Are our Slants "Unsafe"?
"All other factors being equal" meaning what exactly?
It means that you compare apples to apples and oranges to oranges. You don't compare a 1961 unit-body car to a 2011 body-on-frame car. You don't compare a 5,000-pound body-on-frame car to an 1,800-pound unit-body car. That kind of thing. The correlations between vehicle design and construction and vehicle safety performance are anything but obvious. For example, it's popular to believe that you're definitely better off in a heavier vehicle than in a lighter one, but that's not necessarily true. There are much more significant factors in crashworthiness than vehicle size/mass. A great deal of real-world crash data, here in North America as well as abroad, demonstrates it very clearly. Take a look at
this. See especially pages 7-11.
I'm involved with traffic safety research (and, in fact, a member of the National Academy of Science Transportation Research Board, which is the body that put out this report). The human mind is poorly equipped to consider odds, risks, and chances. I own three '60s-'70s cars which, for better and worse, lack a great deal of what is taken for granted as basic safety engineering in today's vehicles. For five years I drove a pickup truck every day (not because I needed to or liked to or especially wanted to), and the good-quality data represented by these charts show I was considerably less safe in the truck than if I were driving, say, a Honda Civic or something — in the real, practical terms of how likely I am to be killed or seriously injured in a crash.
The primary error of North American auto safety regulation is the almost singleminded focus on crashworthiness: Assuming a catastrophic crash is
going to happen and designing the car as a crash cell, with relatively very little attention paid to crash
avoidance. The safest, lowest-cost crash is the one that doesn't happen, but the American regulatory structure requires cost-benefit justification for every mandatory provision of every safety standard, and it is mathematically impossible to determine the cost of a crash that does not happen (means dividing by a zero, a mathematical impossibility). One can estimate or project such a cost, but the law requires
calculation, so regulations based on risk analysis of projected cost savings are not allowed, so we're heavy on crashworthiness regs and lax on crash avoidance.
Crashworthiness engineering is important, of course, but other countries with a more balanced approach that includes more emphasis on crash avoidance have better highway safety stats than ours, per vehicle distance travelled
and per vehicle registered. And they do it while getting between double and triple the overall vehicle on-road-fleet fuel economy.
Back to the question of vehicle size/mass vs. safety (and the study linked in this post): The safety hazards presented by pickup trucks to their occupants are largely because trucks have a high centre of gravity and are therefore tippy. The hazards trucks present to others are due primarily to mass and rigidity combined with poor maneuvrability.
What other factors can we look at and exclude? Well, how about the testosterone effect, showoffs doing dumb things in their trucks that cause crashes? These data don't support it (but neither do they refute it, specifically) as a cause of trucks' greater risk. Take another look at the chart: pickup trucks are outliers on the Y axis (high risk primarily to others), while sports cars with a known-high testosterone factor are outliers on the X axis (high risk primarily to their occupants). Trucks' risk to their occupants is right between that of compact and subcompact cars.
That said, if you take a look at pp. 13-14, there's an interesting comparison of the Ford Crown Victoria and Mercury Grand Marquis. These two cars are identical except for minor trim and decorative elements. Virtually all police cars are Crown Vics, and virtually all Grand Marquis buyers are grandmas and grandpas. Police duty serves as a workable proxy for the kinds of risky driving attributable to testosterone poisoning; look at its effect—it pushes the Crown Vic way up the Y axis! So, perhaps thoughtless behaviour behind the wheel does influence the real safety performance of trucks.
You begin to see how complex this all is…?
