The Collision Investigation Unit has a responsibility to attend all fatal, potentially life-threatening collisions and serious injury Police collisions and provides support to CID and Crime Scene Investigators for major incidents such as murder investigations. On average, the Unit attends, on average 200 incidents per year, of which, between 60 and 80 involve fatalities.

A road death scene is treated as a crime scene and is cordoned off at the earliest opportunity to preserve and secure evidence. Collision Investigators attend the scene, where they analyse, collect, record and interpret all the physical evidence available by way of remotely operated surveying equipment and photography. Whilst every attempt is made to open roads as soon as possible without compromising the investigation, it can be a painstaking process that can take several hours depending upon the complexities of the incident.

Upon completion of the scene analysis, vehicles are removed into secure storage, where a Vehicle Examiner will conduct an examination to establish whether or not any mechanical defects were contributory in that collision. Specialist recovery methods are employed to ensure the integrity of the evidence.

Once all of the available evidence has been gathered, Collision Investigators will, where appropriate, interview any offending driver(s) for offences of Causing Death by Dangerous Driving; Causing Death By Driving without Due Care and Attention whilst under the influence of drink or drugs; Causing Death by Careless or Inconsiderate Driving; Causing Death by Driving Whilst Unlicensed, Disqualified or Uninsured; Dangerous Driving; Driving Without Due Care and Attention.

The final stage is the preparation of case papers for submission to HM Coroner and, where appropriate, to the Crown Prosecution Service.

The advanced surveying equipment and associated software used, allows for the production of detailed scale plans and (where sufficient data exists) animations to assist in the forensic examination and analysis of the scene. Where appropriate, specialist computer programmes are used to assess the level of damage to vehicles gleaning vital evidence relating to impact speeds. Physical evidence such as tyre marks on the road surface can be analysed to provide further evidence of vehicle speed and movement.

All investigations are conducted to the standard set out in the Road Death Investigation Manual which gives guidelines to the Police Service on the many aspects to be considered.