This chapter is intended as an exposure to OR based methods, particularly the analytical approach to modelling railway operations. An overview of several planned operations in railway transportation is provided in an academic context. Some of the applications and the associated models are applied in realistic settings in the transportation industry, and also have demonstrated evidence of acceptance over a long number of years. Primary coverage is on transportation scheduling and the concise discussions are on planning phases, various operations that can be deterministically modeled and analysed, model development, few exercises and real-world stories, wherever appropriate. All sections are adequately provided with the list of references and an interested reader can benefit from a conceptual understanding to model development and to implement and deploy, under some prior knowledge on the basics and programming experience.
Top2. Operations Research: An Overview
Operations Research is a scientific approach that helps decision makers and analysts to make informed decisions in order to improve the quality of operations in a cost effective manner. Most of the operations are concerned about allocating available resources to demands; the problems get more interesting when there are multiple conflicting demands, when the resources are insufficient or in huge excess in comparison to demands, when there are time restrictions, and when there are multiple conflicting demands. Broadly operations managers face two issues: one is to do decide between a set of choices, as which resource may be allocated to which demand and second is when, how long to allocate the resource to the demand (and / or the sequence in which resources are allocated to demands).
Forian et.al (1988) proposed the well-known topology of transportation models with two dimensions: procedures (activities to be performed, demand, generation) and perspectives (strategic, tactical and operational). Effective modeling using OR is to minimize the gaps by carefully matching procedures and perspectives. Specific aspects that are key determinants to right modeling are (i) decision making context, (ii) accuracy required, (iii) availability of suitable data, (iv) state of-the art in modeling, (v) available resources, (vi) data processing capabilities and requirements, and (vii) levels of training and skills. Modeling is a broader term that includes physical, conceptual, mathematical and other kinds of models. Physical models are generally not used in operational design or analysing in transportation; unless a break through archetype engineering technology is introduced in the system. To analyse large, complex systems such as railway transportation, it is necessary to understand the relationships of the components, the detailed operations and functionalities, and interactions between each other. A conceptual model helps in understanding such systems, define goals of each inter-related sub-systems in a view to analyse and evaluate the system on completion. A conceptual model is usually presented as a chart with systems components, or sequence of steps in an analysis, or flow of events. Inter-relations between various components, events that trigger any operations or decision making and all output possibilities are included.