Poznań Metropolitan Railway—Development Opportunities Based on Comparative Analysis

Abstract

The agglomeration railway networks form the backbone of modern urban transport systems, providing safe and reliable access from home to work or school for thousands of residents of agglomeration districts. This article examines the possibilities and directions of development for the agglomeration railway of the city of Poznań, providing a comparative analysis of this system with the networks of the cities of Szczecin and Gdańsk. Each rail system was described and presented in terms of its most important features. The collected data were then collected in tabular form and based on them, a comparison was made using two methods: AHP and COPRAS. Both methods, although with different strengths, indicated the unquestionable advantage of the agglomeration railway in Gdańsk for the adopted assumptions. The Poznań network obtained the weakest result in light of the assumptions. The analysis showed aspects of passenger transport, the improvement of which is crucial for the development of public transport in Poznań, e.g., too low frequency of trains, the need to increase passengers’ awareness of the possibilities of using rail transport, or the need to create stops ensuring a smooth possibility of changing to another means of transport.

1. Introduction

The changing demographics of the whole of Poland, and especially of large cities, are a challenge not only socially and economically, but also in terms of communication. The increasing traffic between provincial cities and the communes located in their vicinity creates a demand for efficiently operating public transport networks. Solutions are sought that are not only economically beneficial, but also meet the constantly growing environmental requirements, and above all meet the requirements of the residents, whom they are ultimately to serve. However, attempts to fit into the above framework, as well as to meet the requirements of the 15 min cities concept, are exposed to a number of threats, which were attempted to be identified by comparing three agglomeration railway systems—the city of Poznań, the city of Szczecin, and the Pomeranian Metropolitan Railway. A typical problem is the so-called commuter paradox: city dwellers move to the outskirts of the city/agglomeration to improve their living conditions (less noise, the possibility of communing with nature, etc.), while they spend most of their time on their daily commute to and from work/school.

There are various solutions, such as the following:

• Reducing transport requirements, e.g., the 15 min city, which enables a better quality of life thanks to the possibility of achieving everything a city resident needs within 15 min on foot or by bike [1];
• Increasing transport possibilities (e.g., using water transport);
• Introducing innovative means of transport (e.g., drones for transporting parcels);
• Introducing intelligent transport systems.

However, problems still remain: congestion, noise, air pollution or stress in general, which causes cities to depopulate, which increases traffic resulting from the need to travel from the outskirts of the agglomeration to the city in order to carry out basic activities (work/study).

Typical transport paradoxes (apart from the commuter paradox) include the following [2]:

• Braess’ paradox (based on the Lewis–Mogridge law), that adding more traffic lanes or building new roads can worsen driving conditions;
• Downs–Thomson paradox—the average speed of cars in a city depends on the speed of public transport vehicles (one of the key priorities should be improving public transport).

Taking into account the currently set goals of sustainable transport policy (introduction of fees for owning passenger cars, increase in the prices of fossil fuels, introduction of electric cars, reduction in the number of passenger cars, etc.), the share of public transport should be increased and the current transport pyramid (based on individual car transport) should be changed to a pyramid based on journeys by vehicles without combustion engines (bicycles, electric scooters, scooters) and pedestrian journeys, as illustrated in Figure 1. Rail transport should be considered a priority option for public transport in light of sustainable development. Combining rail transport (urban railway, tram, metro) with individual transport (city bikes, scooters, electric scooters) seems to be the most rational solution.

