Hi! My name is Alpar. I used to work as a road & bridge designer... First of all you need a reference coordinate (a point on the photo with known X,Y coordinates), then you need a scale reference (a line with a known dimension). You can grab for example a Google Maps photo to overlay with this and scale this image to match the dimensions, and then you can extract a reference line with the ruler of the Google Maps. I don't think you can achieve better precision than 1m. Then you draw two lines at the right and the left margin of the road, and then you make offsets inside. Until you guess the precise road width. So if you have the ax, you need to use the measure command in AutoCAD, then extract the point coordinates. As I said... I don't think you can achieve better precision than 1m, and even that is quite hard, and impossible to verify on just an image. The ax curve is composed by transitional curves like clothoides... You cannot guess where is the exact beginning and where is the ending of one curve. If you have questions I'm happy to help you.