Analysis of Helmet Impact Velocity Experimental Data and Statistical Tolerance Design

OFF THE WIRE
Great name for a 60's band.... Drop Experience

I think the useful part, for those who go to court, is the experiment reports statistically significant test results from lab to lab. That is info that could be used in court, provided the report is not thrown out as hearsay since the experts who wrote the report are not there to testify.

Is it a worthwhile document to present as evidence? I think it depends on what else you have for evidence and what your strategy is. Some of the prefacing info could be useful to substantiate that FMVSS is not applicable after point of sale, but that the primary proof of that is Title 49 Chapter 301, 30102. Applicabiity and Non-Applicability.

Here's the experiment I'd like to see the results of: There are theories we hear over and over, "the visual test" results vary significantly from one LEO to another, or one county to another, and even from one day to another. Catch a cop having a bad day, and you might have rode past him/her with the same helmet every day for the last five years with no incident, then one day, a ticket quota needs to be filled and "badabing badabang!", you 're ticketed and you don't like it.

Warren Woodward wrote:
Thought you'd need the most up to date info for your helmet manufacturing. You'll be relieved to know that what you've maintained all along is now official -- test conditions, helmet locations, and drop experience are not statistically significant factors.
"Drop experience" - gotta love the lingo.

Analysis of Helmet Impact Velocity Experimental Data and Statistical
Tolerance Design
DOT HS 811 305
April 2010

PDF 19 pages:
http://www-nrd.nhtsa.dot.gov/Pubs/811305.PDF

Abstract Helmet impact velocity experimental data is analyzed and
various factors that influence the impact velocity are studied. One of
the main goals of this report is to verify whether a tolerance of +/- 3
percent of mean velocity is feasible and will allow at least 95 percent
of impacts to fall within the proposed impact velocity range.
Statistical methods are applied to the design of impact velocity
tolerances. Calibration procedures and data variances from several
laboratories are also incorporated into this analysis.

5. CONCLUSIONS
. Experimental data of drop tests indicate that two factors are
statistically significant in influencing impact velocities, the
laboratory at which the test was conducted, and the drop height for each
anvil. Conversely, test conditions, helmet locations, and drop
experience are not statistically significant factors in influencing
impact velocities.
. The experimental design data variances are from both test procedures
used by test technicians and laboratory instruments, and the combined
variances are used to design the velocity tolerance ranges.
. All test laboratories have satisfactory calibration standards
comparable with the NIST standard. Lab A has a slightly smaller impact
velocity deviation compared with Lab B, and both are satisfactory.
. It is determined that on average more than 99 percent of impacts will
fall within the impact velocity range, if the +/-3 percent nominal
tolerance range is adopted, and the velocity interval of 97 percent
nominal to 103 percent nominal is acceptable.