Nathan Rose: I approached this case the same way I approach every case. It always begins with gathering the evidence, and that could be physical evidence, could be electronic evidence, could be video evidence, could be testimony and statements. So I’m always looking to gather that evidence. This is a crash that occurred on an interstate highway, and it involved a tractor trailer impacting a motorcyclist on the highway. Essentially what happened is the tractor trailer driver came upon a slow moving vehicle that had had a tire disablement, so the vehicle was limping along in the right lane, traveling about 15 miles per hour according to testimony. That truck driver had about a 2,000 foot straightaway, but he didn’t react to that slow moving vehicle until very late and ended up swerving to the left across the center lane and into the left lane, where the trucks dropped a motorcyclist. In this case, the police did do some investigation. They had a basic diagram that outlined the sequence of events. They had some photographs they took that showed tire marks, showed fluid on the road, showed the rest position of the tractor trailer and the motorcycle. So that was the first step, was beginning to gather that. In this case, questions that I needed to answer were the speed of the tractor trailer throughout the sequence, the speed of the motorcycle, and then the motion of the tractor trailer as it traversed from the right lane, across the center lane, and into the left lane and struck the motorcyclist, then how did those vehicles move following the collision. Then also, inherent in that data from the event data recorder was how did the driver of the tractor trailer respond to the slow moving vehicle that he was attempting to avoid, when did he break and when did he swerve. Most tractor trailers these days have event data recorders on them. Typically, those are integral to the engine control module and they will record data related to sudden decelerations or hard break events that those trucks experience. The vehicle experiences a change in speed, of say for example in this case it was seven miles per hour in a one-second time interval, that’s sufficient to cause the system to record that data. Typically what will be recorded will be the speed of the vehicle, at least the indicated speed, what it would read on the speedometer. It will be whether the brakes are applied or not, engine RPM is another thing that often is reported, things of that nature. We can take that data and it in our reconstruction. PC-Crash is where I’m bringing all that together. I’m bringing together the electronic data with the physical evidence, generating physics-based motion that is in agreement with that electronic data and in agreement with the physical evidence.
Neal Carter: In PC-Crash, we have a diagram that shows the rest positions of the vehicles. It shows the physical evidence, like the tire marks, the scrape marks of the vehicles, and we’re able to simulate that motion of the vehicles coming to rest. In here you can see, as I scrub through this, you can see the tractor trailer, the vehicle that he was avoiding, as well as the motorcycle. After we simulated the motion in PC-Crash, we then brought it to an animation package called 3D Studio Max, and we use that to make our final animation.
Tomas Owens: In cases like this in particular, which is going to be a melding of both physical evidence locations as well as a little bit of interpretation as to what the person or character is actually doing in this case, it’s very important for us to work directly with the engineers to get that evidence from PC-Crash. That gives me kind of a point A and a point B. I know where a character needs to be physically, as well as his relationship to those vehicles. So that told me that his body has to be positioned in such a way that he can leave this physical evidence and have it match with all the physical evidence from the vehicles that have already been determined, partially by engineers, partially by photogrammetry and analysis of the information that we have. At this point, I have positions over time, I know where my vehicles need to be to match the entire scene. I can take this information, bring it into a 3D software, like 3ds Max. That gives me all of the information and positions represented in PC-Crash that I can then use for my analysis of where the character needs to be.
Nathan Rose: Based on my analysis, what I found was that the truck driver in this crash could have avoided the crash had he begun reacting about a second and a half sooner. He could have simply changed lanes into the center lane, which was open, not gone into the left lane, and not struck the motorcyclist. Another key finding was that the crash was not avoidable by the motorcyclist. The time available for him to perceive what was going on and take action to avoid it, there simply wasn’t enough time, and so it was not avoidable to the motorcyclist. When I get to the end of it and I’ve got reconstructed motion in PC-Crash of these vehicles, it’s justified based on physics, based on physical evidence, based on electronic data. All of the techniques that I’m utilizing have been published, they’re widely used in the industry, they’re peer reviewed. I can use this reconstruction data then to go on to produce an animation and that animation is going to be admitted in trial because I can lay out the foundation for each step of the process based on that peer-reviewed literature, based on that research and testing, and based on the principles of physics. In this specific case, this allowed me to go in, testify in a deposition and explain this accent in a very clear way to both sides.