Fatal accidents at railway level crossings in Great Britain 1946-2009

This paper investigates fatal accidents and fatalities at level crossings in Great Britain over the 64-year period 1946–2009. The numbers of fatal accidents and fatalities per year fell by about 65% in the first half of that period, but since then have remained more or less constant at about 11 fatal accidents and 12 fatalities per year. At the same time other types of railway fatalities have fallen, so level crossings represent a growing proportion of the total. Nevertheless, Britain's level crossing safety performance remains good by international standards.The paper classifies level crossings into three types: railway-controlled, automatic, and passive. The safety performance of the three types of crossings has been very different. Railway-controlled crossings are the best-performing crossing type, with falling fatal accident rates. Automatic crossings have higher accident rates per crossing than railway controlled or passive crossings, and the accident rates have not decreased. Passive crossings are by far the most numerous, but many have low usage by road users. Their fatal accident rate has remained remarkably constant over the whole period at about 0.9 fatal accidents per 1000 crossings per year.A principal reason why fatal accidents and fatalities have not fallen in the second half of the period as they did in the first half is the increase in the number of automatic crossings, replacing the safer railway controlled crossings on some public roads. However, it does not follow that this replacement was a mistake, because automatic crossings have advantages over controlled crossings in reducing delays to road users and in not needing staff.Based on the trends for each type of crossing and for pedestrian and non-pedestrian accidents separately, in 2009 a mean of about 5% of fatal accidents were at railway controlled crossings, 52% were at automatic crossings, and 43% were at passive crossings. Fatalities had similar proportions. About 60% of fatalities were to pedestrians.A simple comparison of automatic railway level crossings and signalised road intersections found that in 2005 the numbers of fatalities per 1000 crossings or intersections were similar.     

Factors influencing safety in a sample of marked pedestrian crossings selected for safety inspections in the city of Oslo

This paper reports an analysis of factors influencing safety in a sample of marked pedestrian crossings in the city of Oslo, Norway. The sample consists of 159 marked pedestrian crossings where a total of 316 accidents were recorded during a period of five years. The crossings were selected for inspection because of they were, for various reasons, regarded as sub-standard. The sample of crossings is therefore not representative of all pedestrian crossings in Oslo. Factors influencing the number of accidents were studied by means of negative binomial regression. Factors that were studied included the volume of pedestrians and vehicles, the number of traffic lanes at the crossing, the location of the crossing (midblock or junction), the type of traffic control, the share of pedestrians using the crossing and the speed of approaching vehicles. The analysis confirmed the presence of a “safety-in-numbers” effect, meaning that an increase in the number of pedestrians is associated with a lower risk of accident for each pedestrian. Crossings located in four-leg junctions or roundabouts had more accidents than crossings located in three-leg junctions or on sections between junctions. A high share of pedestrians crossing the road outside the marked crossing was associated with a high number of accidents. Increased speed was associated with an increased number of accidents.     

面向多用户环境的MapReduce集群调度算法研究

针对MapReduce集群现有调度策略在多用户环境下无法根据用户的实际资源需求实现动态资源分配的问题,提出了一种基于历史执行信息(HEI)的MapReduce集群调度算法——HEI Scheduler。该算法通过建立集群作业执行信息的收集和分析机制,得到各用户组资源需求随时间变化的规律,并以作业实际占用slot的时间作为作业占用资源量的衡量标准,进而动态地确定资源池的最小共享资源以及集群剩余资源分配的权值。实验结果表明,执行信息分析机制能够更准确地表征作业对资源的需求,采用集群调度算法HEI Scheduler能够有效地缩短作业的整体执行时间。     

A system for the allocation of safety resources on a road network

This paper presents a complete allocation methodology of resources for safety improvements of a road network. In the first part of the paper, a set of models is estimated to identify so-called “black spots” in the road network. In the second part of the paper, a Linear Programming (L.P.) model is defined for the allocation of a total budget to those projects which ensure the most cost-effective results in reducing road accidents. The specific solution method for the allocation L.P. problem is defined, and its superiority to a cost-benefit analysis for budget allocation is shown through a real world example.     

