Methods
Data from systematic studies control and report sampling effort allowing to estimate standardized roadkill rates (number of individuals killed per area and time span) for different species and areas. However, these studies, and thus their data, are often limited to particular road sections and periods of time. On the other hand, citizen science data can cover wider spatial and temporal windows, but sampling is often not regulated or quantified making the definition of standardized estimates complicated. To avoid methodological issues, data obtained from these two approaches are presented separately.