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Volume 14 Issue 1

The International Compendium for Crash Research

Vehicle Damage and Longitudinal Throwing Distances

When Using Biofidelic Dummies In Comparison To Conventional Dummies

Validation of the HAn-Brach Vehicle-ped Impact Mechanics Model Crash-ol-o-gy

Airbag Myths, Legends & Lore

Review of Engineering Mechanics Applied to Accident Reconstruction Parts 1-2

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BONUS MATERIAL https://spaces.hightail.com/space/YydeLCM6Kz Access Code: CMAG14120 Welcome to the Digital Download feature of Collision Magazine. Use the URL and Access Code above to gain access to a private webpage containing additional bonus material for this issue of Collision Magazine. This issue features PDF presentations from the 2020 EDR Summit held in Houston, Texas this past March. Also included are the bonus materials distributed at the Summit.

2020 EDR Summit Material March 9-11, 2020 | Houston, Texas

The annual EDR Summit focuses on Event Data Recorder research, collection and analysis for vehicle crash investigation. This is the only conference in the United States dedicated to users of EDR Tools and other in-vehicle data. The future of safety systems within vehicles on the road today demand a closer look at how they work and how the data collected can be used to assist your crash investigation. The EDR Summit delivers the next steps in advanced EDR technology for vehicle crash analysis. Most importantly, this summit brings together industry experts from around the world to present on timely topics and case studies. Over the years, the presentations have focused on EDR data found in light trucks, passenger cars, SUVs, motorcycles, heavy commercial vehicles, active safety systems, autonomous driving, and vehicle infotainment systems. Privacy, legistation and legal aspects, including mock trials and mock depositions, have also been presented. The EDR Summit is open anyone who has an interest in learning more about event data recorders and how they are used in vehicle safety and crash investigation. As a result, typical attendees of this Summit include law enforcement, insurance (SIU and claims), government, legal and collision reconstructionists. Therefore, if you are involved with the collection and/or analysis of EDR data from vehicle crashes or forensics you won’t want to miss the EDR Summit! www.collisionpublishing.com

Collision Magazine - Volume 14 Issue 1 1

Contents

Volume 14 Issue 1

inside 1

Digital Download Information

Collision Magazine Info and Advertiser Index

Letter From the Editor

features 6

Validation of the Han-Brach Vehicle-Pedestrian Impact Mechanics Model by R. Matthew Brach, David Fortenbaugh and Jon Van Poppel

Vehicle Damages And Longitudinal Throwing Distances When Using Biofidelic Dummies In Comparison To Conventional Dummies by Annika Kortmann and Tim Hoger

Crashology: Airbag Myths, Legends, and Lore by Wesley Vandiver and Robert Anderson

A Review Of Engineering Mechanics Applied To Accident Reconstruction Part 1: Kinematics by Jai Singh

A Review Of Engineering Mechanics Applied To Accident Reconstruction Part 2: Dynamics by Jai Singh

A How-To Guide For Downloading Toyota’s Vehicle Control History Data by Alan Moore

Utilizing BioMedical Engineering Physical Evidence Analysis for Motorcycle Compared to Pedestrian Collision by Laura Liptai, and Mark Ezra

Gasoline-Powered Golf Cart Acceleration and Hard Braking Performance by Robert D Anderson and Michael Rosenfield

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Collision Magazine - Volume 14 Issue 1 3

Validation of the Han-Brach Vehicle-Pedestrian Impact Mechanics Model R. Matthew Brach, David Fortenbaugh and Jon Van Poppel Engineering Systems Inc.

bstract When it was introduced in 2001, the Han-Brach vehicle-pedestrian impact model was fitted to various experimental data to evaluate its performance against test data to establish the empirical parameters utilized in the model. It was also compared graphically to various data sets and other pedestrian impact models to assess the ability of the model to capture the physics of pedestrian impacts. The current research used experimental data generated at the 2017 ARC-CSI conference in Las Vegas, NV, where detailed data were collected from nu-

Collision Magazine - Volume 14 Issue 1

merous vehicle-pedestrian impact tests, to further evaluate and validate the model. These more detailed data facilitate new comparisons of results produced by the model. The analysis showed that the Han-Brach mechanics model captured the dynamics of these experimental trials. Additional insights into the ranges of the empirical parameters used in the model were generated using these new data. In addition to the analysis using the experimental data, three examples are presented in the paper that show various applications of the Han-Brach mechanics model to reconstruct a variety of vehicle-pedestrian collisions.

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Introduction The variety of algebraic formulas and physics models used for the reconstruction of pedestrian impacts can be separated into three categories: 1) empirical models, 2) mechanics models, and 3) multi-body modeling programs. These three categories have also been previously named as Type I, Type II and Type III, respectively.1 Type I models are generally based on fitting a mathematical function to experimental data resulting in some form of a regression equation that relates the speed of the vehicle to the throw distance (or vice versa). Various accounts of Type I models are available in the literature.3, 4, 5 Numerous Type I models were compiled into a software application.6 Type II models are based on the principles of engineering mechanics including impulse-momentum and rectilinear motion. These models also relate the speed of the vehicle to the throw distance of the pedestrian (or vice versa). Type III models are also based on principles of mechanics, but these models treat the pedestrian as a multibody system and allow for the geometry of the vehicle that interacts with the pedestrian to be explicitly modeled with high fidelity.15 These models may also incorporate finite element methods. Numerous publications exist for each of these three categories and deal with one or more of the generally recognized pedestrian impact configurations: wrap, forward projection, fender vault, roof vault, and somersault.2 The introduction of Type III models is more recent and, due to the complexity of the models, is largely based in dedicated, commercially available software that runs the models. The three most common software programs in the field of crash reconstruction that include these models are MADYMO,7 PC-Crash 8 and HVE.9 Various publications dealing with these programs present the theory behind the models and explore the applicability and validity of these programs.10,11,12,13 Some publications take a broader approach and assess all three types of vehicle-pedestrian accident reconstruction methods.14,15 One paper considers the use of a Type II model to evaluate the results of analysis done using a Type III model.1 The research presented here focuses specifically on the development of the Type II models (mechanics models) used for the reconstruction of vehicle-pedestrian crashes and the validation and use of one of the models specifically (Han-Brach).19 The focus on mechanics models is motivated by a need for a useful method for reconstructing vehicle-pedestrian crashes that incorporates variables

