List of resources on Interial Unlatching/Release:
When Safety Belts Fail
Ronald Cox tried to stop at the railroad crossing but skidded on ice. The train hit the forward driver’s side of his 1990 Ford pickup and dragged it a short distance before it tumbled down an embankment. His wife said when his seat belt unlatched he was thrown out the passenger side door and fatally crushed by his own vehicle. Ford said it inspected the seat belt and concluded Cox hadn’t been wearing it.
Judith Angelo’s 1986 Cougar was hit on the passenger side by a tractor-trailer switching lanes. The car hit a median barrier, rebounded into the truck and rolled over twice. Her seat belt unlatched, she was ejected and suffered severe spinal cord injuries. Ford said it inspected the seat belt and found “no evidence” she had been wearing it.
An oncoming car attempting a left turn struck the left side of Wendy Wiitala’s (sic) 1982 Lynx. Swerving, the Lynx hit another car, Ms. Wiitala’s seat belt unlatched, and she was ejected from the car. Her injuries rendered her quadriplegic. Ford said it had no opportunity to inspect the car or its seat belt before they were destroyed.
Mrs. Thomas Harkneff and her six-year-old daughter were both ejected from their 1982 Granada when it was hit on the driver’s side and their safety belt buckles unlatched. They sustained concussion and facial injuries. Ford says it has no record of having inspected the seat belt.
Were all these victims lying? Had they all forgotten to buckle-up, as automakers would have regulators and consumers believe, or did their safety belts - and those in countless other crashes - indeed fail in their moment of most urgent need?
Three Decades and Counting…
In 1966, during testimony before the U.S. House Committee on Interstate and Foreign Commerce, Consumer Advocate Ralph Nader rapped the back of a latched safety belt buckle on his knee. It came apart. With that demonstration, the terms “inertial release” and “inertial unlatch” entered the auto safety lexicon. So did the term “parlor trick.” They have been hurled back and forth at each other by automakers and safety advocates ever since.
Nader’s demonstration sought to show that, in a crash, a safety belt buckle can unexpectedly unlatch - at the very moment the car’s occupant most depends on its proper functioning. Automakers responded with derision. General Motors said Nader’s charge was “without foundation.” A Ford vice president called it “ridiculous” and the Nader demonstration a “parlor trick.” They contended then, and contend still, that it does not represent anything that occurs in “real world” crashes, arguing that the tension of taut safety belts prevents their unlatching during a crash.
Crash tests, laboratory tests, mathematical analysis and other evidence demonstrate convincingly otherwise: safety belt buckles can and do unlatch in crashes.
1978: NHTSA Ignores Evidence #1
After an investigation team reported to the National Highway Traffic Safety Administration (NHTSA) that the belt buckle in a 1975 Chevrolet Monza had unlatched in a fatal rollover crash, the agency tested the buckles in three 1975 Monzas. It found that a blow on the back could indeed make them unlatch. The agency then ran 225 tests on the buckles of 32 cars manufactured between 1971 and 1978, striking the buckles on the back with a rubber-tipped plunger: they unlatched 50 times, including 11 times when the belts were drawn taut at 30 pounds of tension.
NHTSA’s conclusion was striking in its denial of the facts: it criticized both the results and the testing techniques as not “realistic” enough and said a better testing method needed to be developed.
The agency also reviewed “real world” crash data and said it found no complaints and no clear evidence that buckles had become unlatched in crashes. It suspended further experimentation.
1992: CBS Hits a Nerve
CBS News began investigating reports of failed safety belt buckles in the summer of 1992 for a “Street Stories” report on its 48 Hours program. When a reporter contacted the American Coalition for Traffic Safety (ACTS), an auto industry lobbying group, for an interview on the issue, the president of ACTS immediately alerted Detroit automakers. Detroit hauled out the 1978-79 findings and drew its biggest guns.
A “Response Team” was formed under the direction of ACTS and a “war room” was staffed. The short term objective, according to an internal Ford Memo: “To keep off the air or delay the program.”
The day CBS interviewed a NHTSA administrator, Ford's Washington, D.C., public affairs office monitored the interview and sent headquarters a blow-by-blow description of it, including off-camera discussion.
Letters were fired off to CBS by ACTS and top auto executives warning of an advertising blitz against the network's report. They mailed similar letters to some 15 key news executives across the country and followed up with telephone calls and requests for editorial board meetings.
