I knew that the folks at Union Station can be a little unwilling to allow photography, especially with tripods. I went into a less visible area, set up the camera on the tripod, made a rough guess for a long exposure, and quickly set up in the middle of the aisle, figuring I could get at least one long exposure before I was told to stop. Sure enough, right after I started to take the picture, I heard one of the security guards call about "a man taking pictures using a tripod." They walked over to me and said "I'm sorry, you need to have a release to take pictures with a tripod."
...then they walked me to the office, got me a release, told me how to fill it out, and let me take pictures.
I was sneaky for NOTHING....and too tired to take a lot of pictures.