Barrier Crash Research Articles

Application of Bayesian Semi-Parametric and Hierarchical Models for Analyzing Dispersed Traffic Barriers Crash Data

Introduction: Despite the traffic barriers effectiveness in reduction of the severity of run-off road crashes, the severity of barrier crashes still accounts for a significant fraction of road fatalities. Although extensive research has already been conducted in studying traffic barrier crashes, those studies mostly either consider the severity or frequency of crashes. Here, the equivalent property damage only (EPDO) was used to account for both aspects of crashes. While modeling EPDO crashes, there are challenges associated with that type of dataset including its sparse distribution, and the presence of heterogeneity in the dataset due to aggregation of various crash types. Methods: Ignoring the sparse nature of the data might result in biased or even erroneous results. Thus, in this study we identify factors to barriers EPDO crashes while considering the discussed challenges. Those consideration are especially important as in the next step we will employ the modeling results for conducting the cost-benefit analysis. Two main methods were considered in this study to address the discussed challenges including parametric and non-parametric Bayesian hierarchical models. A semiparametric Bayesian approach was used to relax the normality assumption by using a mixture of multivariate Dirichlet prior, defining a flexible nonparametric model for the random effects’ distribution, and using grouping to account for the heterogeneity due to the structure of the dataset. On the other hand, Bayesian hierarchical models with two distributions of Poisson and negative binomial with similar levels of hierarchy were considered. These models were chosen as closest models to the Bayesian semiparametric model. The incorporated models were compared in terms of deviance information criterion (DIC). Results and Discussion: The results highlighted that although the semi-parametric method outperforms the Bayesian hierarchical model with Poisson distribution, the Bayesian hierarchical model with negative binomial (NB) distribution outperform the semi-parametric model. The findings might be related to the severe sparse nature of the EPDO, which cannot optimally be accounted by semiparametric approach, and the model needs more flexibility. Conclusion: It was found that being unrestrained, driving in interstate system, driving in clear weather, light conditions, and driving in a higher traffic all increase the likelihood of EPDO crashes. Also, while some predictors were significant in less accommodative models of semi-parametric or Poisson models, they were not for Negative binomial model.

Solid safety barriers as a highway traffic noise reduction strategy

Placing solid safety barriers (concrete crash barriers) along a highway, instead of steel guard rail, can help reduce traffic generated noise at nearby sensitive sites. The effectiveness of these barriers on traffic noise levels is dependent on the height of the barrier, the number of traffic lanes, vehicle mix, and the elevation of the receiver relative to the barrier. The effect of solid safety barriers for sites at a variety of distances from a highway has been investigated for both city streets and freeways of various widths using the U.S. Federal Highway Administration Traffic Noise Model (TNM). TNM predicted noise level reductions, attributable to solid safety barriers, were developed for research scenarios in locations with both hard soil and lawn ground types. Results show a readily perceptible and sometimes substantial noise reduction at sites within a few hundred feet of the roadway.

Fibre Mesh in Reinforced Slabs

Abstract: Fiber Reinforced Concrete is gaining attention as an effective way to improve the performance of concrete. Fibers are currently being specified in tunneling, bridge decks, pavements, loading docks, thin unbonded overlays, concrete pads, and concretes slabs. These applications of fiber reinforced concrete are becoming increasingly popular and are exhibiting excellent performance The usefulness of fiber reinforced concrete in various civil engineering applications is indisputable. Fiber reinforced concrete has so far been successfully used in slabs on grade, architectural panels, precast products, offshore structures, structures in seismic regions, thin and thick repairs, crash barriers, footings, hydraulic structures and many other applications. This study presents understanding srength of fibre reinforced conceret. Mechanical properties and durability of fiber reinforced concrete.

Impact Analysis and Structural Optimization of Crash Barriers

The primary thought of this review is to assess the impact absorbance, strength and durability properties using non-linear finite element simulations of analytical model of crash barriers. Before manufacturing and erection of crash barriers on site are generally simulated for impact performance using finite element analysis various parameters are checked such as 1) Crash performance 2) Vehicle trajectory after collision 3) Safety of the vehicular occupant.

