A prospective cohort study on minor accidents involving commuter cyclists in Belgium
Highlights
► Incidence rate of bicycle accidents is 0.896 (95% CI 0.686–1.106) per 1000 h of exposure. ► Only 7% of prospectively recorded bicycle accidents were reported in police statistics. ► Exposure must be taken into account when statements about safety measures are made. ► The ‘safety in numbers’ principle is also applicable for minor bicycle accidents. ► ‘Slipping’ and ‘collision with a car’ are the most cited causes of accident.
Introduction
Cycling is recognized as an excellent way of being physically active and maintaining good health (Oja et al., 1998, Oja et al., 2011, Hendriksen et al., 2000, de Geus et al., 2008, de Geus et al., 2009). Furthermore, increased active transport (walking and cycling) could have a substantial role in meeting targets for urban air quality, greenhouse-gas emissions, and could result in major public-health benefits (Int Panis et al., 2004, Woodcock et al., 2007).
While cycling brings many personal, environmental and societal benefits, important barriers to cycling exist. These include fear of crime/vandalism, bad weather, social pressure, hills and slopes and long commuting distances (e.g. Pucher et al., 1999, Rietveld and Daniel, 2004, Gatersleben and Appleton, 2007, Parkin et al., 2008). Other important barrier to cycling are concerns about traffic safety, with women fearing accidents more than men (Vuori et al., 1994, Byrnes et al., 1999, Garrard et al., 2008, Tin Tin et al., 2010), lack of adequate infrastructure (Pucher et al., 1999, Parkin et al., 2007, Vandenbulcke et al., 2009) and exposure to air pollution (Int Panis et al., 2010, Jacobs et al., 2010). The balance between risks and benefits is a topic of ongoing debate (de Hartog et al., 2010, Int Panis, 2011).
The modern traffic system is primarily designed for motorized vehicles and often fails to make provision for other road users. Pedestrians and cyclists incur higher crash risks than motorists (in particular car drivers) in terms of accidents per distance covered (Pucher and Dijkstra, 2000, van Boggelen et al., 2005, BRSI, 2009, Elvik, 2009, Tin Tin et al., 2010). In Norway, the risk of injury, expressed as fatalities per kilometer while cycling is about 7.5 times higher than for car drivers (Pucher and Dijkstra, 2000, Elvik, 2009). In the Netherlands, for all age groups, about 5.5 times more fatal injuries are recorded per kilometer travelled by bicycle than by car (CBS, 2008). A study in Portland (US) (Hoffman et al., 2010) reported that nearly one in five bicycle commuters will experience an event leading to injury in any given year, regardless of gender, age, body mass index (BMI), or cycling skill level.
Most statistics on bicycle accidents result from retrospective surveys (Jacobson, 2003). A weakness of a retrospective study design is the selection and recall bias, resulting in the fact that especially the most serious injuries will be remembered or registered. It is well known that most road accident statistics strongly underestimate the total number of cycling accidents meaning that only the ‘tip of the iceberg’ is investigated (Dhillon et al., 2001, De Mol and Lammar, 2006, Hoffman et al., 2010), particularly when there is no hospitalization and the cyclist is the only party involved (Veisten et al., 2007, Vandenbulcke et al., 2009). A comparison of hospital admissions related to cycling accidents and police registrations of such accidents show that the latter register only 50% of the total number of cycling accidents in Europe (De Mol and Lammar, 2006) and only 10% in the US (Stutts et al., 1990, Pucher and Dijkstra, 2000). Several authors have estimated that in Belgium only about 15% of the cycling accidents are officially reported (Doom and Derweduwen, 2005, De Mol and Lammar, 2006, BRSI, 2006).
A shortcoming of the current literature and another weakness specific to retrospective study designs is that no precise recording of exposure data (bicycle usage, i.e. travel time, distance, frequency) is available nor is it possible to record such data precisely (Aultman-Hall and Hall, 1998). Yet the recording of exposure data is essential for the calculation of the incidence rate (IR). Data on the numerator (accidents) and denominator (exposure) recorded separately are inadequate to determine an IR, making comparisons between countries or regions within one country difficult (Jacobsen, 2003).
For the implementation of safety measures and the assessment of injury costs, a complete and accurate recording of minor and major accidents and the recording of the cycling exposure is essential. So far, only Aertsens et al. (2010) and Hoffman et al. (2010) have published results of a cohort study of minor bicycle accidents and detailed exposure data simultaneously.
The purpose of this study was therefore to record bicycle accidents, and to gain insight into exposure data during one year, using a prospective study design. The combination of accident and exposure data allows us to calculate the incidence rate of bicycle accidents.
Section snippets
Study design
This study is part of the SHAPES project (Systematic analysis of Health risks and physical Activity associated with cycling PoliciES) which is at the crossroads of health, transport and air pollution research. The aim of the SHAPES project is to analyze the benefits and risks (voluntary and involuntary) of cycling and to advise policy makers in order to facilitate the implementation of integrated policies related to cycling for transport. Within the SHAPES project exposure to traffic exhaust
Participants
After one year, 1849 persons left their e-mail address on the server (Table A, Appendix). Of these, 646 either did not open the first e-mail or did not meet the inclusion criteria. Only those (N = 1187; 68% men) who filled out more than one TD were retained for the data analyses presented in this paper. Thirty-six percent of those retained for the data analysis lived in the BCR, 49% in Flanders and 15% in Wallonia.
Descriptive data of the injured participants are reported in Table B (Appendix) and
Impact of minor bicycle accidents
In Belgium in 2008, 7132 accidents recorded by official police statistics were classified as “minor accidents” (hospitalization of less than 24 h) (NIS, 2009). Based on our data, we can extrapolate the incidence in our study to Belgium. Because only two accidents required hospitalization for more than 24 h, the following estimation is based on 68 accidents. As only 5.9% of the minor cycling accidents are officially reported, it is estimated that 120,881 victims would have suffered from minor
Study limitations
Some limitations of this study should be noted. Due to the nature of the study, well-skilled cyclists, who cycle a greater distance and time than occasional cyclists, are more likely to be captured in the data. The small number of observations may be the reason why the differences between genders or between the regions were not significant. Yet another limitation of this study is that the study population is self-selected.
Conclusion
In this study, a large cohort (N = 1187) of regular (≥2 cycling trips to work/week) commuter cyclists, aged 18–65 years was prospectively followed during a 1-year period, during which exposure and bicycle accidents were registered simultaneously. In total 62 cyclists experienced at least one injury. The registered accidents were classified as ‘minor’ bicycle accidents in 97% of the cases, resulting in abrasions and bruises of the upper and lower limbs. We have demonstrated that a prospective
Ethical issues
The Vrije Universiteit Brussel ethical committee approved the study.
Competing interests
The authors declare that they have no competing interests with respect to the results discussed in this paper.
Acknowledgements
This paper is part of the SHAPES project (Systematic analysis of Health risks and physical Activity associated with cycling PoliciES) which is at the crossroads of health, transport and air pollution research. The aim of the SHAPES project is to analyze the benefits and risks (voluntary and involuntary) of cycling and to advise policy makers in order to facilitate the implementation of integrated policies in different domains related to cycling for transport.
The work reported in this paper was
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