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Winter Performance of SafeLane Overlays Wilfrid A. Nixon, Ph.D., P.E. University of Iowa Iowa City, IA 52242.

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Presentation on theme: "Winter Performance of SafeLane Overlays Wilfrid A. Nixon, Ph.D., P.E. University of Iowa Iowa City, IA 52242."— Presentation transcript:

1 Winter Performance of SafeLane Overlays Wilfrid A. Nixon, Ph.D., P.E. University of Iowa Iowa City, IA 52242

2 Overview Introduction Where was the overlay tested? What did the tests involve? What were the results? What do they say about how the overlay performs in winter conditions? What questions do you have?

3 What is the SafeLane Overlay It uses a special aggregate system This allows it to soak up anti-icing chemicals This keeps the chemicals around longer

4 Where was the Overlay Tested? Original test began in 2003 Wolf River Bridge, Crandon, Wisconsin Showed good results Extended tests to eight other sites for the winter

5 Site Locations Texas, Ohio, Virginia (2 sites), Indiana, New York (2 sites), and Wisconsin (2 sites) Included seven bridges, one exit ramp (Ohio), and one on-ramp (Blatnick Bridge Wisconsin) Of the six bridges treated in , five had only one side treated, for comparison

6 What was involved in the Tests? First, do no harm Collect data about any issues arising with application of chemicals to the overlays –In particular, was any slickness seen? Also gather data about treatments, and any observations on performance of the overlays Where available, compare accident data

7 What were the results? Different amounts of data at each site In some cases, primarily anecdotal In other cases, significant data available The two New York structures are being separately evaluated by New York DOT For the sake of timeliness, only some of the results are reviewed here

8 Ironwood Bridge, South Bend, IN Extensive data available for this site –Data sheets –Anecdotal reports In general, information about pavement temperature, weather conditions, and treatments were supplied Both control and test section were treated with salt brine (for anti-icing) or solid salt as needed

9 Ironwood Anecdotal Information Storm December 1: The bridge westbound (the control section) was slushy and a little slippery. The new bridge eastbound (test section) was just wet. Nothing stuck. We anti-iced Tuesday (two days prior to event). The bridge worked this time. Comments in parentheses have been added to clarify

10 More Ironwood Anecdotes Storm December 14 A little bit of snow just fell and started to turn things a little snotty. We shot the westbound side (control section) and by the time we were going to shoot the eastbound side (test section) it was already melting off. An additional note indicates a few minutes elapsed between the two treatments

11 Tabulated Data for Ironwood Data available for four different storms –December 14 –January 23 –February 12 –February 17 In each case info on road and weather conditions, applications of chemicals and test and control surface conditions

12 December 14 Storm 12 p.m.No snow and Pavement Temperature (PT) = 32º 35 gallons a lane mile of salt brine applied in anti-icing mode Pre-treatment, so no precipitation at this point a.m.Light snow, PT = 26º200 lbs per lane mile of salt Test section clear, control section slushy 12:40 p.m.Freezing rain, PT = 29º 200 lbs per lane mile on control section only Control section had ice, test section was wet 1:40 p.m.Freezing rain and snow, PT = 30º 250 lbs per lane mile on control, 230 on test No report 3:15 p.m.Freezing rain, PT = 31º 200 lbs per lane mile on both Control section had ice, test section was wet 4:05 p.m.Freezing rain, PT = 29º 200 lbs on control section only No report on control section, test section still wet 5:25 p.m.Freezing rain, PT = 29º 250 lbs per lane mile on control section, 230 on test Control section had only wheeltracks bare, test section still wet. 250 lbs per lane mile on control section, 230 on test Control section had only wheeltracks bare, test section still wet.

13 January 24 Storm 9:00 a.m. No snow, PT = 30º Anti-icing at 40 gallons per lane mile Snow and frost were in the forecast 9:00 a.m. Light snow, PT = 30º 200 lbs per lane mile of salt on control section Control section was snow covered prior to treatment, test section did not need treatment

14 February 12 Storm 9:00 a.m.No snow, PT = 21ºAnti-icing at 40 gallons per lane mile No report 9:20 a.m.Light snow, PT = 28º200 lbs per lane mile to control section Control section was snow covered prior to treatment, test section did not need treatment 10:30 a.m.Light snow, PT not recorded 200 lbs per lane mile to control section, 100 lbs to test section Control section had snow present prior to spreading, test section was still wet 12:00 p.m.Light snow, PT = 32º200 lbs per lane mile to control section, 100 lbs to test section Control section had snow present prior to spreading, test section was still wet

15 February 17 Storm 2:00 a.m. Light snow, PT not recorded 220 lbs per lane mile to both sections Both sections had snow prior to treatment – rain in previous days may have removed chemical residual 4:00 a.m. Light snow, PT = 27º 200 lbs per lane mile to control section, none to test section Test section was still clear from prior treatment, control section had icy film prior to this application

16 Blatnick Bridge, Wisconsin Extensive data also available for this on-ramp Both comments and storm reports from January and February Typical chemical applications in this area are lbs per lane mile of granular salt and 20 gallons per lane mile of Magnesium chloride (anti-icing) Test section charged about every two weeks with 15 gallons per lane mile of mag. chloride

