Keywords

1 Introduction

The purpose of the paper is to present the main methodological aspects related to the process of designing ITS systems for urban agglomerations. The principles of applying the system approach, system engineering and in particular the V model are formulated in the following sections of the article and are the result of the authors’ research work carried out in real conditions of designing the ITS system for urban agglomeration.

Despite the fact that selected issues of ITS systems design are well described in the scientific literature in the theoretical aspect [1,2,3,4] there are still relatively few scientific articles presenting engineering aspects, i.e. the problems of implementing theoretical issues while working on real ITS systems.

The authors of this paper had the opportunity to work as independent experts and thus could freely combine theoretical issues with engineering practice - freely, i.e. without any obligations to the contracting authority as well as to the contractor of ITS systems. As a result of such work, it was possible to verify and validate theoretical issues of system engineering based on the real conceptual and design process of ITS. The results and conclusions of these works were presented, among others in the following scientific studies:

  • problems of use of transport model for assessment of ITS configuration [5,6,7,8],

  • problems of concept exploration and feasibility study for ITS project development [9],

  • selected problems of use of systems engineering for ITS development [5],

  • selected problems of functional configuration of ITS [5, 10,11,12],

  • managing traffic congestion problems in aspects of use of ITS [5, 13].

The structure of this paper includes the following sections: Sect. 1 explains the purpose and scope of the issues presented in the paper, Sect. 2 presents systems engineering in ITS design as an essential part of the system approach, Sect. 3 characterizes the possibility of using the V model of systems engineering in ITS project and development, Sect. 4 exemplary results of the application of systems engineering in the pre-project documentation of ITS are presented. The paper ends with a summary and conclusions.

2 Systems Engineering in Project of ITS – as the Main Part of the System Approach

Systems engineering is defined as the science of creating complex systems to guarantee the most effective design, adaptation, testing and operation of all the subsystems that make them up. This term refers to complex systems in which components must be designed, manufactured and integrated to achieve the system’s goal. Systems engineering during the concept and design phases enables the construction of the entire system taking into account the entire system life cycle including the following phases: concept, definition, design and development, manufacture and testing, installation and introduction, production, operation and maintenance, improvement and development, replacement and withdrawal from the use of [14].

The system approach to design is characterized primarily by the following principles:

  • it is system thinking that includes a way of conceptualizing, analyzing and solving problems using concepts in the field of system theory, including system structure and conceptual process for developing solutions and their implementation,

  • uses the main system components, which are: system efficiency goals and criteria, system resources, system elements along with functions, attributes and effectiveness measures, system interactions and system management,

  • takes into account the interdependence of the parts making up the system and cause-effect relationships,

  • it is focused on the overall picture and the final goal of the project, which means considering parts of the system only depending on their contribution to the whole system,

  • allows, due to the holistic nature, to avoid considering problems too narrowly; system planning, i.e. creating its model, must therefore cover the following issues:

    • goals and efficiency criteria of the system,

    • environment and limitations of the system,

    • system resources,

    • system elements, their functions, attributes and efficiency measures,

    • interactions between individual elements of the system,

    • system management,

  • in creating the plan of system, i.e. building its model, iterative procedure and feedback loop are used (interactions between: system goals and system plans, system goals and system requirements); the process includes system analysis phases (requirements and criteria related to each goal and alternative ways to achieve it) as well as system synthesis phases (integration of selected modes of action identified at the stage of system analysis and creation of a model, i.e. plan of system),

  • it uses instruments in the form of system engineering covering the entire system and its life cycle (see Fig. 1), with the system life cycle being observed from at least two basic perspectives - the perspective of the (enterprise) and system engineering perspective.

Considering these principles, it can be assumed that the system approach to ITS system design will ensure the use of modern solutions, better use of existing solutions, integration of knowledge, techniques and transport technologies. Such principles and assumptions allow the integration of elements such as knowledge, techniques and technologies at all stages of the system life cycle.

