It would be great to couple waze with a carpooling app (short and long distance).
A driver, who agrees to give people a ride (for free or not), takes a ride from point A to point B. His route is calculated and defined by the GPS. Then a person living close to the route willing to travel towards B would receive a notification and could join the drivers' route.
This would probably reduce the traffic jams around cities in peak hours.
Waze Carpool app is in development.