FHWA FIELD TESTS

Traditional deicing techniques break the bond between the pavement and ice or snow. Anti-icing techniques use chemicals to lower the freezing temperature of the pavement surface and stop that bond from forming. Anti-icing takes advantage of new, sophisticated weather information systems that predict where and when storms will cause bad winter driving conditions. Mergenmeier contended, "Such anti-icing strategies help keep roads safe for travel, reduce the environmental impact of winter operations, and make post-storm clean-up easier."

To learn under what conditions anti-icing was effective and what methods worked best, the FHWA initiated these field tests. Field testing began during the winter of 1993-94 and continued during 1994-95. The U.S. Army Corps of Engineers Cold Regions Research and Engineering Laboratory is analyzing gathered data. This article reported on preliminary data from the first year of the study.

Researchers assumed when they started field testing that "[t]he key to a successful anti- icing strategy is knowing which chemical to use, in what amount, and when." Local weather, geography, and traffic patterns would determine appropriate strategies, and it was vital to have precise weather forecasts for specific stretches of highway. With accurate information, winter crews could decide what chemicals and methods to use. Some chemicals tested were:

• liquid calcium magnesium acetate (CMA),
• liquid calcium chloride,
• liquid magnesium chloride,
• liquid sodium chloride (salt brine),
• liquid potassium acetate, and
• prewetted solid sodium chloride (NaCl, commonly known as rock salt).

Experimental methods required material spreaders that put down prewetted or liquid materials. These machines worked by "varying the spreading rate, spreading width, and prewetting rate upon demand, while correlating the application rate with the vehicle speed."

RESULTS OF 1993-94 FIELD TESTS

At a Minneapolis conference in August 1994, representatives of the 15 field-test states shared their 1993-94 findings. Mergenmeier described the participants as "enthusiastic." They reported that anti-icing can:

• Reduce the amounts of chemicals needed.
• Prevent black ice or frost on bridge decks when liquid chemicals are periodically applied.
• Require less effort to return the pavement to a bare condition at the end of a storm.
• Reduce the amount of abrasives (sand) used.

Excited about the cost savings, environmental benefits, and improved safety of anti-icing, representatives of the participating states also mentioned that anti-icing would require some improvements and changes. They enumerated the need for:

• Better weather information systems,
• Improved materials and material spreaders, and
• More crew training.