Spatial Analysis - Curves

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I'm still relatively new to the GIS world and wanted to know if anyone has done or knows of ArcMap allowing real-time calculation of curves. Let's say I was to capture GPS points for a road segment; I want the system to automatically calculate the curvature of the road when it crosses some acceptable threshold. Any ideas or suggestions? The part that I'm having a problem with is determining the start and end of the curve. After that I think it would be simple to just use different projections provided by ArcObjects to extract the data needed for the calculation.