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Journal Article

A Bayesian Approach to Cross-Validation in Pedestrian Accident Reconstruction

2011-04-12
2011-01-0290
In statistical modeling, cross-validation refers to the practice of fitting a model with part of the available data, and then using predictions of the unused data to test and improve the fitted model. In accident reconstruction, cross-validation is possible when two different measurements can be used to estimate the same accident feature, such as when measured skidmark length and pedestrian throw distance each provide an estimate of impact speed. In this case a Bayesian cross-validation can be carried out by (1) using one measurement and Bayes theorem to compute a posterior distribution for the impact speed, (2) using this posterior distribution to compute a predictive distribution for the second measurement, and then (3) comparing the actual second measurement to this predictive distribution. An actual measurement falling in an extreme tail of the predictive distribution suggests a weakness in the assumptions governing the reconstruction.
Technical Paper

A Comparison Study between PC-Crash Simulation and Instrumented Handling Maneuvers

2011-04-12
2011-01-1121
Lateral acceleration, roll angle, roll rate, and yaw rate vehicle response from PC-Crash were compared to the MSAI sensor data. The authors modeled 26 handling tests. PC-Crash appeared to be a reasonable tool for modeling gross vehicle response. ...This research compares vehicle dynamic simulations in PC-Crash 8.2 to data recorded during instrumented handling tests conducted by Mechanical Systems Analysis Incorporated (MSAI). ...Vehicle weight, center of gravity (c.g) position, suspension stiffness parameters, tire parameters, steering angle, and vehicle speed data provided by MSAI were used as input for the PC-Crash model. Lateral acceleration, roll angle, roll rate, and yaw rate vehicle response from PC-Crash were compared to the MSAI sensor data.
Technical Paper

A Comparison of Moment of Inertia Estimation Techniques for Vehicle Dynamics Simulation

1997-02-24
970951
The moments of inertia, in yaw, pitch, and roll, as well as the center of gravity height are necessary to successfully model the 3D dynamic behavior of vehicles before, during and after collision. A number of vehicle parameter estimation techniques have been developed and are currently in use in North America and Europe. Many parameters have been measured by NHTSA and others. The estimation techniques are compared to the available measured values, and recommendations are made for best estimating the parameters when measured values are not available. The sensitivity of 3D vehicle collision dynamics and trajectory simulation to variance in the moment of inertia is demonstrated.
Technical Paper

A Critique of Critical Speed Yaw Mark Research

2012-04-16
2012-01-0600
Critical speed yaw marks are commonly used in collision reconstruction to estimate vehicle speed. Research and laboratory testing have demonstrated that critical speed calculations can be used to accurately estimate vehicle speed. Thus, the principles supporting critical speed yaw analysis are fundamentally and theoretically valid and are not being challenged in this study. However, there are observed and documented limitations with respect to the appropriate application and execution of critical speed yaw analysis. This paper reviews the published research to-date and identifies limitations of critical speed yaw analysis. Examples of collision scenes are provided which quantify the inaccuracies associated with the misuse of critical speed yaw calculations. Areas for further research are identified and detailed.
Technical Paper

A Pilot Study at National Highway-8 for On-Site Crash Data Collection and In-Depth Investigation in India

2017-01-10
2017-26-0001
The importance of on-site, in-depth accident research studies has been recognized internationally especially in developed countries. In order to address problems related to road safety, it is important to understand the epidemiology and causation of crashes. For this an in-depth investigation of the crash site, vehicles involved and injury details is required. Detailed crash information helps in analysing the events leading to crash and developing safety measures and/or intervention to reduce crashes. In order to pilot such an activity in India, an in-depth accident data collection activity had been carried out on national highway connecting Delhi to Jaipur (NH-8) for a duration of over a year by a joint team of IIT-Delhi and NATRiP. A total of 1220 road traffic accidents (RTA) notifications were received by the team, of which 186 cases were attended and detailed data was collected in a pre-decided format.
Technical Paper

ASSESSMENT OF THE USE OF SEAT BELTS IN BUSES BASED ON RECENT ROAD TRAFFIC ACCIDENTS IN SPAIN

2001-06-04
2001-06-0019
The most important topic in the field of passive safety of buses and coaches nowadays is the future compulsory use of seat belts. The objective of the study performed by IDIADA AUTOMOTIVE TECHNOLOGY SA and CENTRO ZARAGOZA is to make an important contribution to the existing technical data about this subject. This paper is based on the in-depth analysis of recent road traffic accidents where buses were involved. The first step is the accident reconstruction. A complete injury report including description and causes of occupant injuries is the basis for the correlation of a computer simulation model. Experience in the development of coach seats equipped with seat belts enables the preparation of a comparative model. The hypothesis that the consequences of the accident could have been less severe if the occupants of the bus had worn a seat belt can be evaluated. The conclusions will help the legislators make the right decision.
Technical Paper

