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How a Celebrity's Tragic Death Led to the Rear Underrun Protection System

Every modern commercial semi-truck is equipped with a Rear Underrun Protection System (RUPS), a rigid metal assembly that hangs down from the back of the trailer. Most people probably don't even notice the RUPS or give it a second thought, but there is actually a fascinating story behind its widespread adoption.

On a warm June night in 1966, actress Jayne Mansfield and her family were on a road trip in her Buick Electra, traveling from Mississippi to New Orleans. They never made it. At 2:25 AMthey suddenly came upon a tractor-trailer moving slowly in the right-of-way. The Buick smashed into it at full speed. The passengers in the front seat, which included Mansfield, suffered a gruesome death. Hollywood lore is that Mansfield was decapitated, but in reality her injuries were even more horrific. The bombshell's sudden demise was a national spectacle, but it also raised an important question. How can we prevent this kind of tragedy?

Enter the Rear Underride Protection System, also known as the Mansfield Bar. The crash that killed the Hollywood star brought to light a serious safety hazard in the commercial truck industry. Due to the height differential, a car that hits the rear end of a trailer will take the force of the impact at its weakest point, the windshield. Anyone unlucky enough to be in the front seat will likely be killed instantly, as was the case in the Mansfield crash. The RUPS prevents this by allowing cars to take the impact on their front bumper, which both prevents the vehicle from becoming lodged under the trailer, and allows the car's safety systems to function as they were intended. This simple innovation has saved untold numbers of lives.

Many improvements have been made to the design and functionality of the RUPS over the years. The IIHS TOUGHGUARD award recognizes the safest underride guards in the industry, providing a high standard for trucking companies to strive for. Though the history of the RUPS began in tragedy, its existence improves the safety of anyone who shares the road with commercial trucks.


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