A chemical storage facility was installed in the maintenance yard to contain the anti-icing agent, liquid magnesium chloride. The storage facility included two 6,900-gallon tanks and an electric pump used for chemical circulation and truck loading. When inclement weather was forecast, a truck with a 1,500-gallon tank and a truck with a 1,000-gallon tank were used in concert with spray controls to pre-treat the highway with liquid magnesium chloride. Application rates varied from roughly 10 to 50 gallons per lane mile depending on the type of forecasted weather event. After initial application, maintenance crews regularly checked the status of four “indicator areas” along the highway. When frost on shoulder lanes began to migrate into travel lanes, the highway was retreated to ensure that the chemical concentration did not fall below effective levels.
A before/after study was conducted to determine winter maintenance trends over the period from Winter 1991/1992 to Winter 1999/2000. Yearly averages of labor hours, abrasive quantities, and accident frequency were calculated to compare the periods prior to and following inception of the anti-icing program in 1997. Comparison results are shown in the table below.
Average Labor Hours
Average Abrasive Quantities
Average Number of Accidents
The US 12 anti-icing program was a tremendous success. Depending upon precipitation amount, humidity and pavement temperature; a single application of liquid magnesium chloride was typically effective for three to four days. The program has reduced labor hours by 62 percent, abrasives usage by 83 percent, and winter accident frequency by 83 percent. The successes of District 2 and other ITD districts have fueled expansion of anti-icing programs throughout the state.