and parameters that accommodate the range of physical evidence available after a crash. For example, if the longitudinal ∆V of a vehicle involved in a crash with a pedestrian were known from imaging the event data recorder (EDR) post-crash, this physical evidence cannot be used with empirical models as empirical models do not contain this parameter. Type III multi-body models can incorporate these data, but these tools generally require considerable training and practice to master, and in some cases, significant expense. These Type III models are particularly useful when the motion of the pedestrian (arms, torso, head, etc.) or the interactions between the pedestrian and the vehicle (i.e. hood and/or windshield deformation) need to be analyzed. Vehicle-Pedestrian Mechanics Models Examination of the literature associated with mechanics models for vehicle-pedestrian collisions shows that one of the first publications that presented this topic was the section on pedestrian throw in the book by Collins.16 In this treatment, Collins presented an equation for the throw distance with two components: one component related to the horizontal distance traveled during the airborne trajectory and a second equation for the travel of the pedestrian along the roadway prior to coming to rest. The next paper that tackled this topic was written by John Searle and Angela Searle.17 In that paper, the authors presented a theory for the total trajectory of the pedestrian from impact to rest. The equation presented there provides the speed of the vehicle at impact as a function of the throw distance. The equation is: (1) In this equation, µ is the frictional drag coefficient between the pedestrian and the roadway, S is the throw distance (the total travel distance of the pedestrian from impact to rest), V is the initial velocity of the pedestrian at separation from the vehicle, and θ is the launch angle of the pedestrian relative to the roadway. In the derivation, the height of the center of mass of the pedestrian at impact is assumed to be level with the roadway. In this equation, the value µ applies to the total throw distance, not just the portion of the throw distance in which the pedestrian is engaging the roadway. In a later paper,18 Searle presented the derivation of an alternative formula that also relates the vehicle speed to the throw distance

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Collision Magazine - Volume 14 Issue 1 7

Gasoline-Powered Golf Cart Acceleration and Hard Braking Performance Robert D Anderson and Michael Rosenfield

ntroduction Low speed vehicles (LSV) have been thought of as a low-cost, eco-friendly way to tool around in locations where there would be little interaction with larger vehicles. As of 2010, practically every state allowed LSVs on roadways with speed limits up to 35 mph.1 LSV use on public roads experienced rapid growth since the phenomena began in resort and retirement communities in the 1990’s.2 The standard golf course cart is typically limited by speed governors or gearing to a top speed of 15 mph. Many LSVs are essentially souped-up golf carts.1 An LSV typically has a top speed between 20 and 25 mph, a limited GVWR, and has additional equipment to make it street legal, such as lights, signals, mirrors, windshield, seat belts and a horn.3 Unlike passenger motor vehicles, LSVs are not required to meet Federal Motor Vehicle Safety Standards,4 and golf cart-related injuries have steadily increased with the increased popularity and growing capabilities of these vehicles.5 A compilation of electric golf cart and scooter acceleration, hard brake, stability testing and specifications was presented in Volume 12, Issue 1 of Collision.6 This current study is intended to add to the existing published information by providing acceleration and braking performance, and specifications of gasoline-powered golf carts. The EZ-GO Marathon is a golf cart that is representative of the type found at a golf course. The EZ-GO RXV’s used in this testing were advertised as street legal and they were equipped with headlights, tail lights, turn signals, and a horn, but they did not have a windshield, mirrors or seat belts installed. All test vehicles (Table 1) were gasolinepowered. Model Year 1990 2009 2009

Make and Model EZ-GO Marathon EZ-GO RXV EZ-GO RXV

Wheels and Tires Stock Stock Over-size

Table 1: Test Vehicles

Instrumentation Test vehicles were instrumented with Racelogic data loggers VBOX 3i, Video VBOX Lite, and VBOX Sport (Fig22

