Cleaning roads in winter is determined by weather
conditions, so the Wisconsin DOT uses its own weather information stations to
inform plow operators.
Salt is primarily used to make plowing
easier, but its effectiveness declines below 15 degrees. In low temperatures, common salt may be mixed
with sand, calcium chloride or magnesium chloride to enhance effectiveness and
provide additional traction. Highway crews sometimes do "anti-icing"
– spraying bridge decks, curves, hills and other known trouble spots with a
salt solution - to prevent snow or ice from bonding to the pavement.
Most counties pre-wet salt just before applying
it to roadways. Pre-wetted salt adheres better to pavement, starts the melting
process faster, and can save money by reducing overall salt usage about
25-percent compared to dry salt. Pre-wetting using a salt brine or similar
liquid can also help salt work better at lower temperatures.
During sub-zero temperatures common this winter,
the only practical snow removal technique is plowing.
"Plowing is still the work-horse when it
comes to removing snow and ice from Wisconsin highways," says WisDOT
Winter Maintenance Engineer Mike Sproul. "Salt accelerates melting, but
most importantly, salt keeps snow and ice workable so it can be removed by
plowing." County highway
departments do most of the work, under contract to WisDOT.
60 weather information stations along the state
highway system continually gather and transmit information on air and pavement
temperatures, relative humidity, wind speed and direction, depth of
precipitation on the roadway, and even salt concentrations. The comprehensive
data helps highway departments know how and when to treat specific highways.
Many county snowplows are equipped with
Automatic Vehicle Locators. The AVL systems use global positioning technology
and help county highway superintendents locate plows and determine the de-icing
materials to apply.
All motorists can check road conditions
using the 511 Travel Information System, a
colored-coded map of current driving conditions everywhere in the state. Sproul reminds drivers that state law
requires staying 200 foot behind a working snowplow.
