CHAPTER 3: PHASE 1 IN-DEPTH BICYCLE CRASH STUDY:
3.7 Crash classification and contributing factors
3.7.1 Crash type classification
Information from the participants’ crash descriptions in the questionnaire, participant sketches and site inspections were used to classify all crashes into categories according to road use movement and mechanism of the crash. The RUM codes developed by Main Roads WA were used as a guide for this classification (Appendix 7), however they are not ideally suited to bicycle crashes. Therefore, a crash type classification system was devised based on the actual crash types observed in the study. Crashes were firstly categorised by those involving a crash with a motor vehicle and those not involving a crash with a motor vehicle.
Crashes involving motor vehicles were classified as:
• Rider crash with motor vehicle travelling in a different direction; • Rider crash with motor vehicle travelling in the same direction; • Rider crash with motor vehicle while rider was crossing road to path; • Rider crash with a car door;
• Rider crash with a parked car;
64 Crashes not involving a collision with a motor vehicle were classified as:
• Rider/ rider crash;
• Rider loss of control on carriageway, no object hit; • Rider loss of control, hit road infrastructure;
• Rider hit road infrastructure travelling from road to path; • Rider hit object/ hazard on road carriageway;
• Bicycle malfunction; • Rider/ pedestrian crash.
Each crash in the study is then described by category, in terms of group rider and individual rider crashes, example diagrams provided for the crash types which involved another road user and RUM codes specified where relevant for each crash. Diagrams were sketched using a free online site (Claim Management Services, 2018).
3.7.2 Human, environmental and vehicle factors contributing to crashes
Finally, a detailed examination of factors contributing to crashes was undertaken for the 108 bicycle crashes. A factor contributing to a crash was defined as any human, environmental or bicycle/ vehicle factor which the investigators considered to have contributed to the overall outcome of the crash (Association of European Motorcycle Manufacturers (ACEM), 2004). Two experienced researchers conducted systematic investigations on each crash using information from the participant interviews (questions on factors contributing to the crash and participant crash descriptions), sketches, virtual crash site inspections and the IRIS database (where available) to identify and list all possible factors contributing to each crash.
Each factor contributing to the crash was coded according to definitions used in the Motorcycle Accidents In Depth Study (MAIDS), a large-scale in-depth investigation of crashes involving powered two wheelers in Europe (Association of European Motorcycle Manufacturers (ACEM), 2004). A recent Victorian in-depth motorcycle crash study which was based on the MAIDS study, was also consulted (Allen et al., 2017). The decision to code factors based on previous motorcycle crash studies was made since investigations revealed that the factors contributing to the bicycle crashes in this study fit very well within this classification scheme, with only minor
65 modifications and additions required. While existing in-depth bicycle crash studies were also consulted, these smaller studies focused specifically on older or adolescent rider crashes and did not classify factors contributing to crashes in a systematic manner (Boele-Vos et al., 2017; Vanparijs et al., 2016).
If an identified factor contributing to a crash did not fall under any of the categories defined by the MAIDS study (Association of European Motorcycle Manufacturers (ACEM), 2004) or Allen et al. (2017), a new factor was created. The three factors added for the purpose of this study were: ‘bicycle failure’, ‘view obstruction due to
another rider’ and ‘vertical alignment of the road’. Factors contributing to a crash
present in the motorcycle crash classification schemes that were not relevant to the cycling or WA context were removed, for example ‘tram tracks’. Table 3.2 lists all specific factors contributing to crashes included in this study and their definitions by category. Each individual factor was categorised as ‘human’, ‘environment’ or
‘vehicle-related’ based on the MAIDS study (Association of European Motorcycle
Manufacturers (ACEM), 2004). Sub-categories of factors contributing to crashes were also created for the purpose of analysis for this study. The broad category of ‘human’ factors contributing to crashes contained 13 different specific factors which were subcategorised based on whether the error occurred on the part of the crashed rider, another rider or a motorist. The broad category of ‘environment’ factors contributing to crashes contained 10 specific contributing factors which were sub-categorised into
‘weather/ lighting factors’, ‘road-related factors’ and ‘view obstruction’. The broad
category of ‘vehicle’ factors contributing to crashes contained two specific contributing factors and no subcategories were made.
For each crash, a single primary factor contributing to the crash was agreed upon by the two researchers. This was defined as the specific ‘human’, ‘environmental’ or
‘vehicle’ factor which the research team considered to have made the greatest
contribution to the overall outcome of the crash (Association of European Motorcycle Manufacturers (ACEM), 2004). In addition, where required, one or more secondary factors contributing to the crash were determined. In cases where the two researchers disagreed on the primary and secondary factors contributing to crashes, a discussion took place and agreement was reached.
