suitable railway infrastructure route is a complex process due to the different evaluation criteria resulting from the social and environmental impacts on society, but also due to the high costs and technical pressures on decision-makers. Therefore, a solution proposed by some authors is a multi-criteria approach based on a geographic information system [9; 10; 11]. The environmental impact of the route is an essential issue for both road [12] and rail transport [13], and should be carefully considered before selecting a route. Sustainability in railway infrastructure is an indispensable component in decision-making owing to the influence it enjoys in the selection of a concept for further development [14]. In addition to sustainability, some authors point out [15; 16] that the importance of energy conservation is equally important in sustainable-energy decisions. Decision-making in planning and designing transportation systems is a complex process with social, technical, and economic components [17]. Using an economic evaluation, the authors determined the optimal route for travel between Lanzhou and Beijing [18]. A similar study [19] was conducted for the purpose of economic analysis of railroad infrastructure. It evaluated the impact of methodological changes in the financial and economic evaluation of railroad construction projects in the Czech Republic. In the paper [20], the authors used the method of multi-criteria decision-making for the selection of the most suitable solution of the railroad route, i.e., [21] for the selection of the most suitable alternative of the highway route in Serbia. A similar method for selecting the optimal solution was applied to a concrete example of a railroad project using multi-criteria analysis [22]. Various methods of multi-criteria decision-making have been shown to be appropriate as auxiliary options for the decision on the introduction of a new high-speed train on the Madrid-Valencia route [23]. It is important to consider environmental and geological sustainability criteria in the planning and design of railroad corridors, as shown by the authors [24] for the territory of Sweden. Apart from railroad lines, it is also important to consider the impact of extreme weather conditions on overhead-line infrastructure, as explained in the papers [25; 26; 27; 28]. In addition to infrastructure, special attention should also be paid to railroad safety related to the quality of traction of train wheels on the tracks [29; 30]. New research trends [31] in rail transport are related to the interaction of pantographs and overhead routes, i.e., aerodynamics and active control of pantographs. In addition, contributions address system maintenance, life cycle costs, and reliability [32; 33; 34; 35]. The aim of this paper was the analysis of the evaluation and selection of the optimal railroad route using the multi-criteria analysis method through defined criteria and sub-criteria. The research problem of the paper arose from the formulation of several research questions:  
* RQ1: How can the optimal selection of the Rijeka-Zagreb railway line be achieved by applying the multi-criteria analysis method? * RQ2: Which are the relevant criteria and sub-criteria for the evaluation and selection of the railway route? * RQ3: Is conducting surveys and interviewing experts a relevant method for determining the model for evaluating and selecting the optimal railway route? With respect to the research problem and the defined research questions, the following scientific hypothesis was set for the evaluation and selection of an optimal railway transport route so that the multi-criteria analysis method could be applied. For the selection of the planned railroad route, it is first necessary to define a model for evaluation comprising appropriate criteria and sub-criteria as well as their coefficient of importance Then, an analysis of these criteria has to be performed, which can be produced by a quality selection of the desired outcome using a multi-criteria approach [36; 37].