Line of Sight Visibility Analysis
Often in Accident Reconstruction, visibility from one participant to another becomes the critical issue. Small changes in position of the viewer or the viewing object can result in large functional differences and affect the ultimate question of liability or negligence. In dynamic scenarios ? when one or both objects are moving ? the challenge of determining "What was visible, when" becomes more difficult.
PSI has developed two methods to assist the expert and attorney in determining the functional line of sight and presenting the results of the analysis in a clear, compelling format.
- On-scene visibility analysis
- Object and Scene Laser Scanning
On-scene visibility analysis
The visibility from within a vehicle, whether a piece of construction equipment such as a front-loader or a municipal bus, is constrained by the physical characteristics of the vehicle and the size and position of the object being viewed. Objects such as rear-view and side-view mirrors, A & B pillars and door seams all obstruct the vehicle operators line of sight.
Insert "Vernon" Still picture of Obstruction ConesDepending on the timing of the event, these obstructions can be causal factors in the accident and need to be understood as part of a thorough analysis. PSI is experienced in setting up the necessary site experiments to determine the "functional cones of vision" for any type of vehicle, under static and dynamic conditions.
Insert "Vernon" animationObject and Scene Laser Scanning
When the specific vehicle cannot be brought to a site to perform the on-scene visibility analysis, or if the final analysis will be presented with a view from the operators vantage point within the vehicle, it is necessary to model the vehicle interior in the computer. The 3D Laser Scanner is used to map the vehicle and the resulting Working Model of the vehicle can be used to perform a visibility analysis "virtually".
Insert Laser Pic of Laidlaw Bus interior or Ruelas Front LoaderIn some cases, it is not the vehicle itself, but objects in the scene that may obscure vision, as in the case of bushes blocking line of sight through a turn. The 3D Laser Scanner is used to map the scene, including the obscuring objects, with sufficient clarity and detail to allow a dynamic visibility analysis to be performed virtually, using the computer Working Model.
Insert side-by-side pic of townsend Berm scan and View from Taurus
When we decided to get PSI involved in producing an annimation we had no idea they'd have the impact they would. We were amazed.
Larry Spelling, esq. Wietrab & Wietrab
Results: The defense attorney, assisted by the expert's comprehensive reconstruc- tion, and PSI's computer generated simulation, was able to determine that the physical evidence corroborated the peace officers' version of the inci- dent and conclusively established that the officers' use of deadly force was reasonable. The animation was shown at the settlement conference and the opposing attorney withdrew the case.
