I think I'll add my two cents in here...
Disney currently runs two type of busses. The Rapid Transit Series, or "RTS" bus, which is a standard floor bus, manufactured originally by GMC ('77-'87), later sold to TMC ('87-'94), and finally NovaBUS ('94-'02). The RTS is arguably regarded as the most rugged, durable, and solid transit bus in the world. Currently, Disney has 194 RTS busses in guest service, ranging from 1979-1994 model years.
The majority of our RTS busses are 40' in length and 96" wide. We have 35 remanufactured RTS busses that are widebodies, which means they are 102" wide. The extra 6" really makes a difference for internal aisle space, and I wish all of our RTS busses were widebodies. The actual true capacity of a 40' RTS bus is around 72 people. (Hence our radio call sign for a full bus, "Signal 72") 45 of those people are seated.
Now, with the addition of the All-Stars, AK Lodge, Pop Century, as well as other increases in transportation, Disney decided to purchase more busses. In 1998, we bought 35 used RTS busses, and had them rebuilt. However, this was just a temporary measure. NovaBUS was currently manufacturing the RTS bus up until this past June, however, the decision was made to go with a Low Floor bus. The reasons for this is very simple... the easy entry for everyone. The one downside to Low Floor busses however, is the large wheel wells. This will be found on every low floor bus out there.
The second type of bus that Disney has, is the Low Floor Series, or "LFS" bus, which is manufacured by NovaBUS. They are all 40' in length and 102" wide. Currently, Disney is leasing 47, with 24 more currently being built. As it stands, Disney has no plans of getting more of these type busses. It's important to note that we are Leasing them... they were not purchased, as were the 194 RTS busses. NovaBUS rates the capacity of this bus at 80 passengers, however, seeing as the average guest has strollers and merchandise bags, I'm more inclined to say I get an average of 65-70 passengers on my LFS. 35 of those people are seated.
On a note of environmentality... the RTS busses currently use a Detroit Diesel 6v92 engine (4805-4814 use a DDC series 50). The older versions of these engines get about 8mpg. We are currently replacing many of these engines with "Green" versions... these newer versions of the 6v92 have better fuel economy, and well as a significant reduction of emmissions.
The Nova LFS busses use a Detroit Diesel series 40 engine, mated with an Allision B500 World Transmission with retarter... They get about 12-14mpg, and have about 80% fewer emissions than the older 6v92 models.
As for the future of Disney Transport vehicles... Our 27xx series are getting old. Most of those busses are 20+ years old, and have over 2 million miles on them. They are still very mechanically sound, and in great condition for thier age, however, they are slated for replacement in 2004. What they will be replaced with, is anyones guess. Once our contract for 24 more busses is complete, I think that will be the last of the LFS for Disney. We've encountered too many problems with them, and I don't think Disney has been happy with thier service. Who knows what we will end up with, but I can guess it will be a Low Floor bus.