From a historical point of view, we can actually talk about restoring the situation. For example, in Poland in the years 1970–1980, public transport provided the possibility of communication without the currently popular problem of transport exclusion, which resulted primarily from the difficulties in acquiring passenger cars. From the point of view of the development of transport systems in the agglomeration, rail transport plays a key role, especially the agglomeration railway (naturally integrated with other means of public transport (e.g., fast tram) or individual transport (city bike). Since this type of infrastructure is developing dynamically, it seems reasonable to compare the existing agglomeration railway systems in order to indicate potential development opportunities. Although different networks have been characterized in other papers, there was no attempt to compare different solutions. Such a comparison is not intended to demonstrate the superiority of one network over another, but to indicate which factors require attention in order to improve and popularize rail connections in metropolitan areas. The aim of this article is to conduct a comparative analysis of these networks. This will allow for the assessment of the development opportunities of the Poznań Metropolitan Railway and to establish guidelines for further development directions of the Wielkopolska PKM. When starting the analysis, the authors were aware of the advantage of the Pomeranian Metropolitan Railway over other networks—in Poland, it is a model example of a developed agglomeration railway. This article covers the discussion of the topic of agglomeration transport, description, and analysis of the above-mentioned railway networks, and also presents the results of a comparative analysis using the AHP and COPRAS methods, which are also described in this article. They have been successfully used for years in multi-criteria analyses, although they are based on different approaches.

2. Literature Review and Theoretical Background

The subject of the development and use of the agglomeration railway as the trunk of modern communication trees has been raised many times by many researchers. As Zamkowska [4] rightly notes, the railway should occupy an extremely important place in the modern vision of transport. The undeniable advantages of the railway include its high reliability, safety (very low number of railway accidents), a large amount of existing infrastructure, and a huge advantage in terms of climate protection, due to the low CO₂ emissions caused by rail traffic. The above factors indicate rail transport as the main backbone of the future travel system, especially over long distances. However, apart from travel between large cities, a dense rail network can also create the backbone of agglomeration transport. In accordance with the assumptions of sustainable development, trains should be accompanied primarily by local public transport vehicles, such as buses and rail transport (tram, metro, or agglomeration railway) or individual (bicycles or scooters)—the choice would depend on the remaining distance to be covered and the user’s preferences. In the case of short distances, pedestrian traffic should not be forgotten either. In Poland, the 1990s and 2000s were characterized by significant changes in transport, especially individual transport. The reduction in funds flowing into the railway infrastructure, numerous investments in roads, and relatively cheap cars, especially from the secondary market, led to a situation in which the basic means of transport for many people became the car. However, even earlier, in the 1960s, developed countries began to worry about the phenomenon of cities being consumed by car traffic. In his article, Kopeć [5] recalls the Buchanan Report, which clearly indicated such threats as the destruction of streets as an environment created for residents, excessive noise, air pollution, and even the risk of damage to historic parts of cities. In his work, Koźlak [6] lists among the main causes of the poor condition of transport networks in large cities, among others, too low capacity of road systems, problems with traffic control, and poor condition of road infrastructure, including engineering structures. It also provides data on the increase in the level of motorization: from 258 vehicles per 1000 inhabitants in 2000 to 451 cars per 1000 inhabitants in 2010. Eurostat continues this sequence of data and states [7] that in 2021, this level was 687 cars per 1000 inhabitants, which makes Poles the most motorized nation in the European Union. Koźlak also points to the very high positions of Polish cities in the list of European cities affected by congestion (the phenomenon of chronic congestion of communication routes, their insufficient capacity in relation to needs—or colloquially “jamming”) from 2010. Warsaw and Wrocław took 2nd and 3rd places at that time, and Poznań was also in the top twenty. However, contemporary visions of transport development depart significantly from this pattern. A very strong emphasis on environmental aspects, reduction in greenhouse gases, and increased awareness of the role of physical activity have translated into new concepts of sustainable development. The role of urban railways in today’s world is evidenced by the growing number of agglomeration transport systems based on rail transport. This can be illustrated by the German S-Bahn model (whose historical beginnings date back almost a hundred years). Currently, the S-Bahn operates (in various subtypes) in Berlin, Munich, Stuttgart, Hamburg, and other large German cities. An interesting case is the Oslo agglomeration railway, Lokaltog Østlandet. The Norwegian capital is served by eight railway lines and over 120 stops (in Oslo itself and its surroundings). In Poland, apart from the systems of the cities of Poznań and Szczecin, there are several other agglomeration railway networks. Noteworthy, for example, is the Łódź Agglomeration Railway, established in 2014, which is the basis of the public transport network for an area inhabited by approximately 1.1 million people, or the Tri-City Fast Urban Railway (despite the fact that its routes have diverged from railway line 248, also known as the Pomeranian Metropolitan Railway) [8]. In his review of the existing agglomeration railway networks, Wołowiec [9] also points to lesser-known solutions such as the BiT City Railway (Kuyavian-Pomeranian Voivodeship), the Podhale Regional Railway (Lesser Poland Voivodeship) or the Subcarpathian Agglomeration Railway (Subcarpathian Voivodeship).

