Caught in the Act! Part Three
Mar 18, 2015
3D Laser Scanning – Determining & Illustrating Driver Eye View Obstructions:
In the reconstruction of vehicle accidents, particularly vehicle versus pedestrian cases, one of the issues that often arises is the portion of the scene that the pedestrian was visible to the driver in the moments immediately before impact. A common point of analysis is the so-called “Last Chance to Avoid” point for the driver of the vehicle. How much of the pedestrian, or other vehicle, was visible to the driver at this last chance point and position?
Often there are obstructions present to the drivers line of sight to the object impacted. These obstructions can be from objects in the environment outside the vehicle, such as telephone poles, street signs and foliage adjacent to the roadway and impact location. Other times the obstructions to the driver’s line of sight come directly from features within the vehicle itself. This is very common when commercial vehicles are involved. In a recent Bus vs. Pedestrian case, PSI devised a very accurate and repeatable method to determine and illustrate these obstructions. By utilizing 3D laser scan data and the 3D Working Model, it is possible to quantify the effect of these obstructions and illustrate how they impact the driver's view out on the roadway dynamically, as the objects and vehicles move over time towards impact.
In the recent case where a MUNI bus struck and injured the pedestrian crossing against the light, given the size and close proximity of the bus, (40 feet long, 8 feet wide, 8.5 feet high, the first vehicle in line and approximately 10 feet away when the pedestrian entered the street), it is certain that the bus was available to be seen by the pedestrian. However, the bus driver’s view towards the unexpected late crossing pedestrian is not as certain. The bus itself blocks the driver’s sight to portions of the roadway around the bus. The combination of these obstructions and the pedestrian’s 4’11” height may limit her visibility to the driver. Using the previously captured laser scan data, PSI created a 3D Working Model of the bus interior and driver’s eye position in order to analyze the issue.
Performing this task in the computer via the 3D Working Model has two distinct benefits: the precision and adjust-ability afforded by the computer and the ability to analyze it in context of the environment, derived motions and physical evidence of the virtual accident scene. Visualizing the results in connection with the accident reconstruction and signal timing elements allows a more detailed picture of the dynamic issues at play during the event. By modeling the bus interior and the driver’s eye position, the 3D Working Model creates visible geometry around the bus indicating which areas are not visible to the bus driver. By attaching this visible geometry to the 3D model of the bus as it moves, we can see the interplay between the line of sight obstructions and the position of the pedestrian as she crosses in front of the bus.
Craig Fries is the Founder and President of Precision Simulations, Inc., the foremost forensic analysis and animation firm in the US. In this role he has created or directed over 1,000 3D forensic animations for use in criminal and civil litigation and has maintained a 100% record of non-exclusion at trial. As a pioneer in the field of forensic laser scanning, Craig created the first 3D animation based upon laser scan data ever admitted at trial in the US, and has been at the forefront of the use of the technology in homicide and accident investigation since.