Effects of Vehicle Braking on EDR Pre-Impact Speed

[MSI]

In recent crash investigations with EDR pre-impact data and stability control monitoring data, we have found different speed results when we compare the speed of a vehicle based on the EDR reported pre-impact speed and the Speed calculated and/or simulated through applying the pre-impact recorded decelerations from stability control data.
We are planning on presenting our research data and findings at our presentation in 2024:

• Investigating and Supplementing EDR Data with 3D Simulation
• at the 2024 IPTM Symposium

This forum topic will soon include additional detailed information, references and data as we research and prepare for our presentation

Currently a question was asked on another forum about a quote cited by an expert:

• Q: Someone has claimed that the book “Vehicle Accident Analysis and Reconstruction Methods" indicates that speeds during braking can be underreported by Sensing and Diagnostic Modules by 8% to 18% and significantly more at low speeds.”
  

A: We found that quote came from a recent update (2022) of the book:

• Vehicle Accident Analysis and Reconstruction Methods, 3rd addition, Brach, Brach, Mason

The following information is from a quick read of the book with that EDR quote in mind:

• First the introduction from the SAE site on the book:
  • Introduction:
    • "In this third edition of Vehicle Accident Analysis & Reconstruction Methods, Raymond M. Brach and R. Matthew Brach have expanded and updated their essential work for professionals in the field of accident reconstruction. Most accidents can be reconstructed effectively using calculations and investigative and experimental data: the authors present the latest scientific, engineering, and mathematical reconstruction methods, providing a firm scientific foundation for practitioners. Accidents that cannot be reconstructed using the methods in this book are rare.
      In recent decades, the field of crash reconstruction has been transformed through the use of technology. The advent of event data records (EDRs) on vehicles signaled the era of modern crash reconstruction, which utilizes the same physical evidence that was previously available as well as electronic data that are measured/captured before, during, and after the collision. There is increased demand for more professional and accurate reconstruction as more crash data is available from vehicle sensors. The third edition of this essential work includes a new chapter on the use of EDRs as well as examples using EDR data in accident reconstruction.
      Early chapters feature foundational material that is necessary for the understanding of vehicle collisions and vehicle motion; later chapters present applications of the methods and include example reconstructions. As a result, Vehicle Accident Analysis & Reconstruction Methods remains the definitive resource in accident reconstruction."

Here are some quotes in the book related to the Effects of Braking on EDR Pre-impact Speed:

• Chapter 2, Vehicle Event Data Recorders and Longitudinal Slip page 49
  • "Reust and Morgan [2.51] found from their tests that speeds during braking can be underreported by Sensing and Diagnostic Modules (SDMs) by 8% to 18% and significantly more at low vehicle speeds."
    • 2.51. Reust, T.J. and Morgan, J.M., “Detailed Comparison of Vehicle Speed and the Speed Recorded by an SDM,” Collision 2, no. 2 (2007): 32-40.
• Chapter 7 Event Data Recorders and Crash Reconstruction, p242 section Light Vehicle EDR Data
  • which includes:
    • "Considerable testing has been done to measure the effect of the slip generated under ABS-activated braking on the vehicle indicated speed reported by the EDR, with several references cited here [7.16, 7.17, 7.25–7.29] being but a sample.
      Figure 7.3 [7.19] and Figure 7.4 [7.19] show data collected from numerous sources. These data are presented in the plots in absolute terms rather than by percent."
      "These plots both illustrate graphically that the general trend is an underreporting of the vehicle indicated speed reported by the EDR (i.e., more data points below the thick horizontal Precrash Speed Difference line at 0 than above the line).
      The data show that this is true for steady-state driving (no braking) (included in Figure 7.3) but a larger effect for ABS braking conditions (Figure 7.4)."
  • "Examination of the data from the references and the data in the plots indicate that an underreporting of approximately 5% is an appropriate number for the uncertainty associated with the EDR-reported vehicle speed with ABS braking. This number has been reported in other literature [7.20, 7.30]"
    

• Summary
  • "The coverage of the limited topics here serves as an introduction to the nature of EDR data for Light vehicle (LV) and Heavy vehicle (HV) as it pertains to the material presented in this book. Numerous other topics dealing with EDR data are left for the readers to pursue in the literature and in continuing education classes. Some of these other topics include EDR data in low closing-speed colli sions [7.36, 7.37], the relative timing of the data as reported by the EDR, the asynchronous nature of the acquisition and reporting of the data sets [7.29, 7.38] for LV and [7.39] for HV, use of EDR data in pedestrian impacts [7.40], accuracy of EDR with vehicle rotations [7.41], accuracy of EDR data in side impacts [7.42] and EDR data for motorcycles [7.43]. Compendia of EDR articles have recently been assembled [7.44–7.46] that include additional literature."

