TUCSON, Ariz. -- 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 sport utility vehicle 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 went 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.
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 investigation by the Los Angeles Times, including 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, according to a leading trailer expert and U-Haul consultant.
Yet U-Haul allows customers to pull trailers as heavy as or heavier than their 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.
The company's approach to mitigating the risks of towing relies heavily on customers, many of them novices and 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 swaying 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.
U-Haul 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. 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.
Still, U-Haul says statistics indicate that drivers towing its trailers are less likely to crash than are other motorists. This is so, U-Haul says, because people drive more cautiously when moving their families and belongings.
Shoen said sway-related accidents almost always result from customer mistakes, primarily failing to load the trailer properly and exceeding U-Haul's recommended top speed of 45 mph. The company said both errors contributed to the Sternberg crash.
"U-Haul customers drive the equivalent of to the moon and back over 10 times a day," Shoen said in a recent conference call with investors, "and, regrettably, accidents occur."
In September 2003, Sternberg, Hollander and Sternberg's boyfriend, Michael Lemons, packed her belongings into a 6-foot-by-12-foot U-Haul trailer.
They noticed the trailer was in "horrible condition," Lemons recalled. Springs in the suspension were so corroded that they resembled "stalactites," he said.
Sternberg called a U-Haul help line, and a representative agreed that she should exchange the trailer. But the next morning an employee at a local U-Haul center made minor adjustments and sent her on her way.
As they left Tucson, the trailer began to rock Sternberg's SUV "like a boat," Hollander recalled.
Late that afternoon, the Toyota reached the crest of a hill on northbound I-25 in the Sevilleta National Wildlife Refuge.
Hollander said she was going 45 to 50 mph and gained speed as she went downhill, reaching 60 mph. The trailer started to swerve. Hollander said she tapped the brakes but could not slow the vehicles. The swaying became violent.
The Land Cruiser flipped, ending up on its side in the passing lane of the interstate.
Experts who examined the trailer for Sternberg's family found that its brakes were badly corroded and inoperable.
Without admitting liability, the company settled the lawsuit in May 2005. Sternberg's attorney Patrick E. Broom declined to disclose the terms.
Shoen said in an interview that the condition of the trailer was "totally unacceptable whether we caused the accident or not."
Alan C. Miller and Myron Levin write for the Los Angeles Times.