Hello MissJones89!
Thank you for sharing!
My first impression is these three sentences are very distancing as a reader.
What I mean is: it doesn't feel like I'm getting Cass' POV. (Which is fine if that's what you're going for. But the effect on the reader is that it is difficult to identify with Cass. Which means it could be difficult for a reader to care if Cass is in trouble.)
Knowing the exact speed of the train has been mentioned, so I will use another example
The SECOND sentence:
From her spot in the middle of the rails, she took in the details that gradually appeared as the train got closer.
The bold distances the reader from the situation. From the FIRST sentence, we already know the train is approaching her so that part is redundant.
On top of that, you are telling us 'she took in the details that gradually appeared' which filters the experience through her.
If you want the reader distanced, these sentences are fine (though I'd remove the redundacy from the SECOND).
If you want the reader to feel closer to Cass, you don't need the second sentence at all. It could be something like:
Cass (stood? was tied?) in the middle of the tracks, a black freight train barreling toward her.
(Then you could go right in to your third sentence and describe the train, or get us inside her head. I know I'm curious what her opinion of the situation is.)
This would help me connect to the character more, which makes me care about the character's story more.
Hope This Helps Some!
--Spukug--