My main response to Jarrett's post, though, is simply "Why?". He writes, "I'm just suggesting that the mobility offered by a transit service is an independently assessable feature that some people might want to decide if they care about." But do they care, and if they don't, why would they start? And why do we care whether they care? Because they'll start a campaign against this service? Because they'll stop using it and starve it of fares?
What I'm missing from these posts is a sense of overall goals. I've got them right up at the top of the page: "Reducing pollution, Increasing efficiency. Reducing carnage, Improving society, Transportation for all." I suppose that mobility would come under the headings of increasing efficiency and improving society. ...
My purpose in this blog is to help you be sure that the projects you support actually implement your goals. In terms of Cap'n Transit's stated goals, I'd say that if we don't meet a citizen's mobility needs on public transit, and she lacks another alternative, she'll do one of two things -- (a) drive her own car or (b) not make the trip. Outcome (a) has negative impacts for three of the Cap'n's goals ("Reducing pollution, Increasing efficiency. Reducing carnage"). Outcome (b) means that the citizen doesn't do something she wanted to do, and a quantum of economic/social/cultural life of her city is lost because she stays home. So it seems to me that outcome (b) is negative for his last two goals, "improving Society," and "Transportation for All."
(In passing, I'd note that "Improving Society" isn't quite adequate as a goal statement, because the word improving begs the question of what kind of improvement you want to see [much as the word convenience does]. I mean, Hitler thought he was improving his society too. In deciding that a citizen staying home is counter to a goal of "improving society," I've had to use my notion of what counts as improvement of society, and am therefore insinuating my values while claiming to talk about the Cap'n's. So watch out for the verb to improve unless it's followed by something measurable like speed, efficiency, coverage, or for that matter, mobility.)
You can object, at this point, that the hypothetical person may not make her mode choice based on mobility, so ridership outcomes may not match the mobility outcomes. A hypothetical person might choose not to use a service because of non-mobility issues such as ride quality, "look and feel," legibility etc. I submit that in the case of streetcars, we really don't know how much of their ridership advantage is based on intrinsic features of the technology, as opposed to logically separable improvements (many of them mobility improvements) made at the same time. Meanwhile, we do know a lot about how quantifiable mobility values such as travel time affect mode choice; well-calibrated factors for this are inside of every multi-modal transportation model.
I think in order for us, Jarrett's audience, to value the goal of mobility, he needs to explain it in terms of our own goals - and not hypothetical ones. Otherwise it's a tool without an application. A provocative discussion, but not quite as productive as it could be.