Highway crews apply science, salt to keep winter roadways open
January 23, 2014
Winter in Wisconsin can bring any combination of snow, wind, ice and brutally cold temperatures. The tools and strategies county highway crews employ to battle winter storms include plow blades, pre-wetted salt, anti-icing and global positioning systems.
The Wisconsin Department of Transportation (WisDOT) contracts with county highway departments to help keep state and federal highways clear of snow and ice. Currently, about 90-percent of 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.
"Plowing is still the work-horse when it comes to removing snow and ice from Wisconsin highways," said 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."
Salt’s effectiveness against snow and ice declines as temperatures drop below 15-degrees. In lower temperatures, salt may be mixed with sand, calcium chloride or magnesium chloride to enhance effectiveness and provide additional traction. During sub-zero temperatures like Wisconsin has experienced this winter, the only practical snow removal technique is plowing. Prior to certain weather situations, 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.
WisDOT oversees about 60 remote weather information stations along the state highway system that 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 know where plows are located, what routes have been covered, and how much de-icing materials should be applied to roadways.
"County highway crews do an outstanding job keeping roadways open, but safe winter travel is really in the hands of individual motorists," Sproul said. "State law requires drivers stay back at least 200 feet from an active snowplow. Prior to a trip, people can check road conditions using the 511 Travel Information System. When conditions get really bad, motorists should simply stay off the roads so snowplow operators can do their jobs. If you have to travel, buckle-up, slow down, leave plenty of following distance and keep your cell phone handy in case you slide off the road. If that happens, call 911, stay in your vehicle, and wait for help to arrive."
For more information, contact:
Mike Sproul, WisDOT Bureau of Highway Maintenance
(608) 266-8680, firstname.lastname@example.org