(CNN)Batteries are heavy. That's why, generally, electric cars weigh considerably more than otherwise similar gasoline-powered vehicles. Take the GMC Hummer EV, for instance. The Edition 1 version, which has lots of batteries for additional driving range and power, weighs over 9,000 pounds. That's roughly three times the weight of a Honda Civic.
That has important implications for safety, but it's more complicated than the traditional thinking that revolves around issues of mass and speed.
In terms of crash safety, that extra weight actually helps people inside electric vehicles. Insurance claim statistics show that people in electric vehicles are less likely to be injured in a crash than people in otherwise similar gas-powered vehicles.
This could be attributed to the fact that electric vehicles aren't carrying a large metal engine under the hood, so they have more empty space that can cushion occupants. But the same injury claims trends hold true for hybrid vehicles, said Insurance Institute for Highway Safety spokesman Joe Young. Hybrids also have added weight from batteries as well as an engine under the hood. So the difference seems largely attributable to sheer mass.
But that extra weight can be bad news for people who get hit by electric vehicles, as the added impact force gets transferred to the other, lighter vehicle.
Why heavier is better -- but only for those inside
It's a matter of simple physics. When two moving objects hit one another, the heavier one will tend to carry on in more or less the direction it was going. The lighter one, on the other hand, will change direction abruptly. Even if that lighter vehicle doesn't get smashed in, that jarring deflection is bad for the people inside. Meanwhile, for the people in the heavier vehicle that just punches its way through, that extra weight can be a lifesaver.
Other electric vehicles also weigh more than similar gasoline-powered models. The Ford F-150 Lightning will weigh about 1,600 pounds more than a similar gas-powered F-150 truck. Similarly, the electric Volvo XC40 Recharge weighs about 1,000 pounds more than a gas-powered Volvo XC40.
The GMC Hummer EV Edition 1 has the longest driving range and the most power of any version of that truck, and long range and big power mean a lot of heavy batteries. Those heavy batteries, plus heavy-duty off-road parts, are the reason it weighs so much, General Motors spokesman Mikhael Farah said.
In developing the Hummer EV, a lot of thought went into minimizing the chances of a crash for the sake of both the Hummer's occupants and others on the road, Farah said. For instance, a variety of collision avoidance technologies, such as lane keeping assistance and pedestrian detection, which are available on many modern vehicles, will be standard equipment on the Hummer EV, which will have a starting price of around $80,000.
Of course, vehicles getting heavier is hardly new, nor is it unique to electric vehicles. The average weight of passenger vehicles has been increasing for the past 40 years, according to a report from the Environmental Protection Agency, from an average of about 3,200 pounds to nearly 4,200 pounds. That's largely due to consumer preferences shifting towards trucks and SUVs and those vehicles, themselves, getting heavier.
And it's not weight in itself that's the issue from a safety standpoint. It's the differences in weight between vehicles. That, too, is something that has always existed as long as small cars have shared roads with heavy trucks. When a small car and a truck meet in a crash, the weight difference there is so large it would hardly make a difference if the truck was electric, said David Zuby, senior vice president for vehicle research at the IIHS. But when two passenger vehicles crash into each other, if one of them is carrying 1,000 pounds of batteries, that could make a difference in the outcome.
There are, theoretically, steps automakers could take to soften the blow when heavy electric vehicles crash into lighter gasoline-powered ones, Zuby said. For instance, vehicles could be designed with additional collapsible space beyond what's needed to protect occupants themselves. That could be a tough sell to consumers, though.
"The only way you can do that is by making vehicles bigger than they are," he said, "and bigger in a way that isn't really usable to the person who buys the car."
Hitting the pavement
Heavier vehicles can also have an impact on road surfaces and bridges but experts differ on how much of an issue that will really be. Most roads, highways and bridges are designed to take the weight of huge commercial trucks that are much, much heavier than even the stoutest electric passenger vehicles.
Maria Lehman, an infrastructure engineer with the consulting firm GHD and president-elect of the American Society of Civil Engineers, said that repeated pounding by the extra weight of all these vehicles could take its toll over time, shortening how long road surfaces might last.
"I have more concerns about [Chevrolet] Suburbans that are all-electric than [Chevrolet] Bolts because of the weight," she said. " It becomes the composite effect of all that weight over lots of cycles."
Not to worry, though. David Orr of Cornell University's Local Roads Program said the smallest local two lane roads can easily stand up to the heft of the GMC Hummer EV. Yes, there are more passenger vehicles than trucks but the difference in sheer numbers, even if those SUVs and cars weigh more, still won't hurt the roads.
"It'd have to be a much higher percentage than you think," he said.
Regardless, even if electric vehicles were going to grind down pavement faster, that's a small price to pay for the benefits of a healthier environment, said Doug Mensman, Director of Transportation for the City of Los Angeles.
"If it is going to have to be just additional or more frequent infrastructure maintenance or reconstruction," he said, "then that may be the price that we, as a society decide that we're willing to factor into future budgets to get these benefits."