Generalized railway tank car safety design optimization for hazardous materials transport: addressing the trade-off between transportation efficiency and safety

North America railways offer safe and generally the most economical means of long distance transport of hazardous materials. Nevertheless, in the event of a train accident releases of these materials can pose substantial risk to human health, property or the environment. The majority of railway shipments of hazardous materials are in tank cars. Improving the safety design of these cars to make them more robust in accidents generally increases their weight thereby reducing their capacity and consequent transportation efficiency. This paper presents a generalized tank car safety design optimization model that addresses this tradeoff. The optimization model enables evaluation of each element of tank car safety design, independently and in combination with one another. We present the optimization model by identifying a set of Pareto-optimal solutions for a baseline tank car design in a bicriteria decision problem. This model provides a quantitative framework for a rational decision-making process involving tank car safety design enhancements to reduce the risk of transporting hazardous materials.     

Improving the design of higher-capacity railway tank cars for hazardous materials transport: optimizing the trade-off between weight and safety

As with many aspects of modern industrial society, decision-makers face trade-offs in considering hazardous materials transportation equipment and practices. Tank cars used for transport of hazardous materials can be made more resistant to damage in accidents through use of a thicker steel tank and other protective features. However, the additional weight of these features reduces the car's capacity and thus its efficiency as a transportation vehicle. In this paper the problem of tank car safety versus weight is developed as a multi-attribute decision problem. North American railroads recently developed specifications for higher capacity tank cars for transportation of hazardous materials including enhanced safety design features. A group of tank car safety design features or "risk reduction options" (RROs) were analyzed with regard to their effect on the conditional probability of release in an accident, and their incremental effect on tank car weight. All possible combinations of these RROs were then analyzed in terms of the reduced release probability per unit of weight increase and the Pareto optimal set of options identified. This set included the combinations of RROs that provided the greatest improvement in safety with the least amount of additional weight for any desired level of tank car weight increase. The analysis was conducted for both non-insulated and insulated tank cars and used two objective functions, minimization of conditional probability of release, and minimization of expected quantity lost, given that a car was derailed in an accident. Sensitivity analyses of the effect of tank car size and use of different objective functions were conducted and the optimality results were found to be robust. The results of this analysis were used by the Association of American Railroads Tank Car Committee to develop new specifications for higher capacity non-insulated and insulated, non-pressure tank cars resulting in an estimated 32% and 24% respective improvement in safety.     

Effects on accidents of periodic motor vehicle inspection in Norway

An extensive programme of periodic motor vehicle inspection was introduced in Norway after 1995, when the treaty between Norway and the European Union (EU) granting Norway (not a member of the EU) access to the EU inner market took effect (The EEA treaty). This paper evaluates the effects on accidents of periodic inspections of cars. Trucks and buses were not included in the study. Negative binomial regression models were fitted to data on accidents and inspections created by merging data files provided by a major insurance company and by the Public Roads Administration. Technical defects prior to inspection were associated with an increased accident rate. Inspections were found to strongly reduce the number of technical defects in cars. Despite this, no effect of inspections on accident rate were found. This finding is inconsistent with the fact that technical defects appear to increase the accident rate; one would expect the repair of such defects to reduce the accident rate. Potential explanations of the findings in terms of behavioural adaptation among car owners are discussed. It is suggested that car owners adapt driving behaviour to the technical condition of the car and that the effect attributed to technical defects before inspection may in part be the result of a tendency for owners who are less concerned about safety to neglect the technical condition of their cars. These car owners might have had a higher accident rate than other car owners irrespective of the technical condition of the car.     

