The sudden rise in car accident deaths could be amplified by a new generation of electric vehicles

by Kyle Stock | Bloomberg

All things being equal, choosing an electric car over a vehicle with an internal combustion engine is likely to be a better move for the planet, thanks to engines that don’t emit greenhouse gases as they go.

But all things aren’t always equal: Battery-powered cars and trucks tend to be much heavier than their gas-burning counterparts. This extra volume translates into a mixed bag of benefits and concerns, especially when it comes to safety. Michael Anderson, a professor at the University of California, Berkeley who co-authored the study “Pounds That Kill: The External Costs of Vehicle Weight,” explained that heavy vehicle passengers tend to be better off in the event of an accident.

“What you’re really doing is pushing the other car you’re hitting out of the way and exposing you to slower deceleration forces,” he said.

At the time of his studies, 2011, Anderson was concerned about what the tide of SUVs and full-size trucks might mean for road fatalities. He was a visionary. In the years that followed, the number of deaths on the roads in the United States rose in parallel with the average weight of an American car. Anderson was less interested in electric vehicles, because he believed batteries would appear first in hatchbacks and sedans such as the Nissan Leaf and Tesla Model S, another thesis that emerged. However, in the next few months, the safety landscape will change dramatically, as many large and heavy electric vehicles hit the streets. By the end of the year, about 18 new battery-powered SUVs and pickups will be available for American buyers to choose from.

“What matters is the mean weight is less than the heterogeneity,” Anderson says. “There may be a window where it is very unsafe to drive (small gas-powered vehicles) and have multi-vehicle accidents.”

Related: Study says SUVs and trucks hit pedestrians more than cars

Consider the GMC Hummer EV, which tips the scales at roughly 9,100 pounds, which is roughly the equivalent of two Chevrolet Silverado pickups. It’s hard to imagine any collision he might be involved in as being a minor collision. Ironically, as more drivers choose big trucks over family cars, some consumers who prefer smaller cars are turning to trucks as a form of defense.

Despite the extra pounds, most of the current crop of electric vehicles lags on mileage in line with — and sometimes better than — gas vehicles of a similar size, according to data compiled by Consumer Reports. There are several reasons for this. Automakers are installing many of these vehicles with larger brakes, for example. Second, electric cars have regenerative braking systems in which electric motors slow the machine slightly while power is being generated. Brembo, which supplies many brakes to automakers, says regenerative systems often fully compensate for the added weight, which is typically at least 10% more than the weight of a similar combustion vehicle.

Finally, electric cars tend to have better weight distribution and lower centers of gravity than gas-powered cars, thanks to the heavy battery that is sealed under the machine’s floor, so the braking force is evenly distributed between the four wheels and the tires have more friction with the road. “All of this counteracts the added momentum,” says Jake Fisher, the engineer who leads the car tests for Consumer Reports. “In a physical equation, it cancels out.”

In Polestar cars, regenerative braking via the engine handles a lot of deceleration, including in relatively sudden stops, Christian Samson, head of product characteristics, said in an email. However, its engineers did not take this into account when deciding the size of the brake lining.

“The friction brakes are dimensional and able to handle all of the car’s brakes despite having the regeneration system, which actually handles the bulk of the deceleration,” Simson explained.

Audi engineers say the regeneration systems in its current electric cars handle up to 95% of decelerations and stops, including about 30% of deceleration in the event of an emergency. The Audi e-tron, for example, stops faster than the company’s Q7 SUV, according to Consumer Reports, even though it’s 14% heavier. In fact, the e-tron’s brakes are used so little that Audi had to design a special protocol to prevent pad wear.

Of course, the stopping distance is only appropriate when the brakes are engaged. If the driver of an electric mammoth vehicle accidentally steps on the accelerator, does not pay attention or cannot see the car’s path well, its full mass will withstand, situations that may be exacerbated by the rapid, violent acceleration most electric motors are capable of. About four pedestrians were killed by left-hand pickup trucks for every fatality caused by a conventional vehicle in the same position. The Insurance Institute for Highway Safety blames poor visibility and links the decade-long increase in pedestrian deaths to overcrowded vehicles.

The problem caught the attention of federal regulators. In March, the National Highway Traffic Safety Administration proposed updating its five-star safety ratings program for new cars. If the change is made, automakers will, for the first time, have to build with pedestrians in mind to score high.

Leave a Reply

%d bloggers like this: