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A Literature Review on Motorcycle Collisions

B. Huang and J. Preston

Transport Studies Unit

Oxford University


The Transport Studies Unit, University of Oxford, was commissioned by the Association of Chief Police Officers (ACPO), in conjunction with the Police Foundation, to review the literature on motorcycle accidents. This included a review of the data on national motorcycle accidents, motorcycle user demographics and trends in the motorcycle market. It also included a review of the types of motorcycle accidents, their causes and primary and secondary prevention measures. It is well known that motorcycles have the potential to be a safety hazard. For example, in Great Britain in 2002 the number of people killed or seriously injured (KSI) using two wheeled motor vehicles was 147 per 100 million vehicle kilometres. The comparable casualty rate for car users was 5 per 100 million vehicle kilometres. The all injuries casualty rate for two wheeled motor vehicles was 556 per 100 million vehicle kilometres compared to 50 per 100 million vehicle kilometres for car users. However, there have been some improvements in motorcycle safety. For example, between 1982 and 1996 the number of KSI casualties reduced from 16,281 to 5,640, but by 2002 the number of KSI casualties had increased to 6,686.

This recent increase in accidents seems to be correlated with increased motorcycle ownership and use. In particular, there has been a big increase in the number of highpowered machines (with an engine size of 500cc or above). There were 155,000 such machines in 1992 but by 2002 their number had increased to 482,000. Moreover, there have been significant changes in the demographics of those involved in motorcycle accidents. In 1982 almost half of all KSI casualties were under 20, by 2002 this had decreased to a little over 1 in 10. By contrast 30 to 39 year olds accounted for less than 1 in 10 KSI casualties in 1982 but by 2002 accounted for around a third of such casualties. National data seem to confirm the anecdotal evidence that born-again riders are posing a road safety problem.

Studies carried out in several countries show that between half and three-quarters of motorcycle accidents involved collision with another vehicle. Among these multiple vehicle accidents, the driver of the other vehicle often violated the motorcycle right-of-way. Furthermore, a study of accident typology suggests that five main types account for over 80% of fatal accidents in the US: ran off road; ran traffic control; oncoming collision, oncoming right-turn collision; and motorcyclist down. Among them, motorcycle running off road is the most common type, which accounts for 41% of the total. These are often late night, weekend crashes involving a drunken motorcyclist.

The literature suggests two main groups of causes. The first group relates to difficulties in motorcycle detection as a result of the poor conspicuity of motorcycles due to their smaller size (leading to poor sensory conspicuity) and lower frequency (leading to poor cognitive conspicuity) than other road vehicles, as well as the visual limitations of other road users. The second group relates to problems of motorcycle use, including excessive risk taking by certain riders and alcohol impairment. For example, in the US in 1998 over one in three motorcyclists involved in fatal accidents were intoxicated, although this was an improvement on earlier studies where the figure was more than a half.

Preventative action involves a mixture of education, engineering and enforcement measures. Primary accident prevention involves reducing the number of accidents. The motorcyclist licensing and rider training regimes in the UK are reviewed, including the Police Assessed Ride Programme in Scotland. These regimes are then compared with graduated licensing schemes in New Zealand and parts of Canada and the United States. The other form of primary prevention involves conspicuity improvements including daytime running headlights and the colour and fluorescence of the vehicle (and rider). Secondary measures may not reduce the number of accidents per se, but can reduce the severity of such accidents. The two main types of measures reviewed are motorcycle design, including brakes, airbags and leg protection, and motorcycle helmets and other protective equipment.

Since the mid 1990s there has been an increase in motorcycle casualties in Great Britain, in marked contrast to the previous downward trend. For example, the number of motorcycle related KSI casualties reduced by 65% between 1982 and 1996 but has since increased by almost 19% between 1996 and 2002. This increase is almost entirely due to increased ownership and use of motorcycles. Indeed the KSI casualty rate per motorcycle vehicle kilometre continues to fall (down 12% between 1994/8 and 2002).

However, some important changes in motorcycle ownership and use also seem to have occurred. With respect to motorcycle ownership, the big change has been in machines of 500cc and above, with their numbers trebling over the last ten years (1992-2002). With respect to motorcycle use, the data, and particularly the data on accidents, suggest that this is no longer the domain of young men. For example, in 1982 the under 20s accounted for 49% of motorcycle casualties but by 2002 this had decreased to under 12%. By contrast, the 30-39 age group made up 8% of motorcycle KSI casualties in 1982 but by 2002 this had increased to 33%.

There is thus some statistical support for anecdotal evidence that the born again motorcycle rider is becoming something of a public health problem. Further work is required to quantify the extent and nature of this problem and in particular to determine the extent to which the problem of increased casualties amongst older motorcycle users is due to middle aged men returning to motorcycling or existing motorcyclists upgrading to more powerful machines as they get older. This will be important in framing new policy towards rider training and licensing which to date has focused on younger riders and less powerful machines and has assumed a continuity of motorcycle use.

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