There are also some conditions in which anti-icing is not recommended, such as prior to rainfall events, during heavy snowfall events (more than 1 inch per hour), in areas with blowing or drifting snow, or if a bond has already formed between the pavement and ice or snow. An RWIS helps an operator decide if these conditions are present.
After a storm event begins, information from an RWIS can be used to make decisions concerning deicing operations. When temperatures drop below 25° F, there is little moisture available to dissolve salt, and if salt remains in solid form, it cannot melt ice and snow. Prewetting may be used under these weather conditions to help extend the effectiveness of salt by providing the necessary moisture, allowing the salt to begin working immediately.ADDING NEW TECHNOLOGIES
Additional technologies have recently entered the market to supplement existing tools. Russ Alger, a professor at Michigan Tech University in Houghton, has developed a two-part surface treatment for pavements consisting of an epoxy and aggregate application. This material, when applied to bridge decks, absorbs anti-icing/deicing chemicals and releases them over a long period. Last fall, Minneapolis-based Cargill purchased the licensing rights and technology to market this product, which they have dubbed SmartLane.
Bob Persichetti, general manager of Cargill's SmartLane business, said, “Wisconsin DOT has been testing it on the Wolf River Bridge in Crandon for two years. Before the application, the bridge had been averaging eight traffic accidents per year. Last winter, and thus far this winter, there have been no accidents on the bridge.”
Advancements also have been made in software developed to aid in the analysis of storm data and choice of control strategy. The Snow and Ice Management Association offers a product that allows input of weather forecasts, snow characteristics, deicer properties, and application rates. From this information, the amount and application rate of deicer is calculated for a particular event.
Other software works with automatic vehicle locator (AVL) equipment. Bret Hodne, superintendent of operations with the city of West Des Moines, Iowa, said, “We are converting our fleet to an AVL system that is tied into the material-spreading equipment. This system will let us know how much material is being applied both ‘live' in the field and the total amount at the end of the storm.”
Walter Link, Flagstaff district maintenance engineer with the Arizona DOT, said in his district, “all spreaders are computer controlled. Many of the spreaders have a printout function. All operators are required to keep a detailed TAPER (temperature, application, product, event, and results) log that is turned into the district office for collation and review.”
Some states also have installed a fixed automatic spray technology (FAST) system. FAST consists of a permanent anti-icing installation that can be programmed to automatically apply chemical from a series of sprays embedded in or near the roadway. The Minnesota DOT has implemented FAST systems on several bridges throughout the state. Linda Heath, maintenance agreements and research engineer with the Metro District of the Minnesota DOT, said, “The FAST system has really worked well. Our installation on Interstate 35 West over the Mississippi River in Minneapolis has reduced snow- and ice-related crashes by 45% and callouts by at least 50%. With these benefits, the system has paid for itself.”
A FAST system can be activated offsite or from computerized controls located onsite. Because chemical is placed automatically and only when conditions warrant, departments save on labor and chemical costs. More importantly, damage to vehicles and injury or loss-of-life also are prevented.
Even with all this technology, experienced personnel remain an essential part of the operation. “A well-trained employee is still the most crucial piece of snow-fighting equipment,” said Link.