The most important features of the agglomeration railway were summed up during the meeting of the Transport Research Observatory entitled “Agglomeration Railway 2022: needs and expectations, difficulties and barriers”. These features include a high frequency of connections, a multitude of stops, a regular timetable, and special rolling stock [10].

Among the advantages of introducing agglomeration railway networks, it is worth mentioning their fundamental role in integrating metropolitan areas. The agglomeration railway is not only to provide a communication solution for a given area, but can also in itself cause the development of the region [11], in a classic way becoming an example of positive feedback. The railway provides the backbone of sustainable transport; in times of striving to minimize the negative impact on the environment, it is a determinant of a fast, reliable, and ecological way of moving, which can be effectively combined with other means of transport, such as buses, bicycles, or electric scooters. The previously mentioned low number of accidents in rail transport results not only from its collision-free nature, but also from the increasing care for the safety of passengers at stops and stations. In their work, Tomov and Dimitrova [12] indicate the numerous advantages of using barriers (screens) protecting the edge of the platform before the train arrives. And although this study focuses on underground railways, these solutions are currently also used on “overground” railway lines. The launch and development of the agglomeration railway network has a significant impact on the way metropolitan residents travel. An example of this is the Fast Agglomeration Railway in Kraków. As Kulpa et al. [13] have reported, survey studies have shown that 26.3% of respondents have given up on car transport, and 18.3% have given up on private carrier services and have switched to SKA agglomeration trains. The fact that passengers are keen to use rail connections within the agglomeration is evidenced by survey studies on the Fast Urban Railway in Warsaw, described by Wocial and Rokicki [14]. An amount of 88% of respondents have used this means of transport. As many as 60% of people who use the SKM in Warsaw use this means of transport to commute to work or school. When asked about the reason for choosing this means of transport, 37% indicated availability, and 34% the speed of travel. Unfortunately, it is also necessary to mention the disadvantages, or more precisely, the difficulties associated with the agglomeration railway. The biggest problem is of course the high cost of railway investments, as well as the subsequent maintenance of infrastructure (especially railway stations). In dense urban development, the mere routing of new rail routes can cause dissatisfaction among residents. As indicated by Połom and Tarkowski [15], the example of the Pomeranian Metropolitan Railway indicates further points that require improvement, in particular, cooperation between the agglomeration network manager and local governments and efforts to introduce a single transport plan so that public transport means to cooperate with each other and to not compete. Kopeć, when analyzing the development of the Pomeranian Metropolitan Railway [16], also points to insufficient integration with regional transport, as well as individual transport. In the previously mentioned studies on SKM passengers in Warsaw, only 37% of respondents declared that they choose rail as a daily means of transport within the agglomeration. As Anioł [17] notes, the example of the GZM Metropolis railway shows that passenger engagement is diverse even within a single agglomeration network. Among the analyzed stops, the passenger potential amounted to about a dozen percent, although there are also cases where this potential exceeds 100% (indicating the phenomenon of commuting from a more distant place in order to use the railway). As shown in the above analysis of literature, from the point of view of sustainable development, rail transport is a solution with exceptionally favorable characteristics compared to road or air transport. Of course, water transport is an interesting alternative, but its range is significantly limited due to the network of waterways and the costs of maintaining navigability. It is necessary to outline a development program for the agglomeration railway in Wielkopolska. It may be valuable for this purpose to compare the Poznań PKM to other similar metropolitan railways and to assess it, which will allow for confirmation of the accuracy of development plans or setting new directions for development. For this purpose, the authors decided to compare three solutions: in Gdańsk, Szczecin, and Poznań.

