Analyzing the uncertainty of simulation results in accident reconstruction with Response Surface Methodology

This paper is focused on the uncertainty of simulation results in accident reconstruction. The Upper and Lower Bound Method (ULM) and the Finite Difference Method (FDM), which can be easily applied in this field, are introduced firstly; the Response Surface Methodology (RSM) is then introduced into this field as an alternative methodology. In RSM, a sample set is firstly generated via uniform design; secondly, experiments are conducted according to the sample set with the help of simulation methods; thirdly, a response surface model is determined through regression analysis; finally, the uncertainty of simulation results can be analyzed using a combination of the response surface model and existing uncertainty analysis methods. It is later discussed in detail how to generate a sample set, how to calculate the range of simulation results and how to analyze the parameter sensitivity in RSM. Finally, the feasibility of RSM is validated by five cases. Moreover, the applicability of RSM, ULM and FDM in analyzing the uncertainty of simulation results is studied; the phenomena that ULM and FDM can hardly work while RSM can is found in the latter two cases. After an analysis of these five cases and the number of simulation runs required for each method, both advantages and disadvantages of these uncertainty analysis methods are indicated.     

基于痕迹检验的交通事故再现鉴定案例分析

交通事故再现是确定交通事故责任和事故成因的方法之一。在利用事故再现仿真软件进行交通事故再现过程中,应以交通事故现场痕迹的客观事实为依据。结合一起汽车与两轮车碰撞的交通事故案例,通过交通事故现场痕迹检验,分析交通事故形态,确定相关仿真再现参数。利用PC-crash软件,建立汽车、两轮车和人体模型,进行事故重建,并利用路面痕迹、车体痕迹、人体痕迹等对再现结果进行了验证。在鉴定中将事故过程再现与现场痕迹鉴定结合起来,提高了交通事故鉴定的客观性和科学性。     

Analysis and application of relationship between post-braking-distance and throw distance in vehicle-pedestrian accident reconstruction

Through theoretical analysis and introduction of some empirical parameters, the relationship between post-braking-distance and throw distance was studied concentratedly. Here, the post-braking-distance is the distance a vehicle will travel from the impact position to when it comes to a complete stop. Two useful formulas which are meaningful in vehicle-pedestrian accident reconstruction were finally obtained. The first one can be used to calculate impact speed according to throw distance, while the other one can describe the relationship between post-braking-distance and throw distance. Their feasibility has been validated by comparing with other scholars' empirical formulas and simulation results of software Pc-Crash, respectively. The relationship between post-braking-distance and throw distance has very bright application perspective in vehicle-pedestrian accident reconstruction such as helping policemen obtain more useful evidences, validating credibility of the throw distance, judging whether the vehicle is fully braked or not, determining the impact position etc. Finally its application was demonstrated by three cases, in which the impact speed was also calculated. All results until now have shown that conclusions obtained in this article are feasible and helpful in vehicle-pedestrian accident reconstruction.     

Uncertainty of calculation results in vehicle collision analysis

In the analysis of road accidents two types of calculation result uncertainty can be distinguished: modelling uncertainty and uncertainty in calculation results [R.M. Brach, M. Brach, Vehicle Accident Analysis & Reconstruction Methods, SAE International Publisher, Warrendale, 2005]. The problem becomes very important first of all when minor modifications of input parameters or application of different models of the phenomenon lead to a fundamentally different answer to the question posed by the court. The aim of the paper was to prove the necessity of including the problem of uncertainty in calculations related to vehicle collision mechanics and to justify the application of different error analysis methods recommendable in vehicle collision reconstruction. The data file from crash test No. 7 [H. Burg, M. Lindenmann, Unfallversuche, Verlag Information Ambs, Kippenheim, 1982] was used, the selection restricted to the range typical of average police records of collision place. Collision speeds were calculated using two methods: reconstruction and simulation. The analysis of uncertainty was carried out. Maximum and mean square uncertainty were calculated by means of total differential of relevant forms. Since the reconstruction resulted in very broad error intervals of uniform distribution, additional calculations were performed by the Monte Carlo method using algorithm described in [W. Wach, J. Unarski, Determination of vehicle velocities and collision location by means of Monte Carlo simulation method, Special Publication Accident Reconstruction SP-1999, SAE Paper No. 2006-01-0907, 2006].     

