I have a question. I know what O gauge with 3 rails is. Kinda what I always think of Lionel to be. Today at a train show, I saw what looked like O gauge, but it was 2 tracks just like HO. I asked the operator what gauge it was (feeling somewhat stupid doing so) and he said it was O gauge. So, when looking for products, how does one differentiate the two? That is, if I were at a manufacturers web sit, what would I look for when looking for 2 rail and 3 rail engines and cars? PS: I was at the in show in Massachusetts. It's apparently the largest model train show in the US. 'll be back tomorrow with my son.