Compared with crashes with motor vehicles, single-bicycle crashes are an under-recognised contributor to cycling injury and the aetiology is poorly understood. Using an in-depth crash investigation technique, this study describes the crash characteristics and patient outcomes of a sample of cyclists admitted to hospital following on-road bicycle crashes. Enrolled cyclists completed a structured interview, and injury details and patient outcomes were extracted from trauma registries. Single-bicycle crashes (n=62) accounted for 48% of on-road crashes and commonly involved experienced cyclists. Common single-bicycle crash types included loss-of-control events, interactions with tram tracks, striking potholes or objects or resulting from mechanical issues with the bicycle. To address single-bicycle crashes, targeted countermeasures are required for each of these specific crash types.
- functional outcome
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The health benefits of cycling are well established1 and governments and cycling-bodies continue to advocate for increased cycling participation globally.2–4 However, cycling injury rates are on the rise.5–7 Understanding the characteristics of cyclist crashes is critical to developing targeted countermeasures to reduce their occurrence. The literature on crash avoidance strategies for cyclists has mainly focused on collisions with motor vehicles.8–10 Given the increasing rate of single-bicycle fatalities both in Australia and the Netherlands, more information on the characteristics of these crashes is needed.11 12
Single-bicycle crashes are known to be under-reported in police data and thus existing studies of single-bicycle crashes that rely on police data may not accurately represent the extent or nature of the problem.13 14 Furthermore, prior studies of cyclist crashes that have included single-bicycle crashes have commonly focused on multivehicle crashes or crash locations8 15 16 or have been reliant on police or hospital-coded information and thus have not been able to provide detailed insights into single-bicycle crashes.17 To address this knowledge gap, this study aimed to investigate the crash characteristics of a sample of cyclists admitted to hospital following an on-road single-bicycle collision.
Cycling-related trauma patients were prospectively recruited from two hospitals in Melbourne, Australia. The hospitals, The Alfred and the Royal Melbourne Hospital, are the two adult major trauma services (Level 1 trauma centre equivalent) for the state of Victoria. Recruitment occurred between 1 January 2013 and 31 December 2013. Our previous study describes the study methods in more detail.8
Patients were invited to participate if they met the following criteria: emergency admission to The Alfred or Royal Melbourne Hospital for more than 24 hours; admitted for management of a cycling-related injury and eligible for registration on the Victorian State Trauma Registry (VSTR) or the Victorian Orthopaedic Trauma Outcomes Registry (VOTOR). Inclusion criteria for these registries have been described previously.8 Cyclists who had crashes that occurred off-road were excluded from this study.
Recruited cyclists completed a structured interview during their hospital stay. This interview has been detailed previously.8 A trained research nurse conducted the interview with the cyclist which included questions about demographic details, a precise description of the crash circumstances, potential risk factors identified from the literature and the events leading to the crash. Based on the event description, single-bicycle crashes were grouped into five categories: loss-of-control (including sudden braking events to avoid another vehicle and loss of control events in either dry or wet/slippery conditions), interaction with tram tracks, struck object/pothole, bicycle mechanical issue or other.
VSTR and VOTOR data linkage
Data from the structured interview were linked with data collected by the VSTR and VOTOR. Details on these registries, data linkage and information extracted have been described previously.8 Injuries were coded using the International Classification of Diseases 10th Revision—Australian Modification (ICD-10-AM). Functional recovery was quantified using the Glasgow Outcome Scale-Extended (GOS-E), with a GOS-E score of 8 (upper good recovery) representing return to preinjury function.18 Return to work/study (yes/no), defined as returning to work in any capacity or role, was collected for patients who reported working for income prior to injury.
Data were summarised using frequencies and percentages for categorical variables and median and lower and upper quartiles for continuous variables. Comparisons of patients injured in single-bicycle crashes and multivehicle crashes were conducted using univariate logistic regression for categorical variables and the Kruskal-Wallis test for non-normally distributed continuous variables. Data analysis was performed using Stata (V.14.2, Stata, College Station, Texas, USA) and SAS (V.9.4, SAS Institute, Cary, North Carolina, USA). The importance of a variable was assessed by its p value and effect size.
During the study period, there were 129 cycling-related injured patients admitted to the participating hospitals following an on-road crash who consented to participate in the study. Of these, 62 (48%) were single-bicycle crashes and 67 (52%) were multivehicle crashes.
Comparison of single-bicycle crashes and multivehicle crashes
Single-bicycle crashes commonly involved males, cyclists with more than 10 years of experience and cyclists who rode more than three times per week (table 1). Most crashes occurred during daylight hours in clear weather conditions. There were no statistically significant differences in the demographics or crash conditions between single-bicycle and multivehicle crashes (table 1) with the exception of a higher proportion of multivehicle crashes that occurred in marked on-road bicycle lanes.
Compared with multivehicle crashes, patients involved in single-bicycle crashes had a lower injury severity score, but they had similar hospital lengths of stay and similar distributions of discharge destinations (table 2). There were no statistically significant differences in the presence of specific injuries. At 12 months postinjury, 89% of patients were successfully followed up. Of those involved in single-bicycle crashes, 96% had returned to work and 53% had a complete functional recovery at 12 months postinjury. The rate of complete functional recovery was statistically significantly higher in patients involved in single-bicycle crashes (53%) compared with multivehicle crashes (26%) (table 2).