3. Analyzed Case—Poznań Metropolitan Railway

The Poznań Metropolitan Railway (PKM) is currently served by five lines utilizing the existing infrastructure managed by PKP PLK S.A. The network follows a classic star-shaped layout, with the city of Poznań at its center (see Figure 2). The connections radiate outward as follows:

• Gniezno—Kościan;
• Nowy Tomyśl—Września;
• Wągrowiec—Grodzisk Wielkopolski;
• Wronki—Środa Wielkopolska;
• Poznań—Rogoźno Wielkopolskie.

Due to historical circumstances, Poznań has always been well connected to its surrounding municipalities through a railway network, making the railway a natural backbone for metropolitan transportation. During the New Mobility Congress, the Deputy President of Poznań emphasized the city’s commitment to investing in modern public transportation and cycling infrastructure [19].

The metropolitan network is being enhanced with transfer hubs within Poznań, enabling passengers to switch to buses or trams. Additionally, the city is expanding its Park & Ride facilities, allowing commuters to drive to the outskirts of the city and then use urban/suburban public transport or train connections. This latter option will become even more significant with the implementation of the project to open Poznań’s Freight Bypass for passenger traffic. This project (along with complementary initiatives) includes constructing additional passenger service points with transfer infrastructure. It will enable fast travel from one side of the city to the other while bypassing the city center. However, the project faced delays due to challenges in securing necessary funding.

In its current form, PKM allows passengers to use, on average, two connections per hour during peak times (according to data from the Poznań Metropolis Association [18]), offering an alternative to residents’ traditional commuting habits.

An illustrative example of the time difference can be seen between the Poznań Strzeszyn station, serving rail access to the city center for residents of the Podolany district and the neighboring Suchy Las municipality. A commute from this transfer point to the Poznań Główny station takes at least 30 min by bus, a similar time by car (but only outside peak traffic hours), while the train covers the distance in about 10 min.

Nevertheless, it should be noted that compared to the capabilities of some other metropolitan networks (particularly the Pomeranian Metropolitan Railway), offering one connection every 30 min during peak hours remains insufficient.

4. Analyzed Case—Szczecin Metropolitan Railway

The transportation network around the city of Szczecin takes on a different form, influenced by its specific geographical location (proximity to Lake Dąbie, Szczecin Landscape Park, and the national border). The directions of the railway routes are, as a result, more linear compared to the star-shaped network of Poznań (see Figure 3).

The construction of the Szczecin Metropolitan Railway (SKM) is still ongoing. While the work on the existing railway lines and the construction of new stops is progressing relatively smoothly, adapting railway line no. 406 (toward Police) for passenger traffic has proven challenging. The necessary work involves not only building passenger infrastructure but also tasks related to the track system, railway traffic control, and the traction network. However, this is a key element of the SKM project, aimed at providing quick and efficient connectivity between Police and the center of the Szczecin metropolitan area.

Ultimately, the SKM is planned to connect Szczecin with Police, Goleniów, Gryfino, and Stargard, enabling passengers to use dozens of passenger stops, Park & Ride facilities, and other infrastructure that facilitates integrated public transport across the Szczecin metropolitan area.

Similar goals of both transportation systems—the desire to utilize existing railway infrastructure and expand transfer point networks—are aspects that undeniably link the two metropolitan railway systems.

5. Analyzed Case—Pomeranian Metropolitan Railway

The situation of the Pomeranian Metropolitan Railway (PKM) in Gdańsk is markedly different. While the previously described systems were largely based on existing railway networks, the Gdańsk PKM line was built entirely from scratch with the specific goal of serving as a metropolitan railway. The line, constructed outside the PKP PLK network, has been operating passenger connections since 2015 (see Figure 4).