Fig. 1.
figure 1

System life cycle – enterprise view and system engineering view [own study based on [15]]

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During the development of the ITS system concept, systems engineering tools – a field of applied research – defined as “science dedicated to the creation of all complex systems to ensure the most effective design, adaptation, testing and operation of all the subsystems that make them” were used [16]. Among others, the following aspects of this approach were used:

  • a multidisciplinary design team that can be characterized as follows:

    • it is a team performing multifunctional, interdisciplinary, simultaneous work,

    • it is a team that cooperates with the stakeholders of a system, with the main stakeholders being clients, end users and system developers,

    • the creators in the team (system design and construction) cooperate with system users (system operation and maintenance) and system clients (those who finance the system and are its owners),

    • the creators in the team define the following system issues through contacts with other stakeholders:

      • what needs/aspirations should the system meet,

      • formulate system requirements based on the needs/aspirations that define the usefulness of the system, i.e. what exactly the system should implement, i.e. what should be the result of a working system,

      • structure, elements and modularization of the created system, which will cover, in particular:

      • functional and physical structure of the system,

      • components and subsystems are created in such a way that they fulfill the functions necessary to achieve the objectives and meet the requirements of the system’s customers,

      • one of the priorities is a specific way the system functions to meet stakeholder requirements.

  • system life cycle, which means including all phases of this cycle in the creation of the system (see Fig. 1),

  • system life cycle from an enterprise view – includes stages focused on management with decision making, including investment decisions on whether the system should go to the next stage (preliminary study, feasibility study, execution, retirement) or whether the system should be modified, canceled or retired, taking into account decision criteria regarding risk, costs, schedule, functionality etc.; the enterprise perspective applies not only to the system of interest, but also to its subsystems and elements that make up the structure of the system; subsystems and components may have a shorter lifetime than the system of interest in which they are embedded and may require modification during the lifetime of the system of interest,

  • system life cycle from a system engineering view – systems engineering is used at the beginning of the cycle to develop technological or simulation (virtual) prototypes in the concept phase including pre-testing and feasibility studies; then, during the development phase, a system prototype and a pre-production prototype are developed; in the stages of implementation, use and maintenance, system engineering is used in modification (redesign) processes when unwanted and unexpected changes occur, for example due to design errors or failures or the need to take into account new requirements caused by changes in technology, competition or expected threats to system functionality.

The effect of the presented principles of preparing a conceptual design of an ITS system should be a real ITS system that meets current and future requirements, needs and aspirations of stakeholders. Therefore, ITS in the conceptual design is considered as a technical-human system in which the way of considering problems focuses on the whole issue (holistic approach) and not only on its individual elements. ITS is therefore a purposeful set of specific components and relationships between them, and is characterized by the following features and principles specific to systems:

  • there are various interactions between system components and the entire system, as well as between individual system components; the form of these relationships is referred to as the structure of the system, e.g. hierarchical or network structure; a holistic perception of a given phenomenon or synergy effects is observed in this structure,

  • systems have a dynamic character manifested in specific activities resulting from the objectives and tasks implemented by a given system,

  • the set of system components is of particular interest to stakeholders because these components can be changed to suit newly formulated goals; it should be emphasized that among the system stakeholders there is a project team called the creating stakeholder,

  • systems achieve their goals and tasks, so the creation of the system should begin with formulating its purpose,

  • systems can be divided by distinguishing successively subsystems, which are systems in themselves, and distinguishing elements that are the smallest (elementary) parts of the system and its subsystems,

  • systems, subsystems and system elements have specific attributes, expressing their states and qualitative or quantitative properties,

  • systems have their boundary and environment; the environment consists of everything that affects the operation or results of the system and is beyond the control of system conceptualizers,

  • each system has a specific structure composed of elements and subsystems connected by a network of mutual relations,

  • systems, including their subsystems and system components, realize their goals and tasks by processing the input at the system input into the results during a given process, but it should be noted that:

    • input to the system:

      • it can take the form of tangible and intangible resources as well as the steps necessary for the system to work, produce results and achieve its objectives and tasks,

      • it should be possible to control and monitor,

      • it can be as a feedback in the system itself,

    • processes in the system:

      • it is a set of activities that process input into results in the system,

      • it has, among others the following desirable properties: it processes system tasks, effectively achieves the expected results, minimizes input consumption and harmful effects,

    • system results:

      • these are the target results of the system’s operation or the system’s goals,

      • the results are varied: desirable results contribute to the achievement of goals, undesirable or harmful results hinder the achievement of goals and/or negatively affect the environment, neutral results - do not affect the achievement of goals.

