That's the way things often turn out. I've been in quite a number of RV parks that are close to RR tracks or interstates. I'll tell you what, I'll take interstate noise any day over RR noise! I can generally mask interstate noise pretty well by running a fan in my bedroom but a train passing by, blowing its horn and rattling the ground like an earthquake is more than I can take.
As an example, there's a nice RV park in Grants, NM that's priced right and very well kept up but the trains going by all night long cause me to lose a lot of sleep. I actually spent a whole month there last year and when I left my nerves were shot...anxiety, etc. The nearby interstate was not an issue, however. This year I spent only one night at this park on the way to Albuquerque. That was bearable, but no more monthlies for me when RR tracks are close by!