Thanks to the early definition of the new railway line’s role, it was possible to create a network of railway stops complemented by bus stops, bike-sharing stations, and electric scooter stations. All of this is presented to travelers in a unified visual format.

In its current form, the Pomeranian metropolitan network offers nine railway stops, but a twin project—PKM Południe (South)—is planned for the future. Such a large undertaking reflects residents’ satisfaction with the direction of public transport development.

It is also worth noting that the infrastructure manager for the PKM in Gdańsk is the company PKM S.A. This is a significant difference compared to the previously described networks, where the entities associating municipalities and cities do not directly manage the infrastructure or passenger transport.

6. General Comments

Feasibility studies (FS) are the foundation for further project steps and, subsequently, the implementation of construction works in creating metropolitan railways. As part of the FS, several execution options for a given task are prepared, differing in the scope of work, route layout, and technical conditions. Although feasibility studies are often detailed and extensive, they currently focus primarily on the most economically advantageous options. There is also a lack of specific guidelines or a set of best practices for designing metropolitan transportation systems.

One threat to all three metropolitan railway systems is the poor integration of various public transportation modes. An example is the Poznań Strzeszyn passenger stop, located on railway line no. 354. A Park & Ride facility for 50 cars was built at the stop; however, the limited transfer options make the parking lot virtually unused. Drivers often choose to leave their cars on the opposite side of the tracks, in an undeveloped gravel lot.

Nearby, there is the “Strzeszyn PKM” bus stop, but the entire system of train-bus-parking appears inconsistent and chaotic. More promising solutions include the Grunwaldzka Hub in Poznań or the stops of the Pomeranian Metropolitan Railway, where the integration of various transport modes is immediately apparent.

Poznań Strzeszyn also highlights issues with stop infrastructure. The existing shelters on the platforms are small and provide protection from light rain but are insufficient against wind or heavier rain. There are also no toilets, although passenger surveys indicate that users of stops without station buildings would like such facilities near the platforms [22]. While a toilet was built near the Park & Ride facility, this solution presents several issues. The platforms lack signage indicating the presence of the toilet, effectively limiting its use to Park & Ride users. Furthermore, the toilet’s location means that passengers must walk approximately half a kilometer from the platform, potentially crossing a railway level crossing.

This level crossing leads to another problematic aspect: access to the platforms. At smaller passenger stops, there are no underpasses between platforms, forcing passengers to sometimes violate regulations and cross closed barriers at the nearest road crossing before a train arrives. A second issue arises at stops significantly elevated above the surrounding terrain. To ensure access for persons with disabilities and those with limited mobility, projects usually include elevators. While convenient, this solution becomes problematic in the event of breakdowns or vandalism. Ramps are less commonly chosen.

One concept still in the conceptual stage in Poland is the use of modular stations. Their low cost, due to the repetition of elements, makes them suitable for many smaller railway stations, providing the infrastructure elements expected by modern passengers. At the same time, it is essential to recognize the changing role of the station in the eyes of contemporary passengers. As Zamkowska [23] notes, stations are increasingly seen not only as essential elements for passenger service but also as multimodal transportation hubs and service platforms. Gradual modular construction aligns perfectly with this trend, allowing for the gradual development of passenger service points in line with growing interest from users. Modular construction also enables quick assembly/disassembly of modules as needed, for example, to adapt to the needs of persons with disabilities.

A significant challenge for the further development of metropolitan railway networks, not only in Poznań but across Poland, may be cooperation between various entities, such as the track infrastructure manager, the railway property manager, the authorities of the central city/municipality at the heart of the metropolitan area, and neighboring municipalities. It is essential to establish a clear scope of responsibility for each of these entities, particularly regarding funding, to avoid disputes during task implementation.

