Note as of November 17, 2013: I have reviewed this post to correct typos, improve wording, and add headings. I have highlighted substantial changes and additions.
Note as of May 23, 2014: I have added links to reviews of the study.
The “Bicyclists’ Injuries and the Cycling Environment” (BICE) study — of crash and comparison sites on the routes taken by 690 out of the 2335 cyclists treated in the emergency departments of five downtown hospitals in Toronto or Vancouver, May 18 2008 to November 30 2009 — is held by some as conclusive proof of the safety advantage of “cycle tracks” (segregated bikeways in the street corridor). However, it has been extensively criticized by others.
A report from this study is published in the journal Injury Prevention: Harris MA, Reynolds CCO, Winters M, Cripton PA, Shen H, Chipman ML, et al. Comparing the effects of infrastructure on bicycling injury at intersections and non-intersections using a case-crossover design. Inj Prev 2013;19:303-310. doi:10.1136/injuryprev-2012-040561. The report also is online.
Several critics have addressed the content of the report itself. I side with them. The results are wildly out of line with those of previous research, by a factor ranging of as much as 2000%. The large 2007 Copenhagen study found streets with bike lanes and cycle tracks to have a significantly higher bicycle crash rate than the same streets before the special treatments were installed, and even the Lusk et al Montreal study, despite clear bias in route comparisons and statistical errors (see review here), found cycle tracks to be only 28% safer than comparison streets.
Epidemiology smears largely undifferentiated factors into an overall risk, obscuring rather than clarifying what makes for safety. Epidemiologists think of correlation, rather than of mechanisms. Epidemiologists can tell you where crash hotspots are but have very little to say about crash causation and prevention. In the medical field, this is counterbalanced by medical research and clinical practice. Disease prevention through hygienic practices, immunization, and avoidance of risky behaviors is well-understood. In bicycling, there is no such counterbalance, because of a disconnect between epidemiology and the scientific study of crash causation and prevention. This problem is exacerbated by the controversy over whether bicycling advocacy should be based on educating cyclists how to operate safely as individuals, or whether it should place the promotion of increased bicycle use above all other goals — an approach which appeals to public health advocates — including epidemiologists, in their medical milieu, who stress the health benefits of exercise and point out that they outweigh the crash risks. Skills and behaviors which prevent crashes are ignored, as long as the overall health of the population is seen as acceptable.
General comments about the Toronto-Vancouver study
I myself haven’t reviewed the study itself in depth, but I have published two detailed reviews of it:
M. Kary’s first comment letter about Harris et al., unedited
M. Kary’s second comment letter about Harris et al., unedited
An edited version of these replies is available online.
The results of the Toronto-Vancouver study are internally inconsistent, and wildly inconsistent with the results of other studies — see comments in those reviews and below.
I have, however, had a good long look at the PDF of the authors’ presentation at the 2012 Velo City conference. I would like to review a transcript or summary of the discussion which accompanied this screen presentation, but I have not found any to review, and so I’ll just go with the PDF. It provides ample fodder for commentary.
The photos often show facilities with obvious built-in hazards as examples of good design, and show examples of installations with no evident problems as examples of hazardous conditions (e.g., a neighborhood traffic circle on a quiet street shown as an illustration of the stunningly high crash rate which the study found for traffic circles).
One photo is used once as an example of a low-risk facility and again as an example of a hazard.
Other commenters have noted that the study does not address cyclist behavior. It also suggests as one of its main conclusions that cyclists should ride more slowly downhill, not what I would call a practical suggestion. Photos in the PDF indiscriminately show good and poor cyclist behavior — more often poor behavior.
Comments on specific pages of the PDF
p. 2 — I don’t know of any reliable source for bicycle use data in the USA. Concerning an attempt to generate it, see this: http://bikexprt.com/research/cpsc/index.htm. That report actually contains two sets of data and if you compare them, cyclists’ average speed is 1 1/4 mph. — and the author of the report didn’t catch this!
p. 4 Citation of safety in numbers depicts Jacobsen’s descending hyperbolic curve, and describes it as best evidence, though it has repeatedly been demolished as only an artifact of faulty math. See for example the posts and comments here:
https://john-s-allen.com/blog/?p=669
https://john-s-allen.com/blog/?p=1621
Also, the photo on this page shows a cyclist carrying a handbag on the handlebar, hazardous because it interferes with control of the bicycle and can get caught in the spokes.
