Road crews already put up signs. Seems the animals can't read 'em and cross where ever they want to. It seems unlikely the animals would detour out of their way to a bridge or tunnel.

Maybe animal expert knows how to attract animal to the “skyway”? As we keep expand cities, animals not only lost their habitat but also lost their lives because of our need to drive around. This is not fair to them.

It also occurs to me the animal's instincts would make it avoid a bridge. That probably tells them to stay away from areas that don't offer good avenues of escape.

I try to think of car/animal collisions as Darwin's Theory in action. The animals that don't learn to look both ways before crossing won't live to reproduce. Just think...in a couple thousand years this won't be a problem any more.

The problem is not the animal crossing the road, the problem is the human relying on the car too much. This is where you have to start thinking.

car skyways are better for this, while they are more expensive, the animals are more likley to cross under a bridge than over a skyway.

There's a little gadget sold for $10+ that attaches to the front of a car and emits a high-pitched sound that alarms animals. It's meant to deter deer and moose from darting out in front of a car, which they have a tendency to do. Collisions with such large animals are dangerous and costly to drivers too. I suspect this would have deterrent effects on other critters as well. It wouldn't work perfectly, because a slow-moving animal crossing an Interstate wouldn't get warning of far-away cars when he began his incursion. But it might well cut collisions in half.

All that would be needed would be for a licensing agency to buy these in bulk and offer them free to motorists. (After a few pilot projects and studies demonstrated that there'd be a payoff, natch.)

PS: The sound is generated by the wind, not a battery, so it's fairly foolproof.