The aim of the study was to investigate single motorcycle injury crashes (rider loses control over the motorcycle) on rural roads concerning potential influence of road geometry as well as road surface condition. Another aim of the study was to evaluate the effectiveness of road operational and road engineering measures which serve to improve road safety of motorcyclists. To answer the question whether the road geometry can have an impact on motorcycle crashes (rider loses control over the motorcycle), a comparison of 32 safe and 27 unsafe sections was performed. The analyses showed that safe road sections have a lower mean curvature change rate than unsafe road sections. A further analysis of 254 single motorcycle injury crashes revealed that 86 % of these crashes occur in curves and that 82 % of these curves have a radius smaller than 100 m. For this reason, existing crash barriers in curves with a radius of less than 100 m should be equipped with an underride guard as a standard. This should especially apply to road sections with a high average daily traffic (ADT) of powered two-wheelers per day. The question of how deficits of the road surface condition can be a causal factor in motorcycle injury crashes (rider loses control over the motor-cycle) was investigated based on a comparison of the distribution of road surface condition at 77 crash scenes and the distribution of road surface condition of a large part of the federal road network in the federal state North Rhine-Westphalia. The road surface parameter which was much worse at the crash scene than in the road network and whose distribution at the crash scene and in the road network differs statistically significantly, was the unevenness in longitudinal direction (e.g. bumps). All other distributions of road surface condition parameters such as unevenness in transverse direction (rutting), friction value, crack networks, local repairs and potholes did not differ significantly between the crash scene and the road network or were even better at the crash scene. To evaluate the effectiveness of road operational and road engineering measures to improve road safety of motorcyclists the accident commissions were asked via a web-based questionnaire where such measures had already been implemented and whether information about their effectiveness could be provided. In the subsequent before and after comparison it could be shown that the 8 investigated road sections implemented combination of measures achieved a high effectiveness and efficiency in terms of improving road safety for motorcyclist. The evaluation of individual measures was only possible to a limited extent because in almost all cases several measures were implemented at the investigated road sections simultaneously. If a motorcycle crash spot was in a curve, normally a speed limit was introduced, a double solid lane marking applied in the middle of the road and an underride guard was fitted to existing crash barriers. (Author/publisher)
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