p. 5 — the “vehicular cycling” photo shows nothing of the sort. Also, it is no fault of the cyclists, but the street has trolley tracks, which regularly dump cyclists. We had a cyclist die in Boston when his wheels got caught in trolley tracks and he fell under a bus.
p. 12 — Shows a photo of a cycle track where cyclists would be blinded by oncoming motor vehicle headlamps at night and, if the cyclists stray or are forced into the street, they are trapped in the face of the oncoming traffic and cannot get back up over a curb. On the side away from the street, they will be toppled if they stray into the curb. The paved width of the path is marginal and there is no recovery if a cyclist strays off either side. This portrayed as an example of a safe facility. The authors have said that in Vancouver there were no wrong-way cycle tracks. Where is this? Update: See comments on this post. This cycle track is in Ottawa.
p. 15 — Falls due to streetcar or train tracks and other cycling surfaces, or “infrastructure” (What does that mean in this context?) are called collisions. They are not collisions, they are falls. Compare the distinction between a pedestrian’s trip-and-fall incident and a collision between a pedestrian and a vehicle. Calling falls collisions skews the results, making it look as though falls are less important, and collisions (with a vehicle, bicycle or pedestrian), more so.
p. 16 — repeats the same photo of the two-way cycle track.
p. 17 — repeats the “vehicular cycling” photo.
p. 19 — the level of relative risk for cycle tracks and “traffic diversion” streets (bicycle boulevards) is unbelievable. On page 15, we see that nearly half the reported crashes do not involve a motor vehicle. What would then make streets with cycle tracks 2000% and traffic-diversion streets 2500% safer than other streets?
p. 20 — Photos show the only two cycle tracks in the study. Both are distinguished by their lack of cross streets and driveways. Hence, no car-bike collisions! This page makes the claim of 1/20 risk (2000% improvement) for cycle tracks, based on these data and in association with a photo of the separate path — not a cycle track — on the Burrard Bridge in Vancouver. The upper bike lane photo shows a bike lane in the door zone. The lower shared-lane marking photo shows an improperly placed shared-lane marking, in the door zone. The authors do not make such distinctions when comparing crash locations. The authors have recorded intersections and non-intersection locations separately, and so they do not record the effect of design between intersections on the route which cyclists take when entering intersections and so, on crash rates at intersections.
p. 22 — traffic diversion v. traffic slowing — again, defies explanation. The upper left photo shows a cyclist turning past high vegetation which would produce a sight-line obstruction for a slightly shorter cyclist. The lower left photo shows wrong-side parking, which can result in motorists exiting parking spaces unable to see approaching cyclists, see http://www.bikexprt.com/bikepol/facil/lanes/contraflow.htm#scottst. The lower right photo shows a door-zone bike lane, but apparently what the photo is intended to show is the bulbout in the foreground, which would result in a “coffin corner” situation unless right turns are prohibited — note left-turn arrow in background — this is just before an intersection. But also, traffic slowing and traffic diversion are linked techniques, both used together in bicycle-boulevard treatments. How can they be separated for research purposes?
p. 24 — Left middle photo shows cyclists on a path headed for a low curb on a parapet high over a body of water. A path meeting reasonable design standards would have, instead of a curb which would trip up the bicycles, a railing to keep cyclists from going over the edge into the water. Left lower photo shows sharp curves leading to bollards on a bike path. Bollards are a well-known hazard. Yet the study claims greater safety for these than “no infrastructure” (which means, actually, different infrastructure). This same photo is shown again on page 50 as an example of the hazard of bollards. Lower middle photo is captioned as “shared-use path” but is a cramped situation in what appears to be an outdoor mall, nothing that would normally be designated as a shared-use path.
p. 25 — not very surprising except that uphill is rated hazardous. Why? The 1976 Bikecentennial study found a crash rate 4 times as high for cyclists going downhill, see http://www.bikexprt.com/research/bikecentennial/p35accident.htm.
p. 26 — upper left photo shows a cyclist riding downhill too close to parked vehicles. Upper right photo appears to show a cyclist riding on or near the wrong side of a two-way street. Middle left photo shows a cyclist properly ignoring a poorly-placed shared-lane marking while riding downhill. Lower photo shows a hillcrest, car with brake lights on though it is climbing, no cyclist in the photo.
