What actually happened was far different. Out of a field of several hundred people, only a fraction of them participated in the photographic crush estimates portion and the direct crush measurement portions of the field test. I'll admit that I wasn't one of the participants, as I has having too much fun watching motorcycles crash at the other end of the field.
Seventeen people performed hands-on measurements of the crushed van and reported their results. All seventeen were grouped together for the statistical analysis, which in my opinion, is unfortunate. Although there was a space on the data collection form to indicate "experience", I have no idea where this data is in the final paper. It appears that those who were measuring for the first time were grouped together with those who performed measurements like these on a regular basis. From this data set, the photograph of the vehicle provided in the paper, my review of videotape of the crash test involving this particular vehicle and my recollection of what the vehicle looked like, it appears that some of the participants measured simply the bumper level crush, some measured above bumper level crush and some followed the SAE protocol and took the average of the two levels. Since the data collection form provided to each of the participants only included space for one set of measurements, I
can see why there is a signficant range in the reported measurements.
For the single photograph exercise, participants were asked to estimate the "crush and or Equivalent Barrier Speed" of a vehicle from a single photograph. The photograph provided was a side-view of the damage to the rear of a vehicle. There were sufficient landmarks within the photograph to perform photogrammetry and estimate the crush, but it is apparent that this did not occur in this exercise. What did occur is that while participants were in the field, they were handed a package containing the photograph and asked to give an estimate. For the vast majority of the participants, there was no attempt to sit down with the materials and scale the photographs and then use some reasonable method to estimate the EBS. They simply guessed. There were no computer algorithms here, Dr. Wright, there was the good old fashioned guess. The same holds true for the Two-Photograph exercise.
In fact, Dr. Wright, at the bottom of (Wade, you d.s., you didn't number the pages)the first column of the page that contains the three photographs of the vehicles, there is an interesting statements that you might have missed in your overwhelming excitement upon reading the paper. "Most of the participants in this exercise reported that they would not attempt to use information generated in this fashion in a reconstruction without additional details and analysis." That's a good thing.
So, Dr. Wright, you can read whatever your want into whatever papers you wish. As for your critique of the Chalmer's study, I didn't give you a good reference for this paper because I kinda-figured you would have something to say without knowing all the facts. If I were a lay person, and had to make an important decision about something like my safety in an automobile, would I trust the "research" done by a group of chiropractors in southern California or would I trust one of the top research institutes in the world, using data from Volvo (the safest automobile in the world, if you trust the advertisements). It's a no brainer for me.
So long, Dr. Wright. The next time I testify 3,000 miles away from you, I'll try to let you know at least a few hours ahead of time. One thing is for sure, you won't be getting any more free advise on the phone from me, and probably not from anybody on this site.
Bruce McNally
Director of Operations
Northeast Collision Analysis, Inc.
Bruce McNally ACTAR 670
bruce@northeastcollision.com
Use this form to reply to this Thread