Power-Two Wheelers Critical Risk Factors: A European Study George Yannis, Eleni I. Vlahogianni, John C. Golias National Technical University of Athens, 5 Iroon Polytechniou Str, Zografou Campus, 157 73 Athens, Greece Phan Vuthy Centre Européen d’Etudes de Sécurité et d’Analyse des Risques, 132, rue des Suisses, 92000 NANTERRE, FRANCE Peter Saleh AIT Austrian Institute of Technology GmbH Donau-City-Straﾟe 1, 1220 Vienna, Austria Martin Winkelbauer KfV -Austrian Road Safety Board Schleiergasse 18, 1100 Vienna, Austria Abstract The paper summarizes the results of a large European project on the critical risk factors for Power-Two-Wheeler (PTW) safety. Analyses conducted in both a macroscopic and microscopic level in Greece, Spain, Italy, Great Britain, Austria, Finland and Germany revealed a set of critical risk factors as well as their ranking of importance. Among the research questions treated are what are the most relevant PTW accident configurations at European level and why accidents of those configurations take place. The identified critical risk factors cover a wide range of interactions and form important knowledge for structuring guidelines dedicated to PTW users. Moreover the analyses conducted add value to the manner future in depth analyses and accidentology studies should be conducted. 1. Introduction Power Two Wheelers (PTWs) are distinguished into mopeds and motorcycles. Mopeds refer to motorcycles with 50cc engines, restricted top speed (limit 50km/h) and typically are used for short trips and are prohibited in motorways. PTWs differ from regular vehicles both in driving style and patterns and accident characteristics. At first, they are a more economical means of transport, when compared to cars, and more flexible in maneuvering and parking due to reduced size and, thus, more appealing to users in metropolitan densely populated areas with significant portion of congested road network. PTW accidents are potentially more dangerous when compared to car accidents. The small size which most times is accompanied by a relatively powerful engine increases risk and severity of accidents, due to easiness in stability lose at low speeds (difficulty in controlling and coordinating body), type friction loss in pure surface conditions and high acceleration capabilities, speeding associated by the difficulty in braking. Riders must focus on coordinating speed and body lean, and managing traction and control, while navigating various surfaces, curves and conditions. The lack of a protected vehicle compartment means that motorcycle riders and passengers are much more vulnerable to injury in crash situations. Furthermore, the task of operating a motorcycle is much more demanding