The traffic accident casualties dataset contains one record for each casualty involved in a road traffic accident. The reference field number relates to the accident reference number, therefore those casualties with the same reference number were involved in the same accident. All uninjured persons involved in accidents have been omitted from the dataset. The grid reference of the accident may not be exact, and if an accident takes place near a junction the grid reference may be at the point of the junction.
The definition of the severity of injuries sustained can be found in this document from the ADLS website: http://www.adls.ac.uk/department-for-transport/stats19-road-accident-dataset/?detail#ds_jump_overview