Study: Reflectors, white bags reduce wildlife collisionsAug 9, 2015 From staff reports
Wildlife warning reflectors and canvas bags have proven effective in reducing wildlife-vehicle collisions during a three-year study in three Wyoming counties.
The Wyoming Department of Transportation and Conservation Research Center of Teton Science Schools conducted a three-year study, which concluded this spring, to evaluate the effectiveness of wildlife warning reflectors on wildlife-vehicle collisions in Big Horn, Hot Springs and Fremont counties. WyDOT installed these reflectors in 2007-2010 in several of the worst hot spots of deer-vehicle collisions in the state.
The area north of Thermopolis includes the worst single mile in Wyoming for deer-vehicle collisions, with an average of 18 per year for the last six years.
Between 2007 and 2010, WyDOT installed wildlife warning reflectors west of Riverton on 4.7 miles of U.S. Highway 26 between Kinnear and Riverton, and just north of Kinnear; on 6 miles of U.S. Highway 16/20 between Greybull and Basin; on 3.3 miles of U.S. Highway 20 between Wind River Canyon and Thermopolis; and on 8.9 miles of U.S. Highway 20 between Thermopolis and Lucerne.
Testing the reflectors
Part of the study involved covering wildlife warning reflectors with bags to evaluate deer behavior and carcass numbers with and without the reflectors working as they are intended.
Teton Science Schools researchers Corinna Riginos and Morgan Graham found there were 65 percent fewer deer carcasses to pick up in areas where a white canvas bag was placed over the wildlife warning reflectors, compared to areas where non-reflective black bags were places over the posts. The wildlife warning reflectors were 32 percent more effective than black bags, but white bags were 33% more effective than reflectors.
"We certainly didn't expect to find something as simple as a white bag to be even more effective," Riginos said.
Riginos and Graham, in their study summary, "suggest that the white bags are more visible or reflective to deer than the red wildlife warning reflectors and are thus substantially more effective than reflectors."
Riginos said the researchers aren't exactly sure why the low-cost white bags proved more effective than the higher-cost wildlife warning reflectors. The red wildlife warning reflectors cost about $23.50 each, while the white bags cost about $1.50 each.
"Although we recognize that white canvas bags are not a permanent mitigation solution, this price difference illustrates that a cheaper technology may exist that is more effective than the reflectors," Graham and Riginos wrote in their study summary.
Graham and Riginos think the white bags may look like deer tails, which deer move around in "flips of white" in times of danger.
"I think it's something about the moving light, the brightness of it," Riginos said. "Even where we were doing this, the deer ultimately did cross the road when there were no cars. It just made them more aware of the vehicles and less likely to run into the road in front of a vehicle and get hit."
WyDOT plans to use the study results as a basis for continuing to improve safety on Wyoming highways for drivers and wildlife.
"Deer-vehicle collisions are also strongly associated with moderate to high traffic volumes and high speed limits of 65 mph and higher," Graham and Riginos wrote. "As traffic volumes continue to rise, deer-vehicle collisions are likely to increase as well. Limiting vehicle speeds, especially at night, may be another way to reduce collisions. On average, areas with a speed limit of 55 mph have 36 percent fewer deer-vehicle collisions than areas with a speed limit of 65 mph. ... Reducing speed limits to 55 mph at night, dawn and dusk may be an effective and much less expensive way to reduce collisions."
Riginos and Graham, in their study summary, wrote "reducing deer-vehicle collisions in District 5 (Northwest Wyoming) and around Wyoming will likely require a suite of different strategies, some of which may be more or less suitable in different areas."