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Volvo: Safety Beyond the Star Ratings
Electric vehicle batteries add significantly to the weight of vehicles, raising safety concerns among experts.
Heavier, Faster, Less Safe?
American cars have been putting on the pounds. In fact, the US fleet is as heavy as it’s ever been with the average vehicle weighing in at 4,100 lbs. They are also as powerful as they’ve ever been, averaging 275 horsepower. Both of those figures are poised to increase as EVs see broader adoption, which rose to 5.8 percent of new vehicle sales last year and the Biden administration pushing policies targeting a jump to 50 percent of new car sales being EVs by the end of the decade.
Reducing emissions is a laudable goal, and the shift away from internal combustion appears inexorable, however, wide-spread EV adoption will also mean faster, heavier cars on the road, a fact causing concern among industry experts.
EVs Are Putting on the Pounds
Lacking an engine, EVs are mechanically simpler than internal combustion cars. Which is great from an automotive maintenance perspective. But trading that engine for a massive battery pack to power electric motors adds weight to vehicles, a lot of weight. And the larger the vehicle, the larger the battery pack.
The poster child for too big, too heavy EVs is the new Hummer EV which comes in at over 9,000 lbs., that’s around three Toyota Corollas. Despite its extreme weight, the Hummer EV can still rocket from zero to sixty mph in around 3 seconds, such is the torquey power provided by today’s electric motors.
And though the Hummer EV is an extreme case, even converting your average commuter means a significant increase in curb weight. Take the Hyundai Kona for example. Its gas-powered version weighs between 2,899 and 3,327 lbs., depending on the configuration. Its EV version starts at 3,715 lbs. and can reach 3,836 lbs., nearly a half ton more than the base gas model. The F-150, America’s best-selling vehicle, no lightweight itself, gets a whole lot heavier when you add a battery pack. It goes from between 4,021 to 5,740 lbs. to between 6,015 to 6,893 lbs.
Why So Heavy?
So why are car battery packs so darn heavy? Two reasons, current battery chemistry and range anxiety. American car buyers cite range anxiety as a principal barrier to EV adoption. The carmakers’ solution has been to add larger and larger battery packs to extend range, and in the process adding more weight. However, EVs have an inherent paradox with regards to their battery size. Since adding more batteries to the pack adds weight, the vehicle’s energy demand becomes greater. That’s why those heaviest of new EVs like the Hummer EV, Ford Lightning, and Rivian R1T are among the least energy efficient of all EVs. (We’ll get to battery chemistry in a bit, when we look at viable solutions to the EV weight problem.)
Safety Questions Arise
The increasing weight of EVs has safety experts concerned. Jennifer Homendy, Chair of the US National Transportation Safety Board notes that while big and heavy might be good for an EV’s occupants in a crash, big and heavy are bad for whatever that EV crashes into. The greater the mass, the greater the force of impact. Indeed, the National Bureau of Economic Research estimated in 2011 that a 1,000 lbs. increase in a vehicle’s weight increased crash fatality rates by 47%.
Increased speed of EVs only adds to the concern, as Raul Arbelaez of IIHS (Insurance Institute for Highway Safety) puts it, “Vehicles that have higher power and higher power-to-weight ratios have higher crash rates and worse outcomes.” The country has seen a spike in accidents over the past few years, up some 10 percent in the last year alone. Adding faster, heavier EVs could threaten to exacerbate an already growing problem.
Roads & Infrastructure
It’s not just the safety of motorists that will be impacted by heavier EVs, American infrastructure built for lighter vehicles will feel the strain as well. Civil engineers have what’s called the Fourth Power Rule, an equation that calculates how an increase in axle weight results in greater stress (wear and tear) on roadways and bridges. The Fourth Power Rule gets its name from the exponent typical to the formula, which magnifies the road stress of heavy vehicles. For instance, comparing a two-ton car with two axles to a forty-ton semi with five axles (the current max weight being 80,000 lbs.), the semi produces 625 times the road stress as the car does.
What does this imply for heavy EVs? The answer there is twofold. First, it isn’t just passenger cars that are getting electrified, Tesla’s new electric-powered Semi weighs around 27,000 lbs. unloaded with a capacity of between 40,000 and 54,000 lbs. Gas powered semi-trucks range in weight anywhere from 10,000 to 25,000 lbs., which puts the Tesla Semi at the extreme high end. If you noted the combined weight of the Tesla Semi plus payload is more than the federal limit, you’re right. Regulators have given a carve out for electric-powered semi to exceed the 80,000-lbs. limit by one ton to account for the weight of their battery packs and range demands.
On top of this, trucking companies that transport passenger vehicles to market have recently lobbied for a full 10 percent increase in the gross vehicle weight limit, from 80,000 lbs. to 88,000 lbs., due to the increased weight of EVs. This rather than reducing the number of vehicles per shipment.
All this added weight has serious implications for aging roads and bridges. Even small increments in added weight have outsized impacts on road damage. The US Department of Transportation says infrastructure damage geometrically increases with weight, jumping from just 18,000 to 20,000 lbs. results in 50 percent more damage to roadways.
And it’s not just roads, either. Parking infrastructure, aging and designed for the lighter cars of yesteryear, will also come under added strain. The collapse of a hundred-year-old parking garage in Manhattan this past April, though not directly the result of heavy EVs, highlighted for many the problem of a 25 to 33 percent vehicle weight increase that wide EV adoption would represent. Accounting for that increase will mean re-evaluating the structural soundness of older parking garages, with both structural reinforcement and new occupancy limits as likely responses.
Shedding the Weight
That the EVs arriving in greater numbers on American roads result in more dangerous accidents and crumbling roads is not a forgone conclusion. There are solutions to ultra-heavy EVs. First among these would be American car-buyers compromising on the size of their EV purchase. Carmakers have chosen the path of least resistance in marketing new EV models, concentrating on the already popular full-size truck and SUV markets. These large and heavy vehicles only become faster and heavier as they trade internal combustion for electric motors. In other words, the Kona EV is not the problem here.
Since breaking the spell trucks and SUV have over the American psyche is unlikely, the most likely solution to heavy EVs is a change in battery technology. Current lithium-ion batteries are heavy and for every mile of added range, their weight goes up. Solid-state battery technology promises to improve energy density by two to ten times that of lithium-ion batteries, depending on their exact construction and composition. Such increases in energy density will mean solid-state battery powered EVs could offer greater ranges and lower overall curb weights compared to current lithium-ion powered EVs.
Driving Safe, Whether EV or Gas
Of course, solid-state battery powered EVs will be no less powerful. Which gets us to the final piece of the puzzle, drivers. Driving faster and heavier EVs behooves those drivers to be sensible and slow down. While accidents and road fatalities have risen in recent years, the overall composition of the American fleet hasn’t changed nearly as much in that time, meaning those numbers reflect that we have been driving like maniacs. Given the weight and power of the average vehicle on the road is poised to increase with greater EV adoption, educating drivers could be the biggest factor in reducing risk.
