Jerry S Ogden, PhD, PE | University of Colorado Denver (original) (raw)

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Papers by Jerry S Ogden, PhD, PE

Incident scene documentation presents a challenge to the responding police agency and forensic in... more Incident scene documentation presents a challenge to the responding police agency and forensic investigator alike. The police agency investigating an incident may have the luxury of closing a portion or entire section of roadway while conducting an at-scene investigation. However, the investigating authorities must balance proper scene documentation with timely clearing of the roadway to allow for normal traffic operations, all while maintaining safety for officers, first-responders and recovery operations. The forensic investigator may receive immediate or delayed notification of an incident necessitating a scene visit and documentation. If responding soon after the incident, the forensic investigator must balance the need for thorough documentation while not encroaching upon or interfering with an active police investigation. The forensic investigator's participation may be delayed until after the completion of the at-scene police investigation. Under these conditions, the forensic investigator must consider proper and thorough documentation, traffic safety and time management. This paper provides the field investigator with a comparison between the quality of data obtained, the on-scene time to gather evidence, and the time to process the data into a completed scene diagram while documenting a staged collision event at an intersection between a motor vehicle and bicycle. The engineers of OEC Forensics utilized three common methods of scene documentation for this comparison; digital wheel with 200-foot tape, total station survey, and a high-definition survey (HDS) scan using the FARO Focus S 350.

Since the 1990s, domestic passenger vehicles have been equipped with increasingly more sophistica... more Since the 1990s, domestic passenger vehicles have been equipped with increasingly more sophisticated supplemental restraint system event data recorders (EDRs) that have become more commonplace in collision analysis. Many collision analysts are aware that most heavy commercial vehicles are likewise equipped with heavy vehicle event data recorders (HVEDRs) that may trigger during a hard braking or sudden deceleration event — or when the driver activates a signal to trigger an event to the system. Some heavy commercial vehicle engine manufacturers even provide an additional record of the last stop of the vehicle. Unfortunately, there are no uniform standards as to the information recorded or even the triggering criteria for an event regarding heavy commercial vehicles. HVEDR records oftentimes provide valuable information that assists the forensic engineer in analyzing collision or failure events. This paper provides the forensic engineer with HVEDR engine manufacturer download coverage and tools needed (as of the presentation of this paper), and explores anomalies in event recording that the forensic engineer should be aware may exist. A case study pertaining to an HVEDR record of a commercial vehicle having a peculiar recording anomaly is presented. This paper outlines the process of how the anomaly was resolved and the process of plotting the sequence of events for courtroom presentation

Analysis of vehicle deformation from impacts largely relies upon A and B stiffness coefficients f... more Analysis of vehicle deformation from impacts largely relies upon A and B stiffness coefficients for vehicle structures in order to approximate the velocity change and accelerations produced by an impact. While frontal impact stiffness factors for passenger vehicles, light trucks, vans, and sport utility vehicles are relatively prevalent for modern vehicles, stiffness factors for rear and side structures, as well as heavy vehicles, buses, recreational vehicles, trailers, motorcycles, and even objects, are essentially non-existent.
This paper presents the application of the Generalized Deformation and Total Velocity Change Analysis to real-world collision events (G-DaTADeltaV System of Equations) as developed by this author. The focus of this paper addresses the relative precision and accuracy of the G-DaTADeltaV System of Equations for determining the total velocity change for oblique and/or offset vehicle-to-vehicle collisions involving light trucks and sport utility vehicles, which are largely under-represented with modern vehicle A and B stiffness values for side and rear surfaces. The previous paper presented by this author to the Academy addressed the relative accuracy and precision of the G-DaTADeltaV System of Equations as they relate to a first validation using the RICSAC-staged collision database1 As a secondary and more comprehensive validation process, the G-DaTADeltaV System of Equations will be applied to real-world collision data obtained through the National Automotive Sampling System (NASS), which provides the National Highway Traffic Safety Administration (NHTSA) with a comprehensive compilation of real-world collision events representing a broad-based collection of collision configurations from across the country. This data represents a reusable source of information that was collected using standardized field techniques implemented by NASS-trained field technicians. Through using a "core set of crash data components," NASS has demonstrated its utility and applicability to a vast array of statistical and analytical studies regarding traffic safety and vehicle collision dynamics.

Current methods for analyzing motor vehicle deformation utilize a force-deflection analysis for d... more Current methods for analyzing motor vehicle deformation utilize a force-deflection analysis for determining deformation work energy, which relies on vehicle-specific structural stiffness coefficients determined from full-scale impact testing. While the current database is quite extensive for frontal stiffness values for passenger cars and many light trucks, vans and SUVs from the 1970’s up to modern day, the database is devoid of specific crash tests needed for deformation analysis of rear and/or side structures of many vehicles. Additionally, there exists very few structural stiffness coefficients for heavy commercial vehicles, buses, recreational vehicles, heavy equipment or motorcycles necessary for application with the current force-deflection analysis methods.
The primary goal of this research is to develop an accurate, reliable and broadly applicable deformation analysis method that requires the structural stiffness coefficients for only one collision involved vehicle. The developed methodology expands the application of deformation analysis to include unconventional vehicles and other objects and surfaces not supported by the current structural stiffness coefficient database. The G-DaTAV™ System of Equations incorporates linear and rotational effects, as well as impact restitution resulting from conservative forces acting during a given collision impulse. Additionally, the G-DaTAV™ System of Equations accounts for tire-ground forces and inter-vehicular friction, non-conservative force contributions acting on the collision system that are commonly present during offset and oblique non-central collision configurations.
Correlation and descriptive statistics, as well as the raw analysis results, indicate a highly reliable and significantly improved degree of precision and accuracy achieved through the application of the G-DaTADeltaV™ System of Equations when determining vehicular total velocity changes for oblique and offset non-central impacts.

