Underride Accidents are Uncommon but Deadly

Underride accidents, a type of accident involving passenger vehicles and tractor-trailer rigs, are responsible for only about 1% of all highway fatalities annually. However, like their cousin “override” accidents, underride accidents are particularly lethal for the occupants of passenger vehicles involved. In addition, safety groups tend to focus on underride accidents because of the belief that such accidents are preventable, given the proper safety equipment. Underride accidents occur when a passenger strikes a tractor-trailer rig from behind or from the side. Because the trailer in a tractor-trailer 18-wheeler rides much higher than most passenger vehicles, such collisions often result in the passenger vehicle driving under the trailer of the 18-wheeler. This frequently wedges the passenger vehicle under the trailer and essentially cuts the top off the passenger vehicle. Occupants of the passenger vehicles frequently suffer catastrophic, often fatal, upper body injuries, including decapitation. While the federal government has taken some regulatory steps to address the issues, there remain safety groups who are not satisfied with the progress.

Preventing Underride Crashes is Simple, But Complicated

On one level, preventing underride crashes is as simple as installing barriers that make it difficult or impossible for passenger vehicles to drive under the trailer of an 18-wheel rig. Unfortunately, that is not as simple as it sounds. Underride crashes cause far fewer accidents, injuries, and fatalities than do other primary causes such as speeding or driving under the influence of alcohol or drugs. Underride accidents caused an average of 219 traffic deaths annually from 2008 through 2017, accounting for less than 1% of all traffic deaths during that time frame. On the other hand, that number represents more than 5% of all deaths involving large commercial trucks over the same time period. The fact is, underride accidents tend to be fatal, certainly for the people in the passenger vehicles involved.

Federal regulations have long addressed underride accidents, at least in one aspect. Since 1952, trailers on tractor-trailer rigs are required to have underride barriers on the rear of the trailer that are strong enough to keep a passenger vehicle from wedging under the trailer in a rear-end collision. However, there are no similar requirements for such barriers on the sides of trailers. Side underride guards are currently under development, but the solution is more easily envisioned than implemented. Underride guards on the rear of a trailer only need to span the width of the trailer, roughly eight-and-a-half feet. To prevent underride accidents from the side of trailers would require guards that cover most of the length of a trailer on both sides, and trailers are at least 40 feet long and more commonly 48 or 53 feet long. Side guards of that length that are strong enough to prevent a car from crashing under the trailer have, at this point, proven to be far too heavy to be practical. The added weight affects vehicle handling, mileage – already low – and the added weight puts stresses on the trailer frame that render such guards impractical. Until federal regulators finally study the impact, cost, and effectiveness of side underride guards, regulators requiring side underride guards are unlikely to be forthcoming.

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