Mansfield Bars are an incredible, yet simple safety device added to tractor-trailers. I can guarantee you’ve seen them. If you’ve seen a tractor-trailer, then you’ve seen one of the most important safety innovations made to trailers. So, what is a Mansfield Bar, and what exactly makes them historical?
What is a Mansfield Bar?
Simply put, a Mansfield bar is a large metal bar added to the back of a trailer. They’re also called underride bars or underride guards. Many have red and white paint, although I have seen them without the paint as well. While these look like a handy way to climb up into the trailer, they are actually an incredibly important safety feature.
These bars help stop cars from sliding under the trailer during a crash. If a car rear-ends a trailer without these, there is a high chance the car will be crushed under the trailer. The car will sustain much more damage. And as the bottom of the trailers are right at head height, there’s a much higher chance of dying.
The Mansfield bar catches the car before it can go under the trailer, preventing the cabin of the car from being crushed by the bottom of the trailer. In an era where rear-end accidents are on the rise due to distracted driving, these bars have likely saved hundreds of lives.
Why are they called Mansfield bars?
Before 1967, you may not have seen underride protection. Previously in 1953, the federal government mandated the use of underride guards. However, this legislation had no rules about the strength of the guards, how they were to be attached, or how much kinetic energy they had to absorb.
That began to change on June 29th, 1967. Jayne Mansfield, an up and coming actress, was quickly becoming the darling of Hollywood. She woul never get the chance to be remembered for her acting skills.
Mansfield, her lawyer, driver, and children were driving in New Orleans. It was late and dark. A semi had slowed down on US 90 in reaction to a cloud of mosquito fog. The driver didn’t see the semi, slamming the Buick into the rear of the truck. The Buick slid under the trailer, crushing the cabin. Jayne Mansfield, her lawyer, and her driver were all killed. Her children survived the crash through luck. They had been laying down, asleep, in the rear. As they were not sitting up, they were not crushed. The children were injured and rushed to the hospital. Two of her four dogs were killed as well.
The crash was described as “horrific” by witnesses. The actress was described as “decapitated” but this was refuted by later reports. In actuality, she suffered a shearing injury to her head, causing more of a partial decapitation.
Her death was a shock to the nation. She was being groomed as a counter to Marilyn Monroe. Her grisly death did help spur on greater safety regulations for tractor-trailers. Not long after her death were the underride guards mandated by the government. But that’s not quite the end of the story.
The Story Continues
Despite the mandate for underride guards, many of the Mansfield bars were largely worthless. They were apt to crumble when hit. This made them not nearly as effective as they should have been. They were also not that effective when part of the rear is involved. In 1998, additional rules were put in place. These involved how strong the bars must be and standardized the measurements of the guards.
The IIHS, (Insurance Institute for Highway Safety) noticed this in the early 2010’s and began to push for improved safety. They recommended again strengthening the bars and designing ways to ensure the safety of car drivers in low speed crashes and in crashes where the car does not hit the rear dead on. In 2017 the IIHS started to award the manufacturers for enhancing the safety of these bars.
Others are still not satisfied with underride safety. 2017 also saw the revival of a push for complete underride protection. This would involve side guards as well as the now-standard rear guard.
In 2021, a bill was put before Congress to require side underride guards. This is the third time such a bill was written to mandate the side under guards. The bill is still working its way toward being passed.
As someone who spends thousands of miles on the road each year, additional safety measures are very welcome. With any luck, we won’t need to wait for a celebrity to be killed before new measures are put in place.
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