CCTV cameras and 'dash-cams' are becoming more and more common and regularly record crashes and other incidents. Cameras are used at intersections, worksites and on an array of vehicles. The video data may be accompanied by audio and/or GPS data. When these recorders capture an accident, the data can be used to calculate important attributes of crashes such as vehicle speed and acceleration.

The images from CCTV can be used to reconstruct the position of vehicles and other units involved in the collision. Useful video may be taken from inside a vehicle (e.g. a dash cam) or from outside a vehicle (e.g. a stationary CCTV camera). In order to reconstruct movement from image data, the timestamps associated with each image can be used, along with available waypoint data generated from GPS.

In this case, bus CCTV was used to track its position over time. Using GPS, images from the video, and audio, reliable estimates of speed and acceleration could be derived.

The movement of other vehicles, cyclist or pedestrians outside a vehicle can also be tracked successfully. This usually involves removing image distortion and then tracking movement against identifiable landmarks.

In this case the movement of a cyclists in the seconds before he collided with a support vehicle was captured on video by a spectator. Motion tracking can be used to rectify the images (removing the movement of the camera, blue dots) to extract position of the bicycle providing evidence on speed and braking deceleration prior to the collision.

A range of ancillary data can be used in connection with the images from CCTV cameras, both in their own right, or to provide calibration and validation of the CCTV analysis. The types of techniques Hall Technical have developed for analysing video data will become more widely deployed as more incidents are captured by video systems.

Rollover crashes often lead to severe and catastrophic injuries. Injury risks arise mainly from from roof intrusion, from full or partial ejection and hard contact with the interior of the vehicle. Identifying the cause of the rollover, pre-crash speeds and the mechanisms of injury can be challenging but important to to the determination of liability.

The reconstruction of rollover crashes requires consideration of scene evidence, exterior vehicle damage, interior damage, and details of injuries. We can use this evidence to describe the way in which the forces evolve during the crash, between the vehicle and the ground and the occupants with the vehicle interior. hence we are able to correlate vehicle damage with the rollover sequence and hence to understand occupant loads and kinematics, including forces causing ejection and the timing of relevant events.

Correlating scene evidence with vehicle damage can be used to reconstruct the rollover sequence. In this case, overlaying vehicle rotation on a scene diagram provided information that was sufficient to reconstruct the roll. Associated debris was then used to identify the point of ejection for the injured occupant.

Occupant kinematics during these events are governed by the same physical processes as other crash types: the collision between the occupant and the interior can leave clear impressions on the interior surfaces, and large deformations are often associated with specific injuries.

In this case, an unrestrained occupant struck the interior of the door at high speed during ground contact during the rollover. The forces were maintained for long enough to push the window frame out of the door frame so that is was caught by the ground on the next roll, causing the severe deformation of the frame that is visible in the photograph

Although rollover crashes appear chaotic, the discreet events in a rollover do have structure. The roll of restraints in injury prevention are likewise well understood. Our understanding of these crashes and our experience in evaluating post-collision evidence provides allows us to provide reliable opinions in such cases.