procedural cracks and roads - connecting the lines together

Let's see a few movies to see what I mean:

http://www.youtube.com/watch?v=FGvaSwhapSs - procedural road generation

http://www.youtube.com/watch?v=A_6cImV9mEA - same subject.

http://www.youtube.com/watch?v=Vjm7YE0bdt4 - yep.

I wonder how do they do it so that the lines actually stop on another lines? I think this might also useful when it comes to generating cracks on objects which could be written to be able to be destroyed procedurally (?).

Any idea how could we transfer those ideas to unity, and if not, then what could we need to read in order to do that later on? to understand it better.

L-Shaped fractals are a clue, left in the description of some of such links.