NHTSA took the unusual step of repeating to CBS at length and in writing its case that the belt buckles were safe, based on its 1978-79 findings. NHTSA's letter was also sent to other media. A news conference was held in D.C. to counter the charges, again under ACTS auspices, the day after CBS broadcast its report. Full page ads highly critical of CBS were prepared overnight after the report aired and were distributed the next day to national newspapers.
1992: NHTSA Ignores Evidence #2
The day after the CBS report aired, a petition was filed asking NHTSA to do four things:
1. Open a new defect investigation leading to the recall and correction of defective belt buckles.
2. Warn motorists about the "nature and magnitude" of the defect and the hazard it posed.
3. Advise police, researchers and others reporting crash-scene information "that the presence of an unlatched belt following a car crash does not mean per se that the belt was not being worn prior to the crash."
4. Strengthening the governing safety standard, FMVSS 209, whose relevant part now requires only that the "buckle release mechanism . . . be designed to minimize the possibility of accidental release." (Emphasis added. Europe's standard forbids any accidental unlatching.)
NHTSA requested information from Ford and General Motors including: the number of vehicles sold by type of safety buckle; all test results involving safety belt buckles; a description of and the reason for any modifications in buckle design related to the defect, and any complaints or other information on file about "real world" belt buckle failures.
Ford's responses were typical of the industry. It provided a full report on vehicles sold and the types safety belt buckle with which they were equipped, but:
It could find no relevant crash test information, despite internal records showing repeated failures of belt buckles in tests at least as early as "parlor trick" tests in 1971, and a test in 1974 that concluded: "After the seat belt buckle assemblies were impacted a few times, the release spring would weaken, resulting in a lower impact level required for release." (GM also failed to report dozens of belt unlatchings in crash tests.)
It insisted it had made no design changes related to the defect, even though Ford began switching from "side release" (push buttons on the buckle's face) to "end release" (push buttons on the buckle's top edge) designs in the mid-1980s. By 1992, 40 percent of Ford's new cars were equipped with "end release" buckles. It contended the change was for "styling preference" reasons alone. (End-release buckles had already been in wide use in Europe. NHTSA and automakers insist they provide no additional safety.)
It knew of only one buckle failure "allegation," in 1978, but said that buckle had been installed backwards, with its release button against the occupant's body, and that something had struck the back (exposed) face of the buckle to cause it to unlatch. However, the petition asking for the 1992 investigation identified 18 lawsuits alleging that belt buckles had failed in crashes, eight of them against Ford, six against General Motors. Also, Ford's own "Owner Relations/Allegations" database shows a history of customer complaints about buckle failures.
NHTSA ran impact tests on buckles from GM, Ford and Nissan. Buckles unlatched at impact speeds as low as 7.7 miles per hour. In other tests, a human volunteer threw his body hip-first against the buckles 20 times. The buckles unlatched 45 percent of the time.
The agency concluded, however, that the speed at which the body had to impact a buckle to unlatch it was higher than could be achieved in a crash because "properly worn" belts allow only an inch or two of clearance and belt tensions are too high during the crash to permit unlatching. This ignored the reality that belts are almost always worn more loosely than that, and additional slack results from occupants being seated slightly out of position or other factors - for example, the rapid shifts in position that result in multiple-impact crashes and rollovers.
NHTSA again closed its investigation without taking action.
What NHTSA Didn't ‘See'
After examining the record of the 1992 investigation, Syson-Hille and Associates, a private engineering firm, informed NHTSA that:
Seat belt buckles have unlatched in more than a hundred crash tests using dummies, and NHTSA's own data show that these buckle failures occurred at impact speeds similar to those of tests on the buckles themselves when they failed.
Although NHTSA said it had reviewed thousands of crash tests looking for failed buckles, the agency has conducted few tests of the types of crashes likely to result in inertial unlatching - multiple impacts (NHTSA conducts no such tests), and side-impact and rollover crashes (in which test dummies are typically unrestrained.)
Both Ford and General Motors failed to give NHTSA their own test data that showed dozens of buckle failures.
When NHTSA cited its 1978 laboratory testing results, it failed to mention that the tests were run because the agency's own crash investigators had found that a safety belt buckle had unlatched in a real world crash.
