[krisoft]

> They only have to hold animals that at best weight a few hundred pounds.

Uhm. I think there is some misunderstanding here. These wildlife crossings are more than just a plank going over the road. They are basically a bridge with a small patch of forest on them (or whatever vegetation matches the surrounding area).

> To encourage use by wildlife, the bridge will have lush but drought-tolerant vegetation with matte materials to deflect bright headlights and insulation to quiet the roar of cars. Fencing at each end will help funnel them onto the crossing.

I don’t know what is the fair price of a 165-foot-wide (50 m) and 200-foot-long (61 m) overpass holding up a small forest, but I know that the additional weight of the animals crossing is not a significant factor in it at all.

Now obviously if we could convince wildlife to use something much narrower and simpler built like a pedestrian bridge maybe we could drive down the costs, i’m not sure if that has been tested or not.

[Someone]

It has but not for mountain lions. The likes of toads and hedgehogs only need a small below-ground tube (https://en.wikipedia.org/wiki/Davis,_California#Toad_Tunnel), squirrels and marters can be helped with an above-ground rope (https://en.wikipedia.org/wiki/Squirrel_bridge)

One issue with narrow passages is that predators may learn to take advantage of them, eventually driving other wildlife away.