Ron,
Where were you working, RR, town, etc. You never mentioned that in your post. This info is good so I can either avoid it or show up in the middle of January. Best time to shoot steam is in the winter(better steam effects and no damn snakes).
Once at Hinton, WV I was shooting Nickel Plate 2-8-4 on the New River Trip(1987 I think), and was set-up on the hill above the old turntable and engine area. While waiting for the engine to back down my wife spotted several brown snakes heading for my video tripod. She knows I don't like these guys so she gently told me to back up and away before I went ballistic. Another railfan said they were harmless Ribbon Snakes. There must have been about 10-12 of them, like a pack! Finally they moved on after circling a 20-40 foot area for about 15 minutes. I toughed it out and got what turned out to be the last steam engine on the Hinton turntable("All for steam-to a point!")
Steamingly,
Greg Scholl