Make Train Travel Safe? OK … How?

When people talk about why they prefer traveling by train—short haul or long distance, it doesn’t matter—they always seem to conclude by saying, “. . . and there’s none of those security lines you have to go through at the airport!”
That could be about to change.
There’s some serious talk in Congress about needing more and better security for passenger rail. I’m certainly in favor of keeping rail travel safe—who isn’t?—but where do you start and, more to the point, where do you stop?
Should we screen all passengers when boarding? And if so, why? Trying to prevent someone from commandeering a passenger jet traveling 500-plus miles an hour is one thing. But a train? On the ground? On a track?
Security in a major railway station like Chicago Union station is one thing. But are we going to have the TSA in Hutchinson, Kansas, at 2:30 in the morning to screen passengers boarding the Southwest Chief? All three of them?
 In 1995, someone deliberately derailed the Sunset Limited. One dead, 100 injured. It happened 50 miles from Phoenix in the middle of the Arizona desert. That was 21 years ago and they’ve never found the people who did it. What security measures could have prevented that?
The TSA is now costing taxpayers almost $8 billion a year. How much more will it cost if passenger rail is included and what would the TSA guard against. And how? And where?
I’m certainly not opposed to more and better security for train travel. I’m just not sure there’s a practical, effective way to do it.