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NTSB Recommends Stability Systems for Cargo Tank Trailers

On the morning of October 22, 2009, a semi-truck pulling a cargo trailer containing 9000 gallons of liquefied petroleum gas overturned 10 miles northeast of downtown Indianapolis. The trailer detached from the truck and penetrated a steel guardrail in the accident. This caused the gas to escape, form a vapor cloud, and ignite into a fireball.

In the ensuing investigation, the National Transportation Safety Board (NTSB) determined that the crash was caused by the driver’s actions in trying to avoid a car in the next lane after the trailer began to cross into the occupied lane. Investigators also found that the trailer’s high center of gravity contributed to the rollover.

The NTSB has been concerned about rollover accidents involving cargo tank trailers for nearly 40 years. The board has long understood that tankers do not allow much for driver error and are highly susceptible to rollovers. In an interview with, NTSB Chairman Deborah Hersman explained that more than 1,300 rollovers occur each year and that these accidents pose a significant safety risk to the public.

While the NTSB has no rulemaking power, it recommended that the Federal Motor Carrier Safety Administration (FMCSA) and the National Highway Traffic Safety Administration (NHTSA) require all cargo tank trailers exceeding 10,000 pounds be retrofitted with rollover stability control systems. The NHTSA is scheduled to publish a proposal specifying technological standards for stability systems for such trailers. It remains to be seen whether the Administration will require Electronic Stability Control (ESC), Roll Stability Control (RSC), or both systems. Each gives drivers better control over cargo trailers in preventing jackknifes and rollovers.

The difference is that RSC only activates when the system detects roll instability, such as when a truck takes a corner too fast or a sudden maneuver causes one side to lose contact with the road. ESC reacts to both roll instability and skids that could lead to a jackknife. In addition to slowing the vehicle to prevent a rollover, it applies the brakes on the wheels needed to counteract the skid.

Regardless of which systems are required, stability control systems are favored by the industry and have proven effective in saving lives. NHTSA estimates that rollover accidents are responsible for 304 deaths and 2,738 injuries a year. The agency believes that stability control systems will save nearly 66 lives a year and prevent almost 1,000 injuries.