Not a track designer, but you might want to incorporate a crossover around where it's marked "track I and track II".
I would also put a tunnel along the short straight opposite the trestle side.
Not sure what you have planned for the center, but a street and intersection might look good.
Depending on what transformer you have, one transformer can power two tracks - just split the wires coming out of the transformer if you want to keep them separate. If you add the crossovers, you will not need to, but you should add extra power drops on the loops, either way.
