Reducing the risk of wildlife collisions

It’s a risk that’s difficult to quantify

The number of wildlife-vehicle collisions in Washington each year is not precisely known. The Washington State Department of Transportation (WSDOT) gathers information from three sources to ensure we have as complete a collision inventory as possible.

Local and State Patrol officers submit collision reports to WSDOT when there’s a human injury or fatality, or property damage exceeding $1,000. On average, WSDOT receives 1,500 reports each year, with 167 human injuries and one human fatality. However, based on the number of deer and elk carcasses removed from state highways by WSDOT maintenance staff and citizens, we know that the number of collisions is much higher.

Since the mid-1970s, WSDOT has tracked the number of deer and elk carcasses removed by our maintenance staff. These numbers suggest that a minimum of 5,000 collisions with deer and 200 collisions with elk occur each year.

Since July 1, 2016, it’s been legal for citizens to salvage road-killed deer and elk, provided they obtain an online permit within 24 hours of removing the animal. WSDOT obtains these records periodically from the Washington Department of Fish and Wildlife, providing a third source of information. In the first year of legal salvage, citizens reported the removal of 652 deer and 127 elk from Washington highways.

By combining the data from collision reports, maintenance staff carcass removals, and citizen salvage records, WSDOT gets a good sense of where collisions are occurring and uses that information to develop proposals to reduce or eliminate the problem.

Use the links below to learn more about this problem and what WSDOT is doing to reduce the number of wildlife collisions.

Why collisions with wildlife are a concern for WSDOT 

WSDOT works to reduce the severity and frequency of collisions on state highways to the extent that is reasonable. WSDOT strives to identify locations with high wildlife /vehicle collision rates. These locations may indicate areas where highways cross significant wildlife-use areas, such as deer or elk wintering areas or migration routes. We need to consider these areas when managing the highway system. Collisions with wildlife can also reduce wildlife populations, of special concern for rare or sensitive species.

Areas of the state with the highest numbers of road kill

High numbers of wildlife/vehicle collisions frequently occur in areas where large numbers of deer and elk are present directly adjacent to high-traffic-volume highway segments. Areas with some of the state's highest wildlife/vehicle collision rates are:

Photo of Big Horn sheep crossing U.S. 97-A north of Wenatchee.
Eastern Washington

  • State highways in the Spokane area, particularly north of Spokane, where the highways intersect with white-tailed deer wintering grounds.
  • In southeastern Washington, where state route 124 and U.S. 12 follow the Touchet River Valley, an area with an abundance of white-tailed deer.
  • State highways in the Methow and Okanogan River Valleys, which host one of the state’s most prolific mule deer herds, consistently have high numbers of animals killed in collisions each year. 
  • The abundant mule deer population in the Wenatchee vicinity results in high deer collision rates on the busy highways both north and west of the city.
  • On U.S. 97, there are high deer/vehicle collision areas just north of Goldendale.
  • The highest number of elk/vehicle collisions that occur in eastern Washington is on Interstate 90 near the Easton/Cle Elum vicinity and the Ryegrass vicinity west of Vantage. 

Western Washington

  • Deer and elk/vehicle collisions are more widely distributed on the west side of the Cascade Mountains, but there is a high rate of deer/vehicle collisions on Whidbey Island, along State Route 20, and State Route 525.
  • High numbers of elk/vehicle collisions have occurred where highways intersect the Cascade Mountains such as the Packwood-Randle vicinity, east of Sedro Woolley, and on Interstate 90 near North Bend.
  • Highways close to Willapa Bay also experience localized high collision rates involving elk.

Animals most often involved in vehicle collisions

Because of property damage and human injury, most reported wildlife/vehicle collisions are with deer and elk. Each year there are a few collisions with other large mammals such as moose, bighorn sheep, cougar, and black bear. 

The more commonly killed smaller species are raccoons, coyotes, squirrels, rabbits, opossums, frogs, salamanders, and snakes.

Photo of elk crossing State Route 504 in Cowlitz County.

Reducing the risk of collisions with animals that wander onto the highway

An effective method for reducing the risk of wildlife collisions is to use 8-foot high wildlife fencing to prevent animals from entering the highway. WSDOT has installed wildlife fencing in a few key areas, such as along Interstate 90 east of Cle Elum and U.S. 97 alternate route north of Wenatchee. However, fencing is expensive to install and maintain and cannot be used everywhere. Providing safe crossing opportunities like bridges or large culverts can also reduce the number of animals crossing on the pavement, thereby reducing the potential for collisions.

Signs are the most commonly used tool to warn motorists of the possibility of wildlife on the highway. WSDOT installs signs in areas with documented high numbers of deer or elk/vehicle collisions. Flashing signs, or signs with regularly updated messages, are more likely to be noticed and they tend to reduce deer or elk/vehicle collisions more effectively than regular signs. 

Photo of an elk-crossing sign with flashing beacons.

How WSDOT works to help protect wildlife

WSDOT worked with the Washington Department of Fish and Wildlife and other stakeholders on a statewide habitat connectivity assessment that identified areas where wildlife require movement across highways.
In addition to this planning work, WSDOT is incorporating wildlife protection measures in its projects. One example is the Interstate 90 Hyak to Easton project, which is under construction and includes a number of wildlife crossing structures as well as wildlife fencing. 
Photo of an artist's conception of the I-90 wildlife overpass currently in construction.
Other examples around the state include:

  • Wildlife crossing underpass on SR 240 that provides access to habitat in the vicinity of McNary National Wildlife Refuge
  • Bridge near Monroe, on SR 522, which was built with an increased span to accommodate wildlife crossings
  • Bridge and fencing at Butler Creek on U.S. 97
  • Wildlife fence on U.S. 97A

If you install a fence, won’t the animals just cross the highway at another location?

Highly motivated wildlife will find their way around the ends of fenced highway segments, especially if there are no built-in crossing structures. However, combining fencing with suitable crossing structures (wildlife over- or under-passes), reduces the tendency for animals to run around the end of the fences as they learn to use these crossing structures to pass safely to the other side of the road.

Technology or devices considered to reduce road kill

WSDOT has evaluated a number of different technologies for reducing road kill. These included deer reflectors, a laser detection system, and animal activated warning signs. Unfortunately, most of these have not proven to be effective. The only method still in use is the animal activated warning signs used to notify motorists when the elk are near U.S. 101 in Sequim. In place since 2000, this system relies on radio telemetry collars placed on elk to trigger a flashing elk crossing sign. While the system has reduced the number of elk/vehicle collisions, it has several drawbacks including the need to place radio collars on the elk, and false warnings triggered when the elk are near the receiver, but not necessarily crossing the road.

Why doesn’t WSDOT just lower the speed limit in areas where animals are known to cross the highway? 

While lowered speed limits may help reduce the number of wildlife/vehicle collisions, it is difficult to get drivers to comply with the lowered limits. If drivers feel that the lowered speed limit is unreasonable, then they are likely to engage in passing, tailgating, and speeding, which can increase the severity and frequency of collisions. 

Removing dead animals from the highway

WSDOT maintenance workers remove animal carcasses that are a potential hazard or distraction from state highways. In many areas, this work occurs exclusively on weekdays.

In most areas, WSDOT buries carcasses at designated disposal sites, often borrow pits. Citizens may salvage freshly killed animals, this practice becoming legal in most areas of the state on July 1, 2016. In a few areas of the state, where abundant road kill is a chronic problem, WSDOT takes the carcasses to a permitted composting facility. 


Contact Glen Kalisz, Habitat Connectivity Biologist,