find the radius of curvature of road curves

Hi, I am looking for an expert, i have 6 aerial images taken for some roadway ramps, the roads contain of a set of curves connected together (circular and spiral curve), firstly, i want to detect the start and ends of each sub-curves by calculation the radius of curvature at 1 m or 2 m position, then after the start and ends are determined i want to calculate the length and radius of each sub-curves.
please find the attached i uploaded screen-shut example of the radius of curvature with data points