Collision Speed Research Articles

Assessment of the impact speed and angle conditions for the EN1317 barrier tests

ABSTRACTRoadside safety barriers designs are tested with passenger cars in Europe using standard EN1317 in which the impact angle for normal, high and very high containment level tests is 20°. In comparison to EN1317, the US standard MASH has higher impact angles for cars and pickups (25°) and different vehicle masses. Studies in Europe (RISER) and the US have shown values for the 90th percentile impact angle of 30°–34°. Thus, the limited evidence available suggests that the 20° angle applied in EN 1317 may be too low.The first goal of this paper is to use the US NCHRP database (Project NCHRP 17–22) to assess the distribution of impact angle and collision speed in recent ROR accidents. Second, based on the findings of the statistical analysis and on analysis of impact angles and speeds in the literature, an LS-DYNA finite element analysis was carried out to evaluate the normal containment level of concrete barriers in non-standard collisions. The FE model was validated against a crash test of a portable concrete barrier carried out at the UK Transport Research Laboratory (TRL).The accident data analysis for run-off road accidents indicates that a substantial proportion of accidents have an impact angle in excess of 20°. The baseline LS-DYNA model showed good comparison with experimental acceleration severity index (ASI) data and the parametric analysis indicates a very significant influence of impact angle on ASI. Accordingly, a review of European run-off road accidents and the configuration of EN 1317 should be performed.

Pedestrian-Vehicle Accidents Reconstruction with PC-Crash®: Sensibility Analysis of Factors Variation

This paper describes the main findings of a study performed by INSIA-UPM about the improvement of the reconstruction process of real world vehicle-pedestrian accidents using PC-Crash® software, aimed to develop a software tool for the estimation of the variability of the collision speed due to the lack of real values of some parameters required during the reconstruction task.The methodology has been based on a sensibility analysis of the factors variation. A total of 9 factors have been analyzed with the objective of identifying which ones were significant. Four of them (pedestrian height, collision angle, hood height and pedestrian-road friction coefficient) were significant and were included in a full factorial experiment with the collision speed as an additional factor in order to obtain a regression model with up to third level interactions. Two different factorial experiments with the same structure have been performed because of pedestrian gender differences.The tool has been created as a collision speed predictor based on the regression models obtained, using the 4 significant factors and the projection distance measured or estimated in the accident site. The tool has been used on the analysis of real-world reconstructed accidents occurred in the city of Madrid (Spain). The results have been adequate in most cases with less than 10% of deviation between the predicted speed and the one estimated in the reconstructions.

Numerical analysis of Pickering emulsion stability: insights from ABMD simulations.

The issue of the stability of Pickering emulsions is tackled at a mesoscopic level using dissipative particle dynamics simulations within the Adiabatic Biased Molecular Dynamics framework. We consider the early stage of the coalescence process between two spherical water droplets in a decane solvent. The droplets are stabilized by Janus nanoparticles of different shapes (spherical and ellipsoidal) with different three-phase contact angles. Given a sufficiently dense layer of particles on the droplets, we show that the stabilization mechanism strongly depends on the collision speed. This is consistent with a coalescence mechanism governed by the rheology of the interfacial region. When the system is forced to coalesce sufficiently slowly, we investigate at a mesoscopic level how the ability of the nanoparticles to stabilize Pickering emulsions is discriminated by nanoparticle mobility and the associated caging effect. These properties are both related to the interparticle interaction and the hydrodynamic resistance in the liquid film between the approaching interfaces.

免震建物の擁壁衝突時における擁壁－背後地盤の抵抗特性

When extreme large earthquake occurs, a base-isolated building may collide with its surrounding retaining wall. To evaluate precisely the acceleration response of superstructure and the deformation of base isolator, resistance characteristics of a retaining wall with back soil should be made clear. In this study, shaking table tests of model base-isolated building are carried out to investigate the collision with building and retaining wall. We analyze the collisions in detail compared with experiment results and its simulation analysis by 3D-FEM. Furthermore collision responses of an existing base-isolation building are analyzed by 3D-FEM focusing on height and width of retaining wall, rigidity of back soil and nonlinear of retaining wall. The obtained results are summarized as follows. 1) By the shaking table tests of base-isolated model building and its simulation analyses, it is cleared that the height of retaining wall effects to acceleration response of building and its restoring force. The lower height of retaining wall reduces acceleration response of building because of the progression of plasticity of retaining wall and back soil. 2) Collision analyses of an existing base-isolated building show that stress concentrations occur at the bottom of retaining wall and contact area at the corner of building. In the collision with building, the center part of retaining wall contacts at the bottom of building, however the corner part of that contacts along the building foundation. This is because that flange parts of retaining wall inhibit the deformation of that. Therefore flange parts of retaining wall influence greatly to the deformation mode and the maximum strength of retaining wall. 3) Parametric analyses considering collision speed, height and width of retaining wall and rigidity of back soil show the following results. The collision speed effects to the increase of yield stress of retaining wall because of the difference of its deformation mode. In comparison with the height of retaining wall, the width of that effects larger to the strength of its restoring force. Rigidity of back soil increases slightly the maximum strength of restoring force of retaining wall.

