However, because of under-reporting problems and possible bias (for example with differing rates of reporting by vehicle type), police data should be complemented by hospital data, which are the next most useful source. This information — without personal details — should be made easily available for statistical purposes, policymaking and research. These have a limited value on their own, and cannot replace police or hospital data, but can be used to build a more balanced and comprehensive picture, to enrich the main data sources, and as a quality check. Using this method combined with linking police and hospital data may be appropriate to give a fuller picture of road casualties.