What we’re doing to reduce Vehicle/Wildlife Collisions

By guest blogger Jeff Adamson

Wildlife collisions are a worldwide problem and WSDOT is one of hundreds of agencies that have been trying for years to find effective and affordable ways to reduce them. A variety of solutions have been tried with varying degrees of success. Some are applicable in only specific areas or only work for certain species. Others didn’t work at all, cost too much, required too much maintenance, or created undesirable unintended consequences.

Reducing speed limits would seem a simple solution and it’s been tried in many countries. Traffic engineers know that studies have documented that most drivers will drive as fast as the roadway will comfortably allow regardless of the posted speed. (That’s actually how speed limits are set – the speed that 85% of the drivers drive on a particular road, safely traversing it.) The engineers also find that when the speed limit is set artificially low, some drivers will indeed slow down, but most of them don’t. The result is a higher rate of rear-end and head-on collisions. At the same time, lower speeds also have not been shown to significantly reduce the number of wildlife/vehicle collisions.

WSDOT has studied other solutions and conducted many tests on our highways:

  • Those vehicle-mounted plastic deer whistles not only don’t work, but can actually attract some species down onto the roadway. (Unintended consequence)
  • The mirrored reflectors on the road shoulder can work when they’re perfectly aligned and shiny, to scare wildlife back away from the road (only at night), but we found they don’t stay clean and shiny and they don’t stay aligned due to wind, snow plow curls or animals using them for scratching posts. (High maintenance costs and only effective on level terrain.)
We’ve tried high-tech solutions too:
  • We put radio collars on elk near Port Townsend that trigger flashing beacons telling drivers there are animals on the road ahead. We found out that when a collared elk settles down for the night near a receiver, the beacon flashes all night. We also found people would see the beacons, slow down to a crawl looking for the elk, then stop in the roadway to take pictures, if there were really any on the road. This caused rear-end collisions to increase. (Radio collars and capturing the elk to put them on, is also very expensive.)
  • Near Rocky Reach Dam, just north of Wenatchee, we tried a laser beam system developed by Battelle NW Laboratories. It triggered beacons on signs alerting drivers that there were deer on the highway ahead. We found the lasers could only be used for short distances on straight sections of roadway. Anything that broke the beam triggered the beacons, including birds, dogs, mail trucks and snow plow curls. Perfect alignment was critical (high maintenance costs). Even the sun could trigger the beacons depending on the time of year as sunrise and sunset angles changed. Regular commuters soon learned to ignore the flashing beacons.
The most successful solutions we’ve implemented have been in conjunction with fish passage projects where we’ve removed culverts and replaced them with much taller underpasses (bridges) to allow creation of a natural streambed for the fish and enough streambank for wildlife to cross under the highway, too.
Examples: SR 20 in the Methow Valley, and Twisp, also under US 2 east of Stevens pass.

Overpasses also work. The I-90 Snoqualmie Pass East project, now under construction, has plans to include natural land bridges over the freeway to accommodate wildlife migration patterns. The overpasses, however, are located outside of the currently funded five-mile portion of the project from Hyak to Keechelus Dam. We started construction on the Hyak to Keechelus Dam project last year, which does include wildlife underpasses such as bridges and box culverts.

Wildlife fences have recently been showing amazing results in reducing vehicle wildlife collisions in Canada and elsewhere. (A typical installation puts fences on both sides of a highway and funnels animals to under or overcrossings to accommodate their migration patterns.) North of Wenatchee, WSDOT is installing a fence on US 97A between Rocky Reach Dam and Entiat to test whether it can provide an effective/affordable tool to reduce wildlife collisions here.

While this isn’t the worst wildlife/vehicle collision location in Washington, it provides a test of fencing for control of valuable bighorn sheep in addition to deer. Just the design and construction phase of the first part of the project showed fencing costs were higher than for a “deer only” fence due to the modifications required because the bighorn are stronger, more nimble and smarter than mule deer.

The entire project constructs a 9 mile long fence from Rocky Reach Dam to Spencer Canyon, two miles south of Entiat, where (’93 to ’03), there was an average of 30 wildlife/vehicle collisions per year. The goal of the project is to reduce those collisions by 50 to 80%. The first 4 -1/2 mile “upper” section was started last July and completed in December (2009). The second 4-1/2 mile “lower” section is scheduled for construction next year (2011).

While we do not expect to see 50% of the benefit of the whole fence from the half that is completed, we do expect a significant reduction in vehicle/wildlife collisions for the next year. This year also provides time for a 4-season study of the wildlife interaction with the new fencing, its one-way gates and the effectiveness of the cattle guards at the road/driveway accesses. The study will guide our design engineers in making changes that can be incorporated into stage 2 to make that installation even more effective.

While it’s too early to have any statistically valid data, our maintenance crews, State Patrol troopers and Fish and Wildlife biologists say that they’re seeing fewer deer and sheep on the road, finding fewer carcasses and investigating fewer collisions through the corridor.