Context & position
Powered Two-Wheeled vehicles (PTWs) are becoming more and more popular with commuters looking to avoid traffic congestion. However, within the overall context of road accident mitigation, PTWs remain a particularly risky mode of transport. Indeed, PTW users are classified as Vulnerable Road Users (VRU). In France, such riders account for more than 20% of all road fatalities (compared with 15% in Europe as a whole) and 40% of road injuries (ONISR, 2010). In terms of distance travelled, they account for 1.5% of total traffic. Thus, the risk of being killed is 14 per 100 million person-kilometers, which equates to a PTW rider being 21 times more likely to be killed than a car driver. The risk of severe injury (including a permanent handicap) is about 50 times more1.
Despite this high level of risk, sales of PTWs have exploded over the last decade. The fostered modal split from cars to public transportation systems reinforces the trend. One should note a strong reduction in sales for both cars and PTWs in 2012, because of the economic environment being particularly weak. A drastic reduction in travel time is one factor in choosing to use a PTW for commuting. The practice of lane sharing allows PTW users to predict and often maintain a consistent journey time. Whilst such lane-sharing practices are forbidden in many countries, they are often tolerated. Belgium recently authorised the practice in certain circumstances. From a mobility standpoint, one can consider that the practice of lane sharing smooths out traffic flow [SP10]. A recent study conducted in Belgium shows that if half of all PTW commuters chose to travel by car instead, this would result in many more traffic jams. Lane sharing on highways and motorways is not seen as a critical safety factor [CWBT04]. Indeed, in some studies, the practice is considered to be safer [NHTSA00].
Novice riders (including returning riders) are particularly vulnerable. Indeed, in France, young riders aged between 18 and 24 years old are three times more likely to be involved in an accident than people aged between 45 and 64 years old (ONISR1). Both social and economic issues are important; the death of a young man or woman costs on average 1.4 million Euros to the community (ONISR). This is of particular concern when one bears in mind that, on average, more than 600,000 people become novice riders (ONISR) each year. In 2009, 8.9% of the population was aged between 18 and 24 years old, and this class of population accounts for 21.1% of road fatalities. On average, each week, 17 young people are killed on the road and 264 are injured, 149 of them seriously.
Many large-scale research programmes have been undertaken in Europe and elsewhere to understand the factors that contribute to crashes. In particular, the MAIDS and RIDER projects identified accident situations. They paved the way for other projects, such as SAFERIDER (FP7), which aimed to develop Intelligent Transport Systems (ITS). The aim of 2BESAFE (FP7) was to study motorcyclists’ behaviour, and the behavioural and ergonomic factors that contribute to motorcycle crashes (including conspicuity aspects). The French ANR/Predit SUMOTORI and DAMOTO collaborative projects proposed an automatic fall detection algorithm for the early inflation of a wireless airbag jacket. Meanwhile, SIM2CO+ (ANR/Predit) worked to identify risky situations experienced by novice motorcyclists who have just passed their test in order to improve pre-test training in France.
The majority of PTW accidents occur because of interactions with other road users, most noticeably the refusal of car drivers to give way. However, single-vehicle accidents (or those considered as such) are also an important factor. In 2012, in France, a third of fatal PTW accidents occurred without an identified third party (37.7%)2.
The loss of control in bends (including roundabouts and road junctions) is common largely because of the complexity of PTW dynamics and the intrinsic instability of such vehicles. The MAIDS 2004 study showed that about 30% of all PTW accidents occur in bends or at road junctions. One can estimate, therefore, that loss of control in bends accounts for more than 50% of single-vehicle accidents. In 2012, in France, more than a third of all PTW fatalities occurred in bends (248 killed)2.
The banking of motorcycles into bends increases the risk of skidding, particularly when the road surface has become degraded. Trajectory modification in bends is practically impossible, because any jerky braking manoeuvre brings about a modification of the vehicle-rider equilibrium and potentially a loss of control. Proper “reading” of the bend (or, potentially, a sequence of bends), both from a geometric and road surface quality standpoint, is therefore essential. The ESC system from Bosch, which was recently introduced on “high-end” motorcycles only partly responds to the road safety question. Indeed, measures to correct badly balanced front/rear braking are only able to manage situations in which there is “limited” excessive speed. Moreover, the vehicles often used by novices (mid-size segment vehicles, often second hand) are not likely to be equipped with such safety systems in the near future. Indeed, it is estimated that it will be at least twenty years if we look at the time that was needed to introduce ABS onto the motorcycle market. ABS was first introduced in 1992 by Honda and in 1993 by BMW; however, in 2012, only an estimated 13% of the PTW fleet was equipped as such, the percentage being roughly 30% for PTWs over 750cc.
Research on riders of PTW vehicles has only begun fairly recently. Thus, in comparison with the existing literature about car driver behaviour, research into PTW rider behaviour is limited. There remains a lack of knowledge of real riding practices. An understanding of bend-taking behaviour plays a major role in scientific knowledge improvement and road safety. A better understanding would also make it possible to set up new training and retraining measures: this is the primary aim of the VIROLO+ research project. Ultimately, it would help in identifying areas for the design and/or assessment of driving assistance devices dedicated to PTWs.
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1Source : ONISR (French National Inter-departemental Observatory on Road Safety)
2Bilan (2012) la sécurité routière