Of the 62 single-bicycle crashes, 23 (37%) were classified as loss-of-control events, 12 (19%) resulted from interaction with tram tracks, 8 (13%) resulted from striking a pothole or object, 6 (10%) resulted from mechanical issues with the bicycle and 13 (21%) were classified as other events. Loss-of-control events commonly occurred due to sudden braking to avoid another vehicle or cyclist, losing control on a dry descent or losing control in wet/slippery conditions (table 3). Interaction with tram tracks commonly occurred when a cyclist was turning right across tram tracks or when a cyclist was avoiding parking or parked cars on the kerbside. Mechanical issues that contributed to crashes included wheel failures, snapped chains and gearing issues (table 3). There were two single-cyclist only crashes that occurred during race events and three that resulted from interactions with animals (one kangaroo, one wallaby and an Australian magpie).
Our study investigated demographic, crash and injury characteristics between single-bicycle crashes and multivehicle crashes. Single-bicycle crashes accounted for 48% of on-road crashes and, like multivehicle cyclist crashes, commonly occurred among experienced cyclists. Single-bicycle crashes occurred in a variety of scenarios, including loss-of-control events, interactions with tram tracks, striking potholes or objects and resulting from mechanical issues with bicycles. These results suggest that a multifaceted approach to prevention is required to reduce these crash types.
Amid rising rates of fatalities from single-bicycle crashes both in Australia and internationally,11 12 and reflected in the high proportion of single cyclist crashes observed in this study, greater emphasis needs to be placed on preventing single-bicycle crashes. Previous studies of single-bicycle crashes have been reliant on hospital-coded data, such as the International Classification of Diseases (ICD) coding system, which does not provide detailed information on crash characteristics. Prior studies have noted single-bicycle crashes to occur in loss of control events and resulting from striking potholes or road irregularities.17 19 20 However, these data are often limited by police-reported and hospital-coded information, with few other crash details provided.
To our knowledge, this is the first in-depth study of cyclist crashes specifically able to examine single-bicycle crashes. We have demonstrated that the causes and characteristics of these crashes are varied. Loss-of-control events were the most commonly reported crash scenario, which included sudden braking events to avoid another vehicle and loss of control events in wet or slippery conditions. We were not able to ascertain fault in these scenarios; however, consideration should be given to moderating cycling speeds, particularly in wet or slippery conditions (table 4). Interactions with tram tracks accounted for 19% of single-bicycle crashes. In Melbourne, tram tracks are set into the road pavement and have a smooth and often slippery surface and have a gap which is often similar to the width of a bicycle wheel. Suggested preventive measures include prohibiting motor vehicle parking on streets where tram tracks are present and cycling is promoted, increasing awareness of the dangers of tram tracks, bicycle tyre choice and route selection.21 Striking a pothole was noted to occur in three cases and in these cases, improved road maintenance is required to eliminate these crash scenarios, particularly on routes where cycling is common. Mechanical failures were reported in six cases and included wheel failures, snapped chains and gearing issues. Regular bicycle maintenance is recommended to reduce the risk of mechanical failure. Our finding that the majority of cyclists had more than 10 years of cycling experience and rode more than three times per week suggests that the issue of single-bicycle crashes are not limited to novice riders and may be an artefact of cycling frequency.
The major strength of our study is the use of detailed crash information through in-depth interviews. However, there are a number of limitations to note. The in-depth crash investigation techniques used in this study to determine crash characteristics are not possible at a population-level and hence the sample may not be representative of the wider population. However, both the patient and crash characteristics are similar to police-reported single-bicycle crashes previously described in our region.17 Additionally, we excluded patients whose injuries prevented them from consenting for themselves, which likely reduced the number of severely injured cyclists in our sample.
In this sample of hospitalised injured cyclists, single-bicycle crashes accounted for nearly half of all on-road crashes. Single-bicycle crashes occurred in a variety of scenarios and targeted countermeasures are required for each of these specific crash types. Increased emphasis on single-bicycle crashes is required to reduce cycling injury rates.
What is already known on the subject
Understanding the characteristics of cycling crashes is critical to developing injury prevention strategies.
However, the majority of crash avoidance strategies have focussed on collisions with motor vehicles.
As a result, single-bicycle crashes are an under-recognised contributor to cycling injury.
What this study adds
In this sample of hospitalised injured cyclists, single-bicycle crashes accounted for nearly half of all on-road crashes.
Single-bicycle crashes occurred in a variety of scenarios, such as loss-of-control events, interactions with tram tracks, and striking potholes or objects, and targeted countermeasures are required for each of these specific crash types.
The authors would like to acknowledge the contributions of Mandy Brown, Melissa Hart, Carol Roberts, Jasmine Fischer and Adam Rushford.
Contributors BB performed the analysis and wrote the first draft of the manuscript. All authors provided critical feedback on the analysis, interpretation and writing.
Funding This study was specifically supported by a Monash University, Faculty of Medicine, Nursing and Health Sciences Strategic Grant. The Safer Cycling in the Urban Environment Study is supported by an Australian Research Council Grant (Number: LP130100380). The Victorian Orthopaedic Trauma Outcomes Registry (VOTOR) is funded by the Transport Accident Commission. BB was supported by an Australian Research Council Discovery Early Career Researcher Award Fellowship (DE180100825). MRS is supported by a Research Fellowship (#1043091) and PC was supported by a Practitioner Fellowship (#545926) from the National Health and Medical Research Council (NHMRC). BJG is supported by an Australian Research Council Future Fellowship (FT170100048).
Competing interests None declared.
Patient consent for publication Not required.
Ethics approval Ethics approval for the study was obtained from the Alfred Health, Melbourne Health and Monash University Human Research Ethics Committees.
Provenance and peer review Not commissioned; externally peer reviewed.
Data sharing statement Due to ethical restrictions, we cannot share any data.
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