals is very safe. Unlike cinders, it won't crack your windshield or chip your car's paint. Tests have shown that the proper application of anti-icing chemicals produces no negative effects on ground water, surface water or vegetation.
You should wash your car on a regular basis if you drive on roads where anti-icing chemicals are used. These chemicals (along with slush and dirt) can splash your car and build up after a time, leaving a filmy residue on your vehicle. Make car washing a part of your regular maintenance routine, and you'll help keep residue from the winter roads off your car.
Why not use cinders?
In many cases anti-icing chemicals work better than cinders. It keeps snow from firmly sticking to the pavement. De-icing chemicals also last longer than cinders and work in a broader range of conditions. Cinders can be crushed by traffic and produce airborne dust, which contributes to pollution and health concerns. Because cinders are easily blown off roadways by traffic, it requires repeated applications.
Cost efficiency
The use of anti-icing chemicals is usually the most cost-effective alternative when considering the whole picture. By breaking the bond between the pavement and ice or snow, less effort is required for snowplows to get back to bare pavement. This in turn, saves money on overtime, equipment costs and materials used in winter maintenance.
Other ADOT Involvement
ADOT considers that the forecast of difficult driving conditions caused by snow and/or ice warrant immediate response and work by its highway maintenance forces to mitigate these driving conditions until improving weather returns driving conditions to normal. The goal of this work is to enable a reasonable and prudent driver to safely travel the highway. Work may be continuous or intermittent depending on the type of highway, nature of the storm, and the availability and condition of equipment and personnel.
Priority in allocation of snow and ice control resources for ADOT:
1. Interstate highways, freeways, and other highways carrying 3500 ADT*.
2. Highways carrying 1000 to 3500 ADT*.
3. Highways carrying less than 1000 ADT*.
4. Highways that are closed for the winter season.
In addition to these priority routes, ADOT maintenance personnel work in 12 hour shifts during winter storms and anti-icing or de-icing chemicals are used on all routes with the potential for snow and ice. (*Average Daily Traffic)
For more information on magnesium chloride or snow removal,
contact Kent Link, Flagstaff District Maintenance Engineer,
(928)779-7570 or email wlink@azdot.gov
