Martin / Liu Neues verkehrswissenschaftliches Journal - Ausgabe 16

Capacity Research in Urban Rail-Bound Transportation with Special Consideration of Mixed Traffic
1. Auflage 2017
ISBN: 978-3-7431-4760-7
Verlag: BoD - Books on Demand
Format: EPUB
Kopierschutz: 0 - No protection

E-Book, Englisch, 156 Seiten

In urban mixed traffic zones, urban rail-bound transport interacts with road traffic, which includes motorized road traffic as well as non-motorized road traffic. The quality of operation and the capacity of urban rail-bound transport are heavily influenced by the road traffic in urban mixed traffic zones. Capacity research is one of the most important methods for the validation of timetables on an existing or planned infrastructure, for adequate railway capacity design of the infrastructure, as well as the performance evaluation for railway operation. For the urban mixed traffic zones, two developed approaches in this research can be used to carry out capacity research with consideration of the road traffic influences on urban rail-bound transport. As a result of the stochastic influences of road traffic on urban rail-bound transport, the waiting time function will be adapted to mixed traffic conditions, which can derive the recommended area of traffic flow for the situation of urban mixed traffic more plausibly. In addition, an algorithm for modeling an event-driven system is developed for preliminary determining the results of capacity research. Accordingly, the operating performance for urban rail-bound transport with road traffic influences can be determined and evaluated.

Ullrich Martin war nach verschiedenen Tätigkeiten im Eisenbahnbereich und an der TU Braunschweig von 1998 bis 2001 Universitätsprofessor am Lehr- und Forschungsgebiet Verkehrsbau- und Verkehrssystemtechnik der Universität Leipzig. Seit 2001 ist er als Universitätsprofessor am Institut für Eisenbahn und Verkehrswesen und Verkehrswissenschaftliches Institut der Universität Stuttgart tätig.

Autoren/Hrsg.

