How’d the critter cross the road? When it comes to I-90, on overpasses built just for them.

This computer-generated image shows what a “wildlife crossing” will look like when completed.
This computer-generated image shows what a “wildlife crossing” will look like when completed. Washington State Department of Transportation

Q: What is that arch-like structure they’ve built across Interstate 90 just east of Snoqualmie Pass? — Grant S., Bonney Lake

A: Well, Grant, that eventually will be an overpass, but it’s for critters, not cars.

Construction crews working for the state have nearly completed the so-called “wildlife overcrossing” you recently spotted and have begun work on another one farther east, according to Meagan Lott, a spokeswoman for the state Department of Transportation.

The overpasses are parts of that gazillion-dollar improvement project underway on I-90 between Keechelus Lake and Easton Hill.

The overcrossings will help elk, deer and other animals safely roam between habitats on either side of the freeway, according to the Transportation Department’s information posted online.

“I-90 bisects the entire width of this wildlife corridor,” the state reports. “Along with the three lakes in the projected area, the highway is the primary barrier to north-south movement of wildlife.”

It can be a deadly barrier.

From 1996 to 2006, Transportation Department workers removed 160 deer and elk carcasses from either on or adjacent to I-90 in that area, according to state data.

“The numbers do not include animals that were hit and died off the highway or were picked up by others,” according to the online report. “Mortality for smaller mammals, birds, amphibians or any other terrestrial species has not been studied.”

Grant pointed out to us here at Traffic Q&A headquarters that the structure he saw resembles a “Quonset hut/tunnel/whatever” and not really an overpass.

Lott agreed.

“It just looks like these weird arches and tunnels,” she said.

Crews still must build up earthern berms along the edges and over the top of the structure. They’ll also erect fencing that will direct animals to the overcrossing and discourage them from trying to cross the highway, Lott said.

When completed, it should be a win-win for drivers and our furry friends of the forest.

Adam Lynn: 253-597-8644, @TNTAdam