These are snow fences, and Wyoming has over 400 miles of them. They are a simple yet effective way of keeping snow from overtaking the roads.  Tim McGary, WYDOT District Maintenance Engineer, states in the video that if it were not for these snow fences, I-80 would be nearly impossible to keep open during the winter.  When they first opened I-80, it was closed more than it was open. The fences work by breaking the wind causing the snow to fall to the ground and not the road.