Linking roadway crashes and tire–pavement friction: a case study

Tire–pavement friction is a factor that can affect the rate of vehicle crashes. Several studies have suggested that reduced friction during wet weather conditions, due to water on the pavement surface reducing the contact area between the tire and the pavement, increases vehicle crashes. This study evaluates the effect of friction on both wet- and dry-condition crashes. The data for the study were provided by the New Jersey Department of Transportation. Regression analysis was performed to verify the effect of friction on the rate of wet- and dry-condition vehicle crashes for various types of urban roads. It was found that friction is not only associated with the rate of wet-condition vehicle crashes, but it also impacts the rate of dry-condition vehicle crashes. The analysis also suggested that the developed regression models could be used to define the friction demand for different road categories.     

A fully Bayesian before–after analysis of permeable friction course (PFC) pavement wet weather safety

Permeable friction course (PFC), a porous hot-mix asphalt, is typically applied to improve wet weather safety on high-speed roadways in Texas. In order to warrant expensive PFC construction, a statistical evaluation of its safety benefits is essential. Generally, the literature on the effectiveness of porous mixes in reducing wet-weather crashes is limited and often inconclusive. In this study, the safety effectiveness of PFC was evaluated using a fully Bayesian before–after safety analysis. First, two groups of road segments overlaid with PFC and non-PFC material were identified across Texas; the non-PFC or reference road segments selected were similar to their PFC counterparts in terms of site specific features. Second, a negative binomial data generating process was assumed to model the underlying distribution of crash counts of PFC and reference road segments to perform Bayesian inference on the safety effectiveness. A data-augmentation based computationally efficient algorithm was employed for a fully Bayesian estimation. The statistical analysis shows that PFC is not effective in reducing wet weather crashes. It should be noted that the findings of this study are in agreement with the existing literature, although these studies were not based on a fully Bayesian statistical analysis. Our study suggests that the safety effectiveness of PFC road surfaces, or any other safety infrastructure, largely relies on its interrelationship with the road user. The results suggest that the safety infrastructure must be properly used to reap the benefits of the substantial investments.     

Implications of Brexit for environmental assessment in the United Kingdom – results from a 1-day workshop at the University of Liverpool

There is currently a lack of clarity for what the anticipated British Exit from the European Union will mean for environmental assessment (EA) in the United Kingdom (UK) in the medium to long term. It is within this context that a workshop was organised by the Environmental Assessment and Management Centre (University of Liverpool) and held in Liverpool on 14 June 2017, with the involvement of the Ireland-UK branch of the International Association for Impact Assessment. Seven speakers talked on various aspects of the potential implications of Brexit for EA in the UK. The letter provides the key messages delivered by the speakers and in doing so draws out the benefits and risks associated with Brexit. Overall, the workshop concluded with the message that Brexit has the potential to allow EA, and other environmental legislation to be revisited, updated and strengthened.     

Is driving under the influence of cannabis becoming a greater risk to driver safety than drink driving? Findings from a longitudinal study

The present study examined the associations driving under the influence of (a) cannabis and (b) alcohol, and motor vehicle collisions during, in a longitudinal study of a New Zealand birth cohort (n=936). Participants reported significantly (p<.0001) greater rates of driving under the influence of cannabis than driving under the influence of alcohol during ages 21-25. Also, there were statistically significant bivariate associations between increasing levels of both: (a) driving under the influence of cannabis and (b) self-reported driving under the influence of alcohol, and increased risks of active motor vehicle collisions (p<.0001). These associations were adjusted for potentially confounding factors including average distance driven and self-reported risky driving behaviours. After adjustment, the associations between driving under the influence of cannabis and motor vehicle collisions remained marginally significant (p=.064), whereas adjustment for confounding factors reduced the association between driving under the influence of alcohol and motor vehicle collisions to statistical non-significance (p>.70). The results of the present study suggest that, for some populations, the risks of driving under the influence of cannabis may now be greater than the risks of driving under the influence of alcohol.     

Are airbags a dangerous safety measure? A meta-analysis of the effects of frontal airbags on driver fatalities

A meta-analysis has been conducted of the effectiveness of frontal airbags in reducing driver fatalities, and some potential moderator variables for airbag effectiveness have been investigated. The results confirm the assumption that airbags reduce accident fatalities among belted drivers, but the results are too heterogeneous for drawing conclusions about the size of the overall effect. No support has been found for the hypothesis that airbags increase overall fatality risk, as has been found in the study by Meyer and Finney (Meyer, M., Finney, T., 2005. Who wants Airbags? Chance, 18 (19) 3–16). The results do not seem to be affected by publication bias, and no indications of confounding effects of vehicle characteristics or impact velocity have been found. In frontal collisions belted driver fatalities were found to be reduced by about 22% when all types of airbags are regarded together. The revision of the test criteria for airbags in the USA in 1997 has improved airbag effectiveness. For unbelted drivers airbags are neither effective nor counterproductive, but may increase fatality risk in single vehicle accidents. The results show that there is a lack of knowledge about the effects of airbags in accidents that are not frontal collisions.     

