Travel Time Between Zip codes

Hope someone can advice but looking for an API service t开发者_运维技巧hat can provide traveling times between 2 zip codes. These would be driving time. Cant seem to find a service for such a thing.

Can anyone help provide links to any good services they have found?

Something like: http://maps.google.com.au/maps?hl=en&q=90210,+usa+to+98050,+usa&output=kml? The total distance and travel time are in the "Route" placemark...

Would that make much sense? If these are close together then result can vary a lot. Like 92128 and 92127 - could be 0ml or 15ml. Can you, perhaps, get set of coordinates for each ZIP, take some median and then use these 2 point to compute the average distance?