My most recent post on Planetizen.com's blog Interchange takes up the question of whether mobilty and accessibiliy are the same thing. Planners have become enamoured with the idea that accessibility and mobility are independent of each other. Since mobility is usually considered auto-mobility, and therefore care dependent, they aren't so concerned about reducing mobility. The implication is that people are indifferent between living in places that are autodependent (low densities) versus transit-oriented (high density, mixed use) as long as services and other things are "accessible" via other modes.
I challenge this idea and make the case that mobility is a key to accessibility, and this is one reason why the popularity of the automobile persists. I point out:
"Unfortunately, by conflating mobility, accessibility and transportation modes, we leave out the crucial discussion of the trade offs implied by consciously shifting from one transportation mode to another. Simply adding transportation modes to an existing built environment will not necessarily increase mobility or accessibility. If the buses run empty, and bicycle paths go unused, the provision of these alternative modes provides neither greater mobility nor greater access. Indeed, by shifting resources from more productive public investments, including greater capacity for the modes that make sense, overall accessibility may decline."
The discussion threat, as always, is as informative and entertaining as the post itself!