It does this once the phone establishes this? What I want to do is be able to set this up from day one. When I tried out Android for a bit there was a widget that would show you how long it would take to get home based off your current location and the traffic.
After two full weeks on iOS 7 with frequent locations enabled, you'll get this function that you are looking for.
After two full weeks of learning your driving patterns, it will start telling you how long to get to work, how long to get home from work, etc.. But it will also then tell you, anytime you are not home (say at a friend's house for a weekend barbecue), it will tell you how long it will take to get home.
There's no way to do this from day one, but after two full weeks - you will start seeing this behavior (in the third week).