Study Shows Problem of Vehicle-Wildlife Collisions Increasing

The Study

The University of North Carolina's Highway Safety Research Center maintains the HSIS data used in the FHWA study. This linkable data from California, Illinois, Maine, Michigan, Minnesota, North Carolina, Utah, and Washington provides a range of representative information. FHWA contracts the gathering and compiling of the data to: "monitor safety trends, study emerging highway safety issues, conduct highway safety research and evaluate potential countermeasures."

In the present study, FHWA analyzed the data with the specific objectives of learning the characteristics of vehicle- wildlife collisions and determining whether those characteristics would reveal commonalities that could lead to targeted countermeasures. The study used HSIS data reported between 1985 and 1990 from the states of Illinois, Maine, Michigan, Minnesota, and Utah.

Trends

Over seven years, the number of vehicle-wildlife collisions increased by 69 percent--from 21,470 in 1985 to 36,332 in 1991. These increases also represented an increase in the total percentage of all reported crashes that involved a vehicle- wildlife collision--from 4.7 percent in 1985 to 8.2 percent in 1991. Since the data included only those collisions that someone reported and that happened on state-maintained highways, these figures probably significantly understated the problem. While the data documented that vehicle collisions involved several types of animal, deer were by far the animal most frequently hit.

Data from this five-state study showed that from 2 to 10 percent of reported vehicle-wildlife collisions resulted in nonfatal injury to a driver or passengers, and less than 0.1 percent of vehicle-wildlife collisions resulted in one or more driver or passenger fatalities. Data from the national Fatal Accident Reporting System revealed that only 0.3 percent of fatal collisions in 1991 were vehicle-wildlife collisions. This represented a total of 112 fatal crashes where the first harmful event was hitting an animal.

The authors offered several theories about the reasons for these trends. They suggested:

Characteristics of Vehicle-Wildlife Crashes

Most of the reported vehicle-wildlife collisions happened on rural rather than urban roads. In Maine, this study showed that about 12 percent of all the crashes reported on two-lane rural roadways were vehicle-wildlife collisions. In Michigan, that figure rose to more than 33 percent. By contrast, vehicle- wildlife crashes made up under 2 percent of all crashes reported on urban roadways in all five states during the years studied. Average crash rates were lower where average daily traffic rates were higher.

In all cases, more collisions with wildlife happened at night than during daylight hours. Although the figures varied from state to state, 69 percent to 85 percent of vehicle-wildlife collisions were at night. Vehicle-animal collisions most frequently happened between 5:00 a.m. and 8:00 a.m., with 6:00 p.m. to midnight the second-most-common time span for such collisions. While data were not available to correlate vehicle- wildlife collisions with traffic counts at specific times of day, vehicle-wildlife collisions did represent a disproportionate percentage of all reported crashes during these two time periods.

November had the highest number of vehicle-wildlife collisions, and October the second highest. These seasonal peaks occur because fall is the mating season for deer. Describing deer behavior during fall months, Gene Mueller wrote in the Washington Post, "[M]ale deer do inexplicable things and caution by the usually wary animals is cast to the wind."

Breaking roadways into 0.5 kilometer overlapping sections, FHWA researchers evaluated the geographical clustering of vehicle-wildlife collisions on rural roads. They found that few roadway segments had more than one such collision per year, and many sections had none. In Michigan, however, 14 percent of the 0.5 km sections averaged more than one vehicle-wildlife crash per year between 1985 and 1990. Of Michigan's rural roadway sections, about 3 percent reported more than two vehicle-wildlife crashes per year during the six-year time span of the study.

Countermeasures

The authors mentioned countermeasures currently used to reduce vehicle-wildlife collisions:

• advance deer-crossing warning signs;
• management of roadside landscape and vegetation;
• programs to keep animals off roadways (i.e., fences, underpasses, and interceptive feeding areas);
• measures to control the growth of animal populations;
• roadside reflectors that redirect headlight beams to create "optical fences" and stop wildlife from crossing the roadway; and
• deer whistles that mount on vehicles and emit a sound to scare deer off roads.