As cars get heavier, even small speed differences are important in an accident

In late January, safety researchers at the AAA Foundation for Traffic Safety and the Insurance Institute for Highway Safety published a study showing that small increases in speed have major consequences during an accident. After crashing three identical cars at increasing speed, the study showed that a car that passes the test at all levels at 40 mph (64 km / h), with only a 15 percent chance of serious injury, can get a grade of general failure, with a chance score of severe injury at 50 mph (80km / h). At 56 mph (90km / h), the result was even worse; the male 50th percentile crash test dummy had only a 21% chance of escaping serious injuries or worse.

Undoubtedly, the fact that the vehicles are designed to pass a 45 mph (73 km / h) crash test and not something on highway speed has anything to do with the study results. But it is also a reminder of basic physics: a vehicle’s kinetic energy is equal to half its mass multiplied by the square of its speed. Thus, the average US light vehicle – which weighs about 4,000 pounds (1,814 kg) – is 11.2 kJ when traveling at 25 mph (40 km / h), but 22 kJ at 35 mph (56 km / h) , a fact that people can use next time someone complains that city speed limits are too slow.

But speed is literally just part of the equation. Local authorities can set limits on how fast we can drive, but no one will stop you from buying a 5,000 lb (2,268 kg) car instead of a 4,000 lb. And big cars are attractive to the general public. Ironically, much of this trend is fueled by the fact that security sells, and the biggest, heaviest cars are the safest – for their occupants, at least. Pedestrians or people in older or smaller cars? Not much.

All things being equal, a bigger, heavier car will endure worse. You can make up for it in a few ways, as the + 5,000 pound cars like the Porsche Taycan Turbo, Audi RS7 and Aston Martin DBX show. Adaptive quick reaction suspension and excess force are a good way to overcome inertia when it’s time to start moving or changing direction. It all exists, but it comes with its own luggage. Adaptive suspension is expensive and adds a lot of weight on its own. Electric motors are great because they have a lot of torque, but now you need to carry hundreds of pounds of lithium-ion cells, which again is not cheap. And the twin turbo V8s that melt glaciers are increasingly unsustainable because of the melting part of the glaciers.

Powerful engines and smart dampers are great for starting and deflecting. But you can’t really hide the mass of a car when it’s time to slow down or stop. Heavy cars need big brakes and longer braking distances and tires that can handle it all, rain or shine.

Less can be more

At the other end of the spectrum is a light utopia, idealized by designers like Gordon Murray. He puts his money where his mouth is, too; none of his personal cars – including one of those Suzuki Jimnys that everyone loves so much – weighs more than 2,500 pounds (1,134 kg), if I remember correctly.

Lighter cars have a reward for enthusiasts as well as those concerned with safety. The less mass a car has to move, the better it will perform. And you won’t need that much energy to move in the first place. Lighter and less powerful cars have much more accessible limits, which means that you can have fun driving at socially responsible speeds. In fact, I’m still looking forward to my old Ford Ka 1996. At just 59hp (44kW) and 2.002lbs (908kg), it remains etched in my memory as one of the most fun cars to drive everyday.

The real godfather of lightweight was Colin Chapman, founder of Lotus, who may have been more obsessed with weight than Murray. Chapman described his philosophy as “simplifying, then adding lightness”, and that has been a hallmark of Lotus in good times and bad. Some of the bad ones included racing cars that were often too fragile for their own good, with tragic consequences. But the good ones are street cars that outperform any of their rivals and usually at a high price.

Since 1996, Lotus has existed with the success of Elise and other light sports cars derived from its still innovative extruded and glued aluminum chassis. I’ve never driven one yet and I’m sad about it. Maybe, if the pandemic ever ends, the friendly people at the Nashville Motor Museum in Nashville can let me go and do an article about their example.

I drove a Lotus Evora in Monterey in 2019. Yes, a car weighing 3,100 pounds is what goes for today, which sounds crazy when you say it out loud. It was wonderful to drive, but not as good to live as a Porsche 911. Not that you can buy one for much longer: Lotus is closing production lines at its factory in Hethel, England, to retrofit for a brand new car. , known only as Type 131 for now.

I’m very excited to see how the Type 131 develops, as well as how the Lotus adapts to life under Geely’s ownership. The way it works with Volvo’s parts compartment intrigues me in particular – Volvo is also owned by the Chinese company. And I just realized that this means that future Lotuses will run automotive Android. A crossover with the Lotus emblem of some kind seems inevitable, which will generate all kinds of complaints. But if Porsche can make the Macan GTS great to drive, I have no doubt that the Lotus will work its magic.

Still, Murray and Lotus are disparate, and the philosophy of weight reduction still has a long way to go before it becomes a dominant belief in the auto industry. But a man can dream, can’t he?