It's really hard to appraise .io domains because of their usage. Generally they are used by tech start-ups - so if a new tech company called railway sets up, your laughing.
As such, when I do - very rarely - grab an io domain, I try and make sure it's something relevant to new technology and current usage. So recently I grabbed hookups.io - because everyone seems to be launching casual dating apps nowadays. Whether I'll find a user for it remains to be seen, but my worry with railways is that is doesn't sound very modern and I can't think of any clear connection to apps or new tech?
Too many people are doing a quick search for free .io domains and, used to the lack of availability in the .com space, thinking they've struck gold because of all the amazing words available. The problem is, the .io space is radically different, plus the domains carry a hefty renewal fee.