Amtrak says its air is refreshed every 4-5 minutes, though it's not clear what type of filter they use. If you can afford a private room, that limits your exposure to other people. Dining cars are carryout-only right now, and those in private rooms can order meals for delivery. This might be more expensive than some can afford, but if you can, go for it.
As with so much right now, though, the experience of traveling by train is much different. If you're planning a trip by train for the experience -- and for the people you meet along the way, which can be the greatest serendipity of travel -- know that the experience is greatly altered by the pandemic right now.
An addendum on trains:
Amtrak says its air is refreshed every 4-5 minutes, though it's not clear what type of filter they use. If you can afford a private room, that limits your exposure to other people. Dining cars are carryout-only right now, and those in private rooms can order meals for delivery. This might be more expensive than some can afford, but if you can, go for it.
As with so much right now, though, the experience of traveling by train is much different. If you're planning a trip by train for the experience -- and for the people you meet along the way, which can be the greatest serendipity of travel -- know that the experience is greatly altered by the pandemic right now.