An empirical study on V2X radio coverage using leaky coaxial cables in road crash barriers

For current and future automated driving functions, the radio availability of broadband hybrid networking services (e.g. digital broadcasting, mobile radio, dedicated short range communication) is a prerequisite for continuous V2X information exchange. The supply focus for this is explicitly the road route with its lanes. The application of antenna-based solutions for such longitudinal radio cells with hybrid telematics services is expensive from the installation point of view and can only be adapted to new future telematics standards with great effort. A more suitable solution for such longitudinally shaped radio cells for road routes are leaky coaxial cables (LCX), which are already successfully used for tunnel solutions, for example. The paper discusses the installation and radio implementation of broadband LCX solutions (up to 6 GHz) in terms of simulation and surveying. The integration of the LCX into the crash barrier is favored due to low installation effort and easy upgradeability. An installation was realized on an automotive test fields, where preliminary empirical results for radio simulation and coverage were obtained. Based on the simulations and evaluation measurements, it can be shown that the propagated coverage approach is sustainable over all radiated services. Further solution approaches such as the direct insertion of LCX into the roadway and the derivation of vehicle location information are discussed in the outlook of the paper.

An element dependent multiple lag rational function approximation for aeroelastic analysis of cable bridge

Modeling of self-excited aerodynamic forces using the rational function approximation (RFA) is studied. The Scanlan and Tomko model of self-excited forces contain flutter derivatives (FDs) that are function of reduced frequency. Various form of RFAs have so far been proposed to approximate the FDs of flat plate and bluff body deck sections. Herein an element dependent multiple lag (EDML) RFA is considered as an extension of Rogers RFA. This uses different lag coefficients for each element of the aerodynamic force coefficients. The state-space formulation in modal coordinates, using EDML RFA, is developed and applied to a long span cable-stayed bridge for flutter analysis. The formulation uses the basic idea that aerodynamic states involve convolutions arising from partial fractions of the RFA. The finite element model of the bridge is developed, and a geometrically nonlinear static analysis is performed, and mass and stiffness matrices extracted. EDML RFA yields the best fit for all FDs, although certain spikes and fluctuations are observed for some FDs. A marginal decrease in flutter speed is obtained. However, as the proposed EDML RFA based state-space formulation accurately predict FDs, it can be used for bluff body bridge decks with added features like crash barriers that may result in significant change in flutter speed.

Trivariate Copula for Modeling Barriers Crash Severity, Accounting for Policy Endogeneity

Studies have been implemented in the literature to enhance the safety of traffic barriers by identification of the contributory factors to those crashes. However, almost all those past studies are subject to potential pitfalls of just answering the cause-and-effect question by traditional statistical methods, which fail to account for possible endogeneity. Modeling traffic barrier crash severity with traditional statistical methods might be biased as many parameters such as barrier’s types is endogenous to unseen factors including policy makers’ decisions in allocating those barriers. Not accounting for the possible endogeneity in the dataset and ignoring correlation between regressors’ error terms might result in biased or erroneous coefficients’ estimates. That is especially true in the presence of strong correlations across models’ error terms. Thus, this study was conducted to model barriers’ crash severity by taking into consideration the endogeneity and correlations across the models’ error terms. Here, the trivariate copula-based method was implemented to simultaneously model traffic barrier crash severity, shoulder width and barrier’s types, while accounting for interrelationships across the models’ error terms. The results provide strong evidence of correlations between the unseen factors to the selections of barrier’s types, shoulder width installation, and crash injury levels. For instance, we found in the presence of accounting for endogeneity and correlation between unseen factors, concrete traffic barrier type and higher shoulder width installation are negatively correlated with unseen factors contributing to severe barriers’ crashes That is despite the fact that the observed factors of those predictors were found to have a reverse impact on the severity of barriers’ crashes.

