The average annual number of people reported killed or seriously injured (KSI) on the roads, all ages, per billion vehicle miles travelled adjusted. This is calculated as the number of events observed over in the year divided by the the vehicle miles travelled in the area, and the resulting rate multiplied by 1,000,000,000

This indicator includes only casualties who are fatally or seriously injured and these categories are defined as follows: - Fatal casualties are those who sustained injuries which caused death less than 30 days after the accident; confirmed suicides are excluded. - Seriously injured casualties are those who sustained an injury for which they are detained in hospital as an in-patient, or any of the following injuries, whether or not they are admitted to hospital: fractures, concussion, internal injuries, crushings, burns (excluding friction burns), severe cuts and lacerations, severe general shock requiring medical treatment and injuries causing death 30 or more days after the accident. A casualty is recorded as seriously or slightly injured by the police on the basis of information available within a short time of the accident. This generally will not reflect the results of a medical examination, but may be influenced according to whether the casualty is hospitalised or not. Hospitalisation procedures will vary regionally.

This indicator is a revision of an earlier PHOF indicator which reported the rate of KSI events within the local population. The denominator is now the estimate of vehicle miles in the local area - this is preferred because KSI events are expected to be more closely correlated with local traffic than population size. This change particularly impacts Local Authorities with small resident populations but high traffic volumes, such as rural areas with major roads passing through. For these areas, rates would be expected to be reduced in these cases under the new measure.