Study: Make Electric Vehicles Lighter to Get More Benefits

Blake Shaffer of the University of Calgary writes in Nature: "Electric vehicles are here, and they are essential for decarbonizing transport.... Major investments in electric vehicles are welcome news." But he and co-authors Maximilian Auffhammer and Constantine Samaras have some caveats:

"One issue that has received too little attention, in our view, is the increasing weight of vehicles. Pick-up trucks and sport utility vehicles (SUVs) now account for 57% of US sales, compared with 30% in 1990. The mass of a new vehicle sold in the United States has also risen — cars, SUVs and pick-up trucks have gained 12% (173 kilograms), 7% (136 kg) and 32% (573 kg), respectively, since 1990. That’s equivalent to hauling around a grand piano and pianist. Similar trends are seen elsewhere in the world. Electrifying vehicles adds yet more weight. Combustible, energy-dense petroleum is replaced by bulky batteries. And the rest of the vehicle must get heavier to provide the necessary structural support."

Shaffer et al. note a number of ways this is a serious problem, the first being safety: heavier vehicles are more dangerous. He points to a 2013 study in which co-author Auffhammer found that "being hit by a vehicle that is 1000 pounds heavier generates a 40–50% increase in fatality risk."

Using the new Ford F-150 Lightning as an example: It weighs 1,500 pounds more than the gasoline version because of the batteries. Putting a value on the extra lives lost using the U.S. Department of Transport's value of $11.6 million per avoided death, and a value on the carbon saved by going electric, the math shows that the increase in weight of the truck "rivals the climate benefits of avoided greenhouse gas emissions." Shaffer reminds us that weight matters: "Without addressing the weight issue, the benefits for society of going electric will be smaller than they could be in the next decade."

He also notes heavy vehicles generate more particulate pollution due to tire wear (we have written about this and so has the OECD) and they require more materials to build, which we have noted have many tons of embodied or up-front carbon, not to mention more electricity to fill those big batteries.

Shaffer and his co-authors have a number of recommendations for policymakers and manufacturers.

• Tax heavy cars. This will annoy those who believe we should be doing everything possible to promote electric vehicles, but charging fees on the basis of vehicle weight might discourage the purchase of heavy vehicles. "Varying such charges by weight would maintain revenue while incentivizing people to choose vehicles that are more energy efficient and impose fewer social costs It would also reduce other emissions from materials production and manufacturing."
• Shrink batteries. Shaffer notes that most trips are short, far less than the maximum range of batteries, so why push around all the extra weight? This is probably controversial; people still have range anxiety and might want to take the occasional longer trip. If anything, people want more range than most EVs offer now. Fortunately, batteries are getting lighter and more energy-dense all the time.
• Lighten Frames. This is being done now, as manufacturers use more aluminum and stronger alloys of steel. But Shaffer also notes "aluminum production can have nearly five times the embodied carbon emissions of steel."
• Drive Less. This is one dear to this Treehugger's heart: make alternatives to driving more accessible and attractive. "Policies should ensure that alternatives such as walking, biking and public transport are safer, more convenient, accessible, affordable and reliable. Urban designers should consider the impacts of zoning and development on driving patterns to minimize average distances traveled."

One idea that Shaffer and his team didn't mention, which I think is a big opportunity, is to redesign the car, as Canoo is with their electric car that has the interior capacity of a big SUV and the outside dimensions of a compact car. Most electric cars still have a long hood over the space where the engine used to go, and call it a "frunk." Electric pickups still have a vertical wall of metal as if they are covering a giant V8 and are now just storage.

Shaffer teaches at the University of Calgary, in a province where even the premier wears giant pickup trucks as a badge of honor. I thought his call for smaller, lighter vehicles might be a hard sell there, and noted the criticism I have received when complaining about big electric vehicles. He told Treehugger:

"Yes, it’s always challenging writing a critique, even a partial one, about EVs. Either one side is mad at you for “not caring about the environment”, or another is using your words in bad faith to unfairly push back on the transition. We really tried to emphasize the “win-win” story for electric vehicles, i.e. making them clean *and* safer/lighter."

That is a reasonable approach that I will emulate.

"In terms of taxing by weight, as we noted in the piece, there a couple places starting it, albeit with really meaningless marginal rates. I see some potential there as governments look to replace gas tax revenue with more EVs on the road. They’ll increasingly look to registration fees. There will likely be a (reasonable and sensible, imo) push to charge heavier and higher mileage vehicles more. Hence a weight+mileage based fee."

Given the other pressures caused by big vehicles, including a reduction in parking spaces and increased damage to roads due to their weight, not to mention all the complaining people who walk or bike, it is probably inevitable.