I worked for a while with the pneumatic tube systems they have in places like Sainsburies, the tubes ran for quite a distance from the checkouts to the cash room way at the back of the store, those carriers used to travel at phenomenal speeds, we had to install a knife valve ahead of the carriers to slow them down or they would have blasted thru the recieving station.
They did not work on a vacuumn, just reduced air pressure ahead of the carrier and atmospheric pressure behind, very efficient, often thought a scaled up version would be worth looking at.
[This message has been edited by tony draper (edited 28 June 2001).]