How do they know to cross the road through the bridge instead of road. It's not like they understand that the bridge is for them to cross safely.
Also we have to construct many bridges throughout the road across forest area. Isn't it cheaper to build flyover for vehicles instead.
I'm assuming you're asking in good faith.
With these corridors, they fence the road so that the animals can only pass over the bridge. And youre right, sometimes they do raise the road and let animals pass under. It depends on the topography.
downpunxx@fedia.io to 
How do they know to cross the road through the bridge instead of road. It's not like they understand that the bridge is for them to cross safely.
Also we have to construct many bridges throughout the road across forest area. Isn't it cheaper to build flyover for vehicles instead.
I'm assuming you're asking in good faith.
With these corridors, they fence the road so that the animals can only pass over the bridge. And youre right, sometimes they do raise the road and let animals pass under. It depends on the topography.
Here's more information: https://en.m.wikipedia.org/w/index.php?title=Wildlife_crossing
https://youtu.be/RFCrJleggrI?si=EIPxGhw6ZBF6dVSy
This is the first thing to come to mind.....