Characterization of pedestrian accidents and an examination of infrastructure measures to improve pedestrian safety in Israel

The high share of pedestrian fatalities in Israel provided the impetus for this study which looked for infrastructure solutions to improve pedestrian safety. First, a detailed analysis of pedestrian accidents in 2006-2007, with an emphasis on the infrastructure characteristics involved, was performed; it found that 75% of the fatalities and 95% of the injuries occurred in urban areas, the majority of cases occurring on road sections (not at junctions). About 80% of the accidents took place when a pedestrian crossed the road, the majority of them at non-crosswalk locations or at non-signalized crosswalks. International comparisons showed that the characteristics of fatal pedestrian accidents in Israel were similar to the average pedestrian accident in Europe in terms of accident location, time, and the demographic characteristics of the victims. A typology of pedestrian fatalities in Israel was built for the years 2003-2006; it demonstrated a high share of accidents at these locations: in Jewish or mixed-population towns-not at pedestrian crossings on urban street sections, and both at pedestrian crossings and not at pedestrian crossings at urban junctions; in Arab towns; and on dual-carriageway rural roads. Second, based on a literature study, a summary of about 60 pedestrian-safety-related measures was developed. Third, to diagnose the infrastructure characteristics and deficiencies associated with pedestrian accidents, detailed field studies were carried out at 95 urban locations. A major finding revealed that more than 80% of the sites with a high concentration of pedestrian-vehicle accidents in Israel were situated on arterial multi-lane streets belonging to city centers, where on a micro-level there were no indications of major deficiencies in the basic design elements of most sites. Finally, cross-checking of the safety problems identified and the infrastructure solutions available provided lists of measures recommended for application at various types of sites. It was concluded that in order to generate a significant change in the state of pedestrian injury in Israel, a move from spot treatment to a systemic treatment of the problem is required. A systemic inquiry and the transformation of the urban road network should be performed in order to diminish the areas of vehicle-pedestrian conflicts and to significantly reduce vehicle speeds in areas of pedestrian presence and activity.     

Accident prediction model for railway-highway interfaces

Considerable past research has explored relationships between vehicle accidents and geometric design and operation of road sections, but relatively little research has examined factors that contribute to accidents at railway-highway crossings. Between 1998 and 2002 in Korea, about 95% of railway accidents occurred at highway-rail grade crossings, resulting in 402 accidents, of which about 20% resulted in fatalities. These statistics suggest that efforts to reduce crashes at these locations may significantly reduce crash costs. The objective of this paper is to examine factors associated with railroad crossing crashes. Various statistical models are used to examine the relationships between crossing accidents and features of crossings. The paper also compares accident models developed in the United States and the safety effects of crossing elements obtained using Korea data. Crashes were observed to increase with total traffic volume and average daily train volumes. The proximity of crossings to commercial areas and the distance of the train detector from crossings are associated with larger numbers of accidents, as is the time duration between the activation of warning signals and gates. The unique contributions of the paper are the application of the gamma probability model to deal with underdispersion and the insights obtained regarding railroad crossing related vehicle crashes.     

Cost optimal segregated targeting for resource allocation networks

In this paper, a generalised methodology is proposed to target cost optimal allocation of resources in segregated targeting problems. Cost optimal segregated targeting problems are characterised by the existence of multiple zones; each consisting of a set of demands and using a unique resource with given cost and a single quality index (e.g., emissions factor, contaminant concentrations, etc.). All these zones share a common set of internal sources. This paper presents a rigorous mathematical proof of the decomposition principle that decomposes the problem into a sequence of sub-problems. Decomposition of the original problem is performed based on the prioritised costs for each external resource, attached to a particular zone. Prioritised cost of a resource depends on the pinch quality, quality of the resource and its cost. Applicability of the proposed methodology is illustrated by examples from carbon-constrained energy planning and water allocation networks.     

