The most commonly used term to describe a vehicle collision in which a passenger vehicle enters the open space beneath the frame of a tractor trailer is ‘underride.’ This event occurs as a result of an incompatibility of two vehicles’ crash absorbing structures. Many passenger vehicles have their crash absorbing structure, typically strongest at or below hood level, and is lower to the ground than the structural parts of a trailer.
Whether or not the impact is to the rear or the side of the tractor trailer, the disparity between crash absorbing structures often results in increased passenger compartment intrusion, especially at shoulder and head level. These kinds of crashes result in a far greater rate of serious and or/fatal injuries than would be expected from non-underride incidents of similar severity.
Frequency of Underride Incidents
In a 2013 study, conducted by the National Highway Traffic Safety Administration (NHTSA), 934 deaths involving underride occurred in 2008 and 2009. Rear underride was documented in approximately 75 percent of collisions in which the striking vehicle was a light vehicle. The underride was up to the base of the windshield in 36 percent of those collisions, according to the source: Heavy-Vehicle Crash Data Collection and Analysis to Characterize Rear and Side Underride and Front Override in Fatal Truck Crashes.
As documented in March 2017, IIHS Recognizes Semitrailers with Good Underride Guards: almost 15 percent of fatal collisions involving a passenger vehicle and a large truck involved a collision with the rear of the truck, according to research by the Insurance Institute for Highway Safety (IIHS). An IIHS review of a smaller sample of fatal crashes found that 83 percent involving the rear of the truck revealed underride involvement.
United States Regulations Currently Set for Underride
Federal Motor Vehicle Safety Standards (FMVSS) 233 (equipment) and 224 (vehicle) were enacted in 1953 and revised in 1998 to regulate what vehicles need an underride guard and the minimum performance requirements of a guard to reduce or minimize the risk of passenger compartment intrusion. These standards require structure to be no more than 22 inches (560 mm) above ground level and 12 inches (305 mm) in front of the rearmost part of the truck or trailer and to withstand the prescribed loading guidelines.
The load requirements for underride guards are about equivalent to the force of a compact car crashing at 30 miles-per-hour (MPH) in a full overlap collision.
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Standards in Canada are similar, but were updated in 2007 to increase the load capacity to that of a 35 mile-per-hour collision. Europe has regulations for side underride guards. Currently, there is no U.S. requirement for side guards, but as reported by IIHS, in 2015, nearly 20 percent of the passenger vehicle occupants killed in two-vehicle crashes with a tractor-trailer, died when their vehicles hit the side of a tractor-trailer. It is reported that IIHS recently tested a newer product that protects passenger vehicle occupants from the dangers of side impact underride collisions.
Underride Incident Investigations
The focus of many underride investigations is to determine if there was a failure in the passenger vehicle’s safety systems or the tractor trailer’s underride guards that contributed to the magnitude of the crash.
The basic step in any underride investigation is a comprehensive reconstruction of the crash. Reconstruction permits investigators to determine delta-V (change in velocity), or the severity of the collision. With a determined delta-V, investigators can compare vehicle damage, injuries, and passenger compartment intrusion, against anticipated values for crashes of a similar severity.
In instances where injuries and intrusion go beyond anticipated values, there may be grounds to investigate potential defects in safety systems. An inspection should be performed if it is suspected that failed underride guards caused the failure by an excessive collision force or a potential defect in design, material, or assembly.
The investigators include Robson Forensic, a national leader in forensic engineering, providing excellent technical expert testimony, and scientific investigation. The company conducts comprehensive investigations into underride incidents and other complex crash scenarios. They lead the way in crash reconstruction, vehicle crashworthiness, materials science, injury biomechanics, human factors, roadway engineering, toxicology, and more.
Legal Advice and Information
If you or someone you know has suffered injuries associated with a vehicular accident involving a passenger car or a tractor-trailer, you may be eligible for compensation. Parker Waichman LLP offers free, no-obligation case evaluations. We urge you to contact our attorneys at 1-800-YOURLAWYER (1-800-968-7529).