Our Cars’ Weight Problem

Robert Norton:

the new mandate that all auto manufacturers achieve by 2025 a Corporate Average Fuel Economy (CAFE ) standard of 52 miles per gallon — twice the previous requirement of 26 miles per gallon.

At first blush, 52 mpg sounds like a laudable goal. What’s wrong with making more efficient cars? After all, they’ll be more affordable to drive, and simultaneously reduce the nation’s carbon emissions. Talk about a policy twofer!

The problem with the goal is simple: We can get only so far on the mileage front without affecting safety. Allow me, as someone who has spent a lifetime in and around the automotive industry, to explain why.

To get to where the government wants us to be, we start by employing all the engine technology possible to extract every last mile per gallon. This means using direct-injection combustion, variable valve timing, and sophisticated air management that includes more turbo-charging, as well as fine-tuning the engines with the use of sophisticated sensors and algorithms. The industry has done all of that, and today’s engines are impressively efficient.

We next turn to transmissions. These can help save fuel by allowing the engine to run at lower revolutions per minute (rpm). Think of being able to shift gears on a bicycle as you go up or down hills. This helps you get more from each pedal stroke. It is the same for vehicles. Today’s vehicles have progressed far from the original two-gear automatic transmissions; some offer as many as eight gears that automatically maintain engine rpm within a certain range. This has all been done, and the miles per gallon have improved accordingly.

However, all these efforts are not nearly enough to achieve the mandated 52 miles per gallon. So what else can be done? It’s what I call Jenny Craig engineering: reduce car weights, and reduce them massively.

It is a simple matter of physics: It takes less energy to propel a lighter object at a particular speed than a heavier object. You may wonder why so many vehicles suddenly stopped carrying a real spare tire years ago, or why there is so much plastic in vehicles today. Wonder no more: It was for weight reduction.

This is not a new trend; weight-reduction efforts have been ongoing since Jimmy Carter was in office. And they are not aimed just at larger vehicles. The Toyota Prius is slated to shed 500 pounds.

But less weight is a good thing, isn’t it? Well, not always. Why does professional boxing have weight categories that place athletes in competition with others the same size? Why is the NFL so concerned about the head injuries that seem to be happening with more and more frequency as players get bigger and faster?

Because size matters — and we all know it. Take this simple test. Imagine a head-on collision on a two-lane country road at a speed of 40 mph. One of the cars involved is a Cadillac Escalade and the other a Chevy Volt. Which would you want to be in? Which would you want your child in?

In a Cadillac minute, you would choose the Escalade. Because you don’t need to be an automotive engineer to know the big car will crush the small car. The driver in that little car will in all probability be severely injured, maybe killed. You, the driver in the Escalade, may walk away unharmed, or with only minor injuries.

Why? Once again, it’s physics. The force of something heavy and big crashing into something small and light leaves that something much, much smaller.

The same goes for that big heavy vehicle crashing into something stationary, like a wall or a tree. Or something pretty mobile — like a deer — crashing into the vehicle.

Bigger and heavier is simply better when it comes to car crashes, all other things being equal.

We do not have to speculate about the safety ramifications of being in a smaller vehicle; the Insurance Institute for Highway Safety (IIHS) ran a rather expensive series of tests in which it pitted a smaller vehicle against the next size larger vehicle from the same manufacturer. Specifically, they ran a Honda Fit into a Honda Accord, a Toyota Yaris into a Toyota Camry, and a Mercedes C Class into a Smart Fortwo (owned by Mercedes).

Care to guess at the results?

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There are approximately 42,000 motoring fatalities each year in the United States. That is a large number, and it has remained stubbornly at that level. Why, with all the technological innovations that have occurred in so many key areas, such as electronic stability control, anti-lock brakes, and air bags, have we not reduced those numbers significantly? The major reason, I believe, is the smaller vehicles our government has been pushing in order to support the environmental agenda.