A wye with even a modest twenty-four-inch radius has a significant footprint which creates major "human reach in" issues.
Turning wyes are a common feature on prototype railroads and a perennial favorite among modelers. Incorporating them into a layout design? Not always so easy. Model railroads lend themselves to more linear elements. Humans need aisles. We have limits as to how far we can reach. A wye's square/trapezoidal footprint takes up a lot of room and does so in ways that don't dovetail onto your typical, shelf-style, bench work. The prototype isn’t limited by these restrictions. So, what are your design options if you want one?
Wye at located at the base of a peninsula
The first question to ask yourself is whether you want the wye for operational purposes or purely aesthetics. If you want them to actually turn trains, the only place they really fit seamlessly is at the base of a peninsula. Even then it will require a trip around the entire peninsula if you need to access a turnout, uncouple cars, are deal with a derailment. Trying to force a wye into other areas becomes a case of trying to force a square peg into a round hole. Even if you can shoehorn it in, it will very likely disrupt the design as a whole and be problematic to interact with.
N scale wye located at bench work corner.
As a side note, my comments refer to those modeling in HO scale (about 85 percent of the hobby). If you model in N scale, life is easier because the dimensions are so much smaller and reach in distances are less of an issue.
"Suggesting" the existence of a wye by only modeling two legs is the easy way out if you only need to represent it for aesthetic reasons.
If your main reason for including the feature is aesthetic, life becomes much easier. Just model two legs of the wye and “suggest” the existence of the rest of it “off layout”.
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