DOTs Work to Improve Winter Highway Safety and Efficiency
Although snow and ice thrill skiers and skaters in the northern Midwest, they regularly deliver headaches and perils to motorists and those responsible for clearing the roads. Each winter, state departments of transportation work to improve safety and efficiency on their highways while mitigating environmental impacts. In particular, a growing effort targets the negative effects of chlorides from salt use.
However, since salt remains so cost-effective it continues as a staple in winter maintenance efforts, along with fleets of snowplows. Throughout Minnesota, North Dakota, South Dakota, and Wisconsin, though, various strategies and technologies help make the most of available resources. For example, application of a salt and water mixture (salt brine) before or early in a snowstorm helps melt snow and ice before they adhere to the road.
"The liquid brines tend to work faster, and there are less overall chlorides used when salt is in liquid form," said Becky Kikkert, Director, Office of Public Affairs for the Wisconsin Department of Transportation (WisDOT).
In standard salt applications, pre-treating with salt brine or another liquid reduces the amount of material needed. Several studies show that with pre-wetting, up to 30 percent more salt stays on the roadway, WisDOT said.
To increase the efficiency of snow and ice removal efforts, the Departments of Transportation in Minnesota, North Dakota, South Dakota, and Wisconsin all use the Maintenance Decision Support System (MDSS), first put forth by the Federal Highway Administration. This computer-based, customizable system provides winter maintenance personnel with route-specific weather forecast information and optimized treatment recommendations regarding type and amount of material, as well as application times. States utilize the system in slightly different ways; for instance, so far North Dakota has equipped one-third of its snowplow fleet with an iPad to access the program and Minnesota is working toward installation in every snowplow cab.
In addition to these common efforts, each state continues to look at new approaches to improve winter maintenance.
Minnesota's Living Snow Fences
Many states use living snow fences (naturally occurring or designed plantings of trees, shrubs, or native grasses) to trap and control blowing and drifting snow, but the Minnesota Department of Transportation (MnDOT) takes that strategy a step further. Currently, more than 60 landowners participate in MnDOT's program with standing corn rows, hay bales, or other temporary fencing covering 26.9 miles.
"We've had snow fencing for quite a number of years, but it didn't get the attention it needed," said Steve Lund, MnDOT's State Maintenance Engineer. "One of the reasons it's gotten a new emphasis is because we're working on ways to reduce chlorides. Now we're putting a little more money toward snow fencing, from both an employee standpoint and from purchasing ability."
MnDOT appointed Dan Gullickson, already a national expert on living snow fences, as full-time Program Coordinator just over a year ago. His efforts include working with the University of Minnesota to develop a calculator program that predicts where the state most needs snow fences. That information also helps determine participating landowners' compensation based on MnDOT's operational costs beyond routine snowplowing and salt applications, road traffic volume, and crash history in winter conditions.
In addition, "We're making a renewed effort to get involved with construction projects in the design phase, not as an afterthought when the work's all done," Lund. "We've been in catch-up mode in the past; we see a snow trap area then work to get a snow fence. Now we're being more proactive and modifying designs for a better end result. Ditch grades, ditch bottoms, elevations - all that is looked at in a more proactive way to reduce the amount of snow getting to the pavement."
As an alternative to salt treatments, MnDOT has incorporated more potassium acetate. "The price came down a little; that's been one of the dilemmas in the past," Lund said. "There aren't many ways to mitigate the chloride problem, but we think there's a way to mitigate the negative side effects of potassium acetate. As a side benefit, it also has a better working performance at lower temperatures."
MnDOT's Duluth District tested potassium acetate on a stretch of roadway last year and plans to use it in a no-salt pilot this year. The state also utilizes potassium acetate in anti-icing systems for bridges. In fact, the bridge on I-35W over the Mississippi River in Minneapolis features the largest fully-automated anti-icing system in North America.
North Dakota's Beet Juice and New Equipment
The North Dakota Department of Transportation (NDDOT) also uses an anti-icing system called Fixed Automated Spray Technology (FAST). Working in tandem with an environmental sensor station, the FAST system predicts surface freezing temperatures on bridges and applies anti-icing products to prevent slippery conditions. The system operates by pumping liquid through plumbing attached to the side of the structure and connected to spray discs in the deck surface.
NDDOT placed two FAST systems in high-traffic locations. After installation, a study showed a 66 percent reduction in crashes at the I-29 Buxton Bridge south of Grand Forks, North Dakota, and a 50 percent drop at the I-94 bridge over the Red River in Fargo, North Dakota.
To improve de-icing efforts on roadways, North Dakota adds a special ingredient - a sugar beet by-product - to its salt brine. "The "˜beet juice,' as we call it, helps lower the working temperature of salt brine," said Brad Darr, NDDOT Maintenance Engineer. "This provides a benefit in the extreme temperatures experienced in North Dakota to help remove ice from the roadway."
As an added advantage for motorists, a study showed that the sugar beet by-product and salt brine mixture is only one-third as corrosive as salt.
