Further photography/authority overlaps.

[wileypeter]

For the record, if you're wandering around the Union Pacific rail yards (even at the entrance) with a camera, the Police will arrive and civilly but firmly give you the options of leaving voluntarily or in the back of their vehicle.

I suppose as soon as I saw "All Vehicles Beyond This Point Subject To Search" signs I ought to have known what was coming. However, the cops are fairly tolerant if you act like a wide-eyed goof and go on about the underside of the bridge, rather than the trains.