Optimising resource portfolio planning for capital-intensive industries under process-technology progress

This paper addresses the problem of resource portfolio planning of firms in high-tech, capital-intensive manufacturing industries. In light of the strategic importance of resource portfolio planning in these industries, we offer an alternative approach to modelling capacity planning and allocation problems that improves the deficiencies of prior models in dealing with three salient features of these industries, i.e. fast technological obsolescence, volatile market demand, and high capital expenditure. This paper first discusses the characteristics of resource portfolio planning problems including capacity adjustment and allocation. Next, we propose a new mathematical programming formulation that simultaneously optimises capacity planning and task assignment. For solution efficiency, a constraint-satisfied genetic algorithm (CSGA) is developed to solve the proposed mathematical programming problem on a real-time basis. The proposed modelling scheme is employed in the context of a semiconductor testing facility. Experimental results show that our approach can solve the resource portfolio planning problem more efficiently than a conventional optimisation solver. The overall contribution is an analytical tool that can be employed by decision makers responding to the dynamic technological progress and new product introduction at the strategic resource planning level.     

ROBUST TOLERANCE ALLOCATION USING STOCHASTIC PROGRAMMING

Abstract

Tolerance allocation in manufacturing is a prominent industrial task for enhancing productivity and reducing manufacturing costs. The classical tolerance allocation problem can be formulated as a stochastic program to determine the assignment of component tolerances such that the manufacturing cost is minimized. However, tolerance design is a prerequisite to the overall quality and cost of a product; robust tolerance design is particularly important and should be considered. In this paper, robustness is considered in formulating the tolerance allocation problem by minimizing the manufacturing cost's sensitivity. Moreover, from a practical perspective, the process capability index for each component and the upper bound of the manufacturing cost are also considered. To effectively and efficiently resolve the robust tolerance allocation problem, a sequential quadratic programming algorithm embedded with a Monte Carlo simulation is developed. To demonstrate this design method's robustness, two commonly used test problems are solved. The designs devised in this paper have lower manufacturing costs and smaller variations in manufacturing costs than those in previous studies, indicating that the proposed method is highly promising in the robust tolerance design.     

Bayesian methodology incorporating expert judgment for ranking countermeasure effectiveness under uncertainty: example applied to at grade railroad crossings in Korea

Transportation professionals are sometimes required to make difficult transportation safety investment decisions in the face of uncertainty. In particular, an engineer may be expected to choose among an array of technologies and/or countermeasures to remediate perceived safety problems when: (1) little information is known about the countermeasure effects on safety; (2) information is known but from different regions, states, or countries where a direct generalization may not be appropriate; (3) where the technologies and/or countermeasures are relatively untested, or (4) where costs prohibit the full and careful testing of each of the candidate countermeasures via before-after studies. The importance of an informed and well-considered decision based on the best possible engineering knowledge and information is imperative due to the potential impact on the numbers of human injuries and deaths that may result from these investments. This paper describes the formalization and application of a methodology to evaluate the safety benefit of countermeasures in the face of uncertainty. To illustrate the methodology, 18 countermeasures for improving safety of at grade railroad crossings (AGRXs) in the Republic of Korea are considered. Akin to "stated preference" methods in travel survey research, the methodology applies random selection and laws of large numbers to derive accident modification factor (AMF) densities from expert opinions. In a full Bayesian analysis framework, the collective opinions in the form of AMF densities (data likelihood) are combined with prior knowledge (AMF density priors) for the 18 countermeasures to obtain 'best' estimates of AMFs (AMF posterior credible intervals). The countermeasures are then compared and recommended based on the largest safety returns with minimum risk (uncertainty). To the author's knowledge the complete methodology is new and has not previously been applied or reported in the literature. The results demonstrate that the methodology is able to discern anticipated safety benefit differences across candidate countermeasures. For the 18 at grade railroad crossings considered in this analysis, it was found that the top three performing countermeasures for reducing crashes are in-vehicle warning systems, obstacle detection systems, and constant warning time systems.     

多项目管理中企业资源配置效率模型

针对信息环境下企业多项目管理中资源配置这一核心问题,应用随机理论确定了企业资源多项目并行配置中的资源等效效率概念和效率转换系数概念,建立了资源配置效率模型,通过对其数学方程的分析给出了相应的算法.通过资源配置效率模型实现企业资源的合理配置,有效支持多项目管理.     