Improved Multibody Dynamics for Investigating Energy Dissipation in Train Collisions Based on Scaling Laws

This study aimed to investigate energy dissipation in train collisions. A 1/8 scaled train model, about one-dimensional in longitudinal direction, was used to carry out a scaled train collision test. Corresponding multibody dynamic simulations were conducted using traditional and improved method model (IMM) in ADAMS. In IMM, the connection between two adjacent cars was expressed by a nonlinear spring and energy absorbing structures were equivalently represented by separate forces, instead of one force. IMM was able to simulate the motion of each car and displayed the deformation of structures at both ends of the cars. IMM showed larger deformations and energy absorption of structures in moving cars than those in stationary cars. Moreover, the asymmetry in deformation proportion in main energy absorbing structures decreased with increasing collision speed. The asymmetry decreased from 11.69% to 3.60% when the collision speed increased from 10 km/h to 36 km/h.

Investigating the Speed and Rear-End Collision Relationship at Urban Signalized Intersections

Rear-end collisions are often the overrepresented type of collisions at urban signalized intersections. Although these collisions can occur for a variety of reasons, speed can always play a significant role in rear-end collisions, as the stopping distance increases with speed. The study presented in this paper investigated the relationship between speed and rear-end collisions at urban signalized intersections. Collisions, speed characteristics, traffic volume, and geometry data for a group of urban signalized intersection approaches were collected for the analysis. Negative binomial safety performance functions were developed to establish the relationship between collisions and various speed characteristics, while controlling for the traffic volume and road geometry. The goodness of fit of the estimated models was checked with several measures to ensure model adequacy. The results revealed intuitive findings for various parameter estimates of the models. It was found that a 1-km/h increase in the standard deviation of speed was associated with 6.3%, 8.2%, and 5.7% increases in the frequency of total, injury, and property-damage-only (PDO) rear-end collisions, respectively. For both the average and the 85th percentile speed change, the estimated collision reductions were almost the same. An increase in 85th percentile speed by 1 km/h was associated with 1.1%, 1.6%, and 0.9% increases in the frequency of total, injury, and PDO rear-end collisions, respectively. Moreover, as the level of speeding increased, collision frequencies increased exponentially. The results of the study suggest that speed management upstream of the intersection approach could reduce rear-end collisions at urban signalized intersections.

自動車部材のエネルギー吸収特性に基づく衝突速度の算出手法

自動車部材のエネルギー吸収特性に基づく衝突速度の算出手法

Impact Velocity Prediction in a Traffic Accident

Reconstruction of traffic accidents has been so crucial scientific process in order to make impartial and judicious decisions. This study focuses on impact speed prediction of accident sufferers just before the collision in a comprehensive scientific way by using an accident reconstruction software called “vCrash” and Function Fitting Neural Network (FITNET) artificial intelligence method (predictor) in case of absence of skid marks or other clues about calculating impact speeds. A sample real world accident was simulated on the software several times by changing collision speeds to form different deformation on the collision regions of the vehicles in every simulation. Every single deformation amount corresponding to each impact velocity was recorded and used as teaching data for FITNET prediction model. Using 10-fold cross validation, mean squared error (MSE) and multiple correlation coefficients (R) were observed to exhibit performance of the prediction model. The model performed high R (close to 1) and acceptable MSE values. This method aims that, in a probable similar accident scene in future, it will be possible to analyze the impact speeds just by entering average deformation amounts into an application on a portable device at the accident scene without requirement of expensive reconstruction tools and it will be a guide for analysis of other accident types.

