According to http://en.wikipedia.org/wiki/United_States_Postal_Service, the US Postal Service has 36,000 branches, employs over 760,000 workers, and operates the largest civilian vehicle fleet in the world -- 260,000 vehicles, averaging 10.3 MPG, that consume 800 million gallons of fuel each year. It spends an average of $235/year per US residence. First Class mail volume declined 22% from 1998 to 2007, amid rising costs and competition from email and online services. Package delivery is increasing as people shop more online, but there it faces stiff competition.

We think SkyTran can help the Post Office dramatically improve its service frequency while improving its environmental sustainability, even in the face of these challenges. There's something special about a physical mail delivery. In our personal lives, mail brings us evocative physical objects no "eCard" can match. Practically, being able to routinely get a spare part or legal document the same day will make life more efficient. Fully built-out SkyTran systems will have stations every few blocks in urban areas. Most people will pass through the station nearest their house daily. It will be much more efficient for the Post Office and other carriers to put mailbox kiosks in stations, and give people discounts if they pick up their mail and packages there instead of at home. Each carrier's share of the SkyTran can include picking up and delivering several times a day from each of these stations, as well as warehouses and businesses all over town. When postal workers and their cargo arrive by SkyTran, they cut their carbon footprint by a factor of 20: 200 MPG vs 10.3 for a mail truck.

As any authorized member of a household approaches their home station, they are alerted if there is mail waiting -- perhaps they can even preview the items on the in-car screen to see if they want to pick them up yet. At the station, they open a traditional PO box, or they identify themselves at an automated kiosk with their credit card or SkyTran pass, and it dispenses their mail like a vending machine giving you the snack you selected. A friendly neighbor can be authorized to get your mail should you be incapacitated. Businesses can designate employees to pick up their mail at the closest SkyTran station.

With much higher traffic than typical mailboxes, the SkyTran mail kiosks could justify optical readers that scan envelopes and packages as they are deposited and ask the sender to edit the address on a screen if it isn't clear; then print an unambiguous barcode to simplify later sorting. They could also weigh and check the postage and let you add postage with a credit card if it wasn't enough. If no mail enters the system with an unclear address or incorrect postage, costs will be greatly reduced downstream. These measures could almost eliminate "dead letters" and inadequate postage and unreadable addresses, making the sorting and routing far more efficient. (They are analogous to what studies have shown is the most reliable voting system: paper ballots with direct-read scanners in the polling station; so errors are corrected before the voter leaves.)

Even if initially a carrier arrives by truck, s/he can still save lots of time by loading hundreds of mail boxes in one place. Eventually there will be specialized SkyTran cars for mail and package delivery; so it will be efficient to deliver mail in the stations several times a day.

A mailbox 9 inches wide by 12 inches deep, by 6 inches high would accommodate most mail and packages that most residences are likely to get in a day. An automated kiosk 10 feet high (the height of the boarding platform) and 5 feet in diameter could contain 400 mail boxes this size; one or two such kiosks should be enough for most SkyTran stops. A simple robotic arm traveling up and down the vertical center of the silo could stuff envelopes and small packages into each mail box in the standardized shipping boxes can contain a majority of packages. Having two sizes, 9" x 12" x 4" and 9" x 6" x 2" will accommodate most needs and can fit in the mail boxes designated above. Standard plastic containers can be reused by simply re-addressing them. At each mail kiosk at the SkyTran stop, you can get or return empty boxes. Reusing these boxes will drastically cut down on trash volume, making trash collection less expensive.

If we look at the longest distance a piece of mail would travel in the US between cities, that is Bangor Maine to San Diego California for a road distance of 3280 miles. Presuming our SkyTran network took the same distance, at 150mph non-stop, covering that distance would take 22 hours. Including time for processing at either end we ought to be able to get mail between SkyTran stops anywhere in the US in a day.

Using SkyTran for mail delivery is in no way central to the system. It is just one example of the ways businesses and communities will be able to leverage the SkyTran infrastructure to provide new services to people, save money and decrease environmental impacts. Getting several hundred thousand heavily used trucks off the road every day plus airplanes and trains could put a big dent in our use of energy, money and health care facilities.