I'd Rather Fight than Switch(back)
This gimmick is rare on the prototype but all too common on layouts
witchback track arrangements are used on the prototype where there is no alternative -- typically due to limited space and (especially) elevation changes. They are very rare on the prototype* but quite common on some model track plans.
Switchbacks on the model are tempting because our layouts are always proportionally more limited in length than in depth. A switchback arrangement serving multiple industries on each "wing" appears to make better use of our limited space. But this type of switchback spur incurs operating penalties that cause real railroads to avoid their use wherever possible. Some designers rely extremely heavily on this type of track arrangement, but in my opinion this makes the resulting layout look unrealistic and operate inflexibly.
To understand why the prototype avoids switchbacks of this type, here's a simple example similar to a trackplan published in a recent magazine. Industry "A" on the left wing holds five cars, industry "B" on the right wing holds two.
"... this type of switchback spur incurs operating penalties ..."
Real railroaders prefer to make a "Grand Pull" of all the cars in a track at once. This is obviously impossible with the arrangement shown -- at best it will take three maneuvers to pull all five cars from Industry A because of the limited switching lead.
It's even worse if we need to pull cars from Industry B. We have to move cars from Industry A on the left just to make room. As can be seen from the red dotted lines, there is a lot of fore-and-aft movement that might be fun … once. It's easy to see why real railroads who must pay their crews for the hours spent on the job avoid switchbacks with industries on each wing wherever possible.
"It's easy to see why real railroads who must pay their crews for the hours spent on the job avoid switchbacks with industries on each wing wherever possible."
In this configuration, the switcher now needs to run to a yard or run-around to get things rearranged so he can keep working -- for example to return the cars to Industry A if they were not yet loaded or unloaded. This lack of flexibility in the way cars may be handled is one of the major drawbacks of this type of design. As a switching puzzle, it may have some attractiveness, but not as a model of a railroad.
Model crews, too, can grow weary with the tedious shuffling required to move specific cars. So why are layout plans with an over-reliance on multi-industry switchback spurs still being published? Perhaps because these designs look more efficient than they really are. Or perhaps it's because that's one way to show a lot of industries on a very small section of benchwork -- whether practical for operations or not.
Fight the temptation to switchback
Designers must understand the trade-offs of these gimmicks in layout planning. If the prototype avoids multi-industry switchbacks except in the most difficult situations, perhaps we should too.
* Yes, there are some real railroad switchbacks -- logging railroads and others often rely heavily on switchbacks to climb steep slopes. It should also be noted that at times railroads construct switchback leads to reach a particular industry or group of industries. But the type of switchback here, which serves industries on both "wings", is much rarer on the prototype than on model railroad layouts.
"... why are layout plans with an over-reliance on multi-industry switchback spurs still being published?"