A Low-cost IMU/GNSS Cooperative Positioning Method for VANETs in the Urban Environments

It is important to know the key problem of the emerging intelligent transportation systems –relative position, especially in the collision warning and speeds advisory. However, the commercial Global Satellite Navigation Systems (GNSS) receiver cannot up to the standard of these purpose. Fortunately, using Cooperative Positioning (CP) techniques to share the GNSS measurements between vehicles can largely improve the performance of relative positioning in a vehicular ad hoc network (VANET). But in urban environments, the reduced quality or complete unavailability of GNSS measurements challenge the effectiveness of any CP algorithm. In this paper, a new improved tight CP technique is proposed which adds the measurements from low cost inertial sensors. In the enhanced CP method proposed here, vehicles communicate their GPS measurements and inertial measurement unit (IMU) data, and each vehicle fuses local GPS and IMU measurements and those of the neighbours. Experimental results show that the new tight integration CP method can enhance the relative positioning in low GPS coverage environment, such as in very dense urban areas and tunnels.

Analysis of facial injuries requiring ophthalmological care due to frontal vehicle collisions

Motor vehicle collisions are responsible for a large number of ocular injuries. Although ocular injuries require an early ophthalmological examination at the time of trauma to detect any type of ocular dysfunction, some ophthalmological abnormalities are not detected after the facial injury owing to failure of referral ophthalmologists. This study aimed to investigate the prevalence of requiring ophthalmological care by evaluating the patterns and severity of ocular and severe facial injuries from real-world vehicle collisions in Japan. We collected data on vehicle passengers with any facial injuries who were involved in frontal collisions. Data were obtained from in-depth data records from the Institute for Traffic Accident Research and Data Analysis (ITARDA), Japan from 1993 to 2005. Collision information and victims’ medical data were reviewed. The 226 victims had a mean age of 33.3 ± 14.9 years with an equivalent barrier speed of 35.2 ± 13.0 km/h. Thirty (13.3%) victims suffered ocular injury or fractures in the upper or middle face (OIFF). Victims with OIFF had a significantly higher severity of injuries, especially in the face and lower extremities, and suffered from a higher speed of collisions than those without OIFF (p<0.001). Victims wearing seat belts had a significantly lower prevalence of having OIFF than those not wearing seat belts. Most of the victims with OIFF (29/30) were involved in collisions without deployment of airbags. To prevent severe ocular injuries, correct use of seat belts with airbag deployment is required. Additionally, the present study enhances that more victims with OIFF are cared for by ophthalmologists immediately after the collision, improving their quality of life and preventing conflicts owing to inadequate medical management.

Pedestrian injury risk and the effect of age

Older adults and pedestrians both represent especially vulnerable groups in traffic. In the literature, hazards are usually described by the corresponding injury risks of a collision. This paper investigates the MAIS3+F risk (the risk of sustaining at least one injury of AIS 3 severity or higher, or fatal injury) for pedestrians in full-frontal pedestrian-to-passenger car collisions.Using some assumptions, a model-based approach to injury risk, allowing for the specification of individual injury risk parameters for individuals, is presented. To balance model accuracy and sample size, the GIDAS (German In-depth Accident Study) data set is divided into three age groups; children (0–14); adults (15–60); and older adults (older than 60). For each group, individual risk curves are computed. Afterwards, the curves are re-aggregated to the overall risk function.The derived model addresses the influence of age on the outcome of pedestrian-to-car accidents. The results show that older people compared with younger people have a higher MAIS3+F injury risk at all collision speeds. The injury risk for children behaves surprisingly. Compared to other age groups, their MAIS3+F injury risk is lower at lower collision speeds, but substantially higher once a threshold has been exceeded. The resulting injury risk curve obtained by re-aggregation looks surprisingly similar to the frequently used logistic regression function computed for the overall injury risk. However, for homogenous subgroups – such as the three age groups – logistic regression describes the typical risk behavior less accurately than the introduced model-based approach.Since the effect of demographic change on traffic safety is greater nowadays, there is a need to incorporate age into established models. Thus far, this is one of the first studies incorporating traffic participant age to an explicit risk function. The presented approach can be especially useful for the modeling and prediction of risks, and for the evaluation of advanced driver assistance systems.

IMPROVEMENT OF A CARRYING STRUCTURE OF OPEN-TOP WAGON WITH THE PURPOSE OF PROVIDING OF HIS DURABILITY AT HITTING

The article presents the results of investigations of the strength of the supporting structure of the bodyopen-top wagon at shunting impacts taking into account the different speeds. Research literature on thesafety of wagon fleet during the manoeuvres showed that the speed of collision of the wagons in operationexceed the standard. This causes increased force loading bearing structures gondola body and damagingthem. Almost half of all injuries in new wagons occurs when the dissolution from the hills. The greatestpercentage of damages falls on the supporting structures of wagon bodies.With the aim of ensuring the strength of bodies of wagons during shunting impacts to meet theincreasing speeds of the improved load-bearing structures, by putting on the most loaded areas of the framereinforcing plates. The thickness of the lining is selected proceeding from the condition of ensuring thestrength. Calculation of the strength of the body of a wagon carried out using the finite element method.The results of the calculation of the strength of the body of the wagon with respect to the proposedactivities, allowed us to conclude about the feasibility of the technical solutions. In addition, proposedmeasures for improvement of the supporting structure body of a open-top wagon allow you to maintain thetechnical condition at the existing repair facilities.

