For curved structures it's easiest to explain with something like a curving grandstand. at 90 degrees to the track create what you'd like to be the side on view. at the front or back add the curve you want it to follow. then use the "follow me" tool to extrude it around the arc.
I've added a 4 very quick images to give you an idea
Personally I don't add that much detail for the garages, I tend to "cheat" and just draw closed garage doors such as can be seen
on the second image of this design