## 2 Materials and Methods
### Methods  
The proposed methodology is based on the collection, analysis, and use of relevant data to evaluate the societal benefits arising from the establishment of security measures. The outputs are bound for the later use of the \"opportunity cost\" valuation approach. The subject of the paper is to develop and present a methodology for the quantification and evaluation of the socioeconomic impacts of occurrences emerging from railway infrastructure, divided into relevant subcategories, following the scientific literature research and basic principles of economic analysis of public investment projects. Development of the methodology for the evaluation of the socioeconomic impacts of occurrences emerging from railway infrastructure consists of the following steps:  
* Analyzing the Database of Occurrences, defining the categories, and selecting the data for further use. * Defining the key characteristics of occurrences, including health and delay impacts on passenger and freight trains and their economic evaluation. * Determining the expected impact of occurrences by category. The calculation of the amount of the expected socioeconomic impacts of occurrences by the categories of per kilometer of railway line and station is performed in Section 3. The partial steps are described in detail in the following sections. Analysing the Database of Occurrences, Defining the Categories, and Selecting the Data for Further Use  
Occurrences emerging within the railway infrastructure can be classified into three basic groups:  
* A--Serious accidents (A1-A4),
* B--Accidents (B1-B10),
* C--Incidents (C1-C21). Subcategories of occurrences were defined within the mentioned groups of occurrences, which differ mainly in the causes of the occurrences and their impacts. For the purposes of the presented research, the following variables, which are relevant to the methodological procedure, were selected from the Database of Occurrences:  
* Impact on health,
* Death,
* Serious injury,
* Minor injury,
* Material damage,
* Costs,
* Number of delayed passenger trains,
* Total delay of passenger trains,
* Number of delayed freight trains,
* Total delay of freight trains, and
* The cause of the occurrence,
* Technical,
* Human factor,
* Others. These variables are listed in the Database of Occurrences for each specific occurrence. The Database of Occurrences [3] could not be used for further research purposes in its original version without modifications as the recorded variables were developed year-on-year and the data structure was not consistent. The researchers, therefore, made the necessary adjustments for the purposes of its further use. The analysis of the Database of Occurrences was elaborated in order to address the research question of the average, minimum, and maximum annual impact values (number of occurrences, deaths, number of serious/minor injuries, material damage, and costs) of occurrences, with their possible deviation, which was monitored based on the standard deviation. It was subsequently decided, following the results of the analysis, that the follow-up research would not include occurrences due to suicides and those emerging at railway crossings. Detailed results of the above-defined analysis of the Database of Occurrences and conclusions and recommendations resulting from the analysis were published in [20]. Defining the Key Characteristics of Occurrences and Their Economic Evaluation  
The research team defined the information and characteristics of partial occurrences within the Database of Occurrences that provided data on the partial socioeconomic impacts of the occurrences on society. An overview of this information and characteristics is presented in the previous section. Impacts in the form of costs of the removal of material damage or other direct costs incurred are quantified for each individual occurrence and are listed directly in the occurrence database. The research, therefore, focused on the evaluation of the remaining variables.