The procedural generation of city streets?

Question

I read L-Systems, read Parish and Muller, Kelly and McCabe and tried to implement this one , but I really had no luck at all (all my streets tend to go in the same direction, never branch, etc.). Can someone provide some source code or some reference implementation that generates a system of city streets (preferably along the line of arrival and Mueller, but for now I will try something). I have been working on this for several weeks now and am not getting anywhere fast.