Just a shot from the end of a summer excursion. In the 1880s they tried to push a Transcontinental railroad from Los Angeles to Grand Junction CO. It lost to a route further north when the terrain got too bad. That same planned path was later used as the route for the western end of I-70. Now the Railroad grade is basically a frontage road to the Freeway (but a good option if you want to overland across the state trying to stay off pavement.
Nice! I was up there last week, and I wasn't quite dressed appropriately. Underneath the bridge looked really cool! I didn't realize you COULD go under it.
The Ambassador bridge in Detroit is all fenced off. I'd imagine because it's a border crossing.