RICHLAND TOWNSHIP, PA. — Spencer Morrison was a stickler for safety. The middle-school teacher had precious cargo to protect — his 4-year-old triplets, Ethan, Garret and Alaina. Only the best minivan and top-of-the-line car seats would do.

None of that mattered when a trailer — a 3-ton wood-chipper on wheels — broke loose from a truck and careened into oncoming traffic like an unguided missile on April 13, 2006.

It smashed into the minivan and “just blew the vehicle apart,” the local police chief, T. Robert Amann, recalled. Morrison, 37, and two of the triplets died instantly. Ethan suffered a fractured skull and other injuries but survived.

The truck driver, Bradley Demitras, hadn’t checked to make sure the chipper was securely hitched to his vehicle. He also failed to connect the safety chains, which are supposed to keep a trailer attached if the hookup fails. Demitras pleaded guilty to involuntary manslaughter and is serving nine to 18 months in jail.

Runaway trailers are a little-known but persistent cause of devastating crashes, deaths and injuries across the country.

Pinned inside an overturned Ford Explorer on Interstate 5 in Bakersfield, Gabriel Koloszar looked up to see her friend Paulo Aguilar hanging unconscious from his seat belt, his blood dripping down on her.

Rescuers pulled Koloszar out through the windshield. When she tried to stand, another passenger cried out: “Oh my God, Gabby. Your feet!” Only then, she recalled, did she look down to see her mangled flesh.

The trauma of that morning turned to outrage after Koloszar and Aguilar sued U-Haul International Inc., alleging that the accident was caused by a defective tire on the trailer they had been towing.

When their attorneys sought to inspect the tire and rim, they were told that would be impossible.

The evidence had disappeared.

A Kern County Superior Court judge declared in December that he would sanction U-Haul for “extreme negligence” in losing the evidence. Two weeks later, a federal judge in Ohio penalized U-Haul for similar conduct in a separate case.

U-Haul, the leader of the do-it-yourself moving industry, has repeatedly lost, altered or discarded truck and trailer parts sought by injured customers who sued the company, a Times investigation found.

The U-Haul truck was 19 years old, with nearly 234,000 miles on its odometer. It had a history of problems with its emergency brake and was overdue for a safety inspection.

Talmadge Waldrip, 73, of Forney, Texas, was using it to help his daughter move some belongings in September. He drove to a warehouse and killed the engine. Then he put the manual transmission in gear, set the emergency brake and stepped down from the cab, he told family members later.

Instantly, the truck rolled backward. Waldrip tried to climb back in, but the door knocked him to the pavement. The 6-ton truck rolled over his midsection and dragged him, crushing his pelvis.

Nine months and 14 surgeries later, the once-vigorous Waldrip cannot walk and needs round-the-clock care.

U-Haul International Inc. has denied responsibility and says it’s still investigating the cause. Whatever the outcome, the accident shows how the company tries to squeeze the last mile from its vehicles, and how it often fails to meet its own standards for inspecting and maintaining them.

During a yearlong investigation, Times journalists surveyed more than 200 U-Haul trucks and trailers in California and other states and found that more than half were overdue for a company-mandated “safety certification,” a check of brakes, tires and other parts typically required every 30 days.