Safety culture and accident analysis--a socio-management approach based on organizational safety social capital

One of the biggest challenges for organizations in today's competitive business environment is to create and preserve a self-sustaining safety culture. Typically, the key drivers of safety culture in many organizations are regulation, audits, safety training, various types of employee exhortations to comply with safety norms, etc. However, less evident factors like networking relationships and social trust amongst employees, as also extended networking relationships and social trust of organizations with external stakeholders like government, suppliers, regulators, etc., which constitute the safety social capital in the Organization—seem to also influence the sustenance of organizational safety culture. Can erosion in safety social capital cause deterioration in safety culture and contribute to accidents? If so, how does it contribute? As existing accident analysis models do not provide answers to these questions, CAMSoC (Curtailing Accidents by Managing Social Capital), an accident analysis model, is proposed. As an illustration, five accidents: Bhopal (India), Hyatt Regency (USA), Tenerife (Canary Islands), Westray (Canada) and Exxon Valdez (USA) have been analyzed using CAMSoC. This limited cross-industry analysis provides two key socio-management insights: the biggest source of motivation that causes deviant behavior leading to accidents is ‘Faulty Value Systems’. The second biggest source is ‘Enforceable Trust’. From a management control perspective, deterioration in safety culture and resultant accidents is more due to the ‘action controls’ rather than explicit ‘cultural controls’. Future research directions to enhance the model's utility through layering are addressed briefly.     

Energy Efficient Resource Allocation Approach for Renewable Energy Powered Heterogeneous Cellular Networks

In this paper, maximizing energy efficiency (EE) through radio resource allocation for renewable energy powered heterogeneous cellular networks (HetNet) with energy sharing, is investigated. Our goal is to maximize the network EE, conquer the instability of renewable energy sources and guarantee the fairness of users during allocating resources. We define the objective function as a sum weighted EE of all links in the HetNet. We formulate the resource allocation problem in terms of subcarrier assignment, power allocation and energy sharing, as a mixed combinatorial and non-convex optimization problem. We propose an energy efficient resource allocation scheme, including a centralized resource allocation algorithm for iterative subcarrier allocation and power allocation in which the power allocation problem is solved by analytically solving the Karush-Kuhn-Tucker (KKT) conditions of the problem and a water-filling problem thereafter and a low-complexity distributed resource allocation algorithm based on reinforcement learning (RL). Our numerical results show that both centralized and distributed algorithms converge with a few times of iterations. The numerical results also show that our proposed centralized and distributed resource allocation algorithms outperform the existing reference algorithms in terms of the network EE.     

荔枝包装的风险识别与分析

目的解决在荔枝包装过程中风险源难于辨识及定量分析的难题。方法提出一种基于霍尔三维因素空间和模糊故障树的风险识别与定量分析方法。构建荔枝包装的安全事件、时空结构(工位)、事故致因等3个维度的因素集,通过矩阵之间的映射关系和计算分析得到风险基本事件集合。建立荔枝包装的故障树模型,并对风险基本事件进行专家问卷评价。采用梯形模糊数及左右模糊排序法将专家的评判语言转化为风险概率值。结果经计算得到荔枝包装事故发生概率(0.0409)及风险基本事件的概率重要度。结论提出了强化标准化建设,加大技术投入等防范风险事故发生的措施。     

企业研发项目中止决策的灰靶分析模型

中止决策是研发项目过程管理中不可或缺的环节,是企业提高研发效率、改善资源配置的有效手段。根据该问题模糊多属性分类决策的本质,以案例分析为起点,结合模糊集与灰靶决策理论构建求解属性权重、临界点等分类参数的优化模型,利用所得参数计算待判项目的综合靶心矩,最后按照综合靶心矩所属区间对待判项目进行分类决策。将所提方法应用于一个具体的决策分析过程,其可行性和合理性得到验证。     

The dark side of stimulus control--associations between contradictory stimulus configurations and pedestrians' and cyclists' illegal street crossing behavior

Since illegal pedestrian behavior represents a major source of accidents, research investigating possible reasons and risk factors for crossing against the lights is pivotal for enhancing safety in traffic. The present approach regards behavior at signalized intersections as a result of multiple stimulus discrimination. Hence, it is expected that at crossings divided by a median refuge the excitatory potential of a “consecutive green light” or “oncoming pedestrians” (S+*) attenuates the inhibition of crossing behavior induced by the relevant red light (S−). Standardized observations at critical intersections in Braunschweig, Germany, were conducted to investigate these hypotheses. Comparing outside traffic participants’ behavior in the presence of different stimulus configurations identified the assumed S+* as substantial risk factors for illegal crossings. Moreover, the presented model of stimulus control integrates past risk factor research and may help develop future prevention measures.     

