Couple times i realize that when someone who creates map and road directions makes mistake then whole idea to navigate and find alternative way is impossible. Not long ago the city "improve" traffic by changing traffic direction in couple streets around me. Now it's impossible to get to my house via navigation.
So...why to don't implement program with functions to let customers/users to fix it manually. Sometimes it's enough to change one road direction to let navigation find why to the point.
AlexFM
Ps. Please move this topic to Suggestion :)