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ANTI-ICING TECHNOLOGY
By WILLIAM T. SUNLEY, Engineer of Local Roads and Streets
Credits to: Technology Transfer Center, Van Vieregge, Program
Development Technician and Willy Scheller, Program Coordinator.
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Anti-icing is the practice of preventing the formation of bonded snow or ice to the pavement by timely
applications of a chemical freezing-point depressant.
This proactive approach differs from conventional de-icing practices which requires the application of a
melting agent as a reaction to the accumulation of
snow and ice on the pavement.
The anti-icing practice has become a viable strategy as a result of field-tests conducted in 15 states during the winters of 93/94 and 94/95. These tests were
sponsored by the Federal Highway Administration
(FHWA) as a continuation of a Strategic Highway
Research Program (SHRP) project. Though not a new
concept, the FHWA/SHRP program dramatically advanced this practice using a variety of equipment and
materials, notably liquid anti-icers.
Anti-icing is a systematic approach to winter road
maintenance that can be adapted to an agency's
unique conditions and available tools. It includes three
critical components: operations, decision making and
personnel. The operations component consists of the
winter maintenance forces' capability for the timely application of chemicals to the roadway in a solid,
prewetted solid, and/or liquid form. This component
also includes plowing accumulated snow and ice from
the pavement so that a second application of chemicals
can be applied to a clear-as-possible pavement surface
if necessary. The equipment and materials needed to
support these activities consists of spreaders, anti-icing
materials, solid and liquid chemical storage facilities
and plows with appropriate cutting edges. Anti-icing
materials include liquid sodium chloride, liquid calcium chloride, liquid magnesium chloride, liquid calcium magnesium acetate, liquid potassium acetate and
fine-graded salt prewetted with some liquid. Some liquids are used to prewet salt, and some are sprayed directly on the road surface as the anti-icing agent.
Decision-making components necessary to support anti-icing include weather service forecasts, real-time conditions of pavement surfaces and road weather information as determined from road weather information systems if available, nowcasting (the use of
real-time data for short-term forecasting), traffic information, information on present pavement observations and friction measurements from patrols, and
post-storm evaluations of treatment effectiveness.
Anti-icing demands accurate, local weather and storm
prediction data. Applying the material on the roadway
too early or too late may be wasteful and ineffective.
The personnel component consists of stand-by
and call-in procedures, and staff trained to use available weather and pavement data in the decision making process. After the initial application of anti-icing
material, personnel, materials and equipment must be
November 1996 / Illinois Municipal Review / Page 15
available and prepared for re-application as the conditions dictate.
One major benefit to be derived from the use of
anti-icing technology is a better understanding of the
conditions under which anti-icing operations should,
and should not be used. Additional benefits are:
• Improved efficiency and effectiveness of highway
agencies' winter maintenance operations and cost
savings in time, labor, materials and equipment.
• Improved vehicle traction and consequently, highway safety during winter-time conditions.
• Improved levels of service of highways during winter-time conditions.
• Reduction in certain locations of the U.S. in the
quantity of materials (both chemicals and abrasives)
used in snow and ice control,
• Reduced environmental and infrastructure impact
of snow and ice control operations in sensitive areas.
• Improved knowledge concerning the use of liquid
chemicals and prewetted solids in anti-icing operations.
The FHWA/SHRP field tests have shown that
while an anti-icing strategy may not be appropriate for
every storm, it is a valuable tool for fighting some winter storms, for pavement frost control operations and
to help eliminate "black ice" conditions. The tests indicate that anti-icing materials are most effective when
applied prior to the pavement temperature reaching
the freezing point and remain effective until temperatures reach -6 degrees C (20 degrees F). For storms initiating at or continuing into temperatures below -6 degrees C (20 degrees F), agencies should switch to their
deicing program. High winds, heavy drifting and prolonged heavy snow conditions have also limited the effectiveness of anti-icing practices. However, applying
anti-icing chemicals to the pavement prior to the storm
will hinder the snow pack from bonding to the pavement and will aid in snow removal once conditions improve.
Several agencies participating in the tests noted
that anti-icing must be a team effort and that everyone
associated with the anti-icing process must be involved
from the very beginning. Everyone must understand
the new technology and the expectations of new
methods to achieve the desired results. The more information everyone has the easier it is to establish a
program which achieves a higher level of service at potentially less cost. Total team involvement also provides a greater chance of program success.
Another important element of any anti-icing program is advance public information. The public seeing
chemicals spread (especially if the chemical is liquid)
before the snow accumulates will generate some inquiries if not complaints. Advance information can
turn negative attention into positive public reaction. •
Page 16 / Illinois Municipal Review / November 1996
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