My dad had built a couple 4' x 8' tables out of plywood, and we had an HO Scale train layout (no scenery) and an HO Scale slot car track on the same L-shaped layout. The greatest part was that we had the HO scale train crossing, which allowed the HO cars to cross. We had a little trip switch to make the scale railroad crossing lights flash. We had hours of fun, as my brothers used to race each other on the car layout, using Tyco and AFX cars, and I would control the ol' Burlington Northern, towing about 6 rail cars.
Yep, I thought I was in control driving that train. Big Chief Engineer. I'd slow way down as it passed the crossing, my brothers waiting impatiently with their 2 HO cars until the caboose finally crossed....then they resumed full throttle and their race for a few laps until my train came around again....
The fun ended when they realized a Tyco Pro brass chassis McLaren M20, and a similar Chaparral 2J, traveling at high speeds, could knock over an entire HO train at that crossing.