Collision Magazine - Volume 14 Issue 1

ure 1). These data loggers measure and record vehicle speed using the Doppler shift of GPS satellite signals. The sample rate for the VBOX 3i, Sport and Video Lite is 100Hz, 20Hz and 10Hz, respectively. For all three data loggers, the Racelogic reported accuracy for acceleration is ±1% or better, distance traveled ± 0.05%, and speed ± 0.13 mph or better when smoothed with a moving average of 4 samples.7,8,9 The VBOX Lite has the additional ability to record video from up to two cameras allowing a low-resolution image to be viewed as a picture within a picture of a high-resolution image. The video may also be overlaid with virtual gauges, such as a speedometer. The VBOX Sport is waterproof and can be used with its internal GPS antenna or with an external GPS antenna. Vehicle weights were measured with Intercomp Microflex (Micrflex scales) or Intercomp SW scales (SW Scales). The Microflex scales have a 4,000 pound per wheel capacity and the SW scales have a 1500 per wheel capacity. The Intercomp scales report weight in 1-pound increments with a 0.1% accuracy. EZ-GO Marathon The 1990 EZ-GO Marathon is golf course-style golf cart. It had been traveling at top speed in a neighborhood when it rear-ended an occupied stationary minivan parked in the shadows. It was not equipped with seat belts, turn signals, or a horn (Figure 2). The gasoline engine is under the seat, and powers the rear wheels through a CVT belt-drive transmission, with forward and reverse gear selection. Brakes are mechanical drum brakes on the rear wheels. The specifications for the EZGO Marathon are shown in Table 2. Like the electric-powered version, the EZGO Marathon Golf Cart is equipped with rack and pinion steering. The steering wheel had approximate 1½ turns in each direction, which produced approximately 45 degrees of wheel turn in each direction so that the steering gear ratio was approximately 1:12. The EZGO golf cart was instrumented with a Video VBOX Lite and a VBOX Sport. The weight was measured to be 794 pounds using SW scales. Performance was dem-

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Figure 1: VBOX 3i, VBOX Sport, and Video VBOX Lite (left to right) onstrated through a series of hard accelerations from a stop and hard braking (skidding) to a stop. All runs were conducted on level asphalt and unpaved clay roadways with a 200 pound driver. The engine did not idle, so the engine stops running when the accelerator is released. When depressing the accelerator pedal, there was a delay associated with the engine/CVT transmission startup that was not measured on this vehicle.

A top speed of about 14 mph was achieved in about 7 seconds and 90 feet with a 200 pound driver (Figure 3, Figure 4, and Figure 5). Acceleration peaked at about 1.4 seconds and ranged from 0.14 to 0.19 gs and then dropped quickly (Figure 6). The average acceleration to top speed was 0.075 gs.

Hard braking with rear wheel skidding on the asphalt roadway produced accelerations of about -0.30 to -0.34 gs. Hard braking with rear wheel skidding on the unpaved clay roadway produced accelerations of about -0.25 gs. Deceleration while coasting was measured to be about 0.07 gs. The brakes could overpower full accelerator pedal application so that simultaneous hard braking and full accelerator pedal application was indistinguishable from braking alone.

The 2009 EZGO RXV carts were for sale at a dealership and they were advertised as street legal. The carts had street legal equipment including head lights, horn, tail lights, brake lights, and turn signals, but did not have windshields, mirrors or seat belts installed (Figure 7). Both were equipped with rear-facing rear seats. The white cart was equipped with stock 8-inch tires and the red cart was equipped with 12-inch tires. The engine is under the seat, and powers the rear wheels through a CVT belt-drive transmission, with

EZGO RXV

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Collision Magazine - Volume 14 Issue 1 23

A REVIEW OF ENGINEERING MECHANICS APPLIED TO ACCIDENT RECONSTRUCTION Jai Singh, PART 1: KINEMATICS BS, MS, MA, ACTAR Biomechanical Engineering Analysis & Research, Inc.

bstract The subject paper is the first in a series of three papers detailing the application of engineering mechanics, specifically rigid body dynamics, to the field of accident reconstruction. The focus of the subject paper is the development and presentation of the solutions for rigid body kinematics. This presentation is within a framework that explicitly notes the expression frame for each vector quantity along with the derivative frame, when applicable. The two reference frame problem (i.e. a body fixed frame of reference for a rigid body undergoing free motion with respect to an inertial frame of reference)

Collision Magazine - Volume 14 Issue 1

serves as the primary context. In this regard, the presentation proceeds by first stating the two point position vector problem and by defining the direction cosine matrix. The latter is one of the most general methods for representing a change in orientation kinematics. The frame referenced first time derivative is presented and contrasted against the standard non-frame referenced time derivative approach. An important result from the presentation is the derivative transport theorem. This is followed by the presentation of the frame referenced second time derivative. Finally, the solutions for the first and second frame referenced time derivatives are presented for the multibody problem.

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Introduction Engineering mechanics, and specifically dynamics, plays a central and critical role in a large number of typically encountered tasks in the fields of accident reconstruction and biomechanics. This includes, but is not limited to, modeling and understanding vehicle dynamics 16-17, 23, 38, 42 , modeling collision phase responses 2-15, 20, 26-27, 34, 39-40, 44-46, modeling and understanding occupant kinematics 41 and using instrumentation (e.g. accelerometer) data. 1, 19, 33, 35-37, 43 The mathematics that underpins each of these broad contextual areas of application also applies to common tasks that can readily be considered as being preparatory for performing an accident reconstruction. As a simple example in regards to the last statement, consider a situation in which the start and end of a linear tire mark have been measured at the scene of an incident and with the measurements taken with respect to perpendicularly aligned curbs or curbline prolongations. The vector from the start of the tire mark (ra) to the end of the tire mark (rb) is defined as rb – ra = rb|a. The referenced curblines or their prolongations form a planar (i.e. R2) frame of reference with origin located at the intersection of the referenced curblines or their prolongations and with each curbline or prolongation representing a coordinate axis. Suppose, now, that this information is imported into a software package that has its own coordinate system. Furthermore, assume that the software coordinate system is not coincident with the measurement coordinate system and that the origins are not located at the same physical location. For the planar case, this situation is depicted in Figure 1.

