A geometry tool is needed to easily create a Compound Horizontal Curve with Spiral segments.
Having the ability to quickly compute a Spiral-Curve-Spiral-Curve-Spiral between two tangents would be greatly beneficial to the track design work we do. This can be especially important when tracks are constrained to existing corridors or following roadway geometry.
I believe this tool was available in the InRoads Horizontal Curve Set Tools. There are work arounds that can be done but many of them require iteration and identifying at least a few known points along the curves in order to work.