This new Nova examines an interesting subject, which I first encountered about 15 years ago when visiting Banff, Canada for a TV festival. Above the highways of that rugged northern landscape, every so often, were overpasses leading not to other highways, but allowing migrating and grazing animals to cross safely without being hit by moving vehicles. Who came up with ideas like this, and how are they implemented successfully? Welcome to another informative Nova. Check local listings.