Interesting setting. Dice mechanic is a bit generic though.

I love the idea of the subway as a setting. My entry also uses a mechanic where the GM rolls for the number of "encounters" upfront, but the linearness of a subway system really lends itself to that idea. I like the idea of commuters as characters too. I think this probably cries out for either simpler (a route has 4d6 platform stops) or more complex (a subway route generation rulekit) rules governing the creation of the line.

I think this could be made into something really fun and unique, though the dead sun is implied at best. I hope you keep with it.

"Jane! Get me off this crazy thing!" ~ George Jetson

Except this loco-motive will be the end of him.

 Nicely exciting setting, plus a super simple and immediately playable story and backstory, plus easy to handle mechanics. An assumption appears to be needed for what a round consists of: likely each player taking their turns in an agreed on order. 

This game will have to be a lead in to another that actually deals with a dead sun, though.

Solid theme and story. Unique setting. Unnecessary determination between loop or limited travel path... better to choose one or the other and flesh out what that means. A lot of time spent fleshing out a mechanical system that isn't terribly unique or efficient.

I like the premise, but not too much theme relation. I'm also not sure the d6 + ability score model works that well in this format. I've seen a lot of games try it and IMO it seems to rely to heavily on genre subtext not available in the game text to be applicable. Interesting though with the random train though.