| 1 | A layout of the Southern Pacific Railroad during the late Steam/Diesel transition era. |
| 2 | A design tilted more towards operations (although only slightly), than scenic realism. |
| 3 | In order to accommodate a large roster of 2-10-2 "Deck" locomotives, as well as a few 4-10-2 "Southern Pacific" configuration and Cab Forward engines, a minimum radius on mainline curves shall be, wherever possible, 40." |
| 4 | In traversing the mainline, no scene shall be passed through more than once. |
| 5 | To better facilitate operations, minimum aisles of 30" shall be provided. |
| 6 | In order to best utilize the space in assuring a longer mainline, the layout should be of a "mushroom" design, without "duckunders." |