_______________________
FOOTNOTES
Some of the Chapter 7 References

• 7.25. Lawrence, J., Wilkinson, C., Heinrichs, B., and Siegmund, G., “The Accuracy of Pre-Crash Speed Captured by Event Data Recorders,” SAE Technical Paper 2003-01-0889, 2003, doi:https://doi. org/10.4271/2003-01-0889
• 7.28. Ruth, R. and Brown, T., “2009 Crown Victoria PCM EDR Accuracy in Steady State and ABS Braking Conditions,” SAE Technical Paper 2010-01-1000, 2010, doi:https://doi.org/10.4271/2010-01-1000.
• 7.29. Bare, C., Everest, B., Floyd, D., and Nunan, D., “Analysis of Pre-Crash Data Transferred over the Serial Data Bus and Utilized by the SDM-DS Module,” SAE Int. J. Passeng. Cars - Mech. Syst. 4, no. 1 (2011): 648-664, doi:https://doi.org/10.4271/2011-01-0809.
• 7.30. Ruth, R. and Wright, B., “Using E.D.R. Pre-Crash Data to Calculate the Range for Speed at Impact,” Accident Reconstruction Journal 27, no. 3 (2017): 31-37.
• 7.31. Ruhl, R., Senalik, C., and Southcombe, E., “Numerical Methods for Evaluating ECM Data in Accident Reconstruction and Vehicle Dynamics,” SAE Technical Paper 2003-01-3393, 2003, doi:https://doi. org/10.4271/2003-01-3393.
• 7.32. Reust, T., “The Accuracy of Speed Captured by Commercial Vehicle Event Data Recorders,” SAE Technical Paper 2004-01-1199, 2004, doi:https://doi.org/10.4271/2004-01-1199.
• 7.33. van Nooten, S. and Hrycay, J., “The Application and Reliability of Commercial Vehicle Event Data Recorders for Accident Investigation and Analysis,” SAE Technical Paper 2005-01-1177, 2005, doi:https://doi.org/10.4271/2005-01-1177.
• 7.34. Reust, T. and Morgan, J., “Commercial Vehicle Event Data Recorders and the Effect of ABS Brakes During Maximum Brake Application,” SAE Technical Paper 2006-01-1129, 2006, doi:https://doi. org/10.4271/2006-01-1129.
• 7.35. Reust, T., Morgan, J., and Smith, P., “Method to Determine Vehicle Speed During ABS Brake Events Using Heavy Vehicle Event Data Recorder Speed,” SAE Int. J. Passeng. Cars - Mech. Syst. 3, no. 1 (2010): 644-652, doi:https://doi.org/10.4271/2010-01-0999.
• 7.36. Wilkinson, C., Lawrence, J., Heinrichs, B., and King, D., “The Accuracy and Sensitivity of 2003 and 2004 General Motors Event Data Recorders in Low-Speed Barrier and Vehicle Collisions,” SAE Technical Paper 2005-01-1190, 2005, doi:https://doi.org/10.4271/2005-01-1190.
• 7.37. Wilkinson, C., Lawrence, J., Nelson, T., and Bowler, J., “The Accuracy and Sensitivity of 2005 to 2008 Toyota Corolla Event Data Recorders in Low-Speed Collisions,” SAE Int. J. Trans. Safety 1, no. 2 (2013): 420-429, doi:https://doi.org/10.4271/2013-01-1268.
• 7.38. Wilkinson, C., Lawrence, J., Heinrichs, B., and King, D., “The Timing of Pre-Crash Data Recorded in General Motors Sensing and Diagnostic Modules,” SAE Technical Paper 2006-01-1397, 2006, doi:https://doi.org/10.4271/2006-01-1397.
• 7.39. Plant, D., Cheek, T., Austin, T., Steiner, J. et al., “Timing and Synchronization of the Event Data Recorded by the Electronic Control Modules of Commercial Motor Vehicles - DDEC V,” SAE Int. J. Commer. Veh. 6, no. 1 (2013): 209-228, doi:https://doi.org/10.4271/2013-01-1267.
• 7.40. Fugger, T., Randles, B., and Eubanks, J., “The Efficacy of Event Data Recorders in Pedestrian-Related Accidents,” SAE Technical Paper 2004-01-1195, 2004, doi:https://doi.org/10.4271/2004-01-1195.
• 7.41. Ruth, R., Brown, T., and Lau, J., “Accuracy of EDR During Rotation on Low Friction Surfaces,” SAE Technical Paper 2010-01-1001, 2010, doi:https://doi.org/10.4271/2010-01-1001.
• 7.42. Tsoi, A., Johnson, N., and Gabler, H., “Validation of Event Data Recorders in Side-Impact Crash Tests,” SAE Int. J. Trans. Safety 2, no. 1 (2014): 130-164, doi:https://doi.org/10.4271/2014-01-0503.
• 7.43. Fatzinger, E. and Landerville, J., “An Analysis of EDR Data in Kawasaki Ninja 300 (EX300) Motorcycles,” SAE Technical Paper 2017-01-1436, 2017, doi:https://doi.org/10.4271/2017-01-1436.
• 7.44. Armstrong, C., Ed., Event Data Recorder Interpretation, Volume 7A, Collision Reconstruction Methodologies, SAE International, Warrendale, PA, 2019.
• 7.45. Armstrong, C., Ed., Event Data Recorder Interpretation, Volume 7B, Collision Reconstruction Methodologies, SAE International, Warrendale, PA, 2019.
• 7.46. Armstrong, C., Ed., Event Data Recorder Interpretation, Volume 12—Heavy Vehicle Event Data Recorder Interpretation, Collision Reconstruction Methodologies, SAE International, Warrendale, PA, 2019.