Highway Managers can employ a wide variety of wildlife vehicle collision mitigation techniques to reduce the risk of encountering wildlife on the road.
The time of brush cutting in road rights of way can affect vegetation palatability for moose (mid season cutting increases palatability). The composition of revegetation seed mixes can be altered to be less attractive to ungulates.
If erected and maintained properly, 2.4 m fencing can virtually eliminate collisions (97-99%) when both sides of the road are fenced. However, there are strong biological and ecological factors that contraindicate fencing as a blanket solution for all problem areas. Fencing impacts normal animal travel patterns, fragments habitats, and separates herds. The cost to fence both sides of a highway is between $40,000 and $80,000 per kilometre. Maintenance costs can also be significant.
Traditional wildlife warning signs, although frequently used and inexpensive, tend to be ignored by drivers. Studies conducted by Swedish researchers show that 60% of drivers do not even notice traditional wildlife warning signs.
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Animal Detection Systems
Animal detection systems can detect large animals (e.g., deer, elk, moose, or pronghorn antelope) as they approach the road. When an animal is detected, signs are activated which warn drivers that large animals may be present on or near the road. One part of the system detects the animals as they approach the road, and the other part warns the drivers after detection has occurred.
There are two main types of animal detection systems.
Area-cover systems - These systems detect an animal within a certain area and range of a sensor, through passive infrared technology or alterations in an electromagnetic field. With infra-red technology, the area is typically cone-shaped — narrow close to the sensor and wider as the distance from the sensor increases. Infra-red systems detect animals based on body heat and motion. The electromagnetic system detects animals based on alterations in the electromagnetic field caused by the animal's entry into the field.
Break-the-beam systems - These systems detect an animal when the animal's body blocks or reduces an active infrared, laser or radar signal that is transmitted by one sensor and received by another sensor.
The reliability of animal detection systems is influenced by a range of environmental conditions, such as high winds, temperatures or humidity, and operation during day and night periods.
The durabilty and practibility of a system is shown by a consistent performance over time, minimal monitoring and maintenance requirements, size of the equipment (landscape aesthetics), and the road length that the sensors are able to cover.
Animal detection system systems may be vulnerable to "false negatives", which occur if an animal approaches but the system fails to detect it, and "false positives", which occur if the system reports the presence of an animal, but no animal is present.
Several animal detection systems have been evaulated for reliability. The results are written up in the 2009 report The Comparison of Animal Detection Systems in a Test-Bed: A Quantitative Comparison of System Reliability and Experiences with Operation and Maintenance Final Report.
by Marcel P. Huijser, Tiffany D. Holland, Matt Blank, Mark C. Greenwood, Pat T. McGowen, Barrett Hubbard & Shaowei Wang.
Roadside animal warning systems
These systems detect vehicles and then attempt to alert the animals through a range of audio and visual signals from stations placed in the right-of-way.
Vehicle-based driver warning systems
These systems inform drivers of the possible presence of animals in the roadside area using devices present in the vehicles equipped with such a detection system.
Reflectors are prisms mounted on posts along the sides of the road. As vehicle head lights strike the reflectors, beams of light are reflected at 90 degree angles to the road. This reflected light catches the animal's eye and distracts the animal from crossing the road. Installations can cost $10,000 per kilometre. Continuing maintenance to ensure proper cleaning and alignment can cost $500 to $1000 per kilometre. The efficacy of reflector installations is not fully established, and there are conflicting research results. Questions requiring further study include:
BC agencies such as MoT and ICBC are not recommending the use of wildlife reflectors at this time.
A study carried out on the Berry College Campus in northwestern Georgia, USA, concluded that wildlife warning reflectors were ineffective in changing deer behavior so that deer vehicle collisions might be prevented. Evaluation of Wildlife Warning Reflectors for Altering White-Tailed Deer Behavior Along Roadways
Elk on Wildlife Overpass,
Banff National Park, AB
Photo courtesy of Reno Sommerhalder
This is one of the most effective methods to facilitate wildlife movement across roads, and can dramatically reduce the wildlife vehicle collision rate. Long term monitoring after implementation is required so that long-lived species have time to adapt to the structure.