Ullrich, Martin

Liu, Di

Leseproben

2Capacity Research of Rail-Bound Transport
In this chapter, a general summary is made about capacity research for the rail-bound transport of the railway system. Firstly, Subchapter 2.1 manifests the basic concept of capacity research for the railway system. The relevant basic terms will be introduced in Subchapter 2.2. Two major methodologies for capacity research of rail-bound transport, which are the analytical method and the simulation method, will be presented in Subchapter 2.3. 2.1Overview
Capacity research is one of the most important methods for the validation of timetables on an existing or planned infrastructure, for adequate railway capacity design of the infrastructure, as well as the performance evaluation for railway operation [Pachl 2014]. In railway operation, capacity research is a significant issue that evaluates the operating performance of the railway systems. The operating performance is generally considered to be the quality of operation and the number of trains per time unit (hour) running in an investigated railway infrastructure network. The quality of operation usually refers to the waiting time (operational delays) in operation. Therefore, the capacity is inversely proportional to the quality of operation. One goal of capacity research is to improve the performance through optimizing the existing infrastructure and the operating program. Determination of the quality of operation for an investigated area with a concrete timetable and determination of recommended area of traffic flow with a rough operating program can both be achieved with railway capacity research. 2.2Relevant Terms
Relevant terms of capacity research for railway systems in this research project are defined as following: Traffic flow [trains/h] is the number of trains or train paths during a given investigation period within the investigated area [DB Netz AG 2008]. Operating program is the comprehensive description of the performance and requirements of the railway operation, including the number of train runs, the train properties, their structure and sequence, as well as the temporal allocation of the train runs [DB Netz AG 2008]. Train mixture is the structure of the operating program, which is the rough operating program including the characteristics of the various train groups1 in the model and the ratio of the number of trains in each train group. Maximum capacity is a theoretical value and doesn’t meet the requirements of operational quality. It allows for an unlimited congestion situation without keeping the structure of the operating program. It corresponds to the theoretical maximum number of trains and shunting movements on the investigated infrastructure within a given time period [DB Netz AG 2008]. (Maximum) throughput capacity (DS LF) is the average traffic flow of all possible maximum traffic flows per time unit (hour) in the static phase of the operating procedure with various train sequences of a defined rough operating program (train mixture). The throughput capacity (incoming traffic flow = outgoing traffic flow) has to keep the structure of the defined operating program (train mixture) on a given infrastructure. A further increase of traffic flow leads to a slowing growth trend or a change of the operating program (train mix) of the outgoing traffic flow [Chu 2014]. Investigated area is a defined part of the railway infrastructure on which the capacity research will be carried out. Utility factor of capacity is the amount of consumed capacity, which is calculated as the actual traffic flow divided by the throughput capacity. Recommended area of traffic flow is the range of traffic flow to reach a customer-friendly quality of operation with the optimum utilization of a given infrastructure. It is located between the lower limit with the minimum value of relative sensitivity function of the waiting time, and the higher limit with the maximum value of the so-called traffic energy function ([Hertel 1992], [Schmidt 2009] & [Chu 2014]). 2.3Methods of Capacity Research
There are various methods of capacity research, for the description of the operational quality and the further operating performance, the waiting time is one of the most important parameters of capacity research. Moreover, an intermediate result of capacity research is the throughput capacity for a specific operating program on a given railway infrastructure and during a specific time period. There are basically two methods to determine the waiting time and the throughput capacity for capacity research: Analytical method Simulation method 2.3.1Analytical Method The analytical method is a common method for conducting capacity research and is based on mathematic analysis. Using this method allows for the calculation of the capacity of the railway infrastructure including the railway lines and railway nodes (railway stations), and waiting time by means of mathematical expressions given the infrastructure and the characteristics of the operating program ([Potthoff 1969], [Schwanhäußer 1978], [Kontaxi & Ricci 2010] and [Pachl 2014]). The infrastructure and timetable (operating program) are modeled with suitable mathematic models, such as parallel servers and the probability distribution. For the analytical method, the basic theories are the queuing theory and the probability theory [Potthoff 1972]. The investigated area of the railway system can be modeled as a corresponding queuing system. Accordingly, the waiting time can be derived by using mathematical models. For the analytical method, the railway operation process can be described mathematically either by the deterministic expression or the stochastic expression. The analytical method is based on certain assumptions and an investigated operating program by using mathematical methods to assess the capacity of the railway lines and nodes [Liu 2011]. From the mathematical point of view, the stochastic expression is utilized with unknown quantities that are mutually dependent on each other [Kontaxi & Ricci 2010]. On the other hand, the deterministic expression is used with unknown quantities that are mutually independent of each other [Kontaxi & Ricci 2010]. With the analytical method, the infrastructure is studied and calculated with the track lines and railway nodes, which are modeled with suitable queuing systems as single servers or multi-servers. For track lines subdivided into different sections, single severs are used for each direction when applying the analytical method. In addition, in order to measure the capacity of a railway node, it is necessary to analyze the structures of the node in the railway networks as well as the smaller infrastructure elements that make up a railway node. The railway nodes are the points of the network connections where multiple railway lines are linked. The structure of a node consists of two components [Pachl 2016]: the set of tracks (Gleisgruppen) and the set of conflicting sub routes (Teilfahrstraßenknoten). The set of tracks in a node is modeled as multi-servers of a queuing system. Comparably, because the conflicting sub routes in the node are exclusive of each other, its characteristics can be modeled as single servers in a queuing system. For complex railway nodes, many sets of conflicting sub routes are assembled to be modeled as a multi-resource queue (see [Omahen 1977], [Green 1984] and [Nießen 2008]). Through mathematical analysis, an expected value of the waiting time and the line exploitation rate can be ascertained deterministically. Furthermore, the operating program is described mathematically with the analytical method. When using the queuing system, the trains are treated as the customers.. The information from the operating program can be described as a random variable, which is the time interval between the arrival times of two trains, using a suitable distribution (or its variance in the simplest case). The occupation times of a train refer to the service time in the server of a queuing system, which is regarded as a random variable with a proper probability distribution (or its variance in the simplest case). Therefore, the operating program can be represented with a suitable mathematical model. [International Union of Railways (UIC) 2004] describes the compression method to determine the maximum capacity with the time-distance diagram. Through compressing the blocking time stairways and keeping the minimum line headway and the structure of the trains, the consumed capacity of an infrastructure can be derived. However, this compression method as described in [International Union of Railways (UIC) 2004] can only be used under very large restrictions [Lindner 2011]. The line capacity utilized by an operating program can be simply visualized by compressing the blocking time stairways as close as possible together without any buffer time and with keeping the sequence of trains unchanged [Pachl 2016]. According to [Wendler 2002], it is comprehensible that the evaluation of the railway lines capacity research can be carried out using the compression method. With its mathematical formulas and algebraic expressions, the analytical method is mainly utilized to identify the preliminary resolutions and reference values for capacity research [Rossetti 2009]. It is helpful to use the analytical method in relatively simple situations, which may require more effort and time to simulate than to solve the problem [Pachl...