p. 29 — once again repeats the unbelievable results, which contradict those of numerous other studies. Also shows the hazardous two-way cycle track from page 12 again.
p. 31 shows a “bike box” except cyclists are entering from the sidewalk at right angles to the street. This is not what a “bike box” is usually intended for. Also, entering from the right immediately before an intersection has been shown very hazardous, because motorists look left for cross traffic. What is the point of this photo?
p. 32 — Why are traffic circles rated so hazardous? Do we distinguish traffic circles and roundabouts? Why are uncontrolled intersections so hazardous when most of them are between very lightly used streets? How do we account for cyclists’ obeying or disobeying signals?
p. 33 — photo shows a cyclist very far to the right when crossing an intersection, on the crosswalk line. This would require weaving to the right when entering the intersection and to the left, back into the stream of traffic, when leaving it.
p. 34 — shows an intersection where cyclists may enter by pushing a button. There is a narrow entry channel between curbs. There is a risk of striking a curb and crashing.
p. 35 — shows two cyclists waiting at a stop sign. Both are ahead of the legal stop line (though that may be needed in order to see cross traffic). One has her foot on the curb at the corner — this far-right position invites the “right hook”, and prevents others from legally turning right. A commenter on this post has pointed out that to push the button which actuates the signal, cyclists must be in the right-hook position. I can add that the cyclists also must be ahead of the stop line to push that button. to sum up: this installation requires behavior which is illegal as well as hazardous.
p. 36 — The traffic circle shown is a small neighborhood traffic circle on a street with slow, light traffic. What is the hazard then, which raises the reported crash rate for traffic circles so high?
p. 37 — claims greater safety at intersections for streets with separated bikeways. This contradicts the observation and results that such intersections have more conflicts and a higher crash rate, as shown in numerous other studies.
p. 38 — The results reflect the speed, type and volume of conflicting traffic and so do not describe how volume and speed affect risk, or accurately describe the risk which depends on the design of a facility.
p. 40 — How is uphill less dangerous here and more dangerous earlier?
p. 41 — It is surprising that risk does not increase with motor vehicle speed above 30 km/h. What other factors counterbalance speed?
p. 42 — same photos of uphill cyclist on wrong side of road, and downhill cyclist ignoring the poorly placed SLM, as on p. 26.
p. 46 — “Route infrastructure is a strong determinant of injury risks” — This is correlation, not causation. It compares entire countries with one another. There are many other factors which differ among the countries cited.
p. 47 — Shows a different photo of the cycle track also shown on page 12, where cyclists would be blinded by oncoming motor vehicle headlamps at night and, if they stray or are forced into the street, are trapped in oncoming traffic and cannot get back up over a curb. On the side away from the street, they will be toppled if they stray into the curb. The paved width of the path is marginal and there is no recovery if a cyclist strays off either side. This is portrayed as an example of a safe facility.
P. 48 — “Physical barrier between cyclists and traffic.” As mentioned earlier and shown in the photo, the facility used for comparison is no ordinary cycle track in that it lacks intersections and driveways, and so achieves a complete physical separation. Furthermore, the categorization is faulty. Cyclists cannot be removed from traffic unless they are removed from each other — because they are traffic.
The page also claims that previous research did not distinguish between cycle tracks, bike lanes etc. This is blatantly false — several important studies do. I am thinking in particular of Moritz’s 1990s studies and the 2007 Copenhagen study.
p. 49 — claim that reducing motor vehicle speeds is key does not comport with results shown in this study unless motor speed is below 30 km/h (19 mph). That is not the case with most arterial streets. Claim that reducing cyclist speed down hills would reduce crash rate agrees with other studies, but it must be asked: what are the speeds in question? Is a cyclist who is able to keep up with motor traffic thereby more endangered? What are the behaviors that make high cyclist speed more hazardous? How would the authors propose to reduce the speed of cyclists, who want to get where they are going in good time, and rarely can even reach the speed limit? Cyclists then suffer a disadvantage both uphill and downhill. As the study looked only into locations, not behavior, that question begs for an answer.
p. 50 — the same photo of a bicycle path with bollards, previously shown as an example of a safer facility, is now shown as an example of obstacles which should be removed.
p. 51 — claim of objective measurement leaves out the elephant in the room — behavior.
Conclusion
As already mentioned, the numerical results are beyond credibility. It is also clear that the authors do not know what constitutes safe cycling behavior or what their photographs are showing.