计算机模拟再现道路交通事故特点分析

目的将计算机仿真技术应用于道路交通事故鉴定领域，实现道路交通事故发生过程及当事人致伤方式的重建。方法基于对事故现场痕迹、车辆损坏和人体损伤等检验鉴定，利用事故再现软件及高性能计算机计算分析，对40起真实事故的碰撞过程及致伤方式进行重建分析，并以2起典型案例进行说明。结果事故再现效果与现场痕迹、车辆痕迹、人体损伤痕迹有关；40起事故再现中．28起符合性好，9起较好，3起欠理想；碰撞过程的准确再现有助于对致伤方式进行分析。结论计算机仿真模拟重建道路交通事故的发生过程及当事人的致伤方式在辅助道路交通事故鉴定中具有应用价值。     

基于MADYMO软件的交通事故中行人运动机理研究

事故重建、数据分析以及计算机仿真是行人安全防护研究的三个重要手段。行人运动机理的研究对于揭示人-车交通事故的特征具有非常重要的意义。文章以一起真实案例为基础,运用MADYMO仿真分析探讨真实交通事故中行人的运动机理。并以真实的交通事故数据作为验证手段。     

轿车与自行车碰撞事故仿真研究及骑车者致伤特点分析

目的研究计算机仿真技术重建自行车骑行状态下交通事故发生过程,并探讨此技术在分析真实事故中骑车者人体致伤方式、特点及损伤程度上的可行性。方法通过对事故人、车痕迹鉴定和模型建立,构建相关碰撞环境并利用高性能计算机及PC-Crash软件对事故进行再现研究。结果计算机仿真技术建立的人、车模型在模拟碰撞过程中,骑车者发生的运动过程、损伤分布及损伤动力学响应结果与法医学尸表检验人体损伤部位、程度基本吻合。结论利用计算机仿真技术重建自行车骑行状态下的事故碰撞过程、分析骑车者致伤方式及提供损伤部位动力学响应参数等,对于交通伤法医学鉴定及深化交通伤机制研究具有参考价值。     

道路交通事故速度重建技术现状

事故车辆行驶速度是道路交通事故调查的重要内容,也是公安交通管理部门进行事故认定,法院进行司法审判的关键技术依据。目前事故车辆行驶速度调查的主要途径是办案单位委托具有专业技术能力的司法鉴定机构进行速度重建,使用的方法主要有基于事故形态的速度重建、基于模拟软件的速度重建、基于车载记录数据的速度重建和基于视频图像的速度重建。通过从速度重建的技术发展、执业类别和能力验证等方面介绍了我国道路交通事故速度重建技术的发展现状。     

Reconstruction of a real car-pedestrian-accident. Part 2: Modelling and simulation

A real pedestrian-car-crash was reconstructed by use of a multi-body simulation. The main aspect was the use of an individual body surface for the human body model and the car. The simulation allowed a plausible reconstruction of the accident. A good correlation of the contact-pairs in the model and the real forensic data was achieved by variation of the hypothetical szenario.     

Two Simple Formulas for Evaluating the Lower Bound of the Impact Velocity in Vehicle–pedestrian Accidents

Formulas for evaluating the lower bound of the impact velocity are valuable in vehicle–pedestrian accident reconstruction. The theory of classical mechanics and four hypotheses were employed to derive formulas; the research results and simulation/accident tests were employed to validate their feasibility. Then, two simple formulas were developed according to the distance between the rest positions of the vehicle and the pedestrian and the flight‐phase distance. The results showed that the evaluated results by the two proposed formulas are inferior to the existing results. The influence of a roadside step on the impact velocity, which decreased with an increase in the flight‐phase distance and a reduction in the road slope, was evaluated. Based on a real accident, the study concludes that the lower bound can be easily obtained with the proposed formulas, which can be used to determine the evaluated impact velocity during simulations.     

