I think the bypass approach is a commonly used technique when a failure in any component exits the routine ... but it's also common for each of the failures to

I think the bypass approach is a commonly used technique when a failure in any component exits the routine ... but it's also common for each of the failures to be processed differently, which actually looks like the fan-out that happens in a railway switching yard. The author's primary example uses a "layout" I've never seen on a railway (http://fsharpforfunandprofit.com/assets/img/Recipe_RailwaySwitch3.png http://fsharpforfunandprofit.com/assets/img/Recipe_RailwaySw...). Railway switches are expensive, so you never see multiple switches going the same direction between a pair of tracks. If there are two consecutive switches (and going say from left to right), one shunts from track A to track B and the other shunts from track B to track A. When space is limited, a cross-over might be used by these are even more expensive (an provide additional gaps where derailments can happen).