Injury Experience/Crash Performance

Roof Strength / Roof Crush / Headroom Studies

JP Research has had an extensive and high-profile involvement in roof strength research. Jeya Padmanaban has performed numerous statistical analyses of real-world data on relationship between roof strength and occupant injury in rollover crashes.

1995 Roof Strength Study

In 1995, Moffatt and Padmanaban presented a groundbreaking study evaluating the effects of roof strength-to-vehicle weight ratio and aspect ratio on odds of occupant fatality/serious injury in rollover crashes. For that comprehensive study, 60,758 single-vehicle rollover accidents from Florida, Michigan, North Carolina, and Texas were examined to determine the relationship between roof-strength-to-weight ratio and severe occupant injury in rollover crashes. The study concluded there was no relationship between roof strength-to-weight ratio and likelihood of rollover injuries.

2003 Roof Strength Study

In 2003, the 1995 study was updated to include more data, including over 90,000 rollover crashes from eight states. Conclusions supported the 1995 analysis, again finding no relationship between roof strength-to-weight ratio and likelihood of rollover injuries. For details, see Roof Crush Resistance Docket, Submission No. NHTSA-1999-5572-70 (March 4, 2004).

Headroom Study

The 2003 Roof Strength Study also included a headroom analysis, reported separately, that investigated the influence of pre-crash headroom on the likelihood of injury for belted occupants. The analysis concluded that SAE H61 Effective Headroom is not a statistically significant variable in influencing injury for belted drivers, and that roof strength-to-weight ratio remains statistically insignificant.

This research is reported in “Addendum to Docket Submission NHTSA-1999-5572-70,” Roof Crush Resistance Docket, Submission No. NHTSA-1999-5572-79 (April 27, 2004).

Seat Integrated Restraints (SIRS) vs. Conventional Belts

JP Research has performed a detailed statistical analysis comparing the relative effectiveness of SIRS vs. conventional belts in reducing injury risk and ejection risk to belted drivers in rollover crashes. The study concluded that both types of belts are highly effective in reducing injuries / ejections and there is no statistically significant difference between the performances of these belt systems out in the field.

Vehicle Compatibility: USCAR Size/Mass Effects Studies

As part of an unusually complex data evaluation project, JP Research has undertaken a series of vehicle compatibility studies for the United States Council for Automotive Research (USCAR) Safety Working Group. The large, ongoing research project encompasses a series of studies centered on the influence of vehicle size, versus mass, on odds of driver fatality. For these studies, JP Research has investigated 60 vehicle size parameters to determine how vehicle size (separated from mass) affects safety.

The relative importance of vehicle stiffness, along with vehicle mass, bumper height, and other variables, in influencing odds of fatality was evaluated using different definitions for stiffness. Analyses were performed to determine the effect of the various stiffness measures on odds of fatality in two-vehicle frontal crashes.

Alliance Rollover Study

A rollover crashworthiness research project undertaken for the Alliance of Automobile Manufacturers (“Alliance”) Safety Policy Committee used NASS and FARS data to examine the injury experience of belted occupants involved in rollover crashes.

NASS Injury Statistics

At the project’s outset, JP Research developed an accurate statistical estimate of the number of belted occupants seriously injured (AIS 3-6 head/face/neck or torso injury) in rollovers through contact with various injury sources, including “roof contact.” This estimate is presented as an analytical response to estimates made by NHTSA. This phase of the project is detailed in the Roof Crush Resistance Docket, Submission No. NHTSA-1999-5572-119.

In-Depth NASS/CDS Case Reviews

Additionally, an in-depth engineering review was made of individual NASS/CDS cases to explore injury mechanisms to belted occupants in rollovers. To facilitate review of NASS case data, JP Research developed a data management system that allows researchers to quickly extract, summarize, and access relevant information and create comprehensive summaries to aid detailed research. For more information on this project, see Roof Crush Resistance Docket, Submission No. NHTSA-2005-22143-194.