Figure 1: A hypothetical linear tire mark starting at a and terminating at b. The reference frame (oxy) represents the measurement frame (i.e. the frame of reference in which the coordinates of a and b were measured). The reference frame (OXY) denotes a second frame of interest for which the origin is not collocated with o and for which the coordinate axes have a differing orientation from xy. If the software package that was being utilized did not have the capability for assigning new coordinate frames and/or one were asked to explain the underlying mathematics that were being implemented in the assignment of coordinate locations in the new coordinate frame, what would one say? In the first, the tire mark, as a physical entity, is unchanged by the choice of reference frame. Also, the vector rb|a, itself, is not changed by the reference frame. What does change, with a change in reference frame, are the directions along which the coordinate measurements are made or calculated and the scalar distances from each coordinate axis. Intuitively, one can reach the conclusion that the process of assigning new coordinate locations would be a function of the distance between the origins of each coordinate system (translation) and a function of a measure or metric that relates the orientations of the two coordinate systems (rotation). This relatively simple coordinate transformation problem is intrinsic to the mathematics that are employed in the field of engineering mechanics. www.collisionpublishing.com

Collision Magazine - Volume 14 Issue 1 35

linear accelerometers. Journal of Applied Mechanics 42(3): 552-556. 37. Park S and SK Hong (2011) Angular rate estimation using a distributed set of accelerometers. Sensors 11: 10444-10457. 38. Rajamani, R (2012) Vehicle Dynamics and Control (2nd ed.) New York, New York: Springer. 39. Rose NA, SJ Fenton and RM Ziernicki (2004) An examination of the CRASH3 effective mass concept. SAE Technical Paper No. 2004-01-1181. 40. Scurlock BJ and JR Ipser (2014) Rigorous derivations of the planar impact dynamics equations in the center of mass frame. Retrieved from: https://arxiv.org/ abs/1404.0250 41. Shea RT and DC Viano (1994) Computing body segment trajectories in the Hybrid III dummy using linear accelerometer data. Journal of Biomechanical Engineering 116: 37-43.

42. Steffan H and A Moser (1996) The collision and trajectory models of PC-CRASH. SAE Technical Paper No. 960886. 43. Takhounts E, R Eppinger, R Tannous, JQ Campbell, E Power, et al. (2003) Analysis of 3D rigid body motion using the nine accelerometer array system. Injury Biomechanics Research: 31st International Workshop. 44. Zhang J, C Liang, S Wu, R Liu and J Gao (2016) Consistency of calculation results of two typical vehicle collision models. Procedia Engineering 137: 220-224. 45. Zhou J, J Lu and H Peng (2007) Collision model for vehicle motion prediction after light impacts. 20th IAVSD Symposium, Dynamics of Vehicles on Roads and Tracks, Berkley, California, August 13-17, 2007. 46. Zou T, Y Dai, M Cai and J Liu (2012) Discussion on accuracy degree evaluation of accident velocity reconstruction model. Physics Procedia 24: 979-983.

Symbols:

Symbols Cr A Cr A|B

= =

C D A

EC FD A

r

Second time derivative of the vector CrA. The rightmost left superscript and subscript denote the expression and differentiation frames, respectively, for the first time derivative. The leftmost superscript and subscript denote the expression and differentiation frames, EC aA . respectively, for the second time derivative. This is equivalent to FD

C B

A

C B

A 

The angular velocity vector of reference frame A with respect to reference frame B, expressed in the coordinates of reference frame C. First time derivative of the angular velocity vector (follows the same referencing

r

Position vector of point A expressed in the reference frame C. Relative position vector from point B to point A, expressed in the reference frame C. This is equal to CrA – CrB. When the point B is the origin of coordinates of reference frame C, the position vector is simply represented as CrA. First time derivative of the vector CrA where the left superscript denotes the expression frame and the left subscript denotes the frame in which the derivative was taken. This is equivalent to DC vA .

convention). This is equivalent to CB  A .

BR A

a

= =

G O Ei

= = =

B o ei

= = =

n i, ui

The antisymmetric (skew-symmetric) matrix associated with vector a. The direction cosine matrix that transforms coordinates from a departure frame (A) to a destination frame (B). Symbol that denotes the global (inertial) frame of reference. Origin of coordinates for the inertial frame of reference. Orthonormal triad of unit vectors {i: i = 1, 2, 3} for the rectangular Cartesian characterization of the inertial frame of reference. Symbol that denotes the body frame of reference. Origin of coordinates for the body frame of reference. Orthonormal triad of unit vectors {i: i = 1, 2, 3} for the rectangular Cartesian characterization of the body frame of reference. General orthonormal triad of unit vectors {i: i = 1, 2, 3} for the rectangular Cartesian characterization of a frame of reference.

Collision Magazine - Volume 14 Issue 1

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Utilizing BioMedical Engineering

Physical Evidence Analysis for Motorcycle Compared to Pedestrian Collision Laura Liptai, Ph.D., and Mark Ezra, P.E.