Concrete road barriers subjected to impact loads: An overview

CONCRETE BARRIERS PREVENT VEHICLES FROM ENTERING THE OPPOSITE LANE AND GOING OFF THE ROAD. AN IMPORTANT FACTOR IN THE DESIGN OF CONCRETE BARRIERS IS IMPACT LOAD, WHICH A VEHICLE EXERTS UPON COLLISION WITH A CONCRETE BARRIER. THIS STUDY SUGGESTS THAT A HEIGHT OF 813 MM, A BASE WIDTH OF 600 MM, AND A TOP WIDTH OF 240 MM ARE OPTIMUM DIMENSIONS FOR A CONCRETE BARRIER. THESE DIMENSIONS ENSURE THE STABILITY OF CONCRETE BARRIERS DURING VEHICLE COLLISIONS. AN ANALYTICAL AND EXPERIMENTAL MODEL IS USED TO ANALYZE THE CONCRETE BARRIER DESIGN. THE LS-DYNA SOFTWARE IS UTILIZED TO CREATE THE ANALYTICAL MODELS BECAUSE IT CAN EFFECTIVELY SIMULATE VEHICLE IMPACT ON CONCRETE BARRIERS. FIELD TESTS ARE CONDUCTED WITH A VEHICLE, WHEREAS LABORATORY TESTS ARE CONDUCTED WITH MACHINES THAT SIMULATE COLLISIONS. FULL-SCALE TESTS ALLOW THE ACTUAL SIMULATION OF VEHICLE COLLISIONS WITH CONCRETE BARRIERS. IN THE VEHICLE TESTS, A COLLISION ANGLE OF 25°, COLLISION SPEEDS OF MORE THAN 90 KM PER HOUR, AND A VEHICLE WEIGHING MORE THAN 2 T ARE CONSIDERED IN THE REVIEWED STUDIES. LABORATORY TESTS ARE PERFORMED TO TEST BRIDGE CONCRETE BARRIERS IN STATIC CONDITION.

Experimental analysis of the dissipated energy through tire-obstacle collision dynamics

Wheeled vehicles are responsible for a substantial portion of dissipated energy while the share of tire-ground interface is among the most role playing elements in this regard. The vibrations and kinetics of a traversing wheel over an obstacle is a paradigm that can serve as a functional example for energy dissipation of wheeled vehicles. This paper communicates the analysis of the dissipated energy for a traveling wheel at collision time with obstacles while a controlled laboratory condition of the soil bin facility equipped with a single wheel-tester rig was utilized to carry out the experiments. The tests were conducted as affected by wheel load, obstacle height, obstacle geometry, slippage and speed. It was inferred that the increment of collision speed, obstacle height and tire slippage lead to the increase of the dissipated energy; however, the complexity lies in the contradictory effect of wheel load. This can be attributed to the nonlinear wheel dynamics and the vibration attenuation process. It has to be emphasized that the outcome of this study would serve as a functional catalyst for the extensive researches concerned with the machine design industry and the heavy vehicle trafficking management.

차량 정면충돌 및 추돌시 유효충돌속도에 따른 탑승자 상해특성에 관한 연구

Recently, various research studies on frontal collision and rear-ender which occur more frequently compared to others are underway as the public interest on them is growing. This study analyzes scientifically the relationship between effective impact speed and injury incidence for vehicle crash accident reconstruction and presents a relevant model formula. Because real vehicle experiments have certain limitations such as possible injuries, this study efforts to collect and analyze as many materials as possible to substitute real vehicle experiments, including data from various collision tests and human experiments. As a result, this study present a threshold in which head-on collisions and rear impacts do not cause injuries under 7 km/h of effective impact speed, and suggests a model formula showing that injury extent is linearly proportional to effective impact speed through collision speed and amount of plastic deformation. In conclusion, a model formula for estimating effective impact speed and injury incidence newly proposed in this study is expected to be used as a minimum standard of judgment in disputes on the injury extent of passenger in head-on collisions and rear impacts. Furthermore its availability in terms of technological analysis in legal arguments is expected to be very high if this study will be enhanced by referring to scientific analyses of various real accidents so as to apply it in various types of collision accidents.

