The term stinger-steered automobile transporters may not ring any bells, but you know them when you see them. Also called “auto haulers,” “car carriers,” and “stingers,” thousands of these vehicles rumble along interstates, lugging cars in the open air.
Auto haulers—I’ll go with that—are a mainstay of the U.S. transportation system, responsible for picking up cars from ports, rail stations, or factories and delivering them to dealerships. They come in a variety of shapes and sizes, with many capable of securing up to nine vehicles.
The companies that manage auto haulers want to fill every slot when they load them up, but that is becoming difficult. American vehicles are growing more massive, and electrification can add thousands of additional pounds to every vehicle. As a result, carriers are increasingly forced to leave slots empty to keep their total tonnage within federal weight limits. Doing so undermines their efficiency, leading to additional trips that burn fuel, spew emissions, and damage pavement.
The trucking and car industries have put forth a solution. A bill they are promoting in Congress would allow auto haulers to carry an additional 4 tons on each journey. That weight allowance would improve the economics of car hauling while reducing total trips and gas consumption—but it would also destroy highway pavement and deepen the country’s traffic safety crisis, which has already placed Americans at greater risk than those in other wealthy nations of being killed in a crash.
Here’s a better idea: Instead of asking taxpayers and road users to shoulder those costs, what if we built more reasonably sized cars? If we did, the auto carriers’ conundrum would disappear. Indeed, the flare-up over auto haulers reveals yet another societal problem traced to the reckless enlargement of American automobiles. Congress should focus on rightsizing vehicle size—not lifting auto hauler weight limits.
Auto haulers are a subcategory of the roughly 4 million heavy trucks that ferry goods between American factories, ports, rail stations, and retailers. As you might imagine, the companies managing auto haulers (and, indeed, the entire trucking industry) prefer every load to be as full as possible in order to maximize efficiency.
But a heavier load comes with costs, particularly from highway wear and tear. The generalized fourth-power law explains why road damage is disproportionately inflicted by the heftiest vehicles. Developed after extensive federal roadway testing during the 1950s, the law is a rule of thumb showing that roadway stress caused by two vehicles is a function of their relative weight per axle scaled to the fourth power. As a result, a single 80,000-pound auto hauler with five axles can cause around 4,000 times the destruction of a two-ton car. (Like all heavy trucks, auto haulers pay considerable federal taxes, but critics have argued that they remain insufficient to cover the costs of pavement abuse.)
Those extra pounds are dangerous for road safety too. Over 4,700 people died in heavy truck collisions in the U.S. in 2021, around 10 percent of all road deaths. “More mass means more energy in a crash, and it means more time to bring the vehicle to a stop,” said Kristin Poland, the deputy director of the National Transportation Safety Board’s Office of Highway Safety. “Both of those are risks.”
Since the 1970s, federal law has limited the weight of heavy trucks—including auto haulers—operated on interstates to 80,000 pounds. (Additional rules constrain weight per axle.) Although an empty auto hauler can alone weigh 40,000 pounds, federal regulations leave sufficient capacity to transport nine Toyota Corollas (around 1.5 tons each) or Tesla Model 3s (around 2 tons). But heavier cars present a challenge: Just six Cadillac Escalades (around 3 tons) could exceed an auto hauler’s legal limit. Carriers can get creative by mixing heavier vehicles with lighter ones, but their wiggle room has shrunk as carmakers have shifted from sedans toward bulky SUVs and trucks.
Eager to fill its vehicles, the auto hauler industry has been asking Congress for over a decade to loosen these federal rules. In 2015 Congress did pass legislation that allowed cars to dangle a few extra feet off the front and rear of an auto hauler, but the 80,000-pound weight limit has remained.
Now auto haulers and carmakers are making a renewed push, focusing their pitch on the billions of dollars in electric vehicle incentives within last year’s Infrastructure Investment and Jobs Act.