Methods of reconstructing motorcycle collisions have traditionally been limited to speed from ski... more Methods of reconstructing motorcycle collisions have traditionally been limited to speed from skid
marks, speeds from scrapes or gouges, speed from rider ejection, speed from linear momentum, or
sometimes speed from witness observations. Oftentimes, the data necessary for analysis is either misunderstood
or misinterpreted. This paper tests the applicability of using rotational mechanics and specific
models for motorcycle front fork deformation and vehicle deformation when determining motorcycle
impact velocity. Additionally, the results of these methods are statistically tested for significance and
reliability against independent motorcycle impact test data. NAFE Journal June 2012

Conference Presentations by Jerry S Ogden, PhD, PE

Modern methods for analyzing motor vehicle deformation rely upon a force-deflection analysis to d... more Modern methods for analyzing motor vehicle deformation rely upon a force-deflection analysis to determine deformation work energy. Current methods provide acceptable accuracy when calculating the velocity change of vehicles involved in a collision but require significant modification to accommodate oblique and low-velocity collision events. The existing algorythms require vehicle-specific structural stiffness coefficients for each colliding vehicle, determined from full-scale impact testing. The current database of vehicle structural stiffness values is generated mainly through government safety standard compliance testing and is quite extensive for frontal impacts involving passenger cars and many light trucks and SUVs. However, the database is devoid of specific crash testing necessary for deformation analysis of rear and side structures of many vehicles. Additionally, there remains a dearth of structural stiffness coefficients for heavy commercial vehicles, buses, recreational vehicles, heavy equipment and motorcycles, rendering the application of the current force-deflection analysis approach useless for many impacts involving such vehicles. The research presented, known as the Generalized Deformation and Total Velocity Change System of Equations, or G-DaTA∆V™, develops an accurate, reliable and broadly-applicable system of equations requiring knowledge of the structural stiffness coefficients for only one vehicle, rather than both vehicles involved in a collision event, regardless of the impacted surfaces of the vehicle. The developed methodology is inclusive of non-passenger vehicles such as commercial vehicles and even motorcycles, and it also accommodates impacts with objects and surfaces not supported by the current structural stiffness coefficient database. The G-DaTA∆V™ system of equations incorporates the linear and rotational collision contributions resulting from conservative forces acting during the impact event. The contributions of the G-DaTA∆V™ system of equations are as follows: 1. Consideration of non-conservative contributions from tire-ground forces and inter-vehicular frictional energy dissipation commonly present during non-central collision configurations. 2. Ability to solve for collision energy of a two-vehicle system using a single structural stiffness for only one of the colliding vehicles using work/energy principles. 3. Determination of the total velocity change for a vehicle resulting from a given impact event, which results from conservative and non-conservative force contributions. 4. The ability to predict the time period to reach maximum force application during an impact event, allowing for the determination of the peak acceleration levels acting on each vehicle during an impact. The results of applying the G-DaTA∆V™ to full-scale impact tests conducted as part of the RICSAC collision research will be presented. Additionally, analysis of real-world collision data obtained through the National Automotive Sampling System demonstrates a close correlation with the collision values recorded by the vehicle event data recorders (EDRs) as part of the supplemental restraint system airbag control moducles

Accompanying appendix to presentation July 2013 to the National Academy of Forensic Engineers Adv... more Accompanying appendix to presentation July 2013 to the National Academy of Forensic Engineers Advanced Accident Reconstruction Special Seminar. Appendix demonstrates methodology presented, calculation methods and statistical evaluation of methodology to actual collision tests.

Presentation during July 2013 National Academy of Forensic Engineers Advanced Accident Reconstruc... more Presentation during July 2013 National Academy of Forensic Engineers Advanced Accident Reconstruction Seminar Series. Development of methods for determining the impact speeds and severity levels of minor damage accidents using a specially developed Force-Deflection analysis methodology that incorporates impact restitution and tire force contributions into the collision event. Examples to vehicle-to-vehicle testing are provided.

Methods for reconstructing the speeds of motorcycles from collision events are presented. Methods... more Methods for reconstructing the speeds of motorcycles from collision events are presented. Methods for using rotational mechanics, motorcycle fork deformation and vehicle damage models, as well as rider ejection trajectories are explored. A hierarchy of of analysis methods is presented. Part of the National Academy of Forensic Engineers Advanced Accident Reconstruction Series presented in 2010. Also has an applied mathematics appendix that can be provided upon request.