To increase efficiency, NDDOT employs a large number of towplows, which attach to snowplows to clear a wider path of road in one pass. In fact, "We partnered with Viking-Cives in Morley, Missouri, to prototype the new bi-directional towplow," Darr said. "These units are now in production and we own 16 of them."
The bi-directional models allow operators to plow all snow downwind to either the left or right, reducing back drifting across pavement.
South Dakota's Technology and Agricultural Aids
The South Dakota Department of Transportation (SDDOT) also partnered with an outside vendor, Delcan Technologies Inc. of Peachtree Corners, Georgia, to implement an Automatic Vehicle Locator Mobile Data Collection (MDC) System that interfaces with MDSS. The MDC system gathers information from a snowplow's spreader controller, GPS receiver, plow blade sensors, air and road temperature sensors, and other sensing equipment. Through a touch-screen interface, snowfighters can view the data and input driving conditions to receive recommended lane treatments and application rates.
SDDOT and other authorized agencies can access MDC data through an external web browser to monitor the progress of each plow. A follow-up study after installation of the MDC system showed SDDOT's cost of materials spread dropped from $300 to $60 per mile.
In another move to reduce costs, SDDOT began bagging salt with agricultural grain bagging equipment instead of constructing new salt storage structures. Crews load salt into 10-foot diameter polyethylene bags, then seal the bags to create a weatherproof environment. When crews need the salt, they simply slice open a bag.
"We've never run out of salt before, but we've come close," said Brad Norrid, SDDOT's Area Engineering Supervisor in Winner, South Dakota. "We think this process has great potential to help us and other operations serve customers better."
Wisconsin's 100-Year Partnership
In a nationally unique arrangement, "WisDOT does not own or operate a single snowplow," Kikkert said. "Instead, as part of a unique 100-year-old partnership, WisDOT has agreements with all 72 county highway departments across the state who provide the equipment and personnel to handle snow and ice removal from our state highway system, including snowplowing, salting, and liquid applications."
Many, but not all, municipalities work with WisDOT on a state salt bid. "The Department bids separate lines for each county, with a different price in each county due to the variation in transportation costs," Kikkert said. Throughout the winter, "The Department works with counties, actively monitors salt supplies, and makes adjustments as needed. This can include facilitating the movement of salt to areas where it's needed and ordering additional salt as needed."
To help counties maximize efficiency, WisDOT uses computer software to balance and optimize plow routes. They also encourage liquid brine applications to bridge decks, curves, and problem areas prior to winter storms. "WisDOT continues to work with county highway partners on broader, statewide efforts to enhance brine-making facilities and equipment," Kikkert said. "This winter season, we're working with six counties to pilot liquid-only routes. Studies indicate this process can reduce the use of sodium chloride materials by over 50 percent."
With snowfalls averaging anywhere from 40 inches in the southern part of the state to as much as 160 inches along Lake Superior, WisDOT relies on a Road Weather Information System (RWIS) to track weather and pavement conditions. Sixty-eight RWIS sites across the state gather data that helps determine when to mobilize staff and apply anti-icing or de-icing agents, as well as the best agent to use.
Winter Facts by State
- Lane miles under MnDOT responsibility: 30,517
- Equipment: 793 snowplows
- Personnel: 1,813 full-time and part-time snowplow drivers
- Cost of winter 2016-2017: $97 million, 3.1 percent higher than the previous year
- Materials used in 2016-2017: 197,417 tons of salt, 3 million gallons of salt brine, and 46,000 tons of sand
- Lane miles under NDDOT responsibility: 17,256
- Equipment: 350 snowplow trucks; 32 towplows, including 16 bi-directional; 62 payloaders; 16 motor graders; 13 Oshkosh rotary snow blowers; two payloader snow blowers; 70 three-point, tractor-mount snow blowers. In extreme weather events, existing contracts with construction contractors provide additional equipment.
- Personnel: 350 snowplow operators
- Average annual cost of winter storms: $22 million
- Salt capacity: 91,400 tons in 69 stockpiles
- Salt stockpiled as of December: 15,000 to 20,000 tons
- Salt used during a severe storm: 2,000 to 4,000 tons
- Lane miles under SDDOT responsibility: 18,265
- Equipment: 400 snowplows; four bi-directional towplows; 55 snow blowers; 45 specialty equipment units
- Personnel: 368 full-time and 50 part-time employees
- Cost of winter 2016-2017: $18.7 million
- Salt capacity: 93,600 tons in 72 stockpiles
- Salt used in 2016-2017: 49,439 tons
- Lane miles under WisDOT responsibility: 34,339
- Equipment: More than 700 trucks owned by county highway departments
- Personnel: More than 1,500 county highway department employees are licensed to operate snowplows; approximately 770 of them are permanently assigned to the state-maintained highway system
- Cost of winter 2016-2017: $87.8 million, 22 percent higher than the previous year
- Average annual salt use on state highway system: 520,677 tons
- After last winter, 200,906 tons of salt remained in storage sheds. WisDOT purchased 414,218 tons for this winter, with 105,876 tons available to purchase in case of a severe winter.