Originally Posted by MSPeconomist

At some airports, RJs don't have standard jetways on roughly the same level as the gatehouse but instead board using a long sloped ramp with switchbacks, often requiring passengers to go outdoors. IIRC DL does this at JFK for the small RJ gates at the end of the concourse and also the JFK Jitney shuttle bus between terminals, but I've seen it elsewhere too.

The net effect is that these devices avoid stairs but do require that one be able to walk up or down a hill. OTOH, they're relatively easy for wheelchairs.