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Technical Paper

Driver Perception of Lateral Collision Threats

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.
Journal Article

Reconstructing Vehicle Dynamics from On-Board Event Data

These predictions were generated by directly integrating the VCH data and by using the VCH data as inputs to PC-Crash simulations. The predicted positions and headings were then compared to the actual position and heading data measured using differential GPS synchronized to the VCH data record.
Technical Paper

Accuracy and Sensitivity of Yaw Speed Analysis to Available Data

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.

Rollover Crash Reconstruction

According to the National Highway Traffic Safety Administration, “of the nearly 9.1 million passenger car, SUV, pickup and van crashes in 2010, only 2.1% involved a rollover. However, rollovers accounted for nearly 35% of all deaths from passenger vehicle crashes. In 2010 alone, more than 7,600 people died in rollover crashes.” Rollover accidents continue to be a leading contributor of vehicle deaths. While this continues to be true, it is pertinent to understand the entire crash process. Each stage of the accident provides valuable insight into the application of reconstruction methodologies. Rollover Accident Reconstruction focuses on tripped, single vehicle rollover crashes that terminate without striking a fixed object.
Technical Paper

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

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

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

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

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

Pedestrian Throw Distance Impact Speed Contour Plots Using PC-Crash

However, based on investigated pedestrian collisions, the location where the pedestrian has engaged with the vehicle can and does significantly influence the throw distance (and projection) and subsequent impact speed analysis. PC-Crash was used to simulate multiple pedestrian impacts at varying speeds and vehicle impact locations, creating pedestrian throw distance impact speed contour plots.
Technical Paper

Vehicle Acceleration Modeling in PC-Crash

The research reported here offers a validation of this capability, demonstrating that PC-Crash can be used to realistically model the build-up of a vehicle's speed under maximal acceleration. ...In the research reported here, PC-Crash 9.0 was used to model the full-throttle acceleration capabilities of three vehicles with automatic transmissions - a 2006 Ford Crown Victoria Police Interceptor (CVPI), a 2000 Cadillac DeVille DTS, and a 2003 Ford F150. ...In each case, the full-throttle acceleration of the vehicles modeled in PC-Crash showed good agreement with the acceleration of the real vehicles in our road tests.
Technical Paper

Measuring and Modeling Suspensions of Passenger Vehicles

Numerical parameters describing suspension stiffness and damping are required for 3D simulation of vehicle trajectories, but may not be available. This paper outlines a simple, portable method of measuring these properties with a coefficient of variation of 5% on stiffness. 24 of 26 vehicles tested were significantly stiffer in roll than pitch, complicating analyses with models that don't include anti-roll. Suspension parameters did not correlate with static wheel load distribution, and damping coefficient did not correlate with natural frequency. Computer simulations of the speed required to initiate rollover in an S-curve were highly sensitive to the suspension parameters used. When pre-impact tire marks and rollover distance were considered, the simulations became almost insensitive to suspension parameters.
Technical Paper

Uncertainty in Calculations Using Lambourn's Critical Speed Procedure

Critical Speed Formula (CSF) belongs to the canon of tools used in reconstruction of vehicle accidents. It is used to calculate vehicle speed at the beginning of tire yaw marks and, together with the entire methodology of processing the information contained in the marks into the data, is often referred to as the Critical Speed Method (CSM). Its great practical importance as well as recurring doubts as to the reliability make it one of the best experimentally and theoretically studied methods. Although the CSF applies in fact to a point mass, it is used with reference to a vehicle, i.e., an increasingly complicated multi-body system. Accident reconstruction experts point out the particular usefulness of Lambourn's research concerning the CSM in respect to a passenger car.
Technical Paper

Empirical Testing of Vehicular Rotational Motion

Vehicles often rotate during traffic collisions due to impact forces or excessive steering maneuvers. In analyzing these situations, accident reconstructionists need to apply accurate deceleration rates for vehicles that are both rotating and translating to a final resting position. Determining a proper rate of deceleration is a challenging but critical step in calculating energy or momentum-based solutions for analytical purposes. In this research, multiple empirical tests were performed using an instrumented vehicle that was subjected to induced rotational maneuvers. A Ford Crown Victoria passenger car was equipped with a modified brake system where selected wheels could be isolated. The tests were performed on a dry asphalt surface at speeds of approximately 50 mph. In each of the tests, the vehicle rotated approximately 180 degrees with the wheels on one side being completely locked.
Technical Paper

Simulating Moving Motorcycle to Moving Car Crashes

There has been little published research into simulating two-moving motorcycle-to-car collisions for the purpose of accident reconstruction. In this paper a series of two-moving crash tests were conducted to study collisions of this type. These tests used a range of speeds for the cars and the motorcycles involved, with perpendicular and oblique intersection collision impact configurations. The tests were then simulated with two popular crash simulation packages which were not designed to simulate motorcycles. The purpose of this study was to evaluate existing techniques and develop new techniques for simulating motorcycles in these software packages and then to examine the ability of each package to simulate a two-moving motorcycle-to-car crash. The results demonstrate that it is indeed possible to simulate a motorcycle in these packages and that both packages can simulate two-moving motorcycle-to-car crashes reasonably well.
Technical Paper

A Critique of Critical Speed Yaw Mark Research

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 Comparison Study between PC-Crash Simulation and Instrumented Handling Maneuvers

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.