Accuracy of EDR 5 second Pre-Impact Speed calculations

Decided this might be a good time to add a specific topic on Electronic Data Recorders (EDR) and/or Crash Data Recorders (CDR)
MSI
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Accuracy of EDR 5 second Pre-Impact Speed calculations

Post by MSI »

A recent post on another forum included question on EDR reporting data:
  • For the 5 second pre-impact reporting for speed etc how much scatter is there when a vehicle is yawing and/or skidding pre-impact?
    Does the EDR under or over report?
An excellent topic of investigation.
The pre-impact speed is generally determined by taking an average of the wheel rotation for the drive wheels (front wheels, rear wheels, or ALL wheels).
Things that can affect the recording of wheel speed and calculation of vehicle speed are
  • wheel slip,
  • wheel braking,
  • wheel loss of contact with ground
    • any bumps cause any tire to loose contact with roadway?
  • tire inflation
    • different wheel radius
For a quick look at things, we did a quick check of CISS - the NHTSA Crash Investigation Sampling System Viewer
We found a sample Chrysler report (vehicle 1) which demonstrates wheel rotation differences, etc
Here is the crash diagram
CISS sample.png
CISS sample.png (82.82 KiB) Viewed 4651 times
Here is the last second of Vehicle speed and wheel speeds:
EDR ore impact Speed Closeup -1 to 0.png
EDR ore impact Speed Closeup -1 to 0.png (58.68 KiB) Viewed 4704 times
Here is the overall event:
EDR Pre impact speed -5 to 0.png
EDR Pre impact speed -5 to 0.png (52.71 KiB) Viewed 4704 times
Here is the data from the report pages 17-20
EDR report p 17-20.png
EDR report p 17-20.png (784.53 KiB) Viewed 4704 times

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