Relationship between Frontal Stiffness and Occupant Compartment Intrusion in Frontal Crash Tests James Saunders NHTSA

Outline Background Methodology Vehicle classification Results Future research Conclusions

US Rating Systems NCAP IIHS NCAP IIHS

Background  Nolan and Lund (2001) –Improved performance in IIHS Offset did not affect vehicle stiffness  Verma et al. (2003) –Fixed barriers lead to higher front forces  Saunders et al. (2005) –V-to-V tests had higher partner injuries for redesigned vehicles with improved IIHS offset

Methodology Matched NCAP and IIHS vehicles –Model years 1995 to 2006 Calculated stiffness from frontal NCAP tests –Kw400, KwFinal and KwTotal from barrier force and vehicle accelerometers Maximum toepan intrusion from IIHS Examine relationship between test results –Aggregate by vehicle type and weight ranges

Stiffness Calculations

Vehicle Classifications

Results No overall relationship between Kw400 and toepan intrusion –Pickups were only category with a significant trend Trends were different for compact and full size KwTotal had similar results KwFinal had no relationship to toepan intrusion

Kw400 for Passenger Cars

Kw400 for Sport Utility Vehicles

Kw400 for Different Weight PUs

Statistical Hypothesis Testing Pickups had a different relationship between Kw400 and toepan intrusion

Discussion Eight vehicle categories were used to compare stiffness and compartment intrusion –Only pickups had any trend Different relationship for SUVs and pickups –Many pickups and SUVs are built on the same platform –Vehicle selection and limited sample size may have affected results Mix of body integral and body on frame vehicles

Future Research Examine whether R94 Barrier provides a good measure for heavy pickup and SUV intrusion –Designed for smaller vehicles –Bottoms out during offset tests Compare offset performance using progressive deformable barrier

Dodge Stratus Barrier Deformations R94 PDB

Ford F-250 Barrier Deformations R94PDB

Conclusions Only pickups showed relationship between Kw400 and toepan intrusion Heavy and compact pickups had different rate of change of stiffness per occupant compartment intrusion –Statistically significant