Montreal resident, cyclist and mathematician M. Kary has reviewed the study by Lusk et al. of Montreal’s two-way one-side of-the-street barrier-separated on-street bikeways.
The study by Lusk et al. purports to show that the bikeways are 28% safer than riding on comparable streets without the bikeways. Kary points out a number of serious methodological and factual errors which, he contends, invalidate that conclusion.
The review is heavily annotated and is supported by a large number of photographs. Each photo caption includes a link to a Google satellite view or street view, to pinpoint the location.
Here are a few quotes to convey the flavor of the review.
Rachel between St Urbain and Marquette
The authors list this path segment as being 3.5 km long. In fact it is approximately 1.7 – 1.8 km long, and thus has approximately twice the rates of injuries and crashes per kilometre given by Lusk et al. (The authors need to explain how they obtained the lengths they give for all their path segments.)
Construction of the reference and intervention samples
…Since presumably the authors do not count incidents occurring to cyclists travelling along the path but in the terminating intersections, using short path segments as the authors do also lowers the overall number of intersections per kilometre, making for a comparison more favourable to the paths. (Example: for block lengths of 200 m, a 1 km path without the terminating intersections would have incidents resulting from 4 intersections per kilometre, while a 5 km stretch of the same path would have incidents resulting from 4.8 intersections per kilometre— a 20% increase.)
Crash rates described as injury rates
The “What this study adds” box incorrectly compares the (incorrectly calculated, see sections 1.1 and 1.3) injury rate of 8.5 per km reported by the authors with a range of 3.75 to 67 supposedly reported elsewhere. In fact the latter figures are crash rates, not injury rates.
Figure 13: René Lévesque at Maison Radio-Canada
In 1990. renowned CBC journalist and producer Joan Donaldson attempted to cross this two-way path to get a taxi, and was struck down by a cyclist coming from her right. She remained in a coma for at least six months, could not speak at all for three years, and was left permanently brain-damaged and quadriplegic. The cyclist was uninjured. Donaldson died in 2006 from extended complications of the accident. Authors’ method does not count such injuries, for not being to a cyclist.
Enough. Please read the review.