From cloud crash to star birth: star formation in cloud collisions

AbstractWe performed three-dimensional hydrodynamical simulations of idealized giant molecular cloud collisions including star formation and radiative transfer. We found that the characteristics of the colliding systems are similar to the observations of the Spitzer bubbles, suggesting these objects could be created in such interactions. A high velocity collision creates a top-heavy core mass distribution but is not strongly affected by radiation. At lower collision speeds, the HII regions have time to expand within the shock and promote the formation of massive cores.

Shocks in unmagnetized plasma with a shear flow: Stability and magnetic field generation

A pair of curved shocks in a collisionless plasma is examined with a two-dimensional particle-in-cell simulation. The shocks are created by the collision of two electron-ion clouds at a speed that exceeds everywhere the threshold speed for shock formation. A variation of the collision speed along the initially planar collision boundary, which is comparable to the ion acoustic speed, yields a curvature of the shock that increases with time. The spatially varying Mach number of the shocks results in a variation of the downstream density in the direction along the shock boundary. This variation is eventually equilibrated by the thermal diffusion of ions. The pair of shocks is stable for tens of inverse ion plasma frequencies. The angle between the mean flow velocity vector of the inflowing upstream plasma and the shock's electrostatic field increases steadily during this time. The disalignment of both vectors gives rise to a rotational electron flow, which yields the growth of magnetic field patches that are coherent over tens of electron skin depths.

Forward vehicle collision mitigation by braking system based on artificial bee colony algorithm

Decision-making is a crucial step in vehicles' safety systems, which determines the right time for the system to intervene and to take the required action, depending on the current situation of the vehicle. The warning/intervention system becomes active when the driving situation considered unpleasant while still giving the control to the driver. Taking the action of warning, braking and determining the best time for this intervention are important decisions in collision mitigation systems. In this work, a novel system is designed based on artificial bee colony algorithm to enhance the decision-making in such systems. This work c oncentrates on collision mitigation by braking systems only, for front-to-rear accidents. This paper studies cases when the hosting vehicle approaches moving and stationary objects. This work is simulated, and the results are obtained and analyzed which proved the contribution to this work in reducing the collision speed and the stopping distance, in comparison with previous related works.

How to form planetesimals from mm-sized chondrules and chondrule aggregates

The size distribution of asteroids and Kuiper belt objects in the solar system is difficult to reconcile with a bottom-up formation scenario due to the observed scarcity of objects smaller than $\sim$100 km in size. Instead, planetesimals appear to form top-down, with large $100-1000$ km bodies forming from the rapid gravitational collapse of dense clumps of small solid particles. In this paper we investigate the conditions under which solid particles can form dense clumps in a protoplanetary disk. We use a hydrodynamic code to model the interaction between solid particles and the gas inside a shearing box inside the disk, considering particle sizes from sub-millimeter-sized chondrules to meter-sized rocks. We find that particles down to millimeter sizes can form dense particle clouds through the run-away convergence of radial drift known as the streaming instability. We make a map of the range of conditions (strength of turbulence, particle mass-loading, disk mass, and distance to the star) which are prone to producing dense particle clumps. Finally, we estimate the distribution of collision speeds between mm-sized particles. We calculate the rate of sticking collisions and obtain a robust upper limit on the particle growth timescale of $\sim$$10^5$ years. This means that mm-sized chondrule aggregates can grow on a timescale much smaller than the disk accretion timescale ($\sim$$10^6 - 10^7$ years). Our results suggest a pathway from the mm-sized grains found in primitive meteorites to fully formed asteroids. We speculate that asteroids may form from a positive feedback loop in which coagualation leads to particle clumping driven by the streaming instability. This clumping, in turn reduces collision speeds and enhances coagulation.} Future simulations should model coagulation and the streaming instability together to explore this feedback loop further.

Determination of the collision speed of a vehicle from evaluation of the crush volume using photographs

In accident reconstruction analysis of a collision between modern vehicles which have a three-dimensional frontal shape, classical two-dimensional crush measurement and modelling have apparent limits. In this paper, a new model which can calculate the collision speed from the three-dimensional crush volume estimated using two-dimensional photographic data of the collision crush shape is presented. The equation for the crush volume and the collision speed include the mass of the vehicle, and it is composed as a single equation, disregarding the size of the vehicle. The optimal coefficients were obtained through least-squares curve fitting using National Highway Traffic Safety Administration collision test data, and they were validated through actual vehicle collision tests. Additionally, a photogrammetry method using only photographic data of the collision is suggested for immediate application in reconstruction analysis of an actual accident, which can make the measurement of the crush volume relatively convenient and accurate.