Size effects in concrete fracture – Part II: Analysis of test results

This paper presents an analysis of the extensive experimental program aimed at assessing the influence of maximum aggregate size and specimen size on the fracture properties of concrete. Concrete specimens used were prepared with varying aggregate sizes of 4.75, 9.5, 19, 38, and 76mm. Approximately 250 specimens varying in dimension and maximum aggregate size were tested to accomplish the objectives of the study. Every specimen was subjected to the quasi-static cyclic loading at a rate of 0.125mm/min (0.005in./min) leading to a controlled crack growth. The test results were presented in the form of load-crack mouth opening displacement curves, compliance data, surface measured crack length and crack trajectories as well as calculated crack length, critical energy release rate, and fracture toughness (G ₁). There is a well pronounced general trend observed: G ₁ increases with crack length (R-curve behavior). For geometrically similar specimens, where the shape and all dimensionless parameters are the same, the R-curve for the larger specimens is noticeably higher than that for the smaller ones. For a fixed specimen size, G ₁ increases with an increase in the aggregate size (fracture surface roughness). For the same maximum aggregate size specimens, the apparent toughness increases with specimen size. It was clear that the rate of increase in G ₁, with respect to an increase of the dimensionless crack length (the crack length normalized by the specimen width), increases with both specimen size and maximum aggregate size increase. The crack trajectory deviates from the rectilinear path more in the specimens with larger aggregate sizes. Fracture surfaces in concrete with larger aggregate size exhibit higher roughness than that for smaller aggregate sizes. For completely similar specimens, the crack tortuosity is greater for the larger size specimens. The crack path is random, i.e., there are no two identical specimens that exhibit the same fracture path, however, there are distinct and well reproducible statistical features of crack trajectories in similar specimens. Bridging and other forms of crack face interactions that are the most probable causes of high toughness, were more pronounced in the specimens with larger maximum size aggregates.     

Mechanistic–empirical analysis of the results of finite element analysis on flexible pavement with geogrid base reinforcement

A finite-element response model was developed using ABAQUS software package to investigate the effect of geogrid base reinforcement on the response of a flexible pavement structure. Finite-element analyses were then conducted on different unreinforced and geogrid-reinforced flexible pavement sections. In this analysis, the base course (BC) layer was modelled using an elasto-plastic bounding surface model. The results of the finite-element analyses showed that the geogrid reinforcement reduced the lateral strains within the BC and subgrade layers, the vertical strain and shear strain at top of subgrade, and the surface permanent deformation. The higher tensile modulus geogrid resulted in larger reduction of surface permanent deformation. Based on the response parameters computed from the finite element analysis, the improvement of using geogrid for BC reinforcement was then evaluated using the damage models for rutting in the mechanistic–empirical method developed through NCHRP Project 1-37a. The results of mechanistic–empirical analyses showed that the traffic benefit ratio values can reach as high as 3.7 for thin base pavement section built over weak subgrade using high tensile modulus geogrid.     

Practitioners’ perceptions of the Brazilian environmental impact assessment system: results from a survey

Practitioners play a key role in implementing environmental impact assessment (EIA) policies. Gauging their perception can help in designing legislation or regulation reforms and signals what needs more attention in research. The Brazilian EIA system is under review by lawmakers, but there is scant information about the views of professionals. A survey was conducted to inquiry on practitioners’ perception of the Brazilian EIA system regarding: (1) quality of the process, (2) quality of the environmental impact studies (EIS), and (3) proposals to change the system. Four hundred and fourteen professionals participated in an online survey responding to 44 questions. Results show positive perceptions about some aspects of current practice, but there is a clear predominance of negative appraisal both about the quality of the process and the quality of EIS. The poorest practices are the consideration of cumulative impacts and determination of impact significance. As for proposals to change the system, respondents defend the continuity of specific characteristics of the Brazilian system. Essentially, practitioners are calling for incremental changes that do not require any modification in the legislation.     

