Rail was first designed for delivery of people and goods to the places where people are concentrated. Then the business changed, moving bulk materials, some potentially very hazardous, through those same corridors. So it goes.

The first question is: are you in a situation where you could shelter in place? A well sealed dwelling, at some distance to the tracks themselves, is sometimes the best choice. In a car you are highly vulnerable to a chemical cloud; much less so in a dwelling.

The second question: if you really want to bug out, have you considered back-door and back-road options for getting out of Dodge? You would not believe the places that even a little four-banger car can go, given decent tires, an experienced driver, and a thoughtful recon if possible (on foot always wins). But only when the wind is right.

The other thing you might want to do is talk to the emergency preparation people in your local government, and talk to the brass at the local fire hall. They have almost certainly been paying attention to the potential threat, even though nobody else has (or wants to even hear about it). There may be a treasure trove of information there for asking, and lots of carefully considered professional advice -- which you have already paid for in your taxes.

My 2c.