The folk wisdom about getting to church is that people will go as far to a church as they will go to work. That makes commuting data important for church plants, but failing that assume that someone won't take more than a half-hour to get there.
There's a new interesting tool that maps how far someone in Washington, D.C. and a few other cities -- Boston, Seattle, Dallas, New York and Chicago, among others; and Berlin, London, Auckland and Perth overseas -- can get in a certain amount of time on foot and using transit. Important, too, because I have a hard time thinking the suburban "temple in a sea of asphalt" will fare well in a city, or that even near-suburban congregations can depend on this unfortunate staples of American religious life. (That said, it's been more than a decade since I was a member of church that I had to drive to, so I'm a bit of an outlier.)