The present project investigates issues related to two-wheeler behaviour and safety in order to define the parameters of their behaviour resulting in their high risk. Other project sub-objectives concern the obtaining of know-how on the risk factors for two-wheelers and on their behaviour and the design of tools to represent two-wheeler behaviour efficiently. First, the possible causes for two-wheeler road accidents are investigated obtaining data from accident databases to define specific scenarios that contain high risk for two-wheelers. Next, two-wheeler behaviour, conspicuity and risk perception are investigated using a set of tools part of which is designed/customised within the framework of the project. Such tools are instrumented two-wheelers for naturalistic riding studies, questionnaires, riding simulators and video tools. The synthesis of the project results leads to the design of measures for the improvement of two-wheeler road safety.