bstract The engineering investigation of trauma due to motorcycle incidents requires both a forensic analysis of the physical evidence and dynamicsbased accident reconstruction. This case study focuses on the investigation of a motorcycle trip accident on a highway undergoing resurfacing work where a surface height existed between two lanes of travel. Such trip accidents by motorcycles often lead to a secondary impact of the rider by a following or an oncoming vehicle after the motorcycle trip occurs. In this case study it was necessary to determine whether the rider was impacted while lying in the roadway or while standing. Issues of visibility of the lane height difference and angle of attack of the motorcycle toward the pavement height differential are evaluated. In the example discussed, the physical evidence of the trauma, including bone fracture mechanics, was also used to determine that the principal direction of force was consistent with axial loading of the motorcycle rider’s leg at impact. The fracture signature, combined with a dynamics-based motion analysis of motorcycle and rider masses, provided insight into whether the motorcyclist was lying down or standing at the time of vehicle impact and after the initial motorcycle trip and rider separation from the vehicle. Fracture mechanics provides a reliable methodology for unwitnessed trauma. Keywords Biomechanics, biomedical engineering, femur fracture, bone fracture mechanics, pedestrian run over, lower extremity trauma, motorcycle accident reconstruction, vehicle accident. Introduction The motorcycle trip accident investigated presented classic issues of a shallow angle of impact into a raised edge 52

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by a motorcycle. The shape of the higher surface edge, its height above the lower surface of the construction zone, the communication of the type of hazard present, and its relevance to motorcycles were all elements in the dispute that required forensic analysis. The solution was unique and unanticipated. At the time of the accident, the helmeted plaintiff was operating his motorcycle in a lane that had been milled in preparation for resurfacing. The resulting lane surface, open to use by traffic, was lower and rougher than that of the higher and newly resurfaced adjacent lane to the left (approximately a 1.5-2.0-inch height differential). The operator of the motorcycle was driving in the milled lane and attempted to change lane onto the higher surface at a speed consistent with the flow of traffic. However, the motorcycle hit the raised edge of the resurfaced lane at a shallow angle of approach (<20 degrees) which led to an immediate trip and fall over of the motorcycle. Due to the processional gyroscopic forces generated by the deflection of the motorcycle’s front wheel. The steering forces generated by such impacts at highway speeds have been shown to be outside the range of forces that may be likely controlled by a rider.1 The motorcycle traversed the repaved lane, slid on its side, and came to rest in the grassy median. After the motorcyclist was reported to have been run over by the left wheel of a following pickup truck traveling in the left, newly resurfaced lane, despite the pickup truck driver’s attempt to take evasive action. The plaintiff’s first medical record indicated that he was hit while walking back onto the interstate highway to retrieve parts from his motorcycle; however, all other history and plaintiff statements indicated that he was run over while on the ground. Ultimately, analysis of the evidence is consistent with the initial medical record that he was standing or walking at the time of impact.

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Mechanical Engineering Accident Reconstruction Forensic mechanical engineering reconstruction of a road accident often includes recorded measurements, roadway markings, and objects involved in an accident.2 Without this information, an investigating engineer may or may not be able to properly make assumptions for the missing data. In the subject incident, insufficient information was included in the accident report to even allow for educated

assumptions to be generated as to the point of trip of the motorcycle, the angle of slide of the motorcycle relative to the travel direction of traffic, and the total distance of slide of the motorcycle after the trip over at the edge of the resurfaced left lane. Therefore, no independent calculations of the motorcycle’s speed at trip and fall over would be reliable with the available data.

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Collision Magazine - Volume 14 Issue 1 53

Vehicle damages and longitudinal throwing distances when using biofidelic dummies in comparison to conventional dummies Annika Kortmann and Tim Hoger

esides the vehicle damages, the longitudinal throwing distance is also a decisive indicator in pedestrian collisions in order to determine the collision velocity of the vehicle. Previous research has shown1 that the construction of the biofidelic dummy leads to much more realistic vehicle damages in car-pedestrian collisions in comparison to those with conventional dummies. As to whether this also results in changes to the longitudinal throwing distance has so far only been tested with the first generation of biofidelic dummies.2 In order to obtain a direct comparison of the damage differences and the longitudinal throwing distance, crash tests were carried out with the biofidelic dummy from crashtest-service.com GmbH using the same vehicle model with a velocity range from 28 kph to 80 kph and compared with existing crash tests with conventional dummies.

have a different construction. A longer bonnet, a lowered chassis or braking all lead to varying wrap around lengths of the pedestrian,3 and are among other factors to be considered for the height of the head impact.

Introduction

A crash test series at different velocities was carried out, creating a form of EES-catalogue. The crash vehicles were several VW Polo 6R. The biofidelic dummies were laterally approached in most tests and impacted at the centre of the

A difficulty with the determination of collision velocity based on vehicle damages and the comparison of corresponding crash tests is that the vehicles compared may

Similar problems arise when determining the collision velocity based on the longitudinal throw distance of the pedestrian. Furthermore, a none-braking or partially braked car, especially at lower collision speeds, can carry the dummy after the collision. This is followed by a long transport phase in which the dummy is first released from the vehicle when the car is rapidly decelerated. The subsequent occurring longitudinal throwing distances in the crash tests can thereby be extended almost arbitrary and is therefore no longer suitable for limiting the collision speed. Crash series VW Polo 6R and Biofidelic dummies

Figure 1: Crash test vehicle VW Polo 6R (left) and impact situation with a biofidelic dummy (right) for the crash series performed 62

