We have a few large shots, nuthing that we won't be able to handle, but i wanted to get a little bit of izzy's input and anyone else that pretends to know what they're talking about

The big one is: a lady on a bike is gonna shoot 2 cop cars chasing her, a few times until she hits the tires and the cars flip over( and possibly explode).
1) We may get some footage of REAL cop cars driving a bit (my director says its a "public service", but i still doubt it).
2) We may also get some real footage of the chick riding the bike, but there will also ha to be some chroma keying with her on the bike. I'm pretty sure.
3) I'm also pretty sure i don't have the time to do some realistic enviroments, so the 3d cop cars will have to be COMPed onto real footage.
I don't want to take on TOO much, but i want a real challenge here. I also don't want this to look hokey, so i'm a lil uneasy about the whole thing. Does anyone have any thoughts, anyone think of any issues i might run into?
PS were hoping to get this to some film festivals eventually.