An animal detection system with the warning lights activated resulted in 1.52 mi/h lower vehicle speeds (compared to warning lights off) for passenger cars and pick-ups.
Alerting drivers to the presence of large animals in the road at Yellowstone National Park.
Made Public Date

Montana, United States

Yellowstone National Park: Montana,
United States

Animal-Vehicle Crash Mitigation Using Advanced Technology. Phase II: System Effectiveness and System Acceptance

Summary Information

Animal detection systems activate signs that warn drivers when large animals (e.g., deer, elk, moose) may be on or near the road. These systems consist of a detection component that detects large animals, and a warning component that activates signs upon detection. In a typical scenario, a transportation agency or natural resource management agency in response to crash reports and/or road kill data, takes the initiative to treat a specific site with an animal detection system. Previous evaluations of animal detection systems found that these systems frequently produced an unacceptably high number of false alarms due to the difficulties of distinguishing large animals from moving vehicles.


The study area was on US Highway 191 inside of the Yellowstone National Park, with a posted speed limit of 55 mi/hour. The data collection period occurred over two weeks in which there was mostly no precipitation. Researchers installed three traffic counters and road tubes outside and inside of the detection area. The counters recorded the date, time, vehicle type, vehicle speed and gap (in seconds) between vehicles. When vehicles moved in platoons, only the speed of the first vehicle in a platoon was used as a data point when the signs were activated (since the following vehicles may be influenced by the speed of the first one). A sample size of 2,428 vehicles per 24 hour period was used.


The deployment of an animal detection system at Yellowstone National Park found that passenger cars, pick-ups, vans, and trucks with two units or more had lower vehicle speeds by 1.52 mi/hour with warning signs activated compared to warning signs off. Although the difference is small, it is important to note that small reductions when vehicles are traveling at high speeds have a disproportionate decrease in the probability of severe accidents.
The data also showed that the number of collisions with large animals was 58 to 67 percent lower than was expected (but could not be tested for significance due to the variability in the number of collisions and just one year of post installation collision data). Driver opinion of the system documented in interviews revealed that a majority (59 percent) would have liked to see the system stay in place. The system was removed in the fall of 2008 due to high maintenance and a lack of spare parts.
Deployment Locations