Many highway departments just use tangents and simple arcs. Modern CAD & survey software makes layout of spiral transitions much easier, but this is an inherently conservative profession in many ways.
In other words, your approach sounds neat, but does it offer anything for the average pragmatist field practitioner? What are you trying to acheive?
Also, where are you getting your alignment data? Mapping level data are probably not accurate enough for any sort of design work.
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