Performance of Cellular Concrete under Low-Velocity Impact and Penetration

Abstract Cellular concrete, also known as foamed concrete, has been widely used in different geotechnical and nonstructural applications owing to a unique geometric nature that results in low density and high flowability and its low construction cost. The behavior of cellular concrete under impact or penetration has also drawn attention in applications such as engineered material arrestor systems, emergency escape ramps, and crash barriers. The high void content inside cellular concrete allows it to undertake large deformation, which could lead to high energy absorption. However, there is still a lack of fundamental understanding of the energy absorption of the material and response of the material under impact or penetration. This paper carries out an investigation of the response of cellular concrete subjected to low-velocity impact and penetration. Cellular concretes with different foaming agents and with fibers were prepared and evaluated. Experimental results demonstrated the superior ability of cellular concrete in absorbing and dissipating impact and penetration energies compared with conventional concrete. The paper shows that through steadily deforming the internal void structure, cellular concrete can diminish the reaction force caused by a collision and dissipate penetration energy. Results of the study can help to better understand the mechanism of energy absorption of cellular concrete so as to better tailor it for different applications.

Examining crash injury severity and barrier-hit outcomes from cable barriers and strong-post guardrails on Alabama’s interstate highways

Introduction: This study investigates the impact of several risk factors (i.e., roadway, driver, vehicle, environmental, and barrier-specific characteristics) on the injury severity resulting from barrier-related crashes and also on barrier-hit outcomes (i.e., vehicle containment, vehicle redirection, and barrier penetration). A total of 1,685 barrier-related crashes, which occurred on three major interstate highways (I-65, I-85, and I-20) in the state of Alabama, were collected for a seven-year period (2010–2016), and all relevant information from the police reports was reviewed. Features that were rarely explored before (e.g., median width, barrier length, barrier offset or lateral position, left shoulder width, blockout type, and number of cables) were also collected and examined. Two types of longitudinal barriers were analyzed: high-tension cable barriers installed on medians and strong-post guardrails installed on medians and/or roadsides. Method: Two separate mixed logit (MXL) models were used to analyze crash injury severity in median and roadside barrier-related crashes. Two additional MXL models were separately adopted for median and roadside barrier-related crashes to estimate the probability of three barrier-hit outcomes (vehicle containment, vehicle redirection, and barrier penetration). Results: The results of crash injury severity MXL models showed that, for both median and roadside barrier crashes, barrier penetration, female drivers, and driver fatigue were associated with a higher probability of injury or fatal crashes. The results of barrier-hit MXL models showed that longer barrier length, Brifen cable barrier system, and barrier lateral position were significant predictors of median barrier-hit outcomes, whereas dark lighting condition, driving under the influence (DUI), presence of curved freeway sections, and right shoulder width significantly contributed to roadside barrier-hit outcomes. Conclusions: The MXL model succeeded in identifying several contributing factors of crash severity and barrier-hit outcomes along Alabama’s interstate highways. Practical applications: One study application is to design longer barrier run length (greater than 1230 feet or 0.2 miles) to reduce the barrier penetration likelihood.

Application of machine learning technique for optimizing roadside design to decrease barrier crash costs, a quantile regression model approach

Introduction: In-transport vehicles often leave the travel lane and encroach onto natural objects on the roadsides. These types of crashes are called run-off the road crashes (ROR). Such crashes accounts for a significant proportion of fatalities and severe crashes. Roadside barrier installation would be warranted if they could reduce the severity of these types of crashes. However, roadside barriers still account for a significant proportion of severe crashes in Wyoming. The impact of the crash severity would be higher if barriers are poorly designed, which could result in override or underride barrier crashes. Several studies have been conducted to identify optimum values of barrier height. However, limited studies have investigated the monetary benefit associated with adjusting the barrier heights to the optimal values. In addition, few studies have been conducted to model barrier crash cost. This is because the crash cost is a heavily skewed distribution, and well-known distributions such as linear or poison models are incapable of capturing the distribution. A semi-parametric distribution such as asymmetric Laplace distribution can be used to account for this type of sparse distribution. Method: Interaction between different predictors were considered in the analysis. Also, to account for exposure effects across various barriers, barrier lengths and traffic volumes were incorporated in the models. This study is conducted by using a novel machine-learning-based cost-benefit optimization to provide an efficient guideline for decision makers. This method was used for predicting barrier crash costs without barrier enhancement. Subsequently the benefit was obtained by optimizing traffic barrier height and recalculating the benefit and cost. The trained model was used for crash cost prediction on barriers with and without crashes. Results: The results of optimization clearly demonstrated the benefit of optimizing the heights of road barriers around the state. Practical Applications: The findings can be utilized by the Wyoming Department of Transportation (WYDOT) to determine the heights of which barriers should be optimized first. Other states can follow the procedure described in this paper to upgrade their roadside barriers.