7. Methods—AHP Method

To illustrate the differences in the development of an efficient and intermodal metropolitan transportation network, a simplified multi-criteria analysis was conducted using the AHP method. This method, in combination with others, has been used, for example, in analyzing the railway network of the Beijing-Tianjin-Hebei agglomeration [24], in analyzing the transport plan in the Bulgarian railway network [25], and the general advantages of the use of the AHP method in transport problems were presented by Podvezko et al. [26]

The AHP method, developed in the 1970s by Thomas Saaty, involves a comprehensive analysis of a problem by identifying its hierarchical structure [27]. This method considers a verbal evaluation dependent on the decision-maker’s preferences, from which numerical values are subsequently assigned [28].

Thanks to its mechanisms, the AHP method can also evaluate subjectively assigned weights of criteria, making it widely applicable in decision-making processes.

Using the AHP method additionally allows the use of the criteria weight vector generated as a part of the method when applying the COPRAS method.

The AHP method can be divided into two main components. In the first, a comparison matrix (KR) is constructed. This matrix is created by comparing all criteria in pairs and assigning numerical values to these comparisons. The value ranges from 1 to 9, where criteria considered equally important are assigned a value of 1, and the more one criterion is preferred over another, the higher the assigned numerical value.

The comparison matrix is square and has the property that the weight of criterion j relative to criterion i must satisfy the following condition:

$$a_{ji}={\displaystyle \frac{1}{a_{ij}}},$$

(1)

that is, it must be the reciprocal of the weight of criterion i relative to criterion j.

Each element of the matrix is normalized by dividing by the sum of the values in a given column, according to the following relationship:

$$b_{ij}={\displaystyle \frac{a_{ij}}{{{\displaystyle \sum }}_{i=1}^n{a}_{ij}}}.$$

(2)

The final step in this stage is obtaining the weight vector of criteria (WKR). The elements of this vector are determined as the arithmetic means of the row values in the normalized comparison matrix (NKR):

$$w_i={\displaystyle \frac{1}{n}}{{\displaystyle \sum }}_{j=1}^n{b}_{ij}.$$

(3)

The subjective adoption of data for the comparison matrix can lead to inconsistencies arising from possible intransitivity of preferences. For example, if A is deemed more important than B, and B is more important than C, one cannot automatically assume that A is more important than C. To test whether the adopted preferences are consistent, a consistency ratio (CR) must be calculated:

$$\mathrm{CR}={\displaystyle \frac{{\lambda }_{max}-n}{r·\left(n-1\right)}}.$$

(4)

In the above formula, n represents the order of the comparison matrix (number of criteria), r is the average value of random consistency indices (a value dependent on the size of n), and λ_max is the maximum eigenvalue of the matrix.

It is generally accepted that the preference matrix is consistent if the value of CR < 0.1.

The second component of the method involves creating preference matrices for variants under individual criteria (Kj). The mechanism for creating these matrices is analogous to that of the comparison matrix (KR), but instead of determining the importance of one criterion over another, the preference for one variant over another is established in light of successive criteria. The consistency of each Kj matrix is also verified.

The final scores are obtained by multiplying the matrix of variant weights (WK) by the weight vector of criteria (WKR). The most favorable solution is considered to be the one with the highest score.

The major disadvantages of the AHP method include its strong reliance on subjective assessment of the dominance of one criterion/variant over another and its sensitivity to criteria for which all variants are evaluated at a similar level. Despite the apparent neutrality, such criteria can distort the results [29]. Another potential issue is correctly assigning weights between criteria, as assigning values in the range of 1–9 is subject to subjective evaluation, often based on verbal descriptors (distinguishing between “strong preference” and “very strong preference”). However, for general assessments, the AHP method performs very well due to its clarity and simplicity of calculations and is often used in comparative analyses and decision-making support.

This analysis was conducted not only for the two previously discussed networks but also included the Pomeranian Metropolitan Railway (PKM), which stands out not only in terms of length (being the shortest of the analyzed options) but also, and perhaps most importantly, as a railway line designed with a specific goal in mind: to create a modern transportation route aligned with sustainable transport trends (

Table 1. Analyzed data for each railway network.

