The NTSB determined that the probable cause of the collision in Arkansas last year was the truck's brakes, which had been poorly maintained and inadequately inspected.
Three children died on May 31, 2001, when a tractor-trailer exited Interstate 540 at State Highway 282 near Mountainburg, Ark., failed to stop at the bottom of the ramp, and collided with a school bus.
Eight of the truck's 10 brakes were found to be either out of adjustment or nonfunctional, with four of them unable to provide any braking force, even without taking into account heat buildup and drum expansion that occurred while the truck was traversing hilly terrain.
The driver said he had last adjusted the truck's brakes four days before the crash, and had visually inspected them the morning of the accident. However, the Board found that the driver did not follow recommended practice for measuring pushrod stroke during the pretrip inspection, and a visual inspection did not allow him to determine that the brakes were out of adjustment.
The NTSB recommended that the Federal Motor Carrier Safety Administration revise its regulations to require minimum pretrip inspection procedures for determining brake adjustment.
Some of the brakes had been non-operational for a period of time, and the company's vehicles exhibited evidence of poor maintenance. While the mechanic had one year of experience in brake maintenance, as required by FMCSA, he apparently was not prepared to maintain the truck's brakes in safe working order. The Safety Board recommended that FMCSA require formal training and testing to certify all brake inspectors.
"Commercial truck and bus safety issues are on the NTSB's Most Wanted List of Safety Improvements," NTSB Chairman Marion Blakey said. "Tractor trailers represent 4 percent of all vehicles on the road, yet are involved in accidents that result in 12 percent of highway fatalities. The Mountainburg crash is another example of how poor maintenance, countenanced by inadequate government oversight, can lead to tragedy."
This accident is the latest in a series of investigations in which the NTSB has targeted the inadequacy of motor carrier inspections, including compliance reviews. Federal truck safety officials last conducted a compliance review of the company that owned the truck in 1989. Even the Federal Motor Carrier Safety Administration’s post-accident review did not include any truck inspections, charged the safety board. Like previous investigations involving other companies the Board cited in its report, Stuart Trucking had significant safety defects on the accident vehicle and other vehicles, numerous driver violations, and unqualified brake inspectors, yet was still permitted to operate.
The Board reiterated a safety recommendation it had issued in 1999, which urged the Department of Transportation to change the safety fitness rating methodology so that adverse vehicle and driver performance-based data alone would be enough to result in an overall unsatisfactory rating.
A summary of the board's report is available on the NTSB's website,
www.ntsb.gov. The entire final report will appear on the website in several weeks.