Mark: Design is a good start although there are 'spots' that could be improved. Looks like from your TT size, you are planning 'Big Steam'. Good as I like Big Steam! Those long wheelbase things could have issues. Please take the following with a grain of salt as the suggestions are what I would attempt to do. I kinda think 'What would the 1:1 do', and go from there. YMMV
1st - the 'S' curves; 2 are below the RH - one is switch work to get into the return loop, 1 is the top of that return loop, with the 3rd coming out of the return loop on the right.
2nd - track clearances; Lower left, 3 and 4 tracks to the right, gray siding just inside your operator area, blue and yellow track near the top yard/return loop although you may already know to fix these at build time.
3rd - Also, there seems to be a lot of 'spaghetti' trackwork. Why 4 entrance/exits from the TT? Removing the ?cyan and purple ones would give more room in the middle under the TT for industry, city, engine/car service. The 2 tracks going from the left side to the right return loop could be setup as a passing siding with house tracks for switching industry ( if you are so inclined ). You might even move that double crossover on the top around the corner and extend it to the bottom yellow track on your right return loop. The purple track can still come off of it. Doing that would allow yard switching without fouling the main.
4th - if those are 1 foot squares, the radii of the left return loop is pretty tight as are the ones close to them.
5th - The big one. Looks like your top yard is provisioned for an A/D setup. Move the switch to the right enough to handle your biggest engine or consist. That A/D track also sizes your max train length; which means sidings need to be at least that. Also, you might extend your top yard track to the dark yellow track instead of having a switch there; that will give you more room for cars. In order to TT/RH an engine, you have to travel almost 1/3 the distance of the railroad just to get to it. Ya might figure a way to have the TT connected to the A/D tracks.
Too many thoughts? Maybe -or- maybe not. Hope they help in any event!
Later