EVU XXV 2016 – 11 Evaluation of a common practice – to calculate speed from EDR-reported RPM


Evaluation of a common practice – to
calculate speed from EDR-reported RPM.
Karlon Hagendoorn, Aart Spek, Ewoud Wisse
Accident Reconstruction Team within the Digital Technology
Department of the Netherlands Forensic Institute

Abstract

We investigated a case where a 2010 Lexus IS250, equipped with a 6-speed automatic gear box ran
in the left flank of a crossing car. The Lexus had a 04EDR, which was not yet CDR©-supported at the
time and therefore imaged by Toyota personnel using Toyota’s proprietary tool – the ROT. The ROT
revealed a delta-V of 47.6 km/h and the following pre-crash data:


The 122 km/h value is the maximum that the 04EDR can store. Toyota suggested to us that the true
speed be calculated from engine RPM. Apparently, such a speed-from-RPM-calculation is common
practice in the US and is trained with CDR course material [1]. The calculation relies on the assumption
that only certain RPM-to-speed ratios are possible. For this case and under this assumption, only an
initial speed of more than 194 km/h would allow the EDR-reported RPM-pattern. We were asked by the
court to validate this interpretation.

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AutoreKarlon Hagendoorn, Aart Spek, Ewoud Wisse Accident Reconstruction Team within the Digital Technology Department of the Netherlands Forensic Institute
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