When I was driving transit, most of the fleet had hydraulic lifts operating in the forward doorway. They were cumbersome and slow, but just about all coach manufacturers used them. We got three new coaches while I was working there that had a simple ramp that formed part of the floor inside the entry when it was retracted and it rotated up and over to slope down to the sidewalk for disabled passengers to use.
Unfortunately, the coaches had serious reliability issues and were sold off quite quickly.
Frank Damp -Anacortes, WA,(DW- Eileen)
ex-pat Brits (1968) and now ex-RVers, as of 08 Dec 14.