  • systems have limitations that hinder achievement of goals and implementation of tasks; systems may have conflicts between tasks of individual components of its structure, which negatively affects the functioning of the system; resolving a given conflict of this kind is achieved during system integration,

  • the operation of all parts of the system must be coordinated and the system that implements its objectives and meets the requirements through coordinated work is referred to as the integrated system,

  • systems can be open to their environment and in their creation must take into account the system environment; systems can also be closed, i.e. independent and autonomous, not requiring references to the environment.

3 Model V of Systems Engineering in ITS Project and Development

Systems engineering is based on general system theory and in connection with this theoretical basis, allows the use of many different system models. For the ITS system, a V model has been proposed (see Fig. 2) with specific phases:

  • phase of defining and decomposing problems in terms of the system – this phase includes formulating the assumptions of the system, defining system requirements, developing a high-level project containing solutions in the field of subsystems, developing a detailed project that is the specification of the elements of the system, leading to its implementation; the phase of defining and decomposing is a descending analysis, which is a breakdown of the created system into components corresponding to specific systemic problems,

  • integration phase of system components (system synthesis) – this phase involves connecting and coordinating individual system components (activities) that are combined into subsystems and form a constructed system (variants of system) assuming that the system meets defined requirements and meets the needs and requirements of stakeholders of this system,

  • the evaluation phase of the results achieved by the system components and the entire system – is the phase of checking the system results, including verification and validation plans for subsequent levels of decomposition and integration phases; it is also an assessment of the proposed variants of system.

Fig. 2.
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Model V of Systems Engineering for ITS Design [own study based on [17]]

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The main components, which are specific levels of Model V, can be synthetically characterized as follows:

  • the level of system assumptions covers the following scope:

    • goals and tasks – defining the needs and requirements of system stakeholders; developing a basic verification plan (validation → functional utility) of the system at the final stage of implementation,

    • actions necessary to perform – identification of stakeholders related to the system; preparation of the system description from the point of view of its stakeholders, including their aspirations and requirements including efficiency, cost and time requirements; selection of key measures of system performance (its results),

    • results of actions taken – a document describing the essence of the system, including the needs and requirements of stakeholders, restrictions (scope of the system); a document that is a system validation plan that defines the approach that will be used to check the correctness of project implementation,

  • the level of system requirements covers the following scope:

    • goals and tasks – mapping the needs, aspirations and requirements of stakeholders and current capabilities related to the construction of the system, by defining a set of system requirements to meet the needs and requirements of stakeholders,

    • actions necessary to perform – determining the system requirements in the iterative process including obtaining information, specifying requirements, analyzing and reviewing them; documentation, verification and management of requirements; developing ways to verify and accept the system,

    • results of actions taken – a document containing system, functional, efficiency and verification requirements; a document being a system verification and acceptance plan in relation to system requirements,

  • the high level design covers the following scope:

    • goals and tasks – it is a mapping of the system’s functional requirements to the subsystem design requirements,

    • actions necessary to perform – examining the relationship between the elements constituting the system and assigning system requirements to individual subsystems (construction of traceability matrix); grouping of identified functions and requirements takes place in accordance with the so-called system architecture, being a configuration of the main components of the system, enabling the implementation of system functions; each main subsystem should meet one or a set of basic system functions (requirements) listed in the document system requirements; determining the interface levels between systems; definition and selection of alternative solutions composed of configuration elements, taking into account the synthesis of components (existing solutions, new solutions); developing methods for verifying the subsystems constituting the system,

    • results of actions taken - creation of a framework project of the system that meets all the requirements; developing a system architecture that allows you to assign all system requirements to major subsystems (configuration items); a document being a plan for the verification and acceptance of subsystems; a document that is a plan to integrate configuration elements,

  • the level of detailed design covers the following scope:

