So what happens when a standard gauge engine PULLS some narrow-gauge cars - or a narrow-gauge engine PULLS some standard-gauge cars - through one of those third-rail-moving-to-the-other-side crossovers that John Maxwell used to call a "swish"? Does the crew execute a "flying swish" ... and then re-couple the cars to the offset coupler on the other side of the tender or idler car? There would be a similar problem when moving from 3-rail to 4-rail or vice versa, but no problem when PUSHING if the cars are light enough so that a pole can be used.