fitting the x y points then find the radius of roadway cuves

Hi, I am looking for experts, i have some x ,y coordinate points for some roadway curves, selected from aerial images using MATLAB tools, first, i want to smooth the data points since the points selected randomly, then i want to find the length and radius of each sub-curves using k-meaning clustering algorithm or any other algorithm that give desire results。
please find the attached i uploaded screen-shut for one of the data points