What a cute game! I loved the sprites and the mini roadways-esque gameplay. I definitely replayed a few times after I figured out what was going on to try and get a better score, which is the mark of a good gameplay loop.
I didn't quite understand what situations made a train + car disconnect, and it wasn't clear what caused new trains to become available. I definitely think you should expand upon this game! Would be even more fun with some more polish.