Tuesday, the Colorado Department of Transportation put into operation a first-in-the-nation Wildlife Detection System on U.S. 160 between Durango and Bayfield, just east of the Florida River.
The system, a constructed test zone between mileposts 95.6 and 96.6, consists of a cable buried one foot deep and 30 feet from either side of the roadway. This “intrusion-detection” technology by Senstar Stellar has been used for perimeter security by military, prisons, airports and some private land owners, but has never been employed as a wildlife detection system.
“The Environmental Impact Statement for U.S. 160 between Durango and the Florida River pointed to the need for wildlife mitigation on this corridor,” CDOT Resident Engineer Chris Beller said. “We overlaid our accident data with a Division of Wildlife (DOW) map of wildlife migration and it was clear that a high number of animal-vehicle collisions were happening right within a major migration route.”
CDOT, in coordination with the DOW, looked at many solutions, their practicality and their economic and environmental feasibility. Fencing, permanent signs, lighting; all presented solutions that were not quite right for this stretch. Beller explains that the team looked at ways to minimize impacts to the wildlife’s migration while alerting motorists of their presence; a sign that would light up only when wildlife were present seemed the best solution. Detection systems using laser beams, microwaves or infrared technology were considered, but due to the potential for false positives caused by snow, clouds and even branches with such systems, the underground detection system was considered the best option.
The underground cable in the Wildlife Detection System emits an electromagnetic field that can detect the presence of large animals (deer, elk, horses). It then transmits information to a sensor module in that particular zone, which communicates to a central on-site control module that activates electronic signs to warn motorists of wildlife in the roadway vicinity. There are 12 signs (six on each side of the highway) in the test section. When an animal triggers the system, two signs for each direction of travel will light up.
To solve the problem of vehicles tripping the system each time they travel over the cable when using a driveway, crews installed under-pavement loop detectors—like those that help ease traffic flow at many signalized intersections. The loop detectors were placed under driveways, on either side of the cable. When vehicles drive over these loop detectors, the cable receives the message to “ignore” this crossing, and the signs will not light up.
Seven speed radar detectors have also been installed to register motorists’ speed both outside and inside the test zone so that drivers’ base speed and reaction speed can be monitored. The radar system will also monitor traffic counts, useful for follow-up analysis of the data. All the data will be periodically downloaded from the on-site modules and sent to CDOT’s Traffic and Safety staff for review. CDOT in Durango was awarded a CDOT Research Grant for $150,000 that will go to Western Transportation Institute of Bozeman, Mont., to independently evaluate the success of the project.
“The variable we’re looking for is motorist behavior,” CDOT Environmental Specialist Tony Cady said. “To test the validity of this system, we need to determine if there’s a drop in speed and also whether this is a long-term behavior change, or just something motorists stop reacting to after a period of months.”
Contractor Rocky Mountain Enterprises began constructing the system in May 2008, but initial planning and design began back in 2005. CDOT Region 5 Environmental and Traffic staff had secured an initial CDOT Research Grant for $150,000 to implement the project. The local Division of Wildlife participated in the study panel to help guide the use of this funding on the project. The entire project, including equipment, installation and contractor costs, amounts to approximately $1 million. The majority of this came from Federal Hazard Elimination Funds, with other funding from the CDOT Research Grant, CDOT Region 5 Traffic & Safety funds and additional CDOT “hot spot” funds, which go towards select projects that address a critical safety need.
In the test stretch of U.S. 160, between mileposts 94 and 100, an average of 70 percent of all reported collisions involve wild animals. (The percentage, extracted from 1999-2003 data, is lower in the summer months and peaks during wildlife migration season from October through May.)
“This pilot project, aimed at helping reduce animal-vehicle collisions in this area, actually involves three separate test zones,” CDOT Traffic and Safety Engineer Mike McVaugh said. “In the first zone — on the east end — we’ve changed nothing; in the middle zone, our maintenance crews have removed brush within 30 feet of the roadway to extend the clear zones; and in the west zone, we have cleared brush and constructed this Wildlife Detection System.”
This pilot project will need to undergo several years of operation, monitoring and supplemental testing and research before results of its validity can be fully realized.
“We worked with representatives from Senstar this month to test the system and make final adjustments relating to the weather, animal size, programming and other factors,” CDOT Project Engineer Kevin Curry said. “I think we’ve worked out most of the programming bugs — we’ve been collecting data for the past two weeks and things are looking good.”