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E. Spirals
1. Concepts
Spirals were mentioned in the Basic Concepts section of Chapter C. Horizontal Curves. In this chapter, we will go into more detail.
Recall that a spiral arc, Figure E-1, has a constantly changing radius.
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| Figure E-1 |
This characteristic has advantages in route applications, discussed in the next section, as well as presenting computational challenges. While a more complex geometric curve than a circular arc, a few reasonable assumptions can simplify its calculation.