Adam wrote:Ooppps....maybe they did try to control for vehicle model
Well, yes and no. They did control, but none of the data and conclusions show that they separated out classes to look for patterns.
40% of the RHD principal operators in the study were under 25 years old. I would guess that most Delica owners are over 30.
On the other hand, there was no evidence to suggest that crashes involving the RHD vehicles were any more severe than those involving LHD vehicles. Of course, in spite of the non-significance of the insurance rate class in the regression, some of the lack of severity effect might be explained by differences in vehicle use or purpose and where, when, how or how much the vehicles are driven. (p.15)
Notice right after saying there is no difference in severity, the authors try to explain this away as being due to something other than the vehicle being inherently just as safe.
RHD vehicles had a lower risk of injury crash involvement (by 21%). However, the difference observed for injury crashes did not reach statistical significance. (p.11)
So, RHD are a lot LESS likely to be in an injury crash, but if they are, the injuries are similar. Indicated the vehicle is just as crash-worthy. But they ignore the why of the very significantly lower accident rate.
I also "enjoyed" the scare tactics used on page 2 about UK-Continent accidents involving heavy trucks. Completely different situation. There, the issue is the driver being in their own vehicle driving in the opposite environment, not being in familiar environment in unfamiliar vehicle.
Some of the obvious problems I have with this study:
* a 20 year old driver driving a 15 year old RHD is probably quite a different person from a 20 year old driving a 15 year old LHD. One wants a Skyline, the other needs cheap transportation.
* a 20 year old Skyline driver (not meaning to pick on Skylines) is quite different from a 50 year old Delica driver.
* they failed to compare vehicles with similar purchase price. Look at, say, LHD $12,000 Delicas with $12,000 RHD minivans. After all, most people tend to set a price, then look for the best vehicle they can get for that price.
* they failed to show data or accident rates based on vehicle type. They lumped all RHD together. That's what I would do if I was doing the study and found huge differences in accident rates based on vehicle type but that didn't suit my purposes.
This study appears to be a classic case of "There are three kinds of lies: lies, damned lies, and statistics." I've taken several statistics courses, and every study I did, both in class and on the job, I had data and an hypothesis that I could prove or disprove depending on the tests I used. I really enjoyed one time asking the boss, "what conclusion do you want?" She asked, "what does the data say?". I replied, "I haven't looked at the data yet, I'm asking what you want the result to be." She wasn't familiar with the power of statistics.
Clearly, they had conclusions and set out to prove them. They were quite disappointed that they could not show that RHD vehicles are inherently dangerous from a crash-safety standpoint.
Fred