Optimal scrap combination for steel production

In steel production, scrap metal is used for cooling the enormous quantity of heat produced by blowing oxygen on hot metal. Scrap differs in regard to the content of iron and of some tramp elements. The price of the scrap depends on these attributes. Each melting bath unit of steel has its own material constraints for the amount of iron and tramp elements in order to guarantee the desired quality. In addition, the transportation of scrap is restricted because it needs time and space: the scrap is kept in some railroad cars in the scrap hall; empty cars must leave the hall, filled cars must be taken from several railroad tracks in the scrap yard and assembled to a train before transportation to the hall. There are upper limits for the number of cars in the hall and in the train, also for the number of railroad tracks used for assembly.Our objective is to find a minimum cost scrap combination for each melting bath unit of steel that obeys the material and transportation constraints. We model the problem using a MIP (mixed integer linear programming) approach. Real-life situations are solved with the commercial MIP-solver CPLEX. We present computational results which show significant improvement compared to the strategy applied today.     

Analysis of U.S. freight-train derailment severity using zero-truncated negative binomial regression and quantile regression

Derailments are the most common type of freight-train accidents in the United States. Derailments cause damage to infrastructure and rolling stock, disrupt services, and may cause casualties and harm the environment. Accordingly, derailment analysis and prevention has long been a high priority in the rail industry and government. Despite the low probability of a train derailment, the potential for severe consequences justify the need to better understand the factors influencing train derailment severity. In this paper, a zero-truncated negative binomial (ZTNB) regression model is developed to estimate the conditional mean of train derailment severity. Recognizing that the mean is not the only statistic describing data distribution, a quantile regression (QR) model is also developed to estimate derailment severity at different quantiles. The two regression models together provide a better understanding of train derailment severity distribution. Results of this work can be used to estimate train derailment severity under various operational conditions and by different accident causes. This research is intended to provide insights regarding development of cost-efficient train safety policies.     

Compatibility problems in frontal, side, single car collisions and car-to-pedestrian accidents in Japan.

Compatibility problems in car-to-car frontal, side, single car and car-to-pedestrian collisions in Japan are discussed using traffic accident data. The number of serious and fatal injuries is investigated for the subject car and other cars, which are categorized by their class and mass. The aggressivity of the cars is calculated by the number of fatalities, fatality rates and by the number of car registrations. The results show that in car-to-car frontal collisions, cars with a mass of 1150 kg are the most compatible among the current car population. In both car-to-car frontal and side collisions, the sports utility vehicle and mini car are found to be the most incompatible car types with high and low aggressivity, respectively. On the other hand, the accident data show that the wagon and midsize sedan are the most compatible car types. The compatibility of fixed objects in the road environment with cars and cars with pedestrians is also discussed. In a single car collision with a fixed object, the guardrail is the most compatible object and can reduce the fatality rate on prefecture roads by about 60%. The front geometry of the car has large effect on compatibility with a pedestrian.     

A collision model for safety evaluation of autonomous intelligent cruise control.

This paper describes a general framework for safety evaluation of autonomous intelligent cruise control in rear-end collisions. Using data and specifications from prototype devices, two collision models are developed. One model considers a train of four cars, one of which is equipped with autonomous intelligent cruise control. This model considers the car in front and two cars following the equipped car. In the second model, none of the cars is equipped with the device. Each model can predict the possibility of rear-end collision between cars under various conditions by calculating the remaining distance between cars after the front car brakes. Comparing the two collision models allows one to evaluate the effectiveness of autonomous intelligent cruise control in preventing collisions. The models are then subjected to Monte Carlo simulation to calculate the probability of collision. Based on crash probabilities, an expected value is calculated for the number of cars involved in any collision. It is found that given the model assumptions, while equipping a car with autonomous intelligent cruise control can significantly reduce the probability of the collision with the car ahead, it may adversely affect the situation for the following cars.     

Assessment of an explosive LPG release accident: a case study

In the present paper, an accident occurred during a liquefied petroleum gas (LPG) tank filling activity has been taken into consideration. During the transfer of LPG from the source road tank car to the receiving fixed storage vessel, an accidental release of LPG gave rise to different final consequences ranging from a pool fire, to a fireball and to the catastrophic rupture of the tank with successive explosion of its contents. The sequence of events has been investigated by using some of the consequence calculation models most commonly adopted in risk analysis and accident investigation. On one hand, this allows to better understand the link between the various events of the accident. On the other hand, a comparison between the results of the calculations and the damages actually observed after the accident, allows to check the accuracy of the prediction models and to critically assess their validity. In particular, it was shown that the largest uncertainty is associated with the calculation of the energy involved in the physical expansion of the fluid (both liquid and vapor) after the catastrophic rupture of the tank.     

