Access will definitely be an issue as drawn. Twenty four inches is a good rule of thumb to stick with, thirty inches is just about the maximum for most people. Even then, at thirty inches, you run the risk of damaging scenery and equipment if you are not extremely careful. You can make access holes but they can be a very big pain in the neck, both figuratively and literally, when you have to crawl around under the layout to work on something. The older you are, the more so that is true.
"N", the Normal scale!