On 5/10/2014 1:26 PM, David Scheidt wrote:
Frank Krygowski wrote:
:On 5/10/2014 8:40 AM, David Scheidt wrote:
: Frank Krygowski wrote:
: :Some infrastructure fans have bragged about the fact that "It's happening!" -
: :that is, that the big investments in bike lanes, cycle tracks, bike boxes and
: :such have created a surge in bike commuting.
:
: :I'm all in favor of bike commuting and utility cycling. But I've long been
: :aware that the supposed surge has been comparatively minor.
:
: Yeah, the rate of commuting nearly tripled in Chicago from 2000 to 20012.
: Totally trivial change. It more than trippled in Portland. It almost
: doubled in LA, more than doubled in Philly. It doubled (to over 4
: percent) in Minneapolis.
:
: I sugest reading the study (or better, the numbers) and not relying on
: bad websites for summaries.
:
:I've read quite a lot about this issue. Sometimes a headline provides a
:useful summary even if the bulk of the information is elsewhere.
:Yes, I'm aware of cities that have tripled their bike commuting, and yet
:experienced change that was trivial. This happens when the initial bike
:mode share was something like 0.1%, and it rises to something like 0.3%.
All the cities I quoted have rates of well more than 1%.
Right, although as I've previously discussed, the presentation of data
is a bit misleading. Portland has been listed as having a 6% bike
commuting mode share. But it turns out that the 6% applies only to
residents of the city of Portland. It ignores the vast number of
commuters entering from outside the city limits. Again, nobody in
Portland during rush hour could pretend that 6% of the vehicles on the
roads are bicycles.
Also: doesn't it indicate a problem when "more than 1%" is used for
bragging? In most fields, 1% is synonymous with "negligible."
: That apparent difference might be generated as much by the vagaries of
:random sampling as by any real increase. And although it would be
The ACS is
pretty solid statisitical work, their methods and questions are
readily available.
I understand the ACS. I got the questionnaire once, and I'm one of
those people who was counted as a bike commuter. But note what the
League of American Bicyclists says about the results: "Note: ACS numbers
are based on surveys of a sample of the population, so they are just
estimates -- sometimes with large margins of error. Some changes may not
be statistically significant."
And the LAB is at the forefront of trumpeting any little gain. They're
probably the main organization bragging that "Bike commuting rose by
30%!!!" [from 0.5% to 0.6% or whatever]
If you have some real objection to their
methodology, state them. Don't make unsupported handwaving arguements
about 'vagaries of random sampling'.
It's not an objection to their methods. They do what they can with the
funds available. They could reduce the uncertainty in results by
polling more subjects, and they could also ask about bicycling in more
detail. But both changes cost money - IOW, tax dollars.
The statistical fact is, when an event is uncommon, any statistical
measurement of that event will have greater uncertainty, and be more
subject to random variation. _Reliably_ detecting the difference
between 0.5% and 0.6% bike mode share is very difficult.
:certainly trumpeted by agencies promoting cycling, even if it were a
:real increase, it would generate negligible benefits regarding things
:like pollution output, traffic congestion, energy use and the like.
Again, talk about the real numbers, not the ones you made up.
Well, we could talk about these: "NYC NYC Bike Commute Mode-Share Hits
1 Percent!"
http://www.streetsblog.org/2013/09/2...nly-commuters/
(What does it mean when you brag about 1%?)
Or these:
http://en.wikipedia.org/wiki/Modal_share (only six U.S.
cities above 1%.)
Or these:
http://bikeportland.org/2013/09/19/c...es-climb-94248
(years of more and more bike infra, no increase in bike mode share.)
All I'm saying is that the bike lanes, cycle tracks, bike paths, bike
boxes etc. are not going to transform America. They're not going to
produce noticeable reductions in traffic congestion, greenhouse gases
and similar problems. Unless there's some society-wide cataclysm,
people's transportation habits are going to remain much the same as they
are now. The U.S. is never going to look like Amsterdam.
It doesn't bother me, though. I love riding. I'll continue riding for
utility and pleasure, proving that it's possible, enjoyable and beneficial.
--
- Frank Krygowski