Collision Magazine - Volume 14 Issue 1

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Figure 2: Re-enactment (left – biofidelic) of the already available crash tests (right – conventional) – collision velocitiy here: v = 68 kph bonnet by the car, figure 1. The VW Polo was not braked during the collision and was decelerated after a defined short period of time, which was almost the same in all crash tests, to prevent “carrying” with a subsequent transport phase. The controlling, that it did not come to a carrying phase, was done over the videos. The collision speeds in the crash tests were (rounded off) 28 kph, 47 kph, 68 kph and 80 kph. In all tests, the damages and the dummy throwing distance was documented in detail. The new crash series with the biofidelic dummies build on the already existing crash test series carried out by crashtest-service.com GmbH, in which a VW Polo 6R was driven under the previously described impact constellation in six tests against a conventional dummy.4 In the velocity range between 70 kph and 80 kph, the already existing crash tests were carried out again under the same conditions but with the biofidelic dummy, figure 2. Thus, the study not only offers the possibility to investigate the increase in vehicle damage and longitudinal throwing distance with increasing collision speed, but also to make a direct comparison between the biofidelic and conventional dummy. Formation of vehicle damages Table 1 shows an overview of the crash tests carried out. In order to later be able to carry out a complete comparison of damages even in lower velocity ranges, an additional test with a conventional dummy at a velocity of approximately 30 kph has been recorded (see feature “Opel Astra G”). The dummies are all between 1.79 m and 1.83 m in height and weigh between 74 and 90 kg. VW Polo 6R against Biofidelic dummy Figure 3 documents the resulting damages incurred at increasing collision velocities in the range between 28 and 80 kph in a collision with a biofidelic dummy. Both tests in the lower velocity range were carried out for financial reasons with the same vehicle, which is why the dummy was impacted in the first attempt at 27.5 kph left of the centre in www.collisionpublishing.com

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major differences in the damages, there is no deviating trend determined in the longitudinal throwing distance of the biofidelic dummy compared to the conventional dummy. This is also shown by the added trend line of Focken. 6 The longitudinal throwing distances of the biofidelic dummy all lay in the range of the throwing parabola determined by Focken. The throwing distance of the biofidelic dummy therefore corresponds to that of the throwing distance of the conventional dummy. The modified structure of the dummy therefore has no significant influence on the throwing distance.

tion of the collision velocity. At velocities of 90 kph, limb separation is to be expected.

Conclusion

We thank the company crashtest-service.com GmbH for the great cooperation and the extensive documentation of the crash test attempts.

The comparison with the impact tests of conventional dummies has shown that the conventional dummy, especially in the transition range between mid to high collision velocities from 65 kph to 70 kph, has weaknesses due to its hard construction which can lead to significantly different vehicle damages caused because of the lack of the wraparound behaviour during the course of a collision. Through the crash series with the VW Polo 6R and the biofidelic dummy, it was possible to identify that the head impact of the dummy moves nearer towards to the roof edge with increasing collision velocities and at approx. 80 kph there is significant damage to the roof. The more realistic wrapping around of the biofidelic dummy during the collision results in extensive damages, while the conventional dummy causes punctual damages. With the biofidelic dummy, due to its flexibility, it is also possible to demonstrate the functionality of the pedestrian underrun protection system designed by the automotive industry, which should reduce the undergoing of the legs under the vehicle. When comparing the longitudinal throwing distances of biofidelic and conventional dummies no significant differences occurred, in contrast to the damage of the vehicle. The change in structure of the dummy has no significant influence on the throwing distance. Future work In this article, vehicle damages and the throwing distance of the dummies were analysed. In the crash tests the biofidelic dummies, in contrast to the conventional dummies, were “injured”; resulting in fractures and joint injuries, see figure 12. A subsequent “autopsy” of the dummy can then also allow a statement to be made on the expected pedestrian injuries depending on the collision speed. This connection was also analysed by Appel et. al.7 for accidents involving pedestrians and can be used as a further verifica-

Collision Magazine - Volume 14 Issue 1

As part of an expert seminar at crashtest-service.com GmbH, in September 2018 a high speed crash test for a passenger car-pedestrian collision with a biofidelic dummy at over 100 kph was planned and carried out. In a subsequent publication, not only can a connection between vehicle damages and the pedestrian injuries be made, but it is also possible to analyse whether the expected tears also occur with the biofidelic dummy.

References 1. A. Kortmann, Crashverhalten im Crashvergleich: der neue Biofidel Dummy bei unterschiedlichen Szenarien von Pkw-Fußgängerunfällen, VKU 03/2018. 2. S. Hartwig, M. Knape, A. Kunze, M. Weyde, Interdisziplinäre Weiterentwicklung eines optimierten biofidelen Dummys als Fußgängersurrogat bei Full-ScaleCrashtests, VKU 03/18. 3. D. Otte, T. Facius, Abwickellänge WAD des Körpers von Fußgängern und Radfahrern an der Pkw-Front und Relevanz als Einflussparameter für Kopfverletzungen, VKU 02/2015. 4. Technical data oft he used dummies are obtainable at crashtest-service.com GmbH 5. A. Kortmann, Crashverhalten im Crashvergleich: der neue Biofidel Dummy, UREKO SPIEGEL 20/2018. 6. U. Focken, Experimenteller Vergleich des gebremsten und ungebremsten Anstoßes bei der Kollision zwischen Pkw und Fußgängern; Diplomarbeit, Fachhochschule Osnabrück, 1998. 7. H. Appel, U. Wanderer, S. Meißner, G. Schmidt, J. Barz, D. Kallieris, R. Mattern, F. Schüler, Mechanik und Biomechanik des Unfalls, H. J. Wagner (Hrsg.): Verkehrsmedizin, Springer-Verlag, Berlin 1984. Authors Dipl.-Phys. Annika Kortmann, road traffic accident expert at engineering office Schimmelpfennig+Becke GmbH & Co. KG in Münster, Germany. Dipl.-Phys. Dr. rer. nat. Tim Hoger, publicly appointed and sworn expert for road traffic accidents working at engineering office Schimmelpfennig+Becke GmbH & Co. KG in Münster, Germany.

