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Lewis-Mogridge Position (wikipedia.org)
54 points by danielam on June 24, 2019 | hide | past | favorite | 13 comments



I think this is approximately the same as saying that transportation is the limiting factor in city growth?


Yeah. The length of commute that people are willing to tolerate is approximately constant, so as transport provision increases the number of people who work in a given city increases, capped by that same commute time. Given the value of agglomeration effects (there was a recent piece here on how authors are more productive if they work around others), isn't that what we want?


Intuitively there feels like there should be an upper bound on this axiom. For example, imagine a highway 1 mile wide with 50 lanes going each way. That's 220 lanes in each direction. Assume dense traffic with each car taking up 25 of lengthwise- space. A 1 mile stretch of this megahighway would have ~60,000 cars on it. At this density, the 101 between SF and San Jose would be able to accommodate ~2.8 million cars. A quick search reveals that there are only ~2.5 million cars registered in the counties this highway would run through.

So while I don't doubt that this relationship ('traffic increases to fill the available road space') is true for some conditions, it's not a universal law. The real question is finding out where it starts to break down. Maybe there is some merit to building a super wide highway ;)


> A quick search reveals that there are only ~2.5 million cars registered in the counties this highway would run through.

Actual number of cars should be lower after the highway is built because construction would require removing houses to make room for it.


There's disturbingly little empirical data there for what should be a very empirical question.


>traffic expands to meet the available road space

I'm sure this is in many cases true, but there is a danger in mistaking the metrics for the goals here. If people drive less, it makes the numbers look better, but people staying at home saying "it's impossible to get anywhere this time of day" is hardly the mark of an effective transportation system.


Sure but that means your argument for building a new highway needs to be "it will get more people where they are going" and not "it will reduce congestion", and you definitely can't pull any "if people are able to get where they are going faster it will reduce emissions" nonsense, which does get brought up.

And if the problem you are solving is "get more people where they are going" all of a sudden highways no longer look like a cost-effective solution at all, and public transportation looks _a lot_ better. A lot of highway expansion gets justified by the claim that it will reduce congestion, despite a huge amount of empirical evidence and theoretical justifications (e.g. TFA) that it does not.


If interested, there was a similar conversation recently about the Downs-Thomson paradox, noting the relationship between road network improvements and traffic congestion. It's here: https://news.ycombinator.com/item?id=20133027.


Didn't Seattle (or some other major PNW city/area) actually remove or close roads in their area, and saw that congestion decreased overall? I seem to recall reading about that several years ago...

EDIT: fixed PSNW -> PNW


This probably depends on:

- fuel being cheap,

- time spent driving having a low value,

- zoning that discourages high-density development, and

- overhead costs of buying and selling homes high enough to discourage moving nearer to work.


Sometimes it really shows that many early Wikipedia articles were someone's labor-of-love about a relatively obscure topic, and even today there's uneven levels of notability across the encyclopedia.

Instead of these hyphenated iron laws of transportation demand that no one has ever heard of that all say the same thing, the article of "induced demand" ought to suffice, and these formulations, if they exist original sources at all, ought to become references in that article's footnotes.


Almost all "deletion for non-notability because I've not heard of it" reasons should be invalid. Wikipedia deletes far too many people's work in the service of a small number of core maintainers.


I disagree.

First why is granularity at the level of induced demand ok, but not the Lewis-Mogridge position? Why not put it all in the supply and demand page?

Second, if I come across the Lewis-Mogridge position, and Google it not knowing what it is, should I expect, and prefer, a link to a research paper, a broad wikipedia page most of which is irrelevant to my question, or an actual page that answers my question?

Personally I'm a wikipedia maximalist. Record everything, keep it around for posterity. If in 50 years they want to know what we thought about X, they can find out, and we today can reliably find out about X too.

The cost of this page us virtually zero, why not?




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