Monitoring must document that all age classses (adults, sub-adults, juveniles, females with young) are freely using the structure before it can be said that the structure "works".
Different species have different requirements for crossing structures in terms of height, length, light and openess.
Crossing structures are expensive to build and require detailed engineering. Parks Canada has been very proactive in using these structures, especially through Banff National Park. Two 50 metre wide overpasses, and 22 underpasses have been built in Banff National Park.
As part of the ongoing research and monitoring of the crossing structures on the Trans Canada Highway in Banff National Park, remote cameras and other techniques have recorded over 200,000 crossings involving 11 species of large animals.
Banff National Park - Survival on the Move has video footage of how different species react to the various types of crossing structures and describes a DNA-mapping study using hair captured from bear and wolves.
The Highway Mitigation in Banff video highlights the lead researcher, Dr. Tony Clevenger, discussing the Banff Wildlife Crossings project and contains motion activated camera footage of animals using the crossing structures.
Overhead lighting of extended sections of highway may not be practical, but it can be very helpful within city limits, where significant numbers of wildlife-vehicle collisions occur. A study in Alaska showed a reduction of collisions by 70% when lighting was improved.
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The application of scents along the roadside can be used to deter animal crossings. Two types of scents exist; odours associated with predators (wolf urine) and odours associated with bad smells (rotten eggs). This method has had limited success in the United States, but there is not much scientific research completed as yet. It is thought that animals can become habituated to the scents, and it is expensive.
Wolverine Overpass along the Trans-Canada Highway
Banff National Park, AB
Photo courtesy of Reno Sommerhalder
Appropriate highway design can be very effective when habitat, hydolgy, ecological connectivity and population data are incorporated into the planning.
Factors that be modified include road width; number of lanes; right of way, shoulder, and ditch width and depth; plus the addition of structural mitigation methods such as lighting, road surface, fencing, tunnels, and over/under passes.
Judicious and careful application of road salt only when necessary can help to control the number of animals attracted to the road to lick the salt residue. De-icing agents other than common road salt, such as calcium chloride, magnesium chloride, potassium chloride or potassium acetate can be used, but are logistically complex to implement over long stretches of highway.
Information on wildlife collision mitigation in BC can be found in publications from the BC Ministry of Transportation and Infrastructure.
Further information can be found in Section 4.0 of WARS 1988-2007, Wildlife Accident Monitoring and Mitigation in British Columbia, Special Annual Report.
Additional publications from the MoT Environment Management Section include:
For more information contact:
BC Ministry of Transportation and Infrastructure
Environmental Management Section
PO Box 9850 STN PROV GOVT
Many people are convinced that the deer whistles installed in their vehicles are effective at scaring wildlife off the road, however, the independent scientific research does not support this.
The Wildlife Collision Prevention Program does not recommend the use of deer whistles. A summary of the scientific literature is found here.
There are two types of deer whistles.
Automobile manufacturers such as Audi, Volvo, BMW, Mercedes-Benz,and Cadillac are offering animal detection systems which indicate large animals such as deer and moose and provide a warning to the driver if the animal is in danger of entering the vehicle's path. Volvo's system will automatically brake for animals. Audi uses the Night Vision Assistant and Mercedes-Benz has Night View Assist Plus. Cadillac also has Night Vision with a head's up display in the driver's peripheral vision. None have been independently scientifically tested.
Car and Driver magazine compared three of these systems on a driving test ground.
Ensuring that drivers are aware of the risks and hazards that are specific to wildlife will help to make drivers safer on the road. Go to the Hints for the Highway page and the Wildlife Factor page for extensive information on ways that drivers can improve their ability to anticipate and avoid wildlife-vehicle collisions.
Click here to view and/or print an FAQ list about wildlife vehicle collision prevention