Accuracy and Sensitivity of Yaw Speed Analysis to Available Data

2019-04-02
2019-01-0417
Accident reconstructionists rarely have complete data with which to determine vehicle speed, and so the true value must be bracketed within a range. Previous work has shown the effect of friction uncertainty in determining speed from tire marks left by a vehicle in yaw. The goal of the current study was to assess improvements in the accuracy of vehicle speed estimated from yaw marks using progressively more scene and vehicle information. Data for this analysis came from staged S-turn maneuvers that in some cases led to rollover of sport utility vehicles. Initial speeds were first calculated using the critical curve speed (CCS) formula on the yaw marks from the first portion of the S-maneuver. Then computer simulations were performed with progressively more input data: i) the complete tire marks from the whole S-maneuver, ii) measured vehicle mass, iii) measured suspension stiffness and damping, and iv) measured steering history.
Technical Paper

An Analytical Review and Extension of Two Decades of Research Related to PC-Crash Simulation Software

2018-04-03
2018-01-0523
PC-Crash is a vehicular accident simulation software that is widely used by the accident reconstruction community. ...The goal of this article is to review the prior literature that has addressed the capabilities of PC-Crash and its accuracy and reliability for various applications (planar collisions, rollovers, and human motion). ...In addition, this article aims to add additional analysis of the capabilities of PC-Crash for simulating planar collisions and rollovers. Simulation analysis of five planar collisions originally reported and analyzed by Bailey [2000] are reexamined.
Technical Paper

An Investigation into C-NCAP AEB System Assessment Protocol

2017-09-23
2017-01-2009
In order to speed up the development of vehicle active safety technology in China, C-NCAP plans to add AEB and AEB VRU system as assessment items in 2018. With the purpose of studying the assessment protocol of AEB system, we have carried out 400,000 km road information collection and then we acquired the statistics of the operation conditions of dangerous situations. Combined with the traffic accident data collected by CIDAS, we found that the dangerous situations that we usually met were mainly three types, that was CCRs, CCRm and CCRb. Based on what we mentioned above, we analyzed the three kinds of working conditions and gave the corresponding evaluation method. In addition, combined with the actual situation of China, we added two tests of error function. And then we took the actual road experiment of many models of vehicles.
Technical Paper

Analysis of Finite Element Models for Head Injury Investigation: Reconstruction of Four Real-World Impacts

2005-11-09
2005-22-0001
Previous studies have shown that both excessive linear and rotational accelerations are the cause of head injuries. Although the head injury criterion has been beneficial as an indicator of head injury risk, it only considers linear acceleration, so there is a need to consider both types of motion in future safety standards. Advanced models of the head/brain complex have recently been developed to gain a better understanding of head injury biomechanics. While these models have been verified against laboratory experimental data, there is a lack of suitable real-world data available for validation. Hence, using two computer models of the head/brain, the objective of the current study was to reconstruct four real-world crashes with known head injury outcomes in a full-vehicle crash laboratory, simulate head/brain responses using kinematics obtained during these reconstructions, and to compare the results predicted by the models against the actual injuries sustained by the occupant.
Technical Paper

Analysis of a Dolly Rollover with PC-Crash

2009-04-20
2009-01-0822
The current capabilities of PC-Crash for rollover modeling are discussed and suggestions are made for how PC-Crash might be improved for modeling rollovers. ...This paper evaluates the use of PC-Crash simulation software for modeling the dynamics of a dolly rollover crash test. The specific test used for this research utilized a Ford sport utility vehicle and was run in accordance with SAE J2114. ...Next, the test was modeled using PC-Crash. The simulation was optimized to yield a reasonable fit with the actual test dynamics by changing the following parameters in PC-Crash: (1) the friction coefficient associated with each vehicle-to-ground impact; (2) the coefficient of restitution for vehicle-to-ground impacts; (3) the vehicle body stiffness; and (4) the vehicle suspension and damping.
Technical Paper

Comparisons of Devices for Measuring Acceleration vs. Time in Braking Tests

2008-04-14
2008-01-0180
The coefficient of friction between a vehicle's tires and the roadway is a key parameter in any accident reconstruction. With the proliferation of vehicle dynamics software, it is often important to have more details regarding the tires interaction with the road than simply the average deceleration rate. Devices which can provide the peak friction as the braking develops, along with the average deceleration during the fully developed sliding phase, are necessary. There are now products widely available to the accident reconstruction market which provides these parameters as well as detailed acceleration vs. time curves. The following products capable of providing these results were tested: Accelerex, Vericom VC3000, and two general purpose accelerometers made by Silicon Designs and Dimension Engineering. Tests were conducted on wet and dry asphalt surfaces using a variety of passenger vehicles and transit buses which confirmed the agreement between these devices.
Technical Paper

