The real boost will come when driving becomes an automated task. There are technology demonstration platforms (especially in Europe) that include universal vehicles (nobody would "own" them, or you would pay a fare like a taxi, and they are just everywhere) which are tied into a computerized roadway system. You simply get into an empty vehicle (which would ostensibly be parked on the road or in depot stations), program your destination, and off you go - you sit and read the newspaper while the vehicle drives itself. The obvious benefits are:

1) The vehicle would be regulated by the computer network to drive at optimal speeds for fuel efficiency.
2) The routing system could avoid congestion and provide the optimal route for fuel efficiency.
3) The traffic management system would ensure that all traffic flows constantly and smoothly, avoiding stop-and-go situations and traffic backups that lead to higher fuel consumption.

The downside, of course, is that if you're in a hurry, you can't really speed and weave in and out of traffic, but the flip side is that that kind of aggressive driving seldom really presents a significant time savings anyway. Personally I think the world would be a much calmer place if instead of white-knuckling it through rush-hour traffic, you could just take a nap, play a game or read a book. Too bad more people prefer the feeling of independence and control derived from driving for themselves.