This is a brilliant thread. While I'm normally against forcing another person, like the train driver, to be an instrument of my death, desperate times call for desperate measures.
I voted for the "headbutting" method. While always pictured myself jumping under a train, to be crushed by wheels, headbutting is far more effective. Many trains have something called a "cowcatcher" attached to the front at the track level. It's meant to push aside any animal, including the two-legged kind, that wandered onto the track, rather than letting it get under the train wheels and risk derailing it. An adult's waist is above the height of a cowcatcher, and the cowcatcher itself is shorter than the human upper body bent at 90 degrees. (Well, cowcatchers on trains in the 19th century were huge, to effectively push away buffaloes, but cowcatchers on today's trains are much smaller.) Which makes headbutting the train very possible. I'm a railfan, so I know a lot about train design and railroad operations.
Oh, and it's more effective to "headbutt" far from the train stations, since trains travel at higher speeds there. Like using a crossing nowhere near any station. It's also best to use a crossing with a just a signal and no arms. Train drivers know the design of every crossing they pass. And a crossing without arms means it's low-traffic, so the drivers don't expect to come across a pedestrian there. Which means they're less likely to expect someone to use their train as a CTB tool.
The website https://railroads_fra_gov (USA only) may have maps of "usable" railroad crossings. (Replace the underscores with dots.)