Fatal pedestrian-bicycle collisions

Although, fatal collisions between pedestrians and bicycles are relatively rare, they are still of forensic relevance because of the need to explore the circumstances of the accident. Based on three reconstructed cases, situation and injury patterns are presented that might prove useful in future cases: usually the person causing the accident is the cyclist while the pedestrian generally suffers more severe injuries; the situation at the site of accident is important for its reconstruction: end location of the persons involved in the accident, injuries and traces on pedestrians and cyclists, traces at the site of accident and on the bicycle; because of the lack of pre-crash traces and any eyewitness accounts, the pedestrian's injuries are the best starting point for the reconstruction of the accident; a characteristic wound on the lower leg of the pedestrian that reveals the initial impact between the front wheel and the leg is crucial not because of its seriousness, but because of its external morphology; the injuries that can be expected by the following impact between body and handlebar are unspecific and only minor; the most severe injuries to the pedestrian as a result of the accident are caused secondarily by falling and hitting the head on the road; the fall of the cyclist, however, corresponds to a throw-off followed by a sliding phase with less impact load when the head hits the ground [maximum abbreviated injury scale 1 (MAIS 1)]; the cyclists involved are mainly younger persons on fashionable bicycles (here: mountain bikes); in the great majority of cases, the injured pedestrians are frail, elderly people with a lower tolerance of trauma.     

Performance Study of a Score‐based Likelihood Ratio System for Forensic Fingermark Comparison

In this article, the performance of a score‐based likelihood ratio (LR) system for comparisons of fingerprints with fingermarks is studied. The system is based on an automated fingerprint identification system (AFIS) comparison algorithm and focuses on fingerprint comparisons where the fingermarks contain 6–11 minutiae. The hypotheses under consideration are evaluated at the level of the person, not the finger. The LRs are presented with bootstrap intervals indicating the sampling uncertainty involved. Several aspects of the performance are measured: leave‐one‐out cross‐validation is applied, and rates of misleading evidence are studied in two ways. A simulation study is performed to study the coverage of the bootstrap intervals. The results indicate that the evidential strength for same source comparisons that do not meet the Dutch twelve‐point standard may be substantial. The methods used can be generalized to measure the performance of score‐based LR systems in other fields of forensic science.     

Estimating the pre-appearance interval from temperature in Necrodes littoralis L. (Coleoptera: Silphidae)

While estimating post-mortem interval from entomological evidence it is useful to divide it into two separate intervals: the pre-appearance interval (PAI) and the development interval in the case of immature insects and PAI and the presence interval in the case of adult insects. An accurate estimate of PAI is critically important particularly in the case of those insects which appear on remains late in decomposition. In this paper the possibilities of PAI estimation from temperature are evaluated in late-arriving, forensically important carrion beetle Necrodes littoralis. The relationship between PAI of adult and larval N. littoralis and temperature was modelled by using results of succession experiments in forests of Central Europe. In both stages PAI was found to be strongly, inversely dependent on mean daily ground level temperatures averaged for the duration of PAI. Several methods of PAI estimation were proposed and their accuracy was initially evaluated with external successional data.     

Fabric evidence studies of seat belts

Investigations on safety belts give useful informations for the reconstruction of the sitting position of passengers of a car involved in an accident. Two examples from the practice show extraordinary trace combinations.     

