A few things:
*This area on the flatbeds appears to be nonsolid - it's a perfect place to hide a teleporter or similar thing
*Floating rock
*This area around the turbine seems to be quite tight for the cart
*You can build in spawn here - there also don't seem to be any func_respawnrooms, just nobuilds.
*Also consider making multiple exits from the primary spawning area, it can be camped from the central doorway really easily
*Blu would benefit greatly from a forward spawn, the travel time is pretty long near the end of the track
*Red might also need a forward spawn, so they don't have to walk all the way to the start every time they die. Not sure about this one though
*The flatbed carts with the containers on have some very tight spaces around them, potentially find a way to stop players going around the back of them?
This seems like a pretty solid map so far! Can't wait to playtest it.