Intersection of two routes

Question

I have two routes (MKRoute *), which intersects each other. If I add overlay from them I get something like this

http://tinypic.com/view.php?pic=2e3349u&s=8#.VSpjvFy5Kuc

The first one is begins and ends in pins (going upwards), another is going left to right (without pins).

So, like I said, I have MKRoute * objects, which I used for displaying. Is it possible to determine, if this two routes intersects each other?

I've already tried to use

[route1.polyline intersectsMapRect:route2.polyline];

method from MKOverlay protocol, but for this example it returns false. Am I doing it wrong?

Thank you.