正交试验设计辅助Pc-Crash实现事故再现分析

目的利用Pc-Crash实现事故再现分析时,探索由参数敏感性分析方法确定那些对仿真结果有显著影响的参数,通过对这些参数进行合理处理尝试提高仿真结果的精度。方法引入基于正交试验设计的参数敏感性分析方法。结果将此方法应用到Pc-Crash优化计算器内参数敏感性分析的实践中,获得了对碰撞后车辆运行轨迹有影响显著的参数。通过对一实际碰撞试验的再现研究,验证了敏感性分析所得结论在指导优化参数选取方面的有效性。结论研究表明借助正交试验设计辅助Pc-Crash实现事故再现分析具有实用价值。     

基于正交试验的汽车制动纵滑摩擦系数研究

目的通过进行不同因素条件下的汽车制动纵滑摩擦试验,得到不同因素下的摩擦系数,缩小摩擦系数参考值范围,提高事故再现精度。方法在制动纵滑摩擦试验中引入正交试验方法,通过极差分析确定不同因素对摩擦系数的影响程度,对汽车摩擦系数的选取进行可靠计算。结果提出了摩擦系数修正值的使用方法,有效减小摩擦系数参考值的范围,提高事故再现精度。结论事故再现中,通过试验研究方法,准确地选取汽车制动摩擦系数,有效提高了事故再现的精度。     

Computer simulation of the accident with nine victims

In the paper we wish to emphasise the significance of vehicle driving dynamics analysis in the collision phase and occupant load analysis by means of using a software environment. Thereby we also wish to present the results of the simulation of the course of a traffic accident with nine victims that arose from a collision between an Audi A6 passenger car and the VW Caravelle van. In treating the traffic accident the forensic expert was faced with the questions about what caused the injuries to the front passenger in the Audi A6 passenger car, about the way the two vehicles had collided, about their collision velocities, about the way the two vehicles were handled and about the causes that originated the traffic accident. The critical situation on the road was a consequence of the tiredness of the van driver, the inadequate use of the passive safety systems and overloading the van.     

多层螺旋CT与三维重建技术在法医损伤学中的应用

影像学技术发展迅速．已经成为临床诊断、治疗不可或缺的有效工具。利用MSCT与三维重建技术进行虚拟解剖,因为具有非破坏性、可显示特殊部位损伤形态、分析快速且便捷、便于证据保存和出示等特点在法医学尸体解剖中日益凸显优势．在法医损伤学研究及实践鉴定过程中具有较高的应用价值。文章综述了利用MSCT与三维重建技术在锐器伤、钝器伤、高坠伤、交通伤等实践领域的研究成果,并通过实践检案中遇到的典型案例,探讨多层螺旋CT与三维重建技术在法医学损伤鉴定中的应用价值。     

基于交通事故痕迹的自行车行驶状态分析

在以非机动车中发展较快的自行车为例,基于从事故发生接触碰撞的机动车、非机动车和人等上面提取和检验得到的微量物质交换及其表面附着物等证据,提出了认定嫌疑车辆的方法,通过大量相关资料、事故现场案卷以及一些典型案例,将现场痕迹检验鉴定方法进行分类和汇总,主要分析、阐述车辆痕迹方面问题,进而重现事故现场。这为判定机动车与非机动车交通事故中非机动车行驶状态提供了方法和思路,提高了交通事故责任认定的准确性和公正性。     

Fall from a Balcony—Accidental or Homicidal? Reconstruction by Numerical Simulation

In the case presented, conflicting witness accounts and the subject's injuries were highly suspicious of an assault that might have caused the balcony fall. For the reconstruction, a simulation software, originally designed for motor vehicle accident reconstruction, was used. Three scenarios were simulated using the PC‐Crash multibody pedestrian model: (S1) Subject was pushed against and fell over balcony rail, (S2) subject fell off from a seated position, (S3) subject fell off from a prone position on the rail. (S1) could be ruled out due to inconsistent results in terms of landing area and minimum velocity. Realistic results were obtained for (S3) with a fall off from a prone position on the rail. After a few months, the comatose subject awoke and gave an account of what had happened being consistent with the simulation results. This case demonstrates the feasibility of multibody simulations also in cases of nontraffic incidents.