Selected variants of a Memetic Algorithm for JSP – a comparative study

The article aims to address a research gap concerning the adequate configuration of a Memetic Algorithm adapted to solve the Job-Shop Scheduling Problem. The goal was accomplished by means of conducting a comparative study of 16 variants of a Memetic Algorithm, characterised with different places of hybridisation and local search methods applied. The study involved the solution of eleven instances of JSP and the comparison of the results with the results achieved with an Evolutionary Algorithm lacking the mechanism of hybridisation and selected local search methods. The utilitarian significance of the problem also involved the use of assessment measures intended for both practical applications and research purposes.     

Does safety climate predict safety performance in Italy and the USA? Cross-cultural validation of a theoretical model of safety climate

Previous studies have acknowledged the relevance of assessing the measurement equivalence of safety related measures across different groups, and demonstrating whether the existence of disparities in safety perceptions might impair direct group comparisons. The Griffin and Neal (2000) model of safety climate, and the accompanying measure (Neal et al. [NGH], 2000), are both widely cited and utilized. Yet neither the model in its entirety nor the measure have been previously validated across different national contexts. The current study is the first to examine the NGH measurement equivalence by testing whether their model of safety climate predicting safety performance is tenable in both English speaking and non-English speaking countries. The study involved 616 employees from 21 organizations in the US, and 738 employees from 20 organizations in Italy. A multi-group confirmatory factor analytic approach was used to assess the equivalence of the measures across the two countries. Similarly, the structural model of relations among the NGH variables was examined in order to demonstrate its cross-country invariance. Results substantially support strict invariance across groups for the NGH safety scales. Moreover, the invariance across countries is also demonstrated for the effects of safety climate on safety knowledge and motivation, which in turn positively relate to both compliance and participation. Our findings have relevant theoretical implications by establishing measurement and relational equivalence of the NGH model. Practical implications are discussed for managers and practitioners dealing with multi-national organizational contexts. Future research should continue to investigate potential differences in safety related perceptions across additional non-English speaking countries.     

Development of a process envelope for friction stir welding of DH36 steel – A step change

Friction stir welding of steel presents an array of advantages across many industrial sectors compared to conventional fusion welding techniques. However, the fundamental knowledge of the friction stir welding process in relation to steel remains relatively limited. A microstructure and property evaluation of friction stir welded low alloy steel grade DH36 plate, commonly used in ship and marine applications has been undertaken. In this comprehensive study, plates of 2000 × 200 × 6 mm were butt welded together at varying rotational and traverse speeds. Samples were examined microscopically and by transverse tensile tests. In addition, the work was complemented by Charpy impact testing and micro-hardness testing in various regions of the weld. The study examined a wide range of process parameters; from this, a preliminary process parameter envelope has been developed and initial process parameter sets established that produce commercially attractive excellent quality welds through a substantial increase in the conventionally recognised weld traverse speed.     

Phenotypic characterization of keratinocytes migrated from polymer support – in vitro study

The keratinocytes are able to migrate from the poly (2- hydroxyethylmethacrylate) disc if it is transfered to the new Petri-dish colonized with irradiated 3T3 mouse fibroblasts, and form a ring-shaped colony around the disc. The phenotypic characterization of human keratinocytes migrated from these discs was studied using a group of monoclonal antibodies. The keratinocytes in the external periphery of the colony of cells which migrated from the disc express the proliferating cell nuclear antigen (PCNA), 2, 3 chains and 51 integrin receptor. A protein of the desmosome complex, desmoplakin-1, was also expressed. Involucrin and cytokeratin-10 were expressed after prolonged cultivation. These results suggest that the migrated keratinocytes are able to proliferate, recognize extracellular matrix molecules important in the process of the re-epitelization of the wound, and terminally differentiate in vitro. They are encouraging for further experiments with respect to the development of a support for keratinocyte cultivation and for grafting in clinical practice.     

Can a road safety measure be both effective and ineffective at the same time? A game-theoretic model of the effects of daytime running lights

Studies that have evaluated the effects on accidents of daytime running lights for cars have consistently found that cars using daytime running lights are involved in fewer multi-party accidents in daylight than cars not using daytime running lights. However, studies evaluating the effects of mandatory use of daytime running lights have not always found an accident reduction. Although findings are mixed, there is a tendency for the aggregate effects of daytime running lights (i.e. the effects of an increasing share of traffic using daytime running lights) to be smaller than the intrinsic effects (i.e. the difference in accident involvement between cars using and not using daytime running lights). This paper presents a game-theoretic model to explain these apparently inconsistent findings. The game-theoretic model is based on so called Schelling-diagrams, originally introduced by Nobel laureate in economics Schelling. The effects of daytime running lights are modelled by means of Schelling-diagrams. It is shown that it is by no means impossible for cars using daytime running lights to always be safer than cars not using daytime running lights, while the total number of accidents remains constant even if the percentage of cars using daytime running lights increases from, say, 10% to 90%.     

