Q: In looking at the NHTSA crash test database site, I've noted several instances where one of the crush measurements was a negative value of significant magnitude. Can anyone explain why they report the value in this manner. All crashes are 30 mph or 35 mph rigid barrier impacts and in reviewing photographs, the crush profiles seem consistent across the front of the vehicles. All tests were done at different facilities, hence I'm thinking there is a reason for reporting it this way.
A: The question demonstrates some database reporting errors. When you compare the reported values with the values in the full NHTSA report, you will see the error in the reporting process/transcription to the database.
The question emphasizes the need for a careful review of the full report(s) from the NHTSA site (You should use more than 1 test/data point!) NHTSA has a link to the full report for most of the tests. You'll need the actual test number. In the NHTSA reporting there is also listed overall length pre- and post- impact which should provide a clue that the data may be in error.
It is convenient to use 3rd party software vendors for the NHTSA data but that doesn't excuse your duty to take the time to review the actual NHTSA reports and do the calculations independently to verify the veracity of the underlying data and calculation procedures.
Topics related to collision & Trajectory analysis formerly on our 'Registrants only' area however which we get asked about frequently so believe shoud be in the open forum too
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