Highway traffic is an enormous hazard for wildlife; thousands of endangered animals die every year after getting hit by cars and trucks. (To say nothing of the humans that die in these collisions — slamming into an enormous black bear at 60 miles an hour is kinetically equivalent to driving into a brick wall.) Anyway, there’s now an international movement afoot to build traffic overpasses and underpasses catered specifically to animals. A story in yesterday’s New York Times Science section describes one that’s located 50 miles outside Banff, Alberta:

Approached from the woods, the crossover resembles any other sloping hill, covered with brushy grass, shrubs, saplings and even a clump or two of pussy willow.

Earthen berms on either side hide the road and mute the noise of the tens of thousands of cars that pass by daily, winter and summer.

Animals have worn a trail along one edge and, at the top, leave prints on a cleared stretch of dirt, a so-called track pad, monitored by motion-sensitive cameras with night-vision lenses.

It’s working: Researchers have counted tens of thousands of wolves, bears, cougars, and other animals using the overpass in the two years since it was built.

Now here’s a really weird idea: Would this work in an urban setting? Though we tend not to think of cities as hosting much wildlife, in reality places like New York or Toronto teem with everything from squirrels to foxes. They run into problems with traffic too. A terrific story in a recent issue of New Scientist explaining why squirrels are so often greased by cars: They evolved over millenia to cross open spaces as quickly as possible without wasting time to check for predators, because there was nothing they could do hide in that situation, and any delay was just going to increase the likelihood that they’d get killed. (It’s an open question as to whether squirrels will evolutionarily respond to the curious behavior of cars — “predators” that move in predictable straight lines and can be avoided with a modicum of watchfulness.)

In the meantime, though, I wonder if a city could experiment with building little overpasses or underpasses for squirrels? They could actually be quite lovely — metal or wood archworks spanning roads, festooned with climbing vines. Granted, squirrels are hardly endangered species, and it’s possible that automobile deaths constitute an essential herd-culling that is keeping squirrels from booming in population, overrunning cities, and demanding voting rights. But at very least it’d be pretty hilarious to watch ‘em scurrying back and forth across overhighway trellises!