You've got to admit that model railroad operations does tend to focus your mind. Many have said how running on a double-deck layout isn't that distracting; usually you're so focused on your own train that you don't know the action happening on the lower level.
That's also true for keeping track of what's happening near you. One of my first operating sessions almost ended in disaster when the crew switching Campbell started pulling a long train of cars towards San Jose, and a crew in San Jose started pulling a long train of cars towards Campbell. Because there's a curve between the two stations, the crew didn't notice that they were trying to occupy the same track until it was too late.
Soon after, I printed out some of the Operations Road Show paper flagmen, and I keep a few scattered around the layout so crews can guard track and avoid another crew intruding into space they need. Usually this works, though we've got a few flagmen with wheel marks showing that even careful crews sometimes run over flagmen.
John Plocher liked the paper flagmen on my layout, but felt they were insufficiently noticeable. John came up with the elegant solution of the DCC Brakeman, a little PC board cutout of a brakeman with a base that could touch both rails to power an LED. His little brakemen are both human-shaped and light up nicely - a great idea and very nice implementation.
John has put the plans up on his website, but he also had a set of brakemen built and assembled. They're currently for sale at the Train Shop in Santa Clara for around $7; the only work is to solder the figure onto the base, and attach the weight to the base. Go pick a few up for safety!