	Connection Frequency [Minutes]	Estimated Construction Cost [PLN]	Intermodality	Ticket Prices [PLN]	Stop Density [Stops/km]
Szczecin	15	1.2 B	Some train stops connect to a different means of transport	3.60	~0.3
Poznań	30	1.5 B	Some train stops connect to a different means of transport	5.60	~0.2
Gdańsk	7.5	<1.0 B	Each train stop connects to a different means of transport	5.50	~0.4

).

The criteria included connection frequency during peak hours, construction cost of key infrastructure, intermodality, ticket prices, and station density.

Each criterion was evaluated on an ascending scale from 1 to 5, which naturally means the results have a greater margin of error (see

Table 2. Summary of generalized grades.

	Connection Frequency	Construction Cost	Intermodality	Ticket Prices	Stop Density
Szczecin	4	2	3	4	3
Poznań	2	1	3	2	3
Gdańsk	5	4	5	2	5

). However, given that both the Poznań Metropolitan Railway (PKM) and Szczecin Metropolitan Railway (SKM) do not yet exist in their final forms, this level of generality was considered sufficient for a simple analysis.

The results obtained using the AHP method are summarized in the chart below (see Figure 5).

8. AHP Method—Results

The results clearly show the significant advantage of the Pomeranian Metropolitan Railway (PKM) and the poor performance of the Poznań network solution. The reasons for this disparity can be traced to key issues relevant to metropolitan networks. The very short waiting times for trains during peak hours, high station density, and excellent transfer opportunities make the Gdańsk PKM a solution that could serve as a model for future investments. The functional and aesthetic aspect is also worth noting, namely the unified visual identity for all Pomeranian Metropolitan Railway stations.

The reasons for the low score of the Poznań metropolitan network primarily stem from the radial layout of the railway network. On one hand, this ensures the ability to reach the city center directly from any direction, but on the other, it significantly limits network expansion opportunities. This is because the heavily burdened Poznań Główny station has limited capacity for increasing throughput. Trains on the Poznań metropolitan network run with the lowest frequency among the three analyzed options, and this criterion was given significant weight in the analysis.

The current rail infrastructure consists of existing railway lines, and the planned implementation of the Poznań Freight Bypass represents the most expensive investment among the analyzed networks.

9. Methods—COPRAS Method

The results of the AHP method were also compared with those obtained using another method—COPRAS. The comparison was conducted in two approaches. In the first approach, the same simplified evaluation scale (1–5) for each criterion, as used in the AHP method, was adopted. In the second approach, numerical values were used (keeping in mind their variability due to the fact that the SKM and the Poznań PKM are not yet in their final forms). The COPRAS method uses criterion weights, and the weights obtained in the first phase of the AHP method were applied.

The hybrid use of the AHP and COPRAS methods has been previously used in other research fields [30,31]. The authors found that this is an approach that will well fulfill the assumptions of a generalized assessment of significantly different railway networks.

The COPRAS method was developed in Lithuania by Zavadskas, Kaklauskas, and Sarka from Vilnius Tech in 1994. The name is an acronym for “COmplex PRoportional ASsesment”.

Initially, a matrix X is formed containing the values of n variants evaluated under mmm criteria:

$$\mathrm{X}=\left[x_{ij}\right]=\left[\begin{array}{ccc}{x}_{11}& \cdots & x_{1m}\\ ⋮& \ddots & ⋮\\ x_{n1}& \cdots & x_{nm}\end{array}\right].$$

(5)

Each element of the X matrix is then normalized using a summation transformation:

$$\widetilde{x_{ij}}={\displaystyle \frac{x_{ij}}{{{\displaystyle \sum }}_{i=1}^n{a}_{ij}}}.$$

(6)

Unusually, both increasing and decreasing criteria are transformed in the same way, rather than depending on whether they are stimulants or destimulants. This is a significant difference from approaches used by Lithuanian researchers in other methods they developed (e.g., ARAS, WASPAS).

The normalized data do not account for criterion weights; therefore, a weight vector is adopted:

$$w_j=\left[w_1, w_2, w_3, \dots ,w_m\right].$$

(7)

