Using "N" Scale on a "HO" Layout - Model Railroader Magazine

Dual gauge track is only useful to someone who is running models of two different track gauges in the same scale - the most common being HO (16.5mm) and HOn3 (10.5mm) gauge.  It is absolutely useless for running HO and N on the same right-of-way.

HO/HOn3 dual gauge flex is (sometimes) available from Walthers, and possibly from other sources.  While some dual gauge and gauge transition turnouts are (sometimes) available, the only way to be certain that the one key piece of specialwork is available is to hand-lay your own.

If you want odd-gauge dual gauge track you have two choices.  Hand-lay and fugheddaboudit.  OTOH, I am familiar with three narrow to narrower gauge prototype interchanges which didn't have a single dual-gauge switch, or a millimeter of dual gauge track.  Two (Kiso Rintetsu and a minor industrial line on the North coast of Honshu) are defunct.  The third, the Kurobe Gorge Railway, is still operating on a seasonal basis.

Chuck [Modeling Central Japan in September, 1964 - narrow (1067mm) and narrower (762mm) gauge prototypes, 1:80 scale]