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Table 3.2 Definitions of human, environmental and vehicle factors contributing to bicycle crashes Specific factor contributing to crash Subcategory Definition Human factors Alcohol or drug involvementa • Rider error • Other rider error OR • Motorist error
Medical or self-reported evidence of excessive alcohol (>0.05 g/dL) or use of illegal drug known to impair riding or driving near the time of crash.
Conflicting behaviours or pre-occupieda • Rider error • Other rider error OR • Motorist error
The rider or other road user acted in such a way that was unexpected by other road users, or they were distracted by another activity. Decision/ reaction failurea • Rider error • Other rider error OR • Motorist error
The rider or other road user failed to make the correct decision to avoid the dangerous condition or failed to react, based upon his/ her strategy.
Experience/ exposure to similar situationsa • Rider error • Other rider error OR • Motorist error
Lack of experience or exposure specific to the bike, vehicle, physical road environment, weather, or traffic conditions present at the time of the incident. Faulty traffic strategya • Rider error • Other rider error OR • Motorist error
The rider or other road user made a poor decision to perform a manoeuvre or movement. Misjudgement/ control errorb • Rider error • Other rider error OR • Motorist error
The rider or other road user misjudged the situation and/ or failed to control the vehicle within its capabilities (including braking and steering actions).
Perception failurea • Rider error • Other rider error OR • Motorist error
The rider or other road user failed to detect the dangerous condition based upon the strategy that he was using to detect dangerous conditions.
Physical or physiological failurea • Rider error • Other rider error OR • Motorist error
Physical or physiological failure to the rider or other road user, including fatigue, acute or chronic medical condition (e.g. seizure, cardiac failure). Position of bike/ vehicle unsafe or high riskb • Rider error • Other rider error OR • Motorist error
The rider or other road user positioned their vehicle in a way that was deemed as high risk of crash. This includes positioning the vehicle where it was more difficult to be seen by other road users, positioning the vehicle too close to other vehicles, or positioning the vehicle such that negotiating an
67 approaching curve was made more
difficult. Speed inappropriate for conditionsb • Rider error • Other rider error OR • Motorist error
The estimated travel speed of the rider or other road user immediately before the precipitating crash event was judged as not appropriate for the conditions, including the physical road
environment, weather, traffic conditions, or the vehicle. Traffic scan errora • Rider error • Other rider error OR • Motorist error
The rider or other road user did not observe or perceive oncoming traffic or traffic that may have been entering the roadway from some other direction. Unsafe act or high risk behavioura • Rider error • Other rider error OR • Motorist error
The action of a rider or other road user was judged as unsafe or high risk.
3rd or 4th vehicle involvementa • Other rider error OR • Motor vehicle error
The presence or actions of a 3rd or 4th
vehicle contributed to the cause of the crash. Environment factors Adverse weathera • Weather/ lighting
A weather event, including strong winds, heavy rain, or fog.
Natural light conditionsb
• Weather/ lighting
The natural light conditions at the time of the crash reduced visibility for the rider or other road user (including dawn, dusk, dark, and sun glare).
Road design issuea
• Road-related A condition which presented a danger to the rider based solely upon the design of the road.
Road
maintenance issuea
• Road-related Any road condition that was in poor repair or in need of repair.
Slippery road due to
weatherb
• Road-related Road surface grip at or near crash site was significantly reduced as a result of recent weather (e.g. rain).
Slippery road due to loose materialb
• Road-related Road surface grip at or near crash site was significantly reduced due to presence of loose material, including gravel (fine or coarse) and leaf litter. Temporary
traffic hazarda
• Road-related A danger or risk on a carriage-way (excluding a road design or maintenance defect).
Vertical alignment of roadc
68 View
obstructiona
• View obstruction
A temporary (mobile) or fixed obstruction that reduced or blocked visibility for rider or other road user (excluding view obstruction due to another rider). View obstruction due to other rider c • View obstruction
Another rider reduced or blocked visibility for the rider.
Vehicle factors
Bicycle failurec
• Vehicle failure A pre-existing issue or acute failure of a bicycle affecting its safe operation or ability to avoid a crash.
Motor vehicle failurea
• Vehicle failure A pre-existing issue or acute failure of a motor vehicle affecting its safe
operation or ability to avoid a crash
a Contributing factor and definition modified from the Association of European Motorcycle
Manufacturers (Association of European Motorcycle Manufacturers (ACEM), 2004)
b Contributing factor and definition modified from Allen et al. (Allen et al., 2017) c Contributing factor added for purposes of this study