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

Winter Performance of SafeLane™ Overlays

Wilfrid A. Nixon, Ph.D., P.E.

University of Iowa

Iowa City, IA 52242

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?

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

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 2005-06 winter

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 2005-06, five had only “one side” treated, for comparison

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

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

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

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

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

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

December 14 Storm12/13/05 @ 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

12/14/05 @9:40 a.m. Light snow, PT = 26º 200 lbs per lane mile of salt

Test section clear, control section slushy

Same @ 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

Same @ 1:40 p.m. Freezing rain and snow, PT = 30º

250 lbs per lane mile on control, 230 on test

No report

Same @ 3:15 p.m. Freezing rain, PT = 31º

200 lbs per lane mile on both

Control section had ice, test section was wet

Same @ 4:05 p.m. Freezing rain, PT = 29º

200 lbs on control section only

No report on control section, test section still wet

Same @ 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.

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

300-400 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

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

Blatnick Data January1/6/06 @ 4:00 a.m. No precipitation,

pavement temperature (PT) = 31º

21 gallons per lane mile, liquid, anti-icing

Both were clear and dry

1/11/06 @ 4:00 a.m. No precipitation, PT = 27º

18 gallons per lane mile, liquid, anti-icing

Clear and dry

1/19/06 @ 4:00 a.m. No precipitation, PT = 24º

25 gallons per lane mile, liquid, anti-icing

No report

1/22/06 @ 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

1/26/06 @ 4:00 a.m. No precipitation, PT = 17º

27 gallons per lane mile, liquid, anti-icing

Clear and dry

1/30/06 @ 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

Crandon, Wisconsin Information

• SafeLane™ overlay in place for three winters now (installed in Summer 2003)

• Data primarily anecdotal

• Also some safety data

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

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

Crandon Quote

“When the sun went down in the winter, the bridge used to freeze up – it just doesn’t

do that anymore.”

“It just does its job real well.”

Ron Cole, Forest County Highway Department

Implications of These Results

• Lots of data, what do they all mean?

• Look at each of the implications, and talk about their impact

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 2005-06 (salt brine and magnesium chloride brine) no problems of that nature

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)

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

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

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

Fourth Implication

• Apart from Crandon, only one year’s 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

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

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

Summary

• On the basis of the results from the 2005-06 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.

Questions?Report is available at: http://www.cargillsafelane.com/