Powered two wheelers (PTWs) riders are one of the most vulnerable groups of road users. Roadside barriers work quite effectively for passenger cars, but sometimes they are dangerous for motorcyclists, especially guard-rails. These accidents are investigated by means of an analysis of the DGT Spanish National Accident Database and reviewing different in-depth studies. Motorcyclist injury patterns have been identified. A revision of the injury criteria used for head and neck injuries has been carried out to select those suitable to be used in an impact of a motorcyclist against a roadside barrier. Head injury criterion (HIC36) for head injury has been accepted as a valid injury criterion. Regarding the neck, the Mertz criterion was considered in a first stage and some changes have been introduced in order to suit the peculiarities of motorcyclists’ impacts, using adapted methods from the automobile sector related to Out-of-position (OOP) scaling methodology.