A sign says it is under video surveillance. That would explain the light poles we saw on both ends, each with three big lights, and the lights hanging from the ceiling.
I was avoiding taking a photo down the center because I wanted the camera to meter the trusses instead of the "light at the end of the tunnel." But electrons (and magnetic domains) are cheap so I also to a straight portal shot. As I expected, the trusses are darker.
David did catch the under flooring.
This is the current road bridge, which is a little upstream of the wood bridge.
And a view of the wood bridge from the van window. A grey bridge against grey trees is a bummer. I need to revisit this bridge when the trees have their leaves. But I would have to stay overnight in the area to catch it with morning sun.
We also took a picture of a facility that is upstream from the road bridge. We never did figure out what it was.