Accessibility is approachability. One of the things you may want to consider in a job is the accessibility of the managers. If you have a concern, are they available to help, or are they always in meetings or "at lunch"?
Accessibility also refers to the quality of being available when needed. You like the accessibility of the company's customer service because you don't have to wait endlessly on hold in hopes of reaching a human being. Accessibility also refers to how easily a disabled person can negotiate part of a building or structure. The stadium had wheelchair accessibility with ramps and a special seating area.