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Research & Data

Biomechanics & Trauma

Additional Information Human Injury Research

Biomechanics & Trauma conducts cooperative and collaborative research with other organizations around the world to develop tools that help mitigate injury and death in motor vehicle crashes.  Crash test dummies are developed and tested, and NHTSA’s fleet of crash test dummies are maintained within this group.

Many motor vehicle occupants are at increased risk of injury due to physical differences that affect their interaction with the vehicle interior and restraints as well as their response and tolerance to crash loading. Older occupants may sustain more severe injuries due to weaker bones and calcified tissues. Occupant shape, which is associated with body mass index, can lead to suboptimal restraint fit. Vulnerable occupant research is underway to identify the unique challenges of protecting all motor vehicle occupants.


Obesity has been shown to affect injury risk in crashes. This study examines the effects of body mass index on seat belt fit by measuring belt fit in a laboratory study of 54 men and women. The results suggest obesity introduces effective slack into the seat belt by routing the belt further away from the skeleton, which may affect injury risk due to more severe contacts with the interior and “submarining” in frontal crashes. Learn more about the effects of obesity and seat belts.


Unattended Children

The transportation authorization law signed on July 6, 2012, Moving Ahead for Progress in the 21st Century Act (MAP-21), stated that the Secretary of the Department of Transportation “may initiate research into effective ways to minimize the risk of hyperthermia or hypothermia to children or other unattended passengers in rear seating positions.” The law specifically mentions technology capable of providing alerts regarding child passengers, which has been a focus of NHTSA research. Efforts have included monitoring the development of technology-based solutions, conducting product evaluations, and development of a generalized test procedure specific to these reminder systems intended to prevent a child from being left behind in a parked vehicle.

  • Press Release
  • NHTSA and Safe Kids Worldwide Encourage Parents and Caregivers to Take Proactive Steps in Preventing Child Heatstroke in Hot Vehicles
  • Functional Assessment of Unattended Child Reminder Systems (DOT HS 812 187) July 2015 Leaving unattended children in parked vehicles can lead to heat stroke and death, even if only left for a few minutes. These completely preventable deaths warrant special attention. NHTSA conducted research to address the problem by investigating electronic reminders. An unattended child reminder system should have the capability to detect the presence of a child in the vehicle and provide notifications intended to prevent a driver from forgetting the child, either when the vehicle is shut off or if the driver leaves the vehicle vicinity. This report describes observations of system capabilities and outlines methods for assessing both add-on and integrated reminder systems, including assessments of commercially available products. The assessments revealed that the reminder systems were able to detect the presence of a child surrogate in the child restraint seat, though some required more attentive setup by the user. Notification types varied, but all of the evaluated systems provided one or more notifications to remind the user of a child’s presence at the end of a vehicle trip. The level of required user interaction varied among the systems tested, though some required no additional input from the user after initial installation. Absent a framework defining key features and operating parameters, developers of these systems lacked a basis on which to benchmark their designs. The knowledge imparted in this new methodology may assist developers in designing more robust products that are marketed and designed as safety systems to protect children from heat stroke risk in automobiles.

Other Resources

According to the Centers for Disease Control and Prevention (CDC) traumatic brain injury (TBI) is an important public health problem in the United States. TBI is frequently referred to as the “silent epidemic” because the complications from TBI, such as changes affecting thinking, sensation, language, or emotions, may not be readily apparent. The most recent CDC report (Frieden et. al, 2010) estimates 1.7 million people sustain a TBI annually, of them 52,000 die. The report finds that among all age groups, motor vehicle-traffic (MVT) was the second leading cause of TBI (17.3%) and resulted in the largest percentage of TBI-related deaths (31.8%).

To address this issue NHTSA developed a Brain Injury Criterion (BrIC).

The following papers and SIMon software are the products of recent NHTSA brain injury research efforts.

"Injury Assessment Tools" - presented at the 2016 NFL Symposium in Washington, DC 

"Brain Injury Mechanisms - Simplified" - presented at the special session Biomechanics of Traumatic Brain Injury of the 2015 Stapp Conference

SIMon FE Keyword Model

A Modern Perspective on Historical Brain Injury Research IRCOBI Keynote presentation (2015)

SIMon: Simulated Injury Monitor (ver 4.0) zip file

Development of Brain Injury Criteria (BrIC), Stapp Car Crash Journal, Vol. 57 (November 2013)

Kinematic Rotational Brain Injury Criterion(BRIC), 22nd Enhanced Safety of Vehicles Conference (June 2011)

Investigation of Traumatic Brain Injuries Using the Next Generation of Simulated Injury Monitor (SIMon) Finite Element Head Model, Stapp Car Crash Journal, Vol. 52 (November 2008)

On the Development of the SIMon Finite Element Head Model, Stapp Car Crash Journal, Vol. 47 (October 2003)

The Crash Injury Research and Engineering Network (CIREN) is a collaborative effort between NHTSA Human Injury Research, trauma physicians, and experts in the fields of impact biomechanics and mechanical engineering. This collaboration collects detailed data on crashes resulting in serious or disabling injury. Explore CIREN in-depth

NHTSA's Anthropomorphic Test Devices (ATDs), or crash test dummies are used to conduct research on issues relating to biomechanics, occupant protection, and crash dummy research, development, and evaluation.

 THOR 50th Male ATD

 THOR 5th Female ATD

 NHTSA's Biomechanics group

Advanced Automatic Collision Notification (AACN) is a system that provides immediate notification of a motor vehicle crash, along with an estimate of the likelihood of severe injury based on vehicular data (e.g. Delta-V). This system can improve the speed and accuracy of dispatch for motor vehicle crashes and can also help get the right patient to the right hospital by assisting EMS providers in determining which patients need the resources of a trauma center. Quickly routing and evaluating AACN crash data can potentially decrease time to definitive treatment and improve crash victims’ chances of survival, while improving the efficiency of EMS and trauma systems as a whole and conserving costs while increasing public safety.


Computer modeling of human tissue could be traced back to 1950s. However, the knowledge of material characteristics and tolerance of human tissue necessary to build and utilize high fidelity human models was lacking up until recently. Stable mathematical codes capable of simulating high energy impacts, such as those occurring in car crashes, also experienced major advances in recent years allowing for simulation of not only the complex kinematics of human body during the crash event, but also predict the onset and severity of potential injury.

NHTSA is one of the sponsors of GHBMC, Global Human Body Models Consortium.

GHBMC is a consortium of seven auto makers and one supplier created to consolidate individual research and development activities in human body modeling into a single global effort to advance crash safety technology.

Lower Extremities

Crash-induced injuries to the lower extremities, while not usually a serious threat to life, often result in long-term disability with substantial economic costs. These injuries still occur frequently in frontal crashes, regardless of occupant restraint condition. Furthermore, the increasing prevalence of knee air bags in modern passenger vehicles has prompted the need to better understand occupant interaction with this type of safety device. The two primary lower extremity research areas include enhancing computational human modeling capabilities and investigating occupant knee air bag interaction. Other modeling efforts involve refinement of the THOR-Lx finite element model.


Recent observations from field crashes in CIREN and NASS-CDS have indicated an increased incidence of lower spine fractures of restrained occupants in frontal crashes involving newer passenger vehicles. An in-depth review of radiology from CIREN cases suggests the injury mechanism for many of these fractures is more compression than flexion, indicating a load application from the seat up through the pelvis. This research seeks to characterize the injury causation scenario and to determine whether available anthropomorphic test devices (ATDs) can recreate the loading a human occupant would experience with different seat designs and crash pulses.