A new study published in the American Journal of Public Health using injury data from Toronto and Vancouver finds that street infrastructure has a big impact on risk of injury for cyclists.
By Ryan McGreal
Published October 22, 2012
this article has been updated
A new study, titled, "Route Infrastructure and the Risk of Injuries to Bicyclists: A Case-Crossover Study" and published in the American Journal of Public Health, finds that street infrastructure has a big impact on risk of injury for cyclists.
Noting that Canada, Australia, The USA and the UK have much higher cycling injury rates and much lower cycling participation rates than Denmark, Germany, Finland, the Netherlands and Sweden, authors Kay Teschke et al. point out, "helmet use cannot explain the risk difference because helmets are rarely used in the European countries with lower injury rates."
Hypothesizing that the difference in injury risk is related to the design of the bike routes - the European countries with much lower injury rates have a lot more dedicated bicycle infrastructure - the authors developed a study to isolate the effects of the route design from other confounding factors.
Using cycling injury data from Toronto and Vancouver where the injury was serious enough to warrant a trip to the hospital, the researchers conducted a case crossover study to identify the role of the street design where the injury occurred.
The control was clever: the researchers compared the location where each cyclist was injured to a randomly selected section of their route where an injury did not occur. The selection of the control section was weighted according to its length relative to the entire route.
The benefit of this approach is that by using the same population and the same trip for the study group and the control group, the study automatically controls for the personal characteristics of the population and their exposure to various types of route infrastructure.
The researchers presented each injured cyclist with a questionnaire [PDF] to determine the route they had been taking. They also defined 14 specific types of route:
|Major street, with parked cars||Paved city street with at least 2 demarcated moving lanes of motor vehicle traffic, with parked cars on the cyclist's side of the street|
|No bike infrastructure||No bicycle markings on street surface, bike signage on posts may be present|
|Shared lane||Markings on street surface indicating shared bike-HOV lane, shared bike-bus lane, or sharrows indicating bikes and motor vehicles share space|
|Bike lane||Bike-only lane marked with solid or dotted lines on street surface|
|Major street, no parked cars||Paved city street with at least 2 demarcated moving lanes of motor vehicle traffic, no parked cars|
|No bike infrastructure||No bicycle markings on the street surface, bike signage on posts may be present|
|Shared lane||Markings on street surface indicating shared bike-HOV lane, shared bike-bus lane or sharrows indicating bikes and motor vehicles share space|
|Bike lane||Bike-only lane marked with solid or dotted lines on street surface|
|Local street||Paved city street with no demarcated lanes of motor vehicle traffic; car parking may be allowed or not|
|No bike infrastructure||No bike signage or markings on the street surface|
|Designated bike route||Bike signage on the street surface or on posts, indicating designated bike route; may have bicyclist operated traffic signals at intersections with major streets|
|Designated bike route with traffic calming||Bike signage on the street surface or on posts, indicating designated bike route; may have bicyclist operated traffic signals at intersections with major streets; traffic calming measures may include speed humps or bumps, traffic circles, traffic diverters, medians, or street width restrictions via corner bulges or planters|
|Off-street route||Route that is physically separated from traffic, at least on straightaways between intersections|
|Sidewalk or other pedestrian path||Paved path meant for pedestrian use, either alongside city streets or away from streets (e.g., in parks)|
|Multiuse path, paved||Paved path meant for nonmotorized use by pedestrians, cyclists, skaters and others, either alongside city streets or away from streets (e.g., in parks)|
|Multiuse path, unpaved||Unpaved path meant for nonmotorized use by pedestrians, cyclists, skaters and others, either alongside city streets or away from streets (e.g., in parks)|
|Bike path||Paved path meant for cyclist use away from streets, (e.g., in parks)|
|Cycle track||Paved path meant for cyclist use alongside major streets, separated by a physical barrier (e.g., a curb or bollards)|
Of the 2335 cyclists who were admitted to one of the five hospitals during the study period, 741 were known to be eligible for the study and 690, or 93.1%, agreed to be interviewed. Using a major street with parked cars and no bike infrastructure as a baseline, the researchers calculated the adjusted odds ratio for the other 13 types of bike route and found that all other types of route had lower odds ratios.
