You can do modules in HO! Either for a home layout, or as part of a modular group. It works great, the only thing is, there is no way to have a continuous loop in HO on a module, there is in N scale. The N scale trains on Ntrak are breattaking, as they are long, and snake through the mountains. I like HO better, but Ntrak is pretty cool. I think the main thing that N scale is doing is Ntrak, whereas HO is in home layouts, modular, small layouts, etc.