This is more of a wish/invention, because I don't actually believe Americans will ever get their act together enough to implement anything this socialist. Perhaps if you can view it in the most exploitable, free-market way, then that could actually be the future.
The nation's rail lines are updated to connect every district in the country via the main trunk lines, and some high-speed lines are installed in major corridors. Freeways are converted to have rail lanes. Personal vehicles ride double-decker along with frieght on the train, all routed by computer.
Personal vehicles are lightweight, and have little electric, direct-drive motors. Each vehicle holds two people and a few packages. If you need more space, you hook up two vehicles. If you want a mini-van, you hook up three. Once you get to a main arterey, you hook up to other cars. Anywhere you need to go that goes over 25 MPH, your car gets loaded onto a train. All the cars are small -- about the size of a box that has a two-person bench seat in it. So the loading on the train compartments is fast and efficient. You program your destination and preferred route into the console of the car or your PDA or home terminal before your trip. When you leave, your trip hooks up with other compatible trips on the grid, and you can physically hook up with other cars as you approach, thus, you only need one fail-safe driver for a string of cars all hooked up in an ad hoc train, and the hooked up cars become more efficient and safe. When you approach a divergence in your route, your car un-hooks at stopping points or intersections. The network would be able to optimize car hook-ups and trips for short distance (and long distance over real trains).
Shipping items have similar motorized carts, and are accumulated at shipping points, and motored over to the train pickups. Chips in the carts help to route the carts via the train system country-wide, unattended. Communities get larger carts and then distribute the contents like a food co-op or book co-op. Standard shipping containers will come in modular sizes (1x1, 1x2, 1x4, 2x4, 4x4, etc.) and will have tracking chips built-in. The containers will have hard plastic shells and have built-in padding inside. You just grab the container you need, put your stuff in it, and wheel it or carry it to the nearest container-accepting bin, which securely and automatically accepts the containers. The containers are then picked up by truck, and routed, possibly in larger containers, to the train system, and routed all the way to last-mile delivery.
(First published in 2007 here: http://wiki.thinkprank.com/wiki/Laramie/Future )