It’s a nightmare situation on a highway: Your car hits a patch of ice and starts to skid. Unable to regain control, you panic as you veer toward the roadway’s edge.
In emergencies like this, guardrails provide a failsafe. As explained in a federal memo, a guardrail will “deflect a vehicle back to the roadway [or] slow the vehicle down to a complete stop.” Your car will probably be damaged, but guardrails can prevent something much worse.
But some modern vehicles can instead smash through these guardrails, new research demonstrates, sending their passengers hurtling toward a ditch, cliff, or whatever is on the other side. The problem is that thousands of miles of guardrails installed alongside American highways were designed decades ago, when vehicles were much lighter than the behemoths that increasingly dominate the U.S. car market. And cars are only getting heavier: Bulkier electrified versions of big cars are poised to arrive in the years ahead. The risk of huge vehicles tearing through guardrails is yet another reason to expect American car bloat to augur an expensive, and dangerous, roadway future.
The new study comes from the University of Nebraska, which received funding from the U.S. Army to examine the impact of electric vehicles on guardrails. The university is a natural location for such research; its Midwest Roadside Safety Facility designed and tested the metal barriers known as the Midwest Guardrail System that are a familiar sight along American highways. The MGS is a beam with a dip running horizontally in the middle—if you think of a guardrail, you’re probably picturing one. “It’s the most frequently used guardrail system, because it’s the cheapest to install and maintain,” said University of Nebraska engineering professor Cody Stolle, noting that all 50 states use it.
The current version of MGS was developed to withstand cars weighing a maximum of 5,000 pounds, but many of today’s SUVs and trucks exceed that threshold. A Cadillac Escalade, for instance, now weighs over 6,200 pounds, and the latest model of the Ford F-150, the most popular vehicle in America, can tip the scales at almost 5,700 pounds. You don’t really want to hit a guardrail with a vehicle like that, but electrification can make things even dicier. Electric cars often weigh around 30 percent more than a gas-powered counterpart, because big vehicles require enormous batteries to propel them hundreds of miles between charges. The goliath-like GMC Hummer EV weighs a staggering 9,083 pounds, 2 tons more than a gas-guzzling H3.
In their study, the University of Nebraska researchers wanted to see whether guardrails can withstand a collision with a big, modern EV. Their answer: No.
Last October, the researchers directed a passengerless 2022 Rivian R1T truck weighing around 7,000 pounds toward an MGS guardrail at 62 mph and a 25-degree angle, reflecting common highway crash conditions. The Rivian demolished the guardrail, passing through it before striking a concrete barrier that the researchers had installed as a backstop.
The silver lining, Stolle told me, was that the Rivian seemed capable of protecting passengers in that test. “The damage to the interior of the vehicle was very low,” he said, “and the occupant risk in that scenario would not be cause for alarm.” But he noted that in the real world, a guardrail is much more likely to be placed next to a steep dropoff than a concrete barrier. If a car penetrates a guardrail and tumbles down an incline, passengers would face far greater danger.
It’s worth highlighting that this study isn’t really about the merits of EVs. After all, you can buy an EV that weighs less than 5,000 pounds. You just can’t electrify your favorite already-large car—or even buy a hulking gas-powered car—and expect guardrails to work as intended. “Weight is a universal problem; it is not unique to electric vehicles,” Stolle said. “We have similar concerns about the compatibility of the biggest gas-powered cars with our guardrail system.” The 6,700-pound Chevrolet Silverado 1500 already weighs too much, based on the result from this research, and the 8,500-pound Silverado EV weighs even more.
A caveat: This is only one study, using a single truck. Still, its implications are troubling, to say the least. As the average American car grows larger, today’s guardrails could fail in more crashes, creating a new highway hazard and worsening an already dire road safety crisis.
Ensuring that tomorrow’s cars do not slam through metal barriers and fly off the highway would require a wholesale upgrade of the nation’s guardrail installations, which Stolle estimated to cover at least 50,000 miles. Assuming a materials cost of $30 per foot, replacing all MGS guardrails could easily hit $8 billion, not including installation expenses that would drive the price tag much higher. (Retrofits could be less expensive, but Stolle said it’s too soon to know if they would be feasible.) To put that figure in perspective, $8 billion exceeds North Carolina’s entire annual transportation expenditures, and is almost six times Maryland’s transportation maintenance budget.
In a statement, a Federal Highway Administration spokesperson showed little interest in assuming responsibility for a future guardrail overhaul, saying that “states and local governments are responsible for properly selecting, installing, maintaining, and replacing roadside safety hardware, including guardrails,” and requesting that further questions be directed to them.
Who will ultimately foot the bill for reinforced guardrails? You, in all likelihood. There is ample precedent, since car bloat is already known to worsen a bevy of societal problems that range from pedestrian deaths to climate change to roadway erosion. Because the federal government has not imposed taxes to address those costs, all Americans bear the financial burdens of oversize vehicles—no matter how they travel.
Car bloat is not a uniquely American problem; SUV sales are rising around the world, notably in Europe. Places like France, Norway, and the District of Columbia have enacted policies that force owners of the biggest cars to pay fees that at least partially compensate for the costs imposed on everyone else (and potentially nudge consumers toward smaller, less damaging models). But Congress and the Department of Transportation have shown no signs of following suit. In the meantime, a prisoner’s dilemma is catalyzing the shift toward vehicular enormity, prodding even those who prefer a modest-size car to get a bigger one simply to avoid being at a disadvantage on the road.
Unless federal policymakers finally acknowledge car bloat’s dangers, the result will be a dirtier, deadlier, and more expensive transportation network. And a lot of busted guardrails, too.