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crash·ol·o·gy THE SCIENCE OF CRASHES Wesley Vandiver

Robert Anderson

Collision Forensics, Inc.

Biomechanics Analysis

Airbag Myths, Legends, and Lore

xamples of airbag myths include airbags have toxic smoke or powder, negate need for seat belts, might trap you, can cause suffocation, will kill you, do more harm than good, known for killing kids, don’t inflate unless the automobile is traveling above a certain speed, may be inflated by hard braking, won’t inflate unless your seat belt is buckled, etc. Accident investigators, reconstructionists, biomechanics and others regularly address such fallacies. In our field we have our own myths and legends surrounding airbag deployments. For example, a common myth is that deployment is based upon or related to vehicle speeds or Delta V. Airbag system deployment or non-deployment behavior is, at least in part, specified by vehicle acceleration response corridors in various barrier impact speeds and angles. The manner in which the vehicle acceleration changes, or jerk, is used to predict the magnitude of the crash early enough that safety equipment can be deployed in time to be effective in preventing or mitigating occupant injury. This is long before the crash is over and the Delta V becomes known. Given the manner in which information surrounding the early development of airbags was introduced, and the way barrier equivalent velocities and energies are used in accident reconstruction, it is not a surprise that there would be confusion regarding the barrier equivalent vehicle acceleration corridors specified for airbag systems. For example, TRW and NHTSA brochures indicated that an airbag will only deploy in frontal or near-fron-

tal collisions equivalent to barrier impact at about 12 mph 1 and that they offer protection supplemental to seat belts in frontal impacts comparable to or greater than a 10 to 14 mph barrier impact. 2 An Automotive Engineering article in 1993 reported that the design intent was that airbags must deploy at 14 mph BEV, not deploy under 8 mph, and between theses speeds is the gray area where they may or may not deploy. 3 An IIHS Status report indicated that actual deployment thresholds vary somewhat from one airbag design to another, but virtually all systems are made to deploy in crashes equivalent to hitting a solid barrier at 10 to 12 mph. Mercedes and BMW airbags incorporate higher deployment thresholds – more like 15 mph – for people using belts. 4 An IEEE paper in 1993 reported that normally the airbag is deployed if the collision force is equivalent to a 14 mph barrier impact or higher. 5 Accident Reconstruction Journal features declared that “virtually all systems are made to deploy in crashes equivalent to hitting a solid barrier at 10 to 12 mph”6 and that “dual deployment thresholds are already in use in Mercedes and BMW cars. When occupants don’t use belts, the airbags deploy in crashes equivalent to hitting a solid wall at 9 to 12 mph, the typical deployment threshold. Thresholds are higher – more like 16 mph – for people with belts because they are less likely to be injured in lower speed crashes.” 7 Accident Investigation Quarterly features declared that most automakers currently choose thresholds equivalent to a 10 to 12 mph barrier crash 8 and that Mercedes and BMW use dual deployment thresholds

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Collision Magazine - Volume 14 Issue 1 73

A How-To Guide

For Downloading Toyota’s

Vehicle Control History Data Alan Moore, P.E., ACTAR

tarting in approximately 2013, Toyota began equipping Toyota and Lexus models with a function called Vehicle Control History, or VCH. It is a recording capability, housed primarily in the airbag control module, that is triggered by a variety of events (Figure 1). The original intent of the VCH was to assist Toyota in evaluation of alleged sudden acceleration events, but it has developed into a powerful tool for general accident reconstruction use. Since the VCH capability is not well known, this guide was prepared to assist accident reconstructionists in obtaining the data.

Collision Magazine - Volume 14 Issue 1

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Figure 1: Partial List of Vehicle Control History triggers Toyota’s diagnostic tool, Techstream, is required to access the VCH data. First, an SAE J2534-compliant interface device is needed. Toyota recommends the Mongoose MFC, but the more common Nexiq USB-Link also works. The Nexiq will need an OBDII cable, either #448013 or # 493013 depending on the generation, both of which are available at diesellaptops.com. The new CDR900 interface also works, although this function may not be supported by Bosch. Next, a Professional Diagnostic subscription to Techstream is required. An annual subscription is available for approximately $1,295. A 2-day subscription is also available for $65. To obtain the subscription, first set up an account on TIS (Technical Information System) at https://techinfo.toyota.com. This website may need to be visited first to setup the account: https://techinfo. snapon.com/TIS/termbill.aspx?action=new . Within the TIS website, locate the Techstream download section. Click on “Full Install” (Figure 3). First install the Mongoose Pro MFC driver, even if you don’t plan to use it, as it contains components needed for the Techstream install. To do so, find the install file on your

computer, right-click on it and run as administrator. You may need, in Windows 10, to temporarily disable Virus & Threat Protection. After installation, open Techstream which is now installed on your computer. Within Techstream, Go to Setup, VIM Select, and select your Nexiq or other interface device. Also set the user type to “Public User” (Figure 4). Click on Software Registration, then again on Software Registration. Follow the directions to create a key. After doing so, Techstream should open and allow use for the duration of the subscription. If you opted for the much less expensive two-day subscription, it will need to be renewed for the next use. To do so, go to techinfo.toyota.com, but do not log in. Click on “Already have an account?” as shown in Figure 5. Then click on Upgrade/Extend my subscription. After you do this, wait for an email to re-enable your account, click on the link in it. Then you should be able to log in using the upper left login. Occasionally the account may get locked, if you try to login before receiving the email renewal, and a call to tech support is required at 877-762-7666.