    • goals and tasks – mapping the initial framework project (high-level project) into a project that is possible to implement,

    • actions necessary to perform – actions necessary to perform - designing a system composed of configured subsystems that contain appropriately selected components; a detailed design should be made for each component identified in the high-level design; developing a plan for checking (testing) the elements of a detailed system design; checking of individual components in terms of whether they meet the assigned requirements and are suitable for the intended purpose (testing of elements); preparation of the “prototype” system and preparation of project documentation,

    • results of actions taken – a detailed system project will be created that meets all the requirements; a document containing detailed design specifications at the component level,

  • level of integration along with verification and validation covers the following scope:

    • goals and tasks – mapping the hierarchical integration of components, subsystems and the system; checking and verifying components, subsystems and the system in terms of meeting all system requirements; system validation in terms of its correct construction and its usefulness for stakeholders,

    • actions necessary to perform – it is the integration of system components in accordance with the prepared integration plan and high-level project requirements; creating an integration and verification environment that maps the system’s functioning environment, which gives the opportunity to test system components in ex-ante mode; testing the effects of each integration step for the functionality of the integrated subsystem; carrying out up-directed checks, verifications and validations according to developed plans,

    • results of actions taken – confirmation of compliance of the implemented system with all requirements and restrictions; confirmation of the correct implementation of the system; this is included in the document that describes the activities that were performed along with the results (integration plan, integration tests, verification and validation plan, including procedures and results),

  • the level of development, construction and implementation of the system covers the following scope:

    • goals and tasks – creating new or improving existing systems,

    • actions necessary to perform – final creation (construction) of the system and its testing; after conducting acceptance tests, the system is installed, implemented and becomes part of the user’s environment; as part of development, the existing system is being improved,

    • results of actions taken – transformation of the conceptual design into a complete, material end product, which is the built system.

4 An Example of the Use of Systems Engineering in the Pre-project Documentation of ITS

The issues of the application of systems engineering methods and the V model characterized in the previous sections have been checked and specified during work on the ITS system project for the urban agglomeration. This section of the paper presents a synthetic selection of ITS system design problems identified during work on pre-design documentation and analysis of bidders’ questions in an open tender and investor (municipal authorities) responses during the ITS contractor selection process.

Figure 3 presents problems at current status inventory stage, among others problems of TMC’s location (traffic management centers), problems of using existing infrastructure, problems of using ICT networks (sharing existing or build dedicated), problems of transportation model in ITS development.

Fig. 3.
figure 3

Selected problems of the current status inventory stage [own study based on [17]]

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Figure 4 presents problems at design and implementation stage, including problems of preparation of a complete project documentation, i.e. all necessary projects and studies ensuring the launch of the system together with the approval of all necessary arrangements, decisions and permits provided for this type of construction process. In addition, problems of workplace trainings of employees and users in a way that ensures the use and ongoing maintenance of ITS subsystems were indicated.

Fig. 4.
figure 4

Selected problems of the design and implementation [own study based on [17]]

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Figure 5 presents problems at maintenance stage, including problems of ensuring consistency of documentation for the ITS system, ensuring continuity of correct ITS system operation through periodic maintenance activities for devices and software.

Fig. 5.
figure 5

Selected problems of the maintenance stage [own study based on [17]]

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Details of these problems are included in the authors’ work [17].

5 Conclusion

The design of intelligent transport systems has been carried out for many years around the world and in most cases the systems engineering methods are used in this process. However, the current significantly rapid growth of modern ICT technologies, including the Internet of Things, enables the design of very advanced ITS solutions, whose functions in the form of ITS services can be delivered to a much wider group of users and other stakeholders, not just to vehicle drivers and passengers of public transport.

Therefore, it is even more necessary to apply and at the same time modify and develop systems engineering methods throughout the entire ITS life cycle, because the systems engineering principles presented in this paper guarantee orderly, rational and innovative design of ITS solutions.

Such conclusions arise from practical engineering scientific papers discussed in this paper, because the multidisciplinary design team is the main factor through which modern innovative technical solutions are implemented, both throughout the entire ITS life cycle but above all at the concept and design stages ITS.