Railroad capacity tools and methodologies in the U.S. and Europe

A growing demand for passenger and freight transportation, combined with limited capital to expand the United States （U.S.） rail infrastructure, is creating pressure for a more efficient use of the current line capacity. This is further exacerbated by the fact that most passenger rail services operate on corridors that are shared with freight traffic. A capacity analysis is one alternative to address the situation and there are various approaches, tools, and methodologies available for application. As the U.S. continues to develop higher speed passenger services with similar characteristics to those in European shared-use lines, understanding the common methods and tools used on both continents grows in relevance. There has not as yet been a detailed investigation as to how each continent approaches capacity analysis, and whether any benefits could be gained from cross-pollination. This paper utilizes more than 50 past capacity studies from the U.S. and Europe to describe the different railroad capacity defini- tions and approaches, and then categorizes them, based on each approach. The capacity methods are commonly di- vided into analytical and simulation methods, but this paper also introduces a third, ＂combined simulation- analytical＂ category. The paper concludes that Europeanrail studies are more unified in terms of capacity, concepts, and techniques, while the U.S. studies represent a greater variation in methods, tools, and objectives. The majority of studies on both continents use either simulation or a combined simulation-analytical approach. However, due to the significant differences between operating philosophy and network characteristics of these two rail systems, European studies tend to use timetable-based simulation tools as opposed to the non-timetable-based tools commonly used in the U.S. rail networks. It was also found that validation of studies against actual operations was not typically completed or was limited to comparisons with a base model.

China’s railway train speed,density and weight in developing

Purpose–This study aims to analyze the development direction of train speed,density and weight in China.Design/methodology/approach–The development of China’s railway in the past 40 years can be divided into 3 stages.At the stage of potential tapping and capacity expansion,it is important to improve the train weight and density by upgrading the existing lines,and improving transportation capacity rapidly.At the stage of railway speed increase,the first priority is to increase train speed,reduce the travel time of passenger train,and synchronously take into account the increase of train density and weight.At the stage of developing high-speed railway,train speed,density and weight are co-developing on demand.Findings–The train speed of high-speed railway will be 400 km h
1,the interval time of train tracking will be 3 min,and the traffic density will be more than 190 pairs per day.The running speed of high-speed freight EMU will reach 200 km h
1 and above.The maximum speed of passenger train on mixed passenger and freight railway can reach 200 km h
1.The minimum interval time of train tracking can be compressed to 5 min.The freight train weight of 850 m series arrival-departure track railway can be increased to 4,500–5,000 t and that of 1,050 m series to 5,500–6,400 t.EMU trains should gradually replace ordinary passenger trains to improve the quality of railway passenger service.Small formation trains will operate more in intercity railway,suburban railway and short-distance passenger transportation.Originality/value–The research can provide new connotations and requirements of railway train speed,density and weight in the new railway stage.

Model test of the group piles foundation of a high-speed railway bridge in mined-out area

The research on the mechanism of pile-soil-cap-goaf interaction and settlement of high-speed railway bridge located in mined-out area is still relatively rare. By taking the pile group of Guanshandi bridge foundation in Hefei- Fuzhou high-speed railway as the prototype, a model test is carried out. According to the similarity theory, the similar constant is derived and the similar model material is determined. Meanwhile, three types of data including the bearing behavior of piles, and the settlement law, and soil among piles are investigated. It can be found that： the influence of goaf on the bearing capacity of pile is inversely to the loading degree, the larger of loading degree, the smaller impact of goaf on the bearing capacity. There is no negative side friction can been found in pile body and the degree of downward tendency for the barycenter of side friction layout is obvious for piles in goaf. Although the bearing ratio of soil resistance under cap is relatively large, the cap effect is suggested be ignored considering the characteristic of goaf. There is a maximum critical value for the uneven settlement of pile group in goaf, and when the value is reached, the uneven settlement stop growing anymore. In addition, the formula for calculating bearing capacity and settlement of pile group in goaf based on test results, theory analysis and related standard is established.

Reliable optimization of corridor capacity for China high speed railway by considering passenger service

Railway capacity has been extensively investigated for the purpose of utilizing rail infrastructure in a possible efficient strategy.Nevertheless,the estimation of high speed rail(HSR),which is different from common railways in many aspects,is still a challenge work needed to be solved.Consequently,this work focuses on the capacity estimation of HSR corridor.The objectives and constraints are developed for the HSR with the consideration of passenger service level and buffer time uncertainty,and a two-stage optimization model is proposed.The first stage determines the optimal number of trains in terms of the passenger origin–destination demand,and the second stage is a multi-objective mixed integer programming(MO-MIP)aiming to estimate the optimal capacity usage.The branch-and-bound algorithm is extended and applied to the proposed model,and a case study is performed to Beijing–Shanghai HSR line.The optimal solution is obtained,and the sensitivity of the two objectives is analyzed.

An implementation of cellular automaton model for single-line train working diagram

According to the railway transportation system＇s characteristics, a new cellular automaton model for the single- line railway system is presented in this paper. Based on this model, several simulations were done to imitate the train operation under three working diagrams. From a different angle the results show how the organization of train operation impacts on the railway carrying capacity. By using the non-parallel train working diagram the influence of fast-train on slow-train is found to be the strongest. Many slow-trains have to wait in-between neighbouring stations to let the fast-train（s） pass through first. So the slow-train will advance like a wave propagating from the departure station to the arrival station. This also resembles the situation of a highway jammed traffic flow. Furthermore, the nonuniformity of travel times between the sections also greatly limits the railway carrying capacity. After converting the nonuniform sections into the sections with uniform travel times while the total travel time is kept unchanged, all three carrying capacities are improved greatly as shown by simulation. It also shows that the cellular automaton model is an effective and feasible way to investigate the railway transportation system.

Optimal electromagnetic hybrid negative current compensation method for high-speed railway power supply system

To achieve economical compensation for the huge-capacity negative sequence currents generated by high-speed railway load, an electromagnetic hybrid compensation system(EHCS) and control strategy is proposed.The EHCS is made up of a small-capacity railway static power conditioner(RPC) and a large-capacity magnetic static var compensator(MSVC). Compared with traditional compensation methods, the EHCS makes full use of the SVC’s advantages of economy and reliability and of RPC’s advantages of technical capability and flexibility. Based on the idea of injecting a negative sequence, the compensation principle of the EHCS is analyzed in detail. Then the minimum installation capacity of an EHCS is theoretically deduced. Furthermore, a constraint optimization compensation strategy that meets national standards, which reduces compensation capacity further, is proposed. An experimental platform based on a digital signal processor(DSP) and a programmable logic controller(PLC) is built to verify the analysis. Simulated and experimental results are given to demonstrate the effectiveness and feasibility of the proposed method.