“Arguably the only thing Congress did not address [in the infrastructure bill] is the actual transportation of electric vehicles from points of origin such as manufacturing facilities, distribution centers, railheads, and ports to destinations such as dealerships and consumers,” states a letter sent to Congress earlier this year by a coalition including automakers like General Motors, Rivian, and Mercedes-Benz, along with many auto hauler companies.
In April, Rep. Lance Gooden, a Texas Republican, introduced a bill that followed the letter’s requests. The bill proposes a 10 percent increase in auto carriers’ weight limit (which would rise to 88,000 pounds), along with a 10 percent increase in axle weight limits. In their letter, the bill’s industry supporters claimed that passage would annually avoid 16 million miles of auto carrier trips, saving 3.2 million gallons of diesel fuel.
Mike Matousek, who directs the Automobile Carriers Conference within the American Trucking Association, framed the bill as a necessary response to vehicle electrification: “EVs and hybrids, these are cars that weigh more,” Matousek said. “Once you start adding those vehicles to a load, you hit that federal weight limit and you lose capacity.”
He’s right: Electric vehicles’ large batteries make them heavier than their gas-powered counterparts. The Ford F-150 Lightning, for instance, weighs about a third more than an F-150 that runs on gas. However, nothing in the House bill differentiates between electric and gas-powered cars; its passage would lift weight limits for all auto haulers—including those carrying gas guzzlers.
Without passage of the bill, Matousek said, he is unsure how auto haulers will adapt to transport heavier and increasingly electric cars. “Do they bump up their shipping rates? Do they spec a new piece of equipment for transporting vehicles that’s smaller? I don’t know,” he told me. “The hope is to get this additional weight allowance.”
Matousek acknowledged that the bill “would probably require some extra work” for states obligated to provide “reasonable access” on their own roads for heavier auto haulers. SUVs and trucks individually damage state roads more than a modest-sized vehicle, but auto haulers act as force multipliers for pavement destruction. The generalized fourth-power law suggests that a fully loaded, 88,000-pound auto hauler would cause around 46 percent more road stress than one hitting the current 80,000-pound limit. In other words, the bill’s passage would mean that transportation departments should brace for a plague of potholes. (Since the bill does not adjust trucking taxes, it leaves taxpayers to cover the cost of any additional highway repairs.)
The House held a markup session for the bill last month, but passage is still far from assured. Critics have focused largely on the bill’s potential safety risks. The Teamsters slammed it as “a naked giveaway to industry special interests more concerned with profit than the safety of experienced commercial drivers or the driving public.” (The union’s many truck drivers could gain leverage from the additional trips necessary to transport cars on partially full auto haulers.)
Zach Cahalan, the executive director of the nonprofit Truck Safety Coalition, was equally vociferous in his condemnation: “Americans are not asking Congress to compromise public safety to support the environment; only industry has the audacity to make that ask,” he wrote in an email. “Is it really asking too much to be protected from the catastrophic dangers of overweight trucks and to combat global warming at the same time?”
It’s a reasonable question. Indeed, there is another path forward that seems both cheaper and safer: build lighter cars.
Whether powered by gasoline or electrons, American automobiles don’t need to be gigantic; that’s just how automakers are choosing to build them. Vehicular enormity is already causing a slew of societal problems that are borne by the planet (more emissions) and other road users (elevated risk of being killed in a crash). If auto haulers’ weight limits are lifted, we can add a third category: more highway repairs, paid by the general public.
That said, auto hauler companies do face a legitimate problem. It’s in no one’s interest for them to take extra trips—burning millions of gallons of diesel gas in the process—because they cannot utilize their vehicles’ full capacity. But if Congress wants to help, it should leave the weight limit alone and instead focus on incentivizing the production and sale of smaller models. As I’ve argued previously in Slate, weight-based car fees, such as those adopted in Norway and recently proposed in New York state, are a policy tool that could help rightsize the auto market. Not only are smaller cars easier to transport to a dealership, they are also more environmentally friendly and less dangerous to those walking, biking, or inside other vehicles.
The auto carriers’ weight challenges are a problem rooted in car bloat. Better to cure the disease than treat its symptoms.
