I did an amusement park for the Holyoke MA Senior Center in HO scale and we run a N Scale train ride in the park. If you get a small steam engine and some small cars I think you can run on an 18" curve. Our oval is about 24". The HO to N scale works good HO people fit good in an open N Gauge passenger car. O Scale people will be too big for N Scale. HO, N, and Z scale run on DC. I run a HO mining operation on my O Gauge layout that looks good but you couldn't get 18" with the HO>