Researchers at the Insurance Institute for Highway Safety (IIHS) recently voiced concern about the safety implications linked to the weight of new electric vehicles (EVs).
Lithium-ion batteries are very heavy and all that extra weight could pose new danger to other vehicles on the road as well as vulnerable road users like pedestrians and cyclists, notes Raul Arbelaez, vice president of the vehicle research center at IIHS, in a recent article.
EVs are on their way to eclipsing sales of conventional vehicles soon, and they will be here to stay. In his article, Arbelaez explores the potential safety problems and possible solutions.
There’s a significant difference between the first all-electric vehicle IIHS tested — a 3,339-pound 2011 Nissan LEAF — and the current generation of EVs, many of which exceed 6,000 pounds. These are large SUVs and pickups, packed with power that requires a massive battery.
The scary issue is the problem this extra weight poses when one of these extremely heavy EVs crashes into a non-electric car or SUV with a typical weight of 3,000-4,000 pounds. When two vehicles collide, the heavier vehicle pushes the lighter one backward, resulting in higher forces on the people in the lighter vehicle and lower forces on people in the heavier vehicle.
Clearly, all that heft on the part of the latest generation of EVs poses a new hazard to traditional vehicles. Moreover, the extra weight may also present a threat to pedestrians and bicyclists, though the danger for them is not as straightforward. The weight differential between a person and any type of passenger vehicle is already so enormous that the additional weight from an EV battery would make little difference in most cases.
That said, it’s unclear whether or not all EVs have braking performance that matches their additional mass. If the extra weight leads to longer stopping distances, that will likely lead to an increase in pedestrian and cyclist deaths — which already have been on the rise in recent years.
Rapid acceleration is another major concern. Today’s supersized EVs are a double whammy of weight and horsepower, notes Arbelaez. While there were many heavy vehicles on our roads before EVs, a delivery truck isn’t designed to go from 0 to 60 in about three seconds — but the 7,000-pound Rivian R1T pickup is engineered to do so. Even the Kia EV6, a small SUV that weighs about 4,500 pounds, boasts the same rapid acceleration.
The bottom line: If the trend toward heavier, more powerful EVs continues, we will soon be surrounded by a plethora of super-heavy, high-acceleration vehicles all around us — including in residential neighborhoods. That, in turn, means collisions involving a huge weight disparity will be much more likely.
EVs are an important step in the evolution of motor vehicles. But due to the weight issue, long stopping distance, and speedy acceleration, Arbelaez says stakeholders should engage in some fresh thinking about the kinds of vehicles we want on our roads.
As a society, we should consider how much mass individuals should be driving around. There are EVs with more reasonable weights. The heaviest of the new EVs are heavier because they are bigger, but also because larger batteries afford them longer range and higher horsepower.
The ability to travel 400 miles on a charge is convenient but unnecessary for most commutes. As charging speed and infrastructure improves, it will arguably be less important for road trips too.
As for horsepower, Arbelaez wonders if the kind of rapid acceleration the new models boast is really important or even a good idea. Vehicles with extreme levels of power simply encourage more speeding, which leads to more fatal crashes.
Also, automakers should consider other design changes to improve crash compatibility. For example, heavier EVs could be built with additional crush space in their front ends to help compensate for the effect of their extra weight in a crash with another vehicle. Additional space would protect not only occupants, but also people in other, lighter vehicles. With no engine taking up space in the front of the vehicle, there may also be more flexibility to design front ends that are less likely to injure pedestrians and bicyclists.
Finally, expected improvements in battery technology will help by allowing smaller batteries to store more energy and an expanding network of fast public chargers will take away some of the need for long ranges in the future.
In the meantime, Arbelaez says manufacturers should equip all new vehicles with high-performing crash avoidance systems that recognize and brake for pedestrians and bicyclists, in addition to other vehicles, and good headlights that allow drivers to react quickly at night. States and local governments should consider lowering speed limits, factoring in the increased danger from weight disparities, and backing them up with increased enforcement.
Originally posted on Automotive Fleet