# Analysis of Bicycling Trends and Policies in Large North American Cities:
Lesson for New York

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#### John Pucher, Ralph Buehler

#### March 2011

#### University Transportation Research Center 2

This is another survey of statistics so typical of Pucher. The statistics are
justified, made to seem more persuasive, by being submitted to a variety of
statistical tests. Several of these tests are unknown to me, but my ignorance of
these does not change my conclusions about the study, which are based on the
content of the study and not about the reliability of the statistics presented,
and which agree with Pucher’s own conclusions.

Pucher has become much more cautious in his claims. He now admits that he
presents nothing more than correlations between urban characteristics and amount
of cycling. All his study shows is that those cities in which there is much
governmental activity about bicycle transportation have more bicycle commuting,
and even Pucher repeatedly states that the causal relationship, if any, may be
in either direction and there is no way to separate the effect of any one
program.

And a bit more besides. Dense urban cores have higher bicycle mode share, as
do areas with many students. In these two cases, causal relationships probably
exist, but these are not characteristics that can be changed to increase the
bicycle mode share.

Despite Pucher’s presentation of statistics with repeated tests of
statistical reliability, he has made at least one glaring mathematical error. He
has presented a graph of two ratios. Fatalities per cyclist is graphed against
cyclists per worker. Any graph of this form is meaningless, because, whatever
numbers may be used, even random, they produce a declining pseudo-hyperbolic
curve that looks as though increases in bicycle mode share produce decreases in
cyclist death rate. That is, the Jacobsen error.

I need to emphasize that Pucher makes no claim that bikeways reduce cyclist
crashes or how such an effect might be achieved. As he stated in his meeting in
San Diego, when asked about this, he replied that he paid no attention to
engineering but just did (in this case, reported) what was popular.

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