Vehicle Crash Test Ratings Could Be Impacted by New Testing Formula: IIHS

The risk of brain injuries in accidents may be reduced by new rotational head trauma metrics, which have been used by the NFL to help avoid player injuries.

A new report suggests that the NFL’s method for measuring rotational head trauma could improve vehicle crash test evaluations, providing better insights into how airbags can reduce the risk of traumatic head injuries.

Modern vehicles are designed to protect occupants’ heads, particularly in front-facing car crashes, where the airbag cushions the head as it moves forward, preventing contact with hard surfaces. However, the head can also sometimes whip to the side after striking the airbag, potentially leading to a rotational brain injury.

While crash tests have historically lacked an effective way to measure rotational brain injury risks, a report from the Insurance Institute for Highway Safety (IIHS) suggests that adopting a head injury assessment method used in professional sports could improve crash test ratings and enhance vehicle safety measures.

Crash tests are typically conducted using dummies equipped with sensors in the head, torso, arms and legs, allowing engineers to compare measurements to the types of injuries a human might suffer in an identical crash.

A combination of the sensor data, structures surrounding the occupant, and observations of the dummy’s movement during the crash are used to assign vehicle crash test ratings. In crashes where forces, accelerations or rotations contribute to injury, a mathematical formula analyzes these factors.

Vehicle ratings reflect occupant safety during a crash, with people in vehicles with high ratings being less likely to die than those in poorly rated ones. These ratings also help automakers design safer vehicles, including the use of airbags, which have saved more than 70,000 lives.

New Advancements in Crash Test Evaluations

The Head Injury Criterion (HIC) has previously been used to measure linear impacts and assess the risk of skull fractures from hard impacts, but it does not account for high-speed head rotations.

In 2012, rotational motion sensors were added to test dummies, and the brain injury criterion (BrIC) was used to evaluate the risk of brain injury. However, this formula struggles to identify complex head motions and often does not provide clear insights into how to improve airbag performance.

Since then, the University of Virginia has developed a new rotational head injury metric, Diffuse Axonal Multi-Axis General Evaluation (DAMAGE), which the NFL first adopted to assess helmet performance alongside HIC. DAMAGE has also been part of European New Car Assessment Program crash test ratings since 2022.

Becky Mueller, senior research engineer at IIHS,  and her team applied DAMAGE to crash tests and found it more effective than BrIC in measuring successive movements, such as a head hitting an airbag, sliding off, striking the dashboard, and rotating during the rebound. While BrIC treats these events as simultaneous, DAMAGE accounts for the timeline, preventing an overstatement of their effects.

In an analysis of approximately 800 dummies, DAMAGE, HIC and visual assessments showed good head protection in most front and side collisions. However, for 60 dummies, DAMAGE revealed harmful head motions not captured by HIC, suggesting its potential as a valuable addition to existing evaluations.

The research team suggests that vehicles with a high DAMAGE score could offer solutions to reduce injury risks, such as using a deeper, softer front airbag to cradle the head, reducing rotations, and preventing deflection or sideward whipping.

While DAMAGE is not currently included in crash test ratings, the IIHS will continue monitoring it, with scores recorded for all crash tests starting this year in their technical reports.