Find a curved road on google earth, copy it
Then scale it on geogebra and take note of the coordinates.
Now you find the function of best fit. And then calculate the length of the function from point a to b.
In order to find a function of best fit, look for polynomial regression. You use partial differentiation, matrices, and some statistics
Then to find the length of a function, use arc length. This requires basic calculus knowledge.
That was pretty much it. Hope it helps