Interestingly enough, I did find that following some of the advice from the Zombie Survival Guide (a parody book) actually worked well, insofar as urban scenarios are concerned. In Classic mode, you don't want t barricade and hole up until you know the rescue location- otherwise it's breach, search, move, breach. I haven't won yet, but I've gotten pretty close. Roadkill, on the other hand, works a little differently--- I'd say you still need to stay on the move, but once you find the vehicle location, go back to it and barricade yourself once you have all the missing parts while you repair the vehicle.
I was doing very well in Roadkill, until Super Zombie showed up, I decided to run--- and, of course, my survivors scattered to the four winds and were all massacred trying to breach different buildings.
It would be nice if you could tell the game *where* you want all of your survivors to run, as opposed to them scattering to the four winds to their deaths.