Even more interesting, is how many O scale layouts are designed and used for operation?
I designed mine that way and have held regular operating sessions since about the mid 1990s. Most of the guys in my round-robin group that operate and have layouts have HO layouts, some quite large. But the operations are fun regardless of size. I want 8 people to operate mine, and I very seldom have less that 8 want to come to an op session.
