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All About Mansfield Bars and Their Dangers to Drivers

Since semi trucks and other large vehicles don’t have bumpers, they’re required to install Mansfield bars. But what are Mansfield bars, and how do they protect you as a driver?

Mansfield bars, also known as underride guards, are metal bars affixed to the back of semi trucks and trailers. They’re meant to supplement a bumper and prevent passenger cars from sliding underneath semi trucks in the event of a collision.

Named after the tragic death of actress Jayne Mansfield, Mansfield bars are a topic of debate. Although they can protect against certain serious injuries, many believe they don’t do enough to protect drivers.

While Mansfield bars can prevent passenger cars from sliding under semi trucks, impact with these steel bars is not necessarily a good thing. To keep yourself as safe as possible, avoid driving too close to semi-trucks and their Mansfield bars.

Our lawyers are here to help accident victims get the justice they deserve. For a free case evaluation with the Maryland truck accident lawyers at Rice, Murtha & Psoras, call today at (410) 694-7291.

What Are Mansfield Bars?

Have you ever wondered what those metal bars underneath semi-trucks and other large vehicles are? They’re called underride guards or Mansfield bars, which prevent cars from sliding underneath trucks in an attempt to avoid unnecessary car accident injuries.

Semi-trucks don’t have bumpers. That means nothing stops your passenger car from sliding underneath a semi-truck during an accident.

There’s also nothing to absorb the impact of a rear-end collision, which can prevent certain injuries. That is why Mansfield bars exist.

These metal bars, which are mandated for certain large vehicles, can absorb some impact during a rear-end collision between a passenger car and a semi-truck.

The history of Mansfield bars and their current standards have been debated for many years. While many believe that some form of make-shift bumper is necessary for semi trucks and other large vehicles, some think that the current requirements for Mansfield bars don’t go far enough to protect passenger car drivers in the event of an accident.

The History of Mansfield Bars

Mansfield bars are affixed to trailers and semi-trucks in order to prevent cars from sliding underneath large vehicles in the event of a rear-end collision.

These safety precautions have been altered since being federally mandated decades ago and remain a required fixture for trailers and semi-trucks. Understanding the history of Mansfield bars can help explain the reason for their existence and why they remain a feature of debate today.


As trucking became a booming industry in the latter half of the 1900s, it also became clear that such large vehicles posed considerable dangers to other drivers on the roads.

When passenger cars followed these vehicles too closely and were unable to see around them, thus unable to anticipate potential starts and stops, rear-end collisions happened.

Unlike passenger cars, large semi trucks did not have rear bumpers, meaning there was nothing preventing cars from riding underneath a large truck, resulting in serious injuries.

In response to the growing number of injuries and deaths caused by cars riding underneath semi trucks and trailers, federal guidelines were put into place.

Certain vehicles were mandated to install underride guards, which would become known as Mansfield bars in the future, to prevent unnecessary injuries and deaths.

The first regulations for underride guards were passed in 1953. These guidelines have been updated several times since, to include modern vehicles without bumpers.


Originally known as underride guards, Mansfield bars gained their new name about ten years after they were developed. Unfortunately, a tragic accident resulting in several deaths was the cause of the name change.

In June of 1967, popular actress Jayne Mansfield, along with her children, lawyer, and driver, was driving along the highway late at night. Foggy weather coupled with the dark sky resulted in decreased visibility for the driver.

Lack of visibility made Mansfield’s driver unable to see a semi-trailer ahead of them. Unfortunately, once the semi-trailer came into view, the driver could not respond quickly enough. The car, along with its occupants, rode underneath the semi-trailer. This unfortunate accident resulted in the deaths of all the adults in the car, including Jayne Mansfield.

The tragedy caused a resurgent interest in underride guards and their importance. Quickly, the safety precaution became known as Mansfield bars, as it was thought that if the semi-trailer had underride guards, Jayne Mansfield, her driver, and her lawyer may have survived the crash.

Current Regulations

In 1998, changes were made to the original 1953 safety standards for underride guard safety devices or Mansfield bars. More recently, in 2022, the National Highway Traffic Safety Administration (NHTSA) upgraded the underride system again.

NHTSA increased the required strength of Mansfield bars to reduce potential injuries and property damage to passenger car drivers that collide with underride guards at 35 miles per hour.

Compliance with NHTSA regulations is necessary, and trucking companies are responsible for regularly inspecting the efficacy of the Mansfield bars on their vehicles. Trucking companies must also stay abreast of any changes to NHTSA regulations and update Mansfield bars as safety guidelines change.

Are Mansfield Bars Safer for Drivers?

In theory, the concept of Mansfield bars is favorable to drivers who might otherwise slide underneath semi trucks and trailers and sustain serious injuries. However, current underride guard requirements might not protect all drivers on the road. Whether or not Mansfield bars do enough to keep drivers safe is still up for debate.

Currently, side Mansfield bars are not required for semi trucks and other large vehicles. If a side-impact accident occurs, nothing is stopping a passenger car from going underneath a semi-truck. Mansfield bars do not protect drivers from this possibility, only from going underneath a trailer from the rear.

While meant to supplement bumpers, Mansfield bars are not bumpers. They do not necessarily absorb energy in the same way, nor do they ensure that drivers will not sustain injuries if they rear-end a semi-truck or trailer.