The most dramatic was an off-street cycle track, which had an adjusted odds ratio of only 0.11 compared to 1.0 for the baseline. But even adding a bike lane to a major street with parked cars reduced the adjusted odds ratio to 0.69. The odds ratios on multi-use paths (0.79) and sidewalks (0.87) were slightly lower than the baseline but the reduction was not statistically significant.
The results indicate that the presence or absence of parked cars had a significant effect on risk. A major street with no bike infrastructure but no parked cars had an adjusted odds ratio of 0.63, dropping to 0.54 with a bike lane.
There was also a significant risk reduction between major streets and local streets. A local street with no bike infrastructure had an odds ratio of 0.51 compared to a major street with no bike infrastructure.
The authors write, "These findings reinforce some conclusions of our recent review: that busy streets are associated with higher risks than quiet streets; and that bicycle-specific facilities are associated with lower risks." They also noted that cyclists tend to prefer bike routes that are also safer, when those routes are available.
Many route types with positive preference ratings were also among the safest: cycle tracks; local streets; bike only paths; and major streets with bikes lanes and no parked cars. These provide a range of options with potential to both lower injury rates and increase cycling. This in turn may create a positive feedback cycle because increased ridership has been associated with increased safety.
The authors close with the following conclusion, which will be familiar to RTH readers:
As a public health approach, safer route infrastructure offers many advantages: it is population-based and therefore benefits everyone, it does not require active initiatives by individual cyclists, it does not require repeated reinforcement, and it prevents crashes from occurring rather than preventing injuries after a crash has occurred.
Interesting sidenote: Toronto 11 kilometres of bike lanes per 100,000 people, and 1.7% of trips are by bicycle. Vancouver has 26 kilometres of bike lanes per 100,000 people and 3.7% of trips are by bicycle. Vancouver has 2.4 times as many bike lane kilometres per capita and 2.2 times as many bike trips per capita - a very strong correlation between the extent of bike infrastructure and its use.
(h/t to the Atlantic Cities for finding this study)
Update: Updated to add a table of results by route type from the study.
|Variable||No. Injury Sites/No. Control Sites||Unadjusted OR (95% CI)||Adjusted OR (95% CI)|
|Major street route, parked cars|
|No bike infrastructure||155/114||1.00 (Ref)||1.00 (Ref)|
|Shared lane||9/7||0.78 (0.25, 2.41)||0.71 (0.21, 2.45)|
|Bike lane||25/28||0.53 (0.26, 1.07)||0.69 (0.32, 1.48)|
|Major street route, no parked cars|
|No bike infrastructure||112/118||0.65* (0.44, 0.97)||0.63* (0.41, 0.96)|
|Shared lane||13/12||0.66 (0.24, 1.82)||0.60 (0.21, 1.72)|
|Bike lane||35/46||0.47* (0.26, 0.83)||0.54 (0.29, 1.01)|
|Local street route|
|No bike infrastructure||89/116||0.44* (0.28, 0.70)||0.51* (0.31, 0.84)|
|Designated bike route||52/57||0.53* (0.30, 0.94)||0.49* (0.26, 0.90)|
|Designated bike route with traffic calming||49/47||0.59 (0.32, 1.07)||0.66 (0.35, 1.26)|
|Sidewalk or other pedestrian path||52/47||0.73 (0.42, 1.28)||0.87 (0.47, 1.58)|
|Multiuse path, paved||64/56||0.75 (0.42, 1.34)||0.79 (0.43, 1.48)|
|Multiuse path, unpaved||12/11||0.63 (0.21, 1.85)||0.73 (0.23, 2.28)|
|Bike path||21/21||0.54 (0.20, 1.45)||0.59 (0.20, 1.76)|
|Cycle track||2/10||0.12* (0.03, 0.60)||0.11* (0.02, 0.54)|
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