Reducing the threat of in-transit derailments involving dangerous goods through effective placement along the train consist

Train derailments are important safety concerns, and they become increasingly so when dangerous goods (DG) are involved. One way to reduce the risk of DG derailments is through effective DG railway car placement along the train consist. This paper investigates the relationship between DG railway car placement and derailment for different route attributes and DG shipments. A model is presented for estimating the probability of derailment by position, based on the estimated point of derailment (POD) and the number of cars derailing. A DG placement model that considers in-transit derailment risk is shown to provide a sound scientific basis for effective DG marshalling in conventional rail hump yard operations.     

Post-derailment dynamic behaviour of a high-speed train under earthquake excitations

A post-derailment dynamic model of a high-speed train is developed to investigate the post-derailment dynamic behaviours of a high-speed train travelling on a railway bridge during an earthquake. The train model is comprised of two trailer cars and two motor cars. The adjacent two cars are coupled with a coupler model considering the nonlinear characteristic and limit rotation angle of the coupler. A bridge seismic response model is formulated by using the finite element method to evaluate the dynamic responses of the railway bridge under earthquake excitations, and then the responses are used as the input of the post-derailment dynamic model to analyze the post-derailment dynamic behaviours of a high-speed train. Before derailment the high-speed train runs over the rails, the nonlinear Hertzain contact model and the FASTSIM algorithm are employed to estimate the wheel/rail normal forces and tangent forces respectively. After derailment the high-speed train runs on the slab track, the OBBtrees theory is adopted to detect the contact situations between the vehicle components and the track, while the normal forces and tangent forces at the contact points are evaluated by the nonlinear Hertzain contact theory and the Coulomb friction law respectively. Using the post-derailment dynamic model of a high-speed train, the derailment postures of the high-speed train under earthquake excitations are investigated, and the effects of marshalling type of train on the post-derailment dynamic behaviours are further discussed in this study. The results indicate that the trailer car has a better self-protection capacity compared to those of a motor car during a derailment. The marshalling type (TC1 + MC2 + MC3 + TC4) of a high-speed train can easily form the buckling pattern after a derailment, which may contribute considerably to the outcomes of a derailment. Therefore, it is necessary to take some countermeasures to eliminate the buckling pattern of train during a derailment.     

Accident involvement and crash injury rates: An investigation by make, model and year of car

Accident involvement and crash injury rates per million miles of vehicle travel are estimated by make, model and year of car. The accident and injury information was obtained from the North Carolina accident files, while exposure data were derived from paired odometer readings recorded on a statewide sample of motor vehicle inspection receipts.

The resulting estimates show a steady decrease in annual mileage with vehicle age. For the newer model years, large cars have generally higher annual mileages than small cars, and station wagons higher mileages than sedans or hardtops. The accident involvement and injury rates decline for the newer model cars, especially for larger-sized cars. Full-sized cars have the lowest overall accident and injury rates. Among standard-sized cars, two-door cars have higher accident and injury rates than four-door cars, and hardtops higher than sedans or station wagons.     

AVR 单片机在油耗测量中的应用

介绍一种AVR单片机串行通讯在汽车油耗测量中的应用方法．此方法能够将测量结果通过软件控制以数字信号的方式传送给主控单片机．减小了远距离传输的信号衰减和外界干扰．十分适合用于汽车油耗的测量．配合标准容积的油箱使用．测量精度达到了0．1％～0.5％．     

Accident involvement and injury rates for small cars in Japan

A comparison of recent U.S. and Japanese small car accident and injury statistics indicates that the two countries have had dramatically differing experience with such cars. In Japan, for the years 1980, 1981, and 1982, while such cars are involved in more accidents per vehicle or per vehicle kilometer traveled than larger cars, there is a lower likelihood of a fatality if an accident occurs. The lower fatality conditional likelihood more than offsets the higher chance of an accident in 1981 and 1982, resulting in small cars having lower fatality rates per unit of exposure than larger vehicles in those years. The difference is tentatively attributed to the direct and indirect impact of the lower speed limits (80 vs 100 kmh) for such cars in Japan, as well as the greater caution drivers of such vehicles exhibit, as evidenced by the fact that small car drivers cause a significantly lower percent of the accidents they are involved in than larger cars.     

