As the National Highway Transportation Safety Administration, or NHTSA (pronouced nit-sa) wraps-up its investigation into rollover safety standards, it is looking as if the test procedure for Federal Motor Vehicle Safety Standard (FMVSS) 216 will remain the same in the near term. Two changes were considered; one modest and one quite significant.
The first would have involved applying the simulated rollover load at an angle of 10 degrees front-to-rear (with the front contacting first) instead of the currently-utilized 5 degrees. NHTSA evaluated numerous situations and found that this change would have been inconsequention. While a few quick ?back-of-the-envelope? calculations (using grossly oversimplified geometry) tends to support NHTSA?s conclusion, studies of 273 actual rollovers by Dr. Carl Nash showed that a ?substantial number? included an impact angle of more than 10 degrees. Also, as the A-pillar angle gets steeper, such as on many vans and SUVs, the load application angle becomes more critical. It would be interesting to see what scenarios were considered by NHTSA when making this decision.
The second proposal was to replace the static loading test with dynamic rollover testing, such as that used by Volvo during the development of the XC90 (and of course, dynamic testing has been used for some time for frontal and side-impact crashworthiness testing). This was rejected as NHTSA felt that it would be too difficult to perform such testing in a repeatible manner. Keep in mind that each OEM is ?self-certified? with regards to their FMVSS compliance; that is, they each perform their own tests in accordance with established procedures and report the results to NHTSA.
What remains to be seen is how rollover crashworthiness will be legislated in the future. As Volvo internal documents show, strengthened structures go hand-in-hand with belt pretensioners to improve rollover safety, and both are required for maximum effectiveness.