you get points for everything you do (you see them if you click your diary, then click the little envelope on the lower right. your points are in the top right then).
at some amount of points (no idea how many excactly) you will unlock signs that will allow you to switch routes. im at 1000 points now... i think you unlock them around 750.
you start at the basic route then and after a few meters there are signs that you can take to the mountains/beach etc.
hope it helped