Analysis of normal and tangential restitution coefficients in car collisions based on finite element method

In momentum-based impact models used in accident reconstructions, the restitution coefficient is a key role to determine impulses and delta-V accurately in car-to-car collisions. The restitution coefficients can be defined as the normal and the tangential direction in the contact plane, and the same value of the normal and tangential coefficients is employed in a two-dimensional PC-Crash model. Ishikawa (1993) proposed an impact model with the normal and tangential restitution coefficient, however, to the best of the author's knowledge, few studies have further investigated tangential restitution coefficients in detail. In this study, the normal and tangential restitution coefficients of the impact model were investigated based on the finite element (FE) analysis. FE simulations of angled barrier crashes with varying barrier angles as well as 16 car-to-car collisions were conducted. As the contact plane slides, the ratio of the tangential impulse to the normal impulse becomes the same value with the maximum friction coefficient. The tangential restitution coefficient is related to whether sliding occurs on the contact plane, and can be expressed as a function of the impulse ratio. The tangential restitution coefficient decreased with increasing the impulse ratio and is positive in non-sliding collisions and negative in sliding collisions. An approximate expression for the tangential restitution coefficient was formulated as a function of the generalized impulse ratio. The calculated impulses of the impact model with normal and tangential restitution coefficients were closer to the FE analysis than the PC-Crash model which uses a constant restitution coefficient of 0.1.

Investigating mechanical properties and durability of concrete containing recycled rubber ash and fibers

This article investigates the suitability of utilizing end of life rubber tyre particles in concrete as fine aggregate. Rubber ash and rubber fibers were used to develop two series of rubber ash concrete (series I) and hybrid concrete (series II) mixes. The natural fine aggregate was replaced by rubber ash (by volume of 5%, 10%, 15% and 20%) in series I; whereas in series II, the amount of rubber ash was kept constant at 10% and rubber fiber was introduced as replacement of fine aggregate (by volume of 5%, 10%, 15%, 20% and 25%). The concrete mixes were evaluated for compressive strength, flexural strength, resistance to impact loading, fatigue loading, water penetration and shrinkage strain was evaluated. It was observed that inclusion of rubber ash resulted in the improvement of impact resistance of concrete. The results also show that up to 10% rubber ash and rubber fibers can be utilized as fine aggregate to develop feasible and durable rubberized concrete pavements, crash barriers and paver blocks.

Determining vehicle pre-crash speed in frontal barrier crashes using genetic algorithm model adjustment techniques for intermediate car class

This paper introduces another approach to pre-crash velocity determination by the means of genetic algorithm model adjustment (GAMA). This innovative method is based on the standard genetic algorithm approach applied to the problem of determining the dependency of predicted variable on given parameters. The experiment is performed on a database obtained from NHTSA (National Highway Traffic Safety Administration), which contains potent number of data samples regarding frontal vehicle crash tests: i.e. vehicle mass, deformation zone and deformation coefficients C1-C6. Various classes of possible functions are considered and the model for determining the pre-crash speed based on the given parameters is obtained.

