Theory of service means knowledge of what is permanent and normal in producing a service. Traditionally, this knowledge has been accumulated in tacit form in the professional skill of the people involved in the activity, but today more and more of it is being documented in writing by researchers.
Most studies of service use either one of two alternative approaches, that is, they have either descriptive or normative purpose, as can be seen in the diagram on the right. The two resulting theory paradigms differ quite much from each other even when the object of study is the same.
Descriptive theory contains knowledge about past or present activities of producing or using a service but does not much help for modifying it to correspond better to latest requirements. Academic or historical studies are often of this type. They are sometimes categorized in two types: extensive studies of a large number of cases, and intensive studies of one or a few cases.
Normative theory of service contains generally applicable knowledge and tools that can be used in producing the service, especially for optimizing it or planning improvements to it. Research for creating normative theory is usually extensive because it needs a large number of cases for its material.
Moreover, a third type of research can take place in connection of the "request of service" marked in the diagram. It means simply studying and planning the execution of individual tasks, for example preparing for a new type of service, or removing problems in existing service. These case-specific or "intensive" studies seldom produce generally applicable new theory and they will not be discussed in the following.
The goal of the service is another possibility of categorizing theory of service. There are only a few important types of goals of service that have attracted the interest of researchers, which means that by studying them it will be easier to get a good total view on the present theory of service than by perusing hundreds of handbooks of different services. These often used points of view in the current theory of service include:
Technology of the service
Almost all services today make use of special machinery, and each of these machines operates on the basis of a specific technology, i.e. on a base of knowledge about the specific operation of service. An overview of the various technologies related to a given type of service usually follows the typical process of the service.
Economy of the service
The economic study of a service aims at finding an optimum between benefits and expenditures of the activity. For finding an optimum, several statistics are used, such as productivity and profitability.
Quality systems
Many large industries today have a quality system, a special arrangement for the task of defining and steering the quality of the activity
Timing of service
The goal in time scheduling of services is to integrate all the tasks in the chain of producing the service so that no unnecessary waiting occurs and each task is given enough time but no more.
We will use all of Theory about transportation, Rational choice theory, Consumer behavior theory and Theory of Service to adapt with factors of tram use of students in Faculty of Humanities and Social Science (HUSOC) in Mahasarakham University (MSU) research. All of theory in above can help us in a process of the study namely engage with analyze the results, design questionnaire and evaluate the results of the research.