While the article itself is related to automobiles, there is a deeper lesson at work here. The ability to think critically can be applied to any news item, whether scientific, market-related, or even (gasp!) political.

At issue in this New Scientist article are two variables, one of which is important, and one of which isn’t, but is immediately apparent. I’ll cover the unimportant and immediately apparent one first, that is, the inherent physical characteristics of the vehicle itself, by comparing a prototypical SUV to a prototypical sports car.

The prototypical SUV has a rigid frame which is located somewhat higher than the structural components of a typical passenger car, which generally means that in a collision between the two different types, the net energy transfer is more likely to be FROM the SUV and TO the car. Even in most “crossover” and unibody vehicles, the equivalent point to a hypothetical framerail is higher than in a passenger vehicle. This means that, relatively speaking, regardless of the collision type (head on, ass end, t-bone) and which vehicle is in what position (hitter or hittee), the driver in the car is worse off than the driver in the SUV. Some researchers call this “aggressivity” and it is a primary reason I like to drive an SUV – I am safer in it. This “aggressivity” is part of what legislators and car manufacturers have been actively trying to reduce, by altering the frame height of frame-based SUVs, adding in lower frame extensions at the front and rear, and structuring those lower frame extensions (or equivalent unibody components) to collapse and absorb energy in a crash.

The SUV has a higher center of gravity, making it inherently less stable in a crash-avoidance situation. It will not respond as quickly (as evidenced by slalom test times in car rags) and will be more likely to roll over, given the same type of maneuver being attempted.

The SUV cannot stop as quickly as a sports car. Typically the brake design is suboptimal (drums in rear rather than 4-wheel disc brakes, fewer pistons per caliper in the discs, non-vented discs, etc.), and even if the designs were optimized, there are practical limits to the same size and specification set of brakes stopping a mass that is significantly larger.

All this adds up to SUVs being a “relative menace” to other drivers on the road, all other things being equal.

So why, then, do sports cars kill more people per crash, and crash more often, than SUVs?

It’s the DRIVER, Stupid!

This is the second, and by far the more important, variable. All other things are decidedly not equal, and the person who picks the sports car as their primary mode of transportation is more likely (statistically speaking) to be the type that enjoys driving the dogshit out of it – thereby causing more accidents – and those accidents are more likely to “enjoy” higher levels of kinetic energy.

E = M * V^2

Hmm, 33% less mass going 25% faster = a 4% increase in kinetic energy, therefore a 3,000 lb sports car going 50 in a 40-mph zone is carrying more energy than a 4,500 lb SUV going 40 in a 40-mph zone. Do the math on 33% less mass going 33% faster, and you get a 17.9% increase in kinetic energy – something like a lighter sports car doing 80 mph versus an SUV doing 60 mph.

Drivers of sports cars skew younger than drivers of SUVs. Part of this is economics (SUVs are more expensive), and part of this is demographics (SUV owners need space for kids, car seats, dogs, and family groceries). Younger people have (statistically speaking) less ability to quantify risk, and this translates into riskier driving behavior – thereby causing more accidents – and if the risk involves high levels of speed, see the above point about kinetic energy.

Sports cars are more dangerous than SUVs, not because of their inherent characteristics, but because of who chooses to drive them.

This is part of why I’ve been peeved at the nanny-state mindset that has toned down the “aggressivity” of SUVs sold in the U.S. over the last few years. By God, I WANT “aggressivity” in my vehicle, because it keeps me and my family SAFE! Screw the younger drivers in the sports cars who’re causing all the accidents!

This change in vehicle construction, the wrong-headed emphasis on making “safer SUVs,” is a net Reverse Darwinism. It transfers some of the deaths FROM those who cause the most (and most dangerous) accidents (sports car drivers), TO those who not only have managed (for the most part) to live to breeding age and achieve some modicum of material success (SUV drivers and their families).

Totally aside from the vehicle-related and policy-related issues, there’s a deeper point, and that’s about how to think critically. Critics of SUVs have, by and large, missed the most important variable in the dangerousness of vehicles – the driver! The lesson on critical thinking is simple: identify the variables; find which ones matter; focus on them and not other, possibly more readily-apparent variables; examine the implications; rinse, repeat. Apply liberally to all aspects of life …