A study and identification of the time and cost overrun in the construction project

The construction industry features a major impact on all country economies. It is one among the components that contributes to the expansion of any economy. The achievement of the project's goal and goals within the time and budget constraints is critical to any project's success. In this article, an attempt has been made to figure out how much time is delayed and how much cost is overrun on the Kanaka Durga Flyover in Vijayawada. Planning of the Kanaka Durga flyover alignment plan and crash barrier & expansion joints progress map using AutoCAD software were done. It is found that due to river Krishna Pushkaralu, unexpected water overflow at barrage, lack of machinery and its maintenance, lack of skilled labor pool and improper scheduling and high change of project scopes are the explanations liable for delays. As a result, it is often concluded that the careful planning and follow-up will help to stop cost overruns and time delays.

Quasi static axial compression of empty and PU foam filled circular aluminium and light gauge square steel tubes

Abstract For structural applications, Concrete Filled Steel Tubes (CFST) proved as efficient building material. Further study on composite filled tubes to increase strength to weight ratio is evident to improve material efficiency and reduce load on structure. In the recent years, investigations on impact resistance and energy absorption of foam filled thin walled Aluminium and Steel composite tubes have gained importance for mechanical and aerospace applications and also as crash barriers to improve its dynamic characteristics. These are made by metal tube envelopes filled with Polyurethane foam infill material. Present study is carried out to understand the strength and behaviour of PU Foam Filled Tubes for structural applications. This paper presents experimental work on Quasi Static Axial Compression Tests on Empty and PU Foam filled Circular Aluminium and Light Gauge Square Steel Tubes. For Aluminium Tubes, D/t of 40.20 and 30.15 and L/D of 3.32 and for Steel Tubes, b/t of 125, 100 and 83.33 and L/b of 2, 3 and 4 were considered. High density PU foam (of density 150 kg/m3) alone, Empty tubes and Polyurethane foam-filled tubes are tested for quasi-static axial compression experimentally and validated the results with numerical simulation using ABAQUS 6.14–3 software. The mean crushing loads of hollow and polyurethane foam-filled circular Aluminium and Square Steel tubes were calculated from FEM and experimental results. The experimental and numerical values are in agreement. This study reveals that due to composite action between tube and foam, the resistance to buckling has improved significantly when compared to empty tubes even for high L/D & L/b ratios.

Geometry Influence of Far-Side Wall of Tunnel Emergency Bay on the Traffic Safety

Goal of the road safety inspection in the Slovak Republic according to the Act 249/2011 Coll. is to assess the safety level of roads and motorways and to identify potential weak points from the road safety point of view. The results of road safety inspection can then serve as an objective data for traffic administrators and stakeholders for safety improvement as well as for legislators for changes in legislative that influence construction of road infrastructure. One of the potential road safety weak point is the far-side wall of tunnel emergency bay. In case of traffic accident its concrete wall acts as a rigid non-moveable obstacle with the geometry that will not allow practically any sliding of the vehicle (as a standard road safety guardrail would) and vehicle is stopped suddenly on very short distance and in very short time with severe consequences on the vehicle occupants. The focus of the presented article is to examine influence of simple changes to geometry of the far-side of tunnel emergency bay that could be implemented (after legislative changes) in the construction of tunnels. To analyze the problem, we used parametric simulations of vehicle impacts into far-side wall of emergency bay whereby far-side wall was sloped at various angles with respect to road axis. The simulations were performed in PC-Crash simulation software using finite element method module. Results indicate that simple changes to geometry of the far-side of emergency tunnel bay can provide significant reduction of impact severity, even if there are no deformable crash barriers used and impact is still into rigid concrete wall. The results of simulation calculations contribute to the conclusion that although the design and construction of the emergency bay is in accordance with the applicable legislation, it poses a serious safety risk for passengers.

Behaviour of Rubberized Plain and Reinforced Concrete under Impact.(Dept.C)

Utilization of rubber tire waste products in concrete has attracted attention because of energy crisis and the environmental problems. The concrete are postulated to be a potential material especially for construction applications, which are subjected to impact effects such as crash barriers, bridges and roads. In this study, an analysis of rubberized concrete was done by using various proportions of crumb rubber as a replacement of sand by volume [0 %, 15%, 30%, 50% and 100%). The slump for five different mixes was measured. On the other hand twenty plain and reinforced concrete beams with dimensions (10 x 10 x 70 cm) were prepared for impact resistance lest. The impact resistance was measured as a kinetic energy, which generated by falling of a load (15 kg.) from variable distances until the failure occurs. Cubes, cylinders and beams were prepared to study the compressive strength, toughness and impact for rubberized concrete. The concrete mixtures exhibited lower compressive strength than normal concrete, however the samples did not has a brittle failure but it has a ductile failure, and has the ability to absorb large amount of plastic energy under impact strength. On the other hand the results showed that the impact resistance of rubberized concrete was higher.

