We can see on the chart that the process of decision making starts with the identification of a problem (in this case it is the access to railway station services which are offered by the infrastructure manager). In the next step it is the determination of alternative procedures and meeting one of three requirements (it is the requirement for which the intensity is expressed using the rate of utilizing a service by a carrier). In the closing part of the theoretical stage, the alternative solutions (in our case, the urgency to realize modernization or reconstruction measures focused on the most utilized service) are evaluated. Then one of the alternatives is selected; afterwards the decisions are implemented and at the end these decisions are reviewed and evaluated.
3.3. Application of AHP Method in Railway Transport
There exist multiple different methods which basically feature the same principle—the assessment of several variants of solution of a given problem according to selected criteria and a set order of individual variants. Particular methods differ in how the weight of criteria are determined and the degree to which the individual variants of solution meet the selected criteria is evaluated numerically [
14].
In the case of the AHP method, the comparison of criteria as well as of individual variants is based on a so-called expert estimate in which experts on a given field of study compare mutual impacts of two factors [
15]. These evaluations are presented in
Table 4.
For a better arrangement, see
Table 5 where the evaluated indicators and evaluative elements are marked and sorted with letters.
In the first stage of the first step, individual services (criteria) are compared first. They can be compared on different bases. The best way, however, is to compare them on the basis of frequency of their utilization. For different railway stations in the network, however, there exists a different frequency. Thus, it is appropriate to choose one station where the importance of its services is determined by the frequency of their utilization. It will be Štúrovo station in our case, which is an important border transit station between Slovakia and Hungary.
Table 6 presents a pair-wise comparison of services criteria at Štúrovo railway station.
The basis of the AHP method is the recording of individually selected significance values which were compared among alternatives in evaluative forms (
Table 6) in a so-called Saaty’s decision matrix [
17,
18]. The number of individual comparisons can then be calculated using Equation (1).
In our case
n represents the number of elements we want to compare. In the result there are six comparisons in total, which is proved in
Table 6. In
Table 6, red is used for pair-wise comparison of the criteria listed in
Table 5. In
Table 7, red is used to express the importance for pair-wise comparison of criteria by variant. In both cases, the red color emphasizes the degree of importance according to the authors’ expert estimate.
For example, at Štúrovo railway station there were altogether 38 vehicles weighed on the wagon weighbridge in 2017 [
19,
20], however, ŽSR was asked for shunting by few carriers in that year. This is because shunting services are not included in the first access package of ŽSR. This claim would increase the costs of the infrastructure manager for shunting crews which would also be manifested in higher costs of shunting for the carrier. Last but not least, individual companies hire their shunters and wagon supervisors from each other at this station, depending on orders. Therefore number 9 is chosen in the pair-wise comparison of criteria. This way other decisions of authors could be described, too.
In the next stage of the first step, the same comparison of criteria is realized for carriers which utilize these services. It will be a comparison by the importance and frequency of utilization of the service by each carrier. That is the content of
Table 7.
The second step contains the formation of the Saaty’s decision matrix. On the main diagonal the values will equal one, because individual alternatives are compared with themselves here. The other four values (it will be a 4 × 4 matrix) above the main diagonal are determined by the given entity in the comparison. The comparison and assignment of weights is usually determined as follows: the alternative which is located in a column is compared to an element in a top row. The values below the main diagonal will be written as reciprocals of individual weights above their main diagonal according to Equation (2) [
21,
22].
In the first stage of the second step, the Saaty’s matrix will be formed for the provided services (
Table 8).
In the second stage of the second step, the Saaty’s matrix will be created for railway undertakings which utilize services at Štúrovo railway station. A demonstration example is presented in
Table 9.
The third step is characterized by the determination of an eigenvector of the matrix (X
K) and a normalized eigenvector of the matrix (X
KN) according to Equation (3).
where:
In the first stage we will calculate an eigenvector of the matrix and a normalized eigenvector of the matrix for vectors of the criteria matrix in
Table 10.
The second stage of the third step lies in creating the vectors of the matrix by individual criteria which are listed in
Table 11.
Then the fourth step follows, which is focused on the calculation of an eigenvalue of the matrix and the biggest eigenvalue of the matrix. The calculation of the eigenvalue of the matrix is done using Equation (4).
where:
Equation (5) serves for the calculation of the biggest value of the eigenmatrix. For the sake of clarity, the values of the eigenvalue of the matrix as well as the biggest value of the eigenmatrix will be presented within one table.
where:
λmax—the biggest value of the matrix,
n—a dimension of the matrix (4 × 4 in our case),
λi—an eigenvalue of the matrix (in a respective row).
The first stage of the fourth step will comprise
Table 12, where eigenvalues of the matrix and the biggest value of the eigenmatrix will be processed to evaluate the services provided at railway stations.
The second stage of the fourth step comprises the calculation of the eigenvalue of the matrix and the biggest value of the eigenmatrix for individual railway undertakings utilizing the railway station services.
Table 13 presents the individual values.
In the final fifth stage, there will be an AHP decision matrix formed. This matrix is the final decision matrix and, based on the results presented in it, the order of importance of individual services for selected carriers will be set. Afterwards there will be some measures proposed which should be enacted for the modernization of Štúrovo railway station in order to ensure a non-discriminatory access to services.
The decision matrix contains the following indicators:
criteria—four services provided by Štúrovo railway station,
weights of criteria—values of the normalized eigenvector of the matrix from
Table 10,
importance for the entities of railway transport—values of the normalized eigenvector of the matrix from
Table 11,
the weighted sum—it is calculated as a sum of the product of weights and the measure of importance of individual railway undertakings,
the order—the order of utilizing individual services by railway undertakings will be determined by the number of won points.
Table 14 shows the final evaluation of the railway station’s result using the AHP method. The use of this method should give the most accurate results.
It is clear from the table that the carriers ZSSK CARGO and PSŽ have an important position at Štúrovo railway station. On the other hand, the position of Metrans Danubia, a.s., is of a much smaller weight. This is also caused by the fact that for this carrier the priority border crossing is in Komárno–Komárom, and the border crossing Štúrovo–Szob is used as a diversion only in case of closures or other emergency situations.
The biggest value is attributed to the service of stabling sidings which in spite of its “popularity” is not sufficient and shift dispatchers of carriers are forced to utilize other stations, or tell half-truths to persuade train dispatchers of the infrastructure manager to side-track their train in particular. In contrast, shunting services provided by the infrastructure manager feature the smallest weight. These services are utilized by few carriers due to their financial unprofitability.