Tucson — MARISSA STERNBERG sits in her wheelchair, barely able to move or speak. Caregivers are always at her side. Progress is measured in tiny steps: an unclenched fist, a look of recognition, a smile for her father.
Nearly four years ago, Sternberg was a high-spirited 19-year-old bound for veterinary school in Denver. She rented a U-Haul trailer to move her belongings, hitched it to her Toyota Land Cruiser and hit the road with her two dogs and a friend.
That evening, as the Land Cruiser descended a hill in the Chihuahuan Desert of New Mexico, the trailer began to swing from side to side, pushing the SUV as if trying to muscle it off the road.
"I knew something bad was going to happen," recalled Corina Maya Hollander, who was taking a turn behind the wheel. "We both knew."
The Land Cruiser flipped and bounced along Interstate 25. The trailer broke free and careened off the road. Hollander crawled from the wreckage, her head throbbing.
Sternberg, who had been thrown from the SUV, lay sprawled on the highway, unable to move.
"Where are my dogs?" she screamed. "Somebody go find my dogs!"
Sternberg fell victim to a peril long familiar to U-Haul International: "trailer sway," a leading cause of severe towing accidents.
Traveling downhill or shaken by a sharp turn or a gust of wind, a trailer can begin swinging so violently that only the most experienced -- or fortunate -- drivers can regain control and avoid catastrophe.
U-Haul, the nation's largest provider of rental trailers, says it is "highly conservative" about safety. But a yearlong Times investigation, which included more than 200 interviews and a review of thousands of pages of court records, police reports, consumer complaints and other documents, found that company practices have heightened the risk of towing accidents.
The safest way to tow is with a vehicle that weighs much more than the trailer. A leading trailer expert and U-Haul consultant has likened this principle to "motherhood and apple pie."
Yet U-Haul allows customers to pull trailers as heavy as or heavier than their own vehicles.
It often allows trailers to stay on the road for months without a thorough safety inspection, in violation of its own policies.
Bad brakes have been a recurring problem with its large trailers. The one Sternberg rented lacked working brakes.
Its small and midsize trailers have no brakes at all, a policy that conflicts with the laws of at least 14 states.
It relaxed a key safety rule as it pushed to increase rentals of one type of trailer, used to haul vehicles, and then failed to enforce even the weakened standard. Customers were killed or maimed in ensuing crashes that might have been avoided.
The company's approach to mitigating the risks of towing relies heavily on customers, many of them novices, some as young as 18. They are expected to grasp and carry out detailed instructions for loading and towing trailers, and to respond coolly in a crisis.
But many renters never see those instructions -- distribution of U-Haul's user guide is spotty.
To those who receive and read it, the guide offers this advice for coping with a swinging trailer: Stay off the car's brakes and hold the wheel straight. Many drivers will reflexively do the opposite, which can make the swaying worse.
Yet when accidents occur, U-Haul almost always blames the customer.
Proper loading of the trailer is crucial in preventing sway. U-Haul tells customers to put 60% of the weight in the front half and suggests a three-step process to check that the load is balanced correctly.
But the company has declined to offer an inexpensive, portable scale that would help renters get it right.
U-Haul vigorously defends its safety record. Executives say that the company diligently maintains its fleet of more than 200,000 trucks and trailers, and that decades of testing, experience and engineering advances have steadily reduced its accident rates.
"Our equipment is suited for your son and daughter," said Edward J. "Joe" Shoen, chairman of U-Haul and its parent company, Amerco. "On a scale of 1 to 10, I'd say U-Haul is rated 10 in safety."
It is unknown how many U-Haul customers have crashed because of trailer sway. No government agency keeps track of such accidents, and U-Haul declined to provide a comprehensive count or year-by-year figures.
But statistical snapshots the company has produced in civil litigation hint at the scope of the problem and show that it has persisted for decades.
In a lawsuit stemming from the Sternberg crash, U-Haul listed 173 reported sway-related accidents from 1993 to 2003 involving a single trailer model.
In a case from the 1970s, the company disclosed 1,173 such crashes involving all trailer types during a 3 1/2-year period.
In other cases, it has listed up to 650 reported sway-related wrecks from about 1990 to 2002 involving two-wheeled trailers called tow dollies.