Computer Simulation of Steer-Induced Rollover Events Via SIMON

2011-04-12
2011-01-1122
This study examines through computer simulation the reconstruction of on-road vehicle rollover accidents induced by a driver steering maneuver. The three-dimensional vehicle dynamics software package SIMON is used to model a set of four test vehicles as six degree-of-freedom sprung masses with up to five degrees-of-freedom for each unsprung mass. The performance of the simulator's physics model, in the context of accident reconstruction, is evaluated through correlation with full-scale vehicle rollover tests. Of specific interest to this study was simulation of the trip phase of the vehicle's motion. The correlation parameters include vehicle trajectory, speed, heading angle, yaw rate, roll angle, roll rate and lateral acceleration. SIMON's capacity to accurately model the physics of a test vehicle's suspension and tire kinetics in the pre-trip and trip phases of motion is evaluated by modeling a set of four instrumented full-scale tests of steering-induced rollovers.
Technical Paper

Design and Evaluation of an Affordable Seatbelt Retrofit for Motor Coach Occupant Safety

2017-01-10
2017-26-0018
Prevention of passenger ejection from motor coach seats in the case of rollover and frontal crashes is critical for minimizing fatalities and injuries. This paper proposes a novel concept of affordably retrofitting 3-point seatbelts to protect passengers during these significant crash scenarios. Currently, the available options involve replacement of either the entire fleet, which takes time to avoid extremely high costs, or all seats with new seats that have seatbelts which is still expensive. Alternatively, this paper presents the development of an innovative product that can be installed in seat belt-ready bus structures at a fraction of the cost. The efficacy of the design is studied using finite element analysis (FEA) to meet Federal Motor Vehicle Safety Standards (FMVSS) 210 standards for conditions involved in frontal and side impacts.
Technical Paper

Determination of Critical Speed, Slip Angle and Longitudinal Wheel Slip based on Yaw Marks Left by a Wheel with Zero Tire Pressure

2016-04-05
2016-01-1480
This article presents the results of an analysis of the yaw marks left by a car with normal pressure in all tires and then normal pressure in three tires and zero in one rear tire. The analysis is a continuation of research on influence of reduced tire pressure on car lateral dynamics in a passing maneuver, discussed in the SAE paper No. 2014-01-0466. Preliminary analysis of yaw marks has shown, that a wheel with zero pressure deposits a yaw mark whose geometry differs from the yaw mark made by a wheel with normal pressure based on which we could calculate: critical speed, slip angle and longitudinal wheel slip. The aim of the presented research was to analyze the yaw marks left by car with zero pressure in one rear wheel in order to check the possibility of determining the vehicle critical speed, slip angle and longitudinal wheel slip. It was reached by performing bench and road tests during which the vehicle motion parameters were recorded using GPS Data Logging System.
Technical Paper

Driver Perception of Lateral Collision Threats

2020-04-14
2020-01-1198
Immediate collision hazards pose obvious threats to approaching drivers and therefore provoke emergency evasive responses. When the hazard is a vehicle intruding into the lane ahead, how its movement characteristics influence an approaching driver’s response is not well understood. This study examined the relationship between intruding vehicle motion and hazard perception. Seventeen subjects viewed first-person perspective recordings of a simulated vehicle travelling down a two-lane roadway containing several intersections with stop-controlled minor roads. Stopped vehicles were located at approximately half of the minor road intersections. Throughout the study, some vehicles (termed ‘intruders’) accelerated into the subject’s lane of travel at 1 of 6 pre-determined acceleration rates. Subjects were instructed to ‘brake’ their vehicle by pressing the space bar on a keyboard as soon as they perceived that a collision was imminent.
Technical Paper

ERRATUM

2014-04-01
2014-01-0464.01
Technical Paper

EVALUATION OF THE EFFECTIVENESS OF PEDESTRIAN PROTECTION SYSTEMS THROUGH IN-DEPTH ACCIDENT INVESTIGATION, RECONSTRUCTION AND SIMULATION

2009-10-06
2009-36-0398
All of them are analysed in-depth and reconstructed with PC-Crash. The effects of the frontal structure of the vehicles and several active systems, such as BAS and Pedestrian Detection Systems, are evaluated. ...The paper includes the description of the methodology followed for a sample of approximately 140 pedestrian urban accidents in three cities in Spain (Madrid, Barcelona and Zaragoza) and the corresponding reconstructions done with PC-Crash. Then, a methodology to simulate the passive and active improvements (including pedestrian friendly structure, BAS and pedestrian detection system) is defined and applied to all the sampled accidents.
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