The agency said it had done detailed analysis on selected real-world crash reports that indicatedbuckle failure, but inertial release seldom leaves any evidence, and crash reports seldom note the likelihood of belt buckle failure because investigators don't look for it.
Some Hard Facts
Is the problem real or is it, as automakers would have consumers believe, just a "parlor trick"? The evidence is overwhelming that there is, indeed, a problem, and that both automakers and NHTSA know it.
Lab Tests: Mathematical analysis and strobe-light photography of laboratory tests by Blick Engineering and Emtec Corporation concluded that under certain conditions, buckles can unlatch in crashes. The conditions are not unusual in real world crashes, especially rollovers and those involving multiple impacts.
Unlatching can occur if:
At least two inches of slack exists between the belt buckle and the occupant's body. (Five inches of slack and more is not uncommon.) Belt tension is less than 10 pounds. The belt buckle is moving at about the same speed as the vehicle. The occupant's body strikes the buckle at more than 9 miles per hour.
In the tests, buckles swinging from a pendulum against a human hip unlatched 40-50 times at impact speeds between 9 and 15 miles per hour. The engineers noted: "(A)ll subjects stated that the perceived impact force was very low and did not leave any bruises on the impact area."
Air Safety: The Federal Aviation Administration (FAA) reported in 1996 that during an airworthiness inspection it discovered that in seat belt assemblies, "the buckle may inadvertently open on impact, thereby negating (their) safety value…." The buckles, it said, were "not unlike the type…installed in many automobiles, including those manufactured by General Motors and Ford Motor Company."
The FAA field investigator recommended testing all such buckles by pulling the belts taut and striking the face of the buckle, and replacing them "prior to further flight if this test causes buckle disengagement." The FAA said it had looked in vain for "any automotive service bulletin, letter, or recall notice."
Truck Recalls: NHTSA itself, in a 1996 list of safety recalls, included Chevrolet and GMC pickup trucks, listing as the safety defect acceleration forces that had caused seat buckles to unlatch. The recall, presumably, was to reduce the forces, not improve the buckles. Patents: More than 300 U.S. patents and 50 foreign patents for seat belt buckles contain features designed to resist inertial unlatching. At least 50 patents include specific language that the designer's intent is to reduce the likelihood that inertial forces will cause buckles to unlatch in crashes. In 1992, Safetyforum.com informed NHTSA of language in a General Motors patent that calls inertial release "a problem of sufficient magnitude that [industry] would invent and patent these intended solutions."
Europe's Standard: Europe similarly recognizes the problem as real. Its safety standard states that a safety belt buckle "must withstand 5,000 opening and closing cycles…. Its self-release must be impossible, both with the belt slack and under the influence of inertia. The buckle, even when not under tension, shall remain closed whatever the position of the vehicle." The U.S. has no such standard.
False Assumptions: Police and other investigators routinely assume that if a belt buckle is disengaged after a crash, the occupant wasn't wearing the belt. Even if investigators do search meticulously for direct evidence of inertial unlatching, they are unlikely to find it, given that inertial release can occur at impact forces as low as 30 pounds, leaving no trace evidence on either the hardware or the person belted. Automakers' insistence notwithstanding, any conclusion from the lack of such evidence that the safety belt in question was not in use is unwarranted.
Belt Usage Data: Analysis of reported safety belt usage in real world crashes reveals a surprising discrepancy: persons involved in non-rollover crashes are much more likely to be reported wearing safety belts than those in rollover crashes (those more likely to result in inertial unlatching). Almost three-fourths of all car, van and sports utility vehicle occupants involved in non-rollover crashes are reported to have been wearing safety belts, but only a little more than half of those in rollovers.
The data prompted the Syson-Hille and Associates in 1999 to ask that NHTSA reopen its belt buckle investigation yet again. "These data suggest that either the folks involved in rollovers are incredibly careless, or, more likely, that as many as 30 percent of the seat belts originally worn are not remaining fastened in serious rollover accidents," Stephen R. Syson wrote the agency.
'My case by case analysis of more than 100 rollover accidents has resulted in the conclusion that many serious and fatally injured vehicle occupants were reported as being unbelted when, in fact, physical, testimonial and medical evidence proved conclusively that they were belted…. The most likely cause of buckle opening remains inertial separation.'
(03/01/02)
Source: SafetyForum. Available online at: Safety Forum
Inertial Release - Seat Belts Buckles - Page 1
