Wind breaks / snow hedges

Inclement weather is often cited as a contributing factor in serious traffic collisions. In 2008, snowy or windy weather conditions were cited as a contributing factor in 6.9% of collisions in which a road user died and 8.4% collisions in which a road user sustained injuries in Canada. A study of traffic collisions between 1995 and 2005 in Minnesota revealed that 14.5% of fatalities and 10.9% of injuries were the result of crashes that occurred in blowing or drifting snow conditions (Nelson, 2010).

A snow fence reduces the wind velocity and causes the snow to accumulate in a sheltered area so that the wind cannot move it again. However, eventually the area will be “filled” and the fence will no longer be effective. A windbreak fence is designed to reduce wind velocity by at least 75%. The effectiveness of a windbreak fence depends on its density and height (British Columbia Ministry of Agriculture, Food and Fisheries, 1997).

Snow fences can improve visibility and reduce the formation of slush and ice by reducing the mass of snow reaching the roadway, thereby allowing daytime solar radiant heat to accumulate in the pavement and substratum instead of being lost to melting snow that blows onto the road (Tabler, 2005).

Citing studies of the I-80 in Wyoming, Tabler (2005) states that up to 25% of all crashes occurred in blowing snow conditions and where the road was not protected by a snow fence, whereas only 11% occurred under those same conditions in areas that were protected by such fences. The author estimated that the cost to benefit ratio of installing snow fences was 4.2:1. This was determined by comparing the annual average decrease in the number of collisions causing injuries and property damage to the original capital cost of installing and replacing snow fencing (the cost of replacing snow fencing was established on the basis of current prices). Tabler also cited the economic benefits of fences on winter maintenance operations including savings in overtime, contract and operating costs for snow removal equipment and services, and sand and chemical usage for ice control.

Wyatt et al., (2012) studied whether establishing standing corn rows and living snow fences on Minnesota’s roadways could improve driver visibility and road surface conditions, lower road maintenance costs, and reduce traffic collisions attributed to blowing and drifting snow. They found that these could reduce drifting snow, poor visibility and icy road conditions, and reduce snow and ice related collisions by 8%. They could also reduce crashes on curved sections of roadways by approximately 40%.

Scope of the Problem

• Transport Canada (2012). National Collision Data Base.  Retrieved from http://wwwapps2.tc.gc.ca/Saf-Sec-Sur/7/NCDB-BNDC/p.aspx?l=en
• Nelson, W. (2010). USDA and MnDOT promote creation of living snow fences. AGWEEK, March 20.  Retrieved from http://www.agweek.com/event/article/id/65104/publisher_ID/22/

Evidence

• British Columbia Ministry of Agriculture, Food and Fisheries. (1997) Fencing Factsheet. Wind and Snow Fences (Order No. 307.230-1). Retrieved from http://www.agf.gov.bc.ca/resmgmt/publist/300Series/307230-1.pdf
• Tabler, R. D. (2005). Controlling Blowing Snow with Snow Fences. Government Engineering, July-August. Retrieved from http://www.govengr.com/ArticlesJul05/snow.pdf
• Wyatt, G., Zamora, D., Smith, D., Schroeder, S., Paudel, D., Knight, J., Kilberg, D., Current, D., Gullickson, D., Steve Taff, S (2012). Economic and Environmental Costs and Benefits of Living Snow Fences: Safety, Mobility, and Transportation Authority Benefits, Farmer Costs, and Carbon Impacts (Report No. MN/RC 2012-03). Minnesota Department of Transportation Research Services. Retrieved from http://www.esf.edu/willow/lsf/Litterature/Wyatt%202012%20-%20Costs%20and%20Benefits%20of%20LSF.pdf