Modelling driver behaviour towards innovative warning devices at railway level crossings

Improving safety at railway level crossings is costly and as funds are often limited, it is important to search for cost-effective, evidence-based solutions. The effect that the many existing alternative systems have on driver behaviour is not always known. This paper compares driver behaviour towards two novel warning devices (rumble strips and in-vehicle audio warning) at railway level crossings with two conventional warning devices (flashing light and stop sign). Regression models were developed to reflect driver's responses towards the four different types of devices based on data collected from a driving simulation experiment. The regression models include a binary choice model for predicting the probability of a driver stopping or driving through a railway crossing, as well as mixed regression models for predicting the moment at which a driver will produce specific behavioural responses before stopping at a crossing (e.g. initiation of accelerator release and application of foot-pedal brake). Violation results indicated the active systems produced much higher levels of driver compliance than passive devices. Contributing factors, such as age, gender, speed and types of warning devices were found significant at different approach stages to the level crossings. With the application of such behavioural models and traffic conflict techniques in microscopic simulation tools, traffic safety indicators, such as collision likelihood and time-to-collision can be estimated. From these, relative safety comparisons for the different traffic devices are derived.     

Dynamic Resource Pricing and Allocation in Multilayer Satellite Network

The goal of delivering high-quality service has spurred research of 6G satellite communication networks. The limited resource-allocation problem has been addressed by next-generation satellite communication networks, especially multilayer networks with multiple low-Earth-orbit (LEO) and non-low-Earth-orbit (NLEO) satellites. In this study, the resource-allocation problem of a multilayer satellite network consisting of one NLEO and multiple LEO satellites is solved. The NLEO satellite is the authorized user of spectrum resources and the LEO satellites are unauthorized users. The resource allocation and dynamic pricing problems are combined, and a dynamic game-based resource pricing and allocation model is proposed to maximize the market advantage of LEO satellites and reduce interference between LEO and NLEO satellites. In the proposed model, the resource price is formulated as the dynamic state of the LEO satellites, using the resource allocation strategy as the control variable. Based on the proposed dynamic game model, an open-loop Nash equilibrium is analyzed, and an algorithm is proposed for the resource pricing and allocation problem. Numerical simulations validate the model and algorithm.     

Machine Learning Based Resource Allocation of Cloud Computing in Auction

Resource allocation in auctions is a challenging problem for cloud computing. However, the resource allocation problem is NP-hard and cannot be solved in polynomial time. The existing studies mainly use approximate algorithms such as PTAS or heuristic algorithms to determine a feasible solution; however, these algorithms have the disadvantages of low computational efficiency or low allocate accuracy. In this paper, we use the classification of machine learning to model and analyze the multi-dimensional cloud resource allocation problem and propose two resource allocation prediction algorithms based on linear and logistic regressions. By learning a small-scale training set, the prediction model can guarantee that the social welfare, allocation accuracy, and resource utilization in the feasible solution are very close to those of the optimal allocation solution. The experimental results show that the proposed scheme has good effect on resource allocation in cloud computing.     

Safety effects of blue cycle crossings: a before-after study

This paper presents a before-after accident study of marking blue cycle crossings in 65 signalised junctions. Corrections factors for changes in traffic volumes and accident/injury trends are included using a general comparison group in this non-experimental observational study. Analysis of long-term accident trends point towards no overall abnormal accident counts in the before period. The safety effect depends on the number of blue cycle crossings at the junction. One blue cycle crossing reduces the number of junction accidents by 10%, whereas marking of two and four blue cycle crossings increases the number of accidents by 23% and 60%, respectively. Larger reduction and increases are found for injuries. Safety gains at junctions with one blue cycle crossing arise because the number of accidents with cyclists and moped riders that may have used the blue cycle crossing in the after period and pedestrians in the pedestrian crossing parallel and just next to the blue marking was statistically significant reduced. Two or four blue cycle crossings especially increase the number of rear-end collisions only with motor vehicles involved and right-angle collisions with passenger cars driving on red traffic lights.