17 Blatnick Summary Comment The area where the SafeLane was applied holds the chemical longer and when it does become snow covered it seems to still have more traction than the surrounding area. Jeffrey Hall, Minnesota DOT

18 Blatnick Data January 4:00 a.m.No precipitation, pavement temperature (PT) = 31º 21 gallons per lane mile, liquid, anti-icing Both were clear and dry 4:00 a.m.No precipitation, PT = 27º 18 gallons per lane mile, liquid, anti-icing Clear and dry 4:00 a.m.No precipitation, PT = 24º 25 gallons per lane mile, liquid, anti-icing No report 11:00 a.m.Freezing rain and sleet, PT = 29º Solid chemicals applied twice, at 200 lbs per lane mile each time Test site was clear and wet, and was not slippery 4:00 a.m.No precipitation, PT = 17º 27 gallons per lane mile, liquid, anti-icing Clear and dry 4:00 a.m.No precipitation, PT = 21º 23 gallons per lane mile, liquid, anti-icing Clear and dry Solid chemicals applied twice, at 200 lbs per lane mile each time Test site was clear and wet, and was not slippery

19 Blatnick Data February 8:00 a.m.Wet, heavy snow, about 2-4 inches, PT =18º 3 applications of solid chemicals at 200 lbs per lane mile each time Slush present on test site, but it remained clear longer than control site. 7:30 a.m.Snow, air temperature = 22º 2 applications of solid chemicals at 400 lbs per lane mile each time Slush present on both test and control site. No differences between the two were noted 7:00 p.m.Normal snow, PT = 17º1 application of solid chemicals at 200 lbs per lane mile Test site was clear and wet. Accumulation of snow on test site was delayed in comparison to control 6:00 p.m.Wet snow, 1-3 inches, PT =20º 1 application of solid chemicals at 200 lbs per lane mile (pre-wet) Test site was clear and wet. Able to be kept that way with less chemical than control sections. 5:45 p.m.Snow, 1-2 inches, PT= 27º 1 application of solid chemicals at 200 lbs per lane mile (pre-wet) Test site clear and wet, and holding longer than control sections.

20 Crandon, Wisconsin Information SafeLane overlay in place for three winters now (installed in Summer 2003) Data primarily anecdotal Also some safety data

21 Crandon General Comments Since SafeLane installed, a single application of 8-10 gallons of liquid has been effective for up to two to three weeks (depending on intervening weather) in contrast to prior to installation, where frost was a constant problem

22 Crandon Safety Prior to installation, 3 to 4 winter related accidents on the bridge each year Since SafeLane installed, no winter related accidents have occurred Also no early morning phone calls from local law enforcement saying the bridge is icy and requiring overtime to fix

23 Crandon Quote When the sun went down in the winter, the bridge used to freeze up – it just doesnt do that anymore. It just does its job real well. Ron Cole, Forest County Highway Department

24 Implications of These Results Lots of data, what do they all mean? Look at each of the implications, and talk about their impact

25 First Implication No problems with application of liquids to SafeLane Some concern that chemical slickness might occur, especially if liquids applied at warmer temperatures For liquids applied in (salt brine and magnesium chloride brine) no problems of that nature

26 Second Implication Number of instances where the SafeLane section had no snow and/or ice, while the control section did have snow or ice Documented not only for snowfall, but also for ice (Texas) and freezing rain (Indiana)

27 Third Implication Sometimes, snow or ice will accumulate no matter what When that happened, the SafeLane sections could be kept clear with reduced chemical applications (compared to control) Reduced applications often worked better on SafeLane sections than full applications on control sections

28 A Closer Look at the Last Two! Clear that the SafeLane treated sections maintained mobility better than control sections (mobility is a primary goal) Example: 11 in-storm treatments at Ironwood, SafeLane section was clear for 10 of the 11 treatments. Control section had snow, slush or ice present 10 of 11 times

29 More on Ironwood Not only was the SafeLane treated section clear most of the time, it was clear with a reduced level of chemical application SafeLane section had total applications at a rate of 1,260 lbs/LM compared with 2,520 lbs/LM on the control section Significant reduction in chemical needs

30 Fourth Implication Apart from Crandon, only one years testing, but… Improved performance of the SafeLane treated sections appears to translate into a safety benefit Obviously a full blown safety study would need many years of data

31 Safety Summary Texas: - no accidents on SafeLane section during an ice storm, when rest of highway had many accidents (including control section) Blatnick: - no accidents this winter, compared with about 20 over previous 4 years

32 More Safety Ohio Interstate exit: - fewer slide off accidents than in previous years (49 over the past two years) Crandon, Wisconsin: - reduced from 3 or 4 accidents a year prior to treatment with SafeLane to no winter accidents since SafeLane installed

33 Summary On the basis of the results from the winter, the SafeLane overlay provides benefits in both safety and mobility under winter storm conditions, and those benefits may be attained with less chemical than without the overlay.

34 Questions? Report is available at:


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