Analogy of novel TRC crash barriers with RC crash barrier under impact load

The most popular crash barriers made so far are made up of steel-reinforced concrete (RC), which has high flexural rigidity but poor energy absorption. Consequently, when a vehicle collides with such crash barrier, the vehicle is seriously damaged and occupants may be fatally injured due to the severe impact of the collision. Hence, in order to enhance the safety of road users, a pre-fabricated textile-reinforced concrete (TRC) crash barrier prototype is developed using glass and basalt textile as reinforcement. The experimental investigations are carried out on both glass and basalt TRC crash barrier at the laboratory level under impact load to study the level of impact and deceleration rate. The performance of TRC crash barriers are also compared with RC crash barriers of equivalent calibrated reinforcement ratio. The lesser impact force and the lower rate of deceleration and higher energy absorption characteristics were experienced during the impact test for TRC crash barriers when compared to that of conventional RC barrier. Present study indicates that the application of TRC in crash barriers can improve the safety of the occupants and reduces damages to the impacting vehicles.

Bayesian hierarchical modelling of traffic barrier crash severity

Severe vehicle crashes have resulted in a large-scale social and economic loss. As a result, the reduction of those crashes has become one of the key objectives of policy makers. Although traffic barriers have been utilized to reduce the run-of-road crash severity, still those crashes account for a high number of severe crashes. Previous studies of traffic barrier crashes often either ignore the heterogeneity across different traffic barrier types, or just focus on specific types of traffic barriers. Thus, this study developed a Bayesian Hierarchical model (BHM) to identify the contributory factors impacting the severity of traffic barrier crashes while accounting for that heterogeneity. The assessment of model fit, inter-class correlation (ICC) coefficient, and deviance information criterion (DIC) all favoured the use of the BHM. Besides accounting for the heterogeneity between barrier types, the interaction across variables shoulder width and traffic barrier height were incorporated into the analysis. Due to the differences in traffic barrier design and vehicle performance across different roadway classifications, only Wyoming interstate traffic barrier were considered. Results indicated that there is an important interaction term between traffic barrier height and shoulder width so that the impact of these two predictors should not be separated. In addition, having a citation record, negotiating a curve, being a female driver, non-speed compliance, alcohol involvement, and showing emotional signs at the time of crash were factors increasing the severity of traffic barrier crashes. On the other hand, having a turn before hitting a traffic barrier, being a younger driver, and driving in adverse weather conditions were factors that significantly decrease the severity of traffic barrier crashes

Performance Assessment of Crash Barriers used in Road Safety: A Case Study of Malekhu Kurintar Section of the Prithvi Highway

Hill roads in Nepal are comprised of critical geometry and limited roadway clearances. It causes high number of runoff roadway type of accidents with single vehicle. These accidents often carry huge number of fatalities and severe injuries. Installation of crash barriers is the most effective way of preventing such accidents along hill roads. However, the existing practice of construction of crash barriers does not show the satisfactory results. Therefore, this research aimed at the evaluation of typical crash barriers constructed along the valley side of highway. Analysis of the road accident of Malekhu-Kurintar section of Prithvi Highway record shows that this section has relatively higher accident rate and most of the accidents are runoff roadway type. Further, these accidents are mainly caused due to either the absence or the failure of the crash barriers along the valley side of the highway. On the basis of field records, kinetic energy absorbed by the crash barriers and their deflections was investigated by application of computer based analysis tool ABAQUS V6.10. It has given satisfactory results on the deflection of W-beam and plum concrete barriers due to the impact of vehicle moving in various range of speed.