A study on the improvements of new product development procedure performance–an application of design for Six Sigma in a semi-conductor equipment manufacturer

With the pressure of intensive global competition and the trend of shortening product life-cycle, the procedure for new product development (NPD) has become the focus of business concerns and investment of large corporations and the key strategy to upgrade competitiveness of corporations. An effective NPD procedure can meet the demands on quality, time-to-delivery and cost limitations of a corporation. Measuring and analysing the performance of the existing NPD procedure and pinpointing and resolving the problems of the existing NPD procedure is the key to improve the NPD performance to meet a corporation's demands. Six Sigma is a systemic procedure commonly used to improve product quality. This paper proposes a model to evaluate and improve the performance of NPD procedures by following the systemic procedure of Six Sigma and applying criteria defined by application of performance matrix, factor analysis, and theory of constraints. The resulting model is then verified with real life NPD procedures from a certain semi-conductor equipment manufacturer such that corporative competitiveness can be enhanced through the elevating cycle of performance evaluation, problem excavation, causes analysis, and countermeasure determination and execution proposed by this paper.     

Ballistic resistance of the carbon nanotube fibres reinforced composites – Numerical study

The numerical investigations were carried out to determine the ballistic resistance of the carbon nanotube (CNT) fibres reinforced composites. In this paper, the fundamental studies of the reinforcement characteristics are presented. It includes the single fibre mechanical and geometric properties as well as fibres distribution and volume (mass) concentration. The continuum matrix material includes a certain amount of fibres made of CNTs. An impact of the projectile with the sharp nose on the metal matrix composite plate was analysed. The computer simulations were performed with the finite element method implemented in LS-DYNA code. The plane formulation allows analysing extremely dense meshes. The obtained results presented the significant role of the carbon nanotube fibres.     

Capillary effects on flax fibers – Modification and characterization of the wetting dynamics

Introducing bio-based composites has now become an opportunity of development for industry. Accordingly, Liquid Composite Moulding (LCM) processes are increasingly used for manufacturing those composites, mainly in the transportation industry, since they are considered as effective and low cost routes to manufacture bio-based composites fitting high quality requirements, even for parts with complex shape. However observations of a large amount of voids in bio-based composites call for an improved understanding of the local wetting phenomena that occur during impregnation of the natural reinforcements. The purpose of the present work is to study the influence of flax fiber surface chemistry on the local wetting dynamics. Flax reinforcements were submitted to a thermal treatment to modify the chemical composition of fiber surface. In order to analyze the fiber’s wetting behavior, some methods for measuring apparent static contact angles and surface energy were firstly validated on solids of defined geometry, and subsequently applied to untreated and treated flax fibers. The Owens–Wendt’s approach was used to determine both components of apparent surface energy, indicating polar and dispersive interactions in materials. Subsequently dynamic tests were carried out on both types of chopped flax fibers in order to evaluate apparent advancing dynamic contact angles. Considerations about morphological effects have also been included. Finally bio-based composite plates reinforced with untreated and treated flax quasi-UD were simultaneously fabricated by LCM process, and observation of the porosities highlighted some benefits of using treated flax fibers.     

Comprehensive study of the effects of rolling resistance on the stress–strain and strain localization behavior of granular materials

This paper presents the results of a comprehensive study of the effects of rolling resistance on the stress–strain and strain localization behavior of granular materials using the discrete element method. The study used the Particle Flow Code (PFC) to simulate biaxial compression tests in granular materials. To study the effects of rolling resistance, a user-defined rolling resistance model was implemented in PFC. A series of parametric studies was performed to investigate the effects of different levels of rolling resistance on the stress–strain response and the emergence and development of shear bands in granular materials. The PFC models were also tested under a range of macro-mechanical parameters and boundary conditions. It is shown that rolling resistance affects the elastic, shear strength and dilation response of granular materials, and new relationships between rolling resistance and macroscopic elasticity, shear strength and dilation parameters are presented. It is also concluded that the rolling resistance has significant effects on the orientation, thickness and the timing of the occurrence of shear bands. The results reinforce prior conclusions by Oda et al. (Mech Mater 1:269–283, 1982) on the importance of rolling resistance in promoting shear band formation in granular materials. It is shown that increased rolling resistance results in the development of columns of particles in granular materials during strain hardening process. The buckling of these columns of particles in narrow zones then leads to the development of shear bands. High gradients of particle rotation and large voids are produced within the shear band as a result of the buckling of the columns.