Nothing is really "safe", never has been. Let's face it, if someone wanted to put a bomb in a bookbag and carry it on the Amtrak train what would stop them? Nothing that is in place now. It would be like a Madrid-style bombing. Ride the train yourself and see how many hundreds of bags are on board. The one way it would be much safer is if the trains had bomb sniffing dogs on board as well as having all passengers test their bags before boarding. All the Amtrak tickets I ever bought say something about producing photo ID, but I've never once been asked for ID anytime I rode.
What can be done now it to educate conductors to look out for mischeif behavoir. Passengers should look for this too. Remember how they caught the shoe bomber on the AA plane? It was keen eyed passengers and a stewardess who saw the guy acting suspicious playing with his shoes and a lighter.
I flew just after the 9/11 tradgedies and let me tell you, everyone on that plane was on pins and needles. Anytime someone would get up to go to the can, everyone on board would watch them like a hawk just to make sure they were innocently making their way to the toilet. People should always be that vigillant, it would help stop bombings and stuff.