A lot of people view the DDA as meaning "we've got to be wheelchair accessible" and leave it at that. In the simplest terms though, if something is at ideal wheelchair height then it is utterly inaccessible to anyone of average height who has trouble bending their back or legs. The solution is to account for both separately if they cannot be accounted for in one fell swoop. In much the same way as a supermarket has 10 disabled spaces and 200 regular spaces, so a row of payphones in a train station might have 3 at regular height and one low down, and a bank might have 7 regular cashier counters and one low cashier counter. It's preferable to have a catch-all solution if possible though, like light-switches at 4ft (where I can hit it from a chair or from standing) rather than at 5ft, and light-pull-cords that go all the way to the ground rather than being tied off 5ft in the air. The solution of the future would be remote-controlled lights, or motion-sensor lights.