In addition, the height of Mansfield bars does not prevent all passenger cars or vehicles, like motorcycles, from sliding underneath. So, drivers can still sustain serious injuries when involved in an accident with a semi-truck, despite the existence of Mansfield bars.

Underride guards can, and often do protect drivers from fatal injuries. However, these bars can cause severe damage to other vehicles.

Depending on the height of your car, an underride guard could break your windshield. If you are not wearing a seatbelt during the time of an accident, you might make an impact with a Mansfield bar yourself, which can be extremely dangerous.

The general consensus is that while Mansfield bars can prevent accidents and injuries, they may not go far enough to protect all drivers on the road. Although the NHTSA provides guidelines for Mansfield bars, trucking companies can improve upon those guidelines and install bars with better impact absorbency if they so choose.

Current Truck Accident Statistics

Even though Mansfield bars might protect some drivers from serious injuries during semi-truck accidents, they don’t prevent collisions from happening. Remember, underride guards, are situated at the back of a semi-truck and only come in handy during a rear-end collision.

Mansfield bars do not affect the number of semi-truck accidents yearly. It’s possible that underride guards do prevent injuries and deaths in certain situations, although critics of these safety devices would argue they don’t do enough.

The National Highway Traffic Safety Administration, which is the agency that dictates regulations for Mansfield bars, releases updated statistics regarding large truck accidents annually. Interestingly, among all two-vehicle fatal crashes involving large trucks in 2022, the most common impact point on the other vehicle was the front at 32%.

That means that in 32% of fatal collisions, passenger cars collided with the back of a large truck, where Mansfield bars would be. Again, this was the most common point of impact for fatal car accidents involving large trucks in 2020, according to the NHTSA. The NHTSA also found that large trucks were struck in the rear about three times more often than other vehicles during the same year.

In 2020, just under 5,000 people were killed in accidents involving large trucks. According to the NHSTA, this was a one percent decrease in fatalities from 2019. Of the large truck accident fatalities in 2020, about 71% of the deaths were occupants of other vehicles, like passenger cars. Compared to other drivers in 2020, like passenger car drivers and motorcyclists, drivers of large trucks were involved in a higher percentage of fatal collisions.

Even with Mansfield bars, semi trucks are involved in many fatal car accidents each year. So, while underride guards might limit certain injuries in some cases, they do not totally prevent fatal collisions or serious injuries. This is certainly something to keep in mind when driving near semi-trucks and other large vehicles.

Common Injuries from Mansfield Bars

While Mansfield bars can prevent passenger cars from sliding underneath large trucks and trailers, they pose their own risks. Learning about common injuries caused by Mansfield bars is important so that drivers understand the risk of impact.

While they are meant to be safety devices, underride bars might cause injuries in certain circumstances. After all, they are steel bars that sit at about eye level underneath a semi-truck. They can cause serious injuries to drivers upon impact, injuries that might be similar to those victims would sustain if they slid underneath a semi-truck.

Impact with Mansfield bars can result in broken bones, serious head trauma, and even decapitation. The chances of these injuries increase when trucking companies fail to place Mansfield bars at the correct height or when passenger car drivers fail to wear their seatbelts.

The chance of injury also changes depending on the exact impact point. When passenger cars hit Mansfield bars head-on, and all the regulations are met, the chance of severe injury decreases. However, when passenger cars hit Mansfield bars at an angle, the chance of injury increases.

Speed also plays a factor in whether or not passenger car drivers might sustain a serious injury upon impact with Mansfield bars. The current NHSTA guidelines state that Mansfield bars must be able to absorb the impact of a vehicle moving at 35 miles per hour, head-on. If a passenger car collides with Mansfield bars at a higher speed, occupants may be more likely to sustain serious injuries.

What if Mansfield Bars Injured You During an Accident?

If Mansfield bars did not protect you from injury during an accident with a semi-truck, call an attorney. If a semi truck’s underride guards fail to meet NHSTA guidelines, you might be able to file a lawsuit for compensation. Successfully filing such a claim can require a thorough investigation into a trucking company’s negligence, so hiring an experienced lawyer is wise.

Certain vehicles, like semi trucks and trailers, are required to have underride guards in the United States. If a large truck does not have these bars, passenger cars may be more likely to slide underneath, causing serious injuries to drivers. If you were recently injured in a collision with a semi truck because of the vehicle’s lack of Mansfield bars, reach out to an attorney right away.

A lawyer may be able to help you file a lawsuit against a negligent trucking company to recover compensation for your injuries. Remember, certain large vehicles must have Mansfield bars that meet the safety guidelines set by the NHSTA.

Trucking companies must also regularly inspect these safety devices to ensure they work as intended. Failure to abide by the NHSTA’s guidelines is considered negligence and a breach of duty of care owed to other drivers on the road. Therefore, you may be able to file a lawsuit for compensation if Mansfield bars caused your injuries during a semi truck accident.

Call Our Attorneys After a Semi Truck Accident

If you were recently injured in a semi truck accident, our attorneys can help. For a free case evaluation with the Ocean City truck accident lawyers at Rice, Murtha & Psoras, call today at (410) 694-7291.