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Man.... I substitute "contrapositive" when I meant "converse", and I get an entire thread dedicated to the subject. As a computer scientist who should know better, I suppose I deserve it. :)

That said, non-modal Boolean logic, while often studied as part of rhetoric, is (unfortunately) not of much use in public policy debates. You seldom find iron-clad premises on which to base an argument or conclusion; circular reasoning (with elaborate cycles of inference) is commonplace, confusion of correlation, causation, and coincidence abound--and to top it off, in many subjects the only data you have available is anecdotal; and seldom controlled for the parameter you want to test.

The study of rhetoric and logic is important in developing a finely-tuned bullshit detector. But demonstrating anything in the positive (as opposed to falsifying blatant crap) frequently requires expensive and time-consuming empirical research--and even if such research is done with sound methodology, it still will get attacked by those who dislike the result. (The debate around climate change is an obvious example). Obviously, we can't set up experiments on the effect of streetcars vs busses on development; the best we can do is try and draw useful inferences from the data that's out there.


"Monorails never get stuck in traffic." would lead no one to conclude "If I'm not stuck in traffic, then I'm on a monorail." What it might lead people to conclude is "If I want to avoid getting stuck in traffic, I want a monorail." Which is a matter of judgment, but certainly not illogical.

Nobody ever claims that streetcars are the only way to get development. What they do claim is that they are a good way to bring about development. No false logic there.

I'm sorry, I just don't see much substance here. People are often bad at statistical reasoning, but they're okay with basic logic -- though not in formal language. If you want B, and A reliably brings about B better than not A, then you should do A. The answers aren't pretty -- you have to go and compare how good A and its alternatives are at producing B. Exercises in formal logic won't help.

Michael D. Setty


You've obviously opened a hornet's nest with your recent line of discussion. Here's another tack.

As most of us know, the usual rule of thumb for walking distance to local buses is a maximum of 1/4 mile. For rail transit such as light rail and heavy rail this number is about 0.5 mile, or perhaps up to a kilometer.

I'm curious if you have any information on typical walking distances to bus rapid transit, and frequent bus service in general? Your recent work for Canberra has an allusion to this (750 meters) but not a lot of detail. I'm curious about this, because I haven't been able to find any information about BRT/frequent bus service walking distances in the U.S.

Michael D. Setty

I'd add some of the worst offenders in crafting dubious associations between ideas are the Gadgetbahners (for example, those hanging out at http://groups.google.com/group/transport-innovators.

Their funniest, most dubious formulation is "Rail is 19th Century technology."

Of course, such logic falls apart when it is pointed out that "the wheel is 5th millenium BC technology," " concrete is Roman technology." and so forth.

Jarrett at HumanTransit.org


Yes, it's obviously silly to believe, in the present tense, that "If I'm not stuck in traffic, then I'm on a monorail." But why is it more logical to state the same thing as a relationship between desires, "If I don't want to be stuck in traffic, I want a monorail?"

If your goal is really to not be stuck in traffic, then you should investigate all the possible options for not being stuck in traffic, and pick the best one. And it's well established that to not be stuck in traffic, you just need a form of transit that doesn't mix with traffic, period. Monorails are just one of many such types of transit.

And if, as it turned out in Seattle, monorails aren't that good at actually getting built on budget and with acceptable community impacts, then it isn't logical to want a monorail. As it played out in Seattle, the decision to want a monorail actually resulted in people being stuck in traffic for a decade longer than necessary.

This is not an argument about monorails, of course. But I am pointing out that when we transfer our desire for A onto proposed project B, we often blow it, and end up supporting something that doesn't serve our desire at all.

And I do contend that watching the underlying logic can help us be smarter about those things.

Jarrett at HumanTransit.org

Scotty. I agree completely that logic is better at tearing down arguments than at building them. But I do think that there are stronger and weaker logical paths to get us from a desire for outcome A to a project B that will actually deliver that outcome. Scientifically, we do that by observing a correlation between similar projects and similar outcomes in other places, while understanding that similarity will always be a matter of degree and open to debate.

But I would also argue that if (unlike climate change) we are talking about something like real estate value, which is fundamentally an aggregation of what a lot of people think, it's logical to ask "is this value based on a lot of people thinking something that's just untrue (e.g. streetcars are a mobility improvement)?" Because if so, there's a danger that at some point in the future, the truth may become apparent to more people.

Personally, I don't think for the moment that the value of land in the Pearl District is going to crash as people discover that the streetcar isn't especially fast or reliable. The Pearl District's real virtues are in all the things you can do just by walking.

But knowing what I know as a transit professional, would I spend more for a condo on a streetcar line than for an identical condo in an identical neighborhood on a bus line? No, I personally wouldn't do that. I'd judge the latter as the better long-term investment, because it's more likely to be underpriced right now due to the prevalence of disapproval about buses, and the likelihood that the bus experience will continue to improve.

Jarrett at HumanTransit.org

The citations aren't ready to hand, but I suspect you'll find something about this if you research the LA Metro Rapid, which raised the quality of limited-stop service over local-stop service on the same line. There's probably data on the degree to which the rapid stops drew customers from further.

I think you could also construct a fully-informed-rational-actor model to assess how far you should be willing to walk to a Rapid stop in order to optimise your overall trip time. It would certainly show that you should be willing to walk further to a rapid stop than to a local stop.

And of course there's a lot in the literature about rail rapid stops drawing from as far as 1 km (obviously this is a hazy edge, as different people have different threshholds). From the rail data, you'd just need to decide how much of that attraction is about rail as opposed to the mobility rail provides. My inclination is always to assume the latter, but that's partly an extrapolation from how I make decisions as a fully informed rational actor who likes walking, and shouldn't be the last word.


I think your point here isn't really about logic so much as it is about doing careful evaluation of options. Technology A leads to outcome B but isn't very good at it, whereas technology A' ....

There's a lot hiding in a statement like "If I want to avoid getting stuck in traffic, I want a monorail." As I said, it's a matter of judgment whether monorail is the right way to avoid getting stuck in traffic, and such a statement is the end result of a process involving reason and emotion -- it is not the logic itself. So whether it's logical depends on how well that process was carried out.

I think the main problems lie not in the kind of reasoning people engage in, but in how accurately they weigh the costs and benefits and how well they predict practice from theory.


How much of the development around streetcar lines in Portland and Seattle was the product of subsidies? Have we seen development follow the introduction or re-introduction of streetcars in areas that didn't subsidize this redevelopment? Does land next to buses or brt lines attract the same level of subsidies? If not why not?

Do federal or state programs increase funding if there are rail lines involved? Or is the decision to redevelop purely a local one and the locals end up pushing the transit oriented development along the rail lines to pump up ridership numbers along the rail lines?

Lastly are any of these newer street car lines going through areas outside the CBD? Are streetcar lines a pretext the downtown interests use to get government subsidies for the CBD?

Jarrett at HumanTransit.org

Good questions, Ed, which I'll leave to the streetcar experts on the thread. At least in Portland's case, the capital funding flowed the other way: an assessment on property owners along the route provided a large chunk of the money to build the Portland Streetcar. However, tracing the ongoing flows of subsidy and government preference that affect rail vs bus outcomes can be the work of a lifetime ...

Funny thing, this wasn't a post about streetcars originally ... but somehow we keep coming back there ...


Hm, this whole discussion reminds me of this cartoon.

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