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Collision Magazine - Volume 14 Issue 1 81

Figure 10: Downloaded FFD data (above) Figure 11: PCS Data Viewer for Freeze Frame Data and images (right) Some things to keep in mind when using Techstream and VCH:

•

Portions of the Techstream software and subscription process are challenging, especially when renewing the two-day subscription. Some patience and troubleshooting may be required.

There are frequently discrepancies in the key cycle counters between CDR, VCH, and FFD data. Other methods, such as the odometer, must also be considered in validating the data.

•

Before using Techstream on an active case, definitely considering getting access to a newer Toyota to experiment with.

This guide should be considered a starting point, and does not cover all the necessary tasks to obtain and preserve the data.

•

This is a rapidly changing technology, especially on its use with Advanced Driver Assistance Systems, so you should expect differences between this guide and vehicles you may encounter in the future.

While most of the VCH data is contained in the airbag module, other data such as the FFD images are stored elsewhere in the vehicle. There is not currently a published method for direct-to-module download of VCH data, although this will likely change in the future.

•

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Collision Magazine - Volume 14 Issue 1 87

A REVIEW OF ENGINEERING MECHANICS APPLIED TO ACCIDENT RECONSTRUCTION Jai Singh, PART 2: DYNAMICS BS, MS, MA, ACTAR Biomechanical Engineering Analysis & Research, Inc.

bstract The subject paper is the second in a series that focuses on the role and application of rigid body engineering mechanics, specifically dynamics, to the field of accident reconstruction. Building upon the foundation of kinematics, presented previously, the focus of the subject work is the derivation of the Newton-Euler equations of motion in both the inertial frame of reference and in the body frame. The approach taken is the sequential defining and partitioning of forces that are in-

Collision Magazine - Volume 14 Issue 1

ternal and external to a system under consideration, defining the mass center, defining the translational and angular momentum vectors and then defining the mass moment of inertia matrix in both frames of reference. These definitions are used to develop the equations of translational dynamics (Newton’s second law of motion) and rotational dynamics (Euler’s equation). The importance of frame selection and body frame origin of coordinates placement is discussed. Finally, the solution for the kinetic energy of a rigid body undergoing free motion is presented.

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Introduction The first paper in this series focused upon establishing the conceptual framework for engineering kinematics problems that involve multiple frames of reference.1 The direction cosine matrix (DCM) was introduced as a descriptor for orientation kinematics and for coordinate frame transformation. The concept of frame referenced derivatives was presented, contrasted against standard time derivatives and used for defining the derivative transport theorem. A modified nomenclatural framework, based upon the work of Jazar,2-5 was presented. This framework allowed for the inclusion, in the symbolic representation of derivative variables, of both the expression frame and derivative frame. For the two frame problem, starting with the position vector, it was shown that there are a total of four forms for the velocity solution (one form for each combination of the derivative frame and expression frame). It was further shown that there exist a total of eight forms for the acceleration solution for the two frame problem. These areas within the purview of engineering kinematics, individually and in their totality, serve as a necessary foundation for the development of the theory of engineering dynamics and its presentation. Kinematics focuses on the study of motion of objects without specific consideration of forces and moments. Dynamics, on the other hand, focuses on the study of the motion of objects with specific consideration of mass and force as well as inertia and moment. The subsequent review proceeds by first developing the mathematical framework that relates forces and moments that are either internal or external to a system under consideration and the resultant acceleration experienced by the system. The term system, as used herein, may refer to a collection of discrete rigid bodies as well as a continuous single rigid body. This is followed by defining the mass center (i.e. center of mass) of a system under consideration. The mass center serves an important role when the origin of a body frame of reference is placed at the mass center in regards to simplifying the form of certain equations. From a notational standpoint, the single left superscript (the expression frame) and left subscript (the derivative frame) notation employed in the previous work for velocity is retained herein for terms that are direct functions of velocity. The double left superscript and double left subscript notation employed in the previous work for acceleration, with the first script pair referencing the expression and derivative frames for the first derivative and the second script pair referencing the expression and derivative frames for the second derivative, is also retained herein for direct functions of acceleration. These notational factors are first manifested in defining the translational and angular momentum, of a system, in the inertial frame of reference. This is followed by introducing the body frame mass moment of inertia matrix. The introduction of these topics is preparatory for defining the Newton-Euler equations of motion. The primary equation for translational dynamics is Newton’s second law of motion, which is valid in an inertial frame of reference. The definition in the inertial frame of reference is followed by presenting the valid form of the relationship starting with the body frame (B frame) linear momentum and then using the derivative transport theorem to take the frame referenced derivative with respect to the inertial frame of reference (i.e. the G frame). The application of a kinematic transform (premultiplication by a DCM) to the resultant is shown to reproduce the inertial frame of reference solution. The primary equation for rotational dynamics is Euler’s equation. The relationship between the angular momentum and angular velocity, in each frame, are first presented. Euler’s equation is first derived in the inertial frame of reference. The difficulty arising from the G frame formulation of Euler’s equation, that being the time varying nature of the G frame moment of inertia matrix, is described. This issue is then resolved by developing the appropriate body frame formulation of Euler’s equation, in which the mass moment of inertia matrix is time-invariant for a rigid body, and showing that the application of a kinematic transform to the solution yields an equivalent result to the inertial frame formulation. Finally, the solutions for the kinetic energy associated with a system undergoing free motion (i.e. translation and rotation) are presented. www.collisionpublishing.com

Collision Magazine - Volume 14 Issue 1 89

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