Modeling of disturbances of the magnetic field of a rail around a transverse crack

A generalized model for finding magnetic field and signals from the objects of the railroad is proposed. A 3D model of the primary field of a defect-free rail excited by a pilot alternating current is developed. The mathematical models of the secondary field of the rail disturbed around a transverse wedge-shaped crack and a rectangular crack are developed. We compare the images of signals from a transverse wedge-shaped defect obtained in the course of modeling with actual defects, such as, e.g., transverse cracks.     

A meta-analysis of studies concerning the safety effects of daytime running lights on cars

A meta-analysis of 17 studies that have evaluated the effects on traffic safety of using daytime running lights (DRL) on cars is presented. A distinction is made between studies that have evaluated the effects of DRL on the accident rates of each car using it and studies that have evaluated changes in the total number of accidents in a country following the introduction of mandatory use of DRL. Three different definitions of the measure of safety effects are compared and their validity discussed. It is concluded that the use of DRL on cars reduces the number of multi-party daytime accidents by about 10–15% for cars using DRL. The estimated effects on the total number of accidents of introducing DRL laws are somewhat smaller, 3–12% reduction in multi-party daytime accidents, and are likely to contain uncontrolled confounding effects. There is no evidence to indicate that DRL affects types of accident other than multi-party daytime accidents.     

Speed as a measure of driver risk: Observed speeds versus driver and vehicle characteristics

This investigation was performed to determine relationships between driver and vehicle characteristics and freely chosen speeds of cars on a two lane road with little commercial or residential development. Speed is taken as a measure of a driver's willingness to expose himself to risk of accident, in the same way that short freeway headways were interpreted in an earlier study. A total of 6638 passenger car speeds were measured by radar while each oncoming vehicle was simultaneously photographed. Driver and vehicle characteristics were derived from the photographs, both by direct observation (vehicle type, driver sex, presence of front seat passengers, seat belt use) and from the car license plate through the use of State vehicle registration and driver licensing files. The State files provided the car mass and model year and the owner (usually driver) age, sex, and recorded accidents and violations. Higher speeds were observed for younger drivers, drivers with prior accidents and convictions, newer cars, heavier cars and cars with no passengers.     

厦门地表水油污染的油种指纹鉴定

厦门地表水主要有从九龙江取水的北溪引水渠和坂头水库等,系厦门饮用水源。为保证自来水水质,自1989年至1994年开展厦门地表水水质调查,无论定期取样或临时抽样,早期均发现有石油烃污染。经带毛细管色谱柱的程序升温气相色谱作正构烷烃油种指纹鉴定,为船舶的柴油和汽车的机油、废油污染地表水。其中还检出如苯并(α)芘等多环芳香烃化合物,经美国罗得岛大学海洋研究生院有机地球化学实验室测定确认了这一结论。通过有关方面进行污染源治理,现水质得以恢复,自来水中苯并(α)芘已符合饮用水标准。     

轮轨油污染黏着特性的研究

运用数值算法研究了轮轨在油污染时的黏着特性。以部分弹流理论为基础借助于多重网格作为数值计算工具建立了二维轮轨在油污染状态下考虑表面粗糙度的轮轨黏着计算模型。研究了在有油污染情况下轮轨间接触压力分布以及列车运行速度和接触压力对轮轨黏着系数的影响。给出了轮轨介质接触时的固体承载及液体动压分布。计算结果表明:随着速度的提高,黏着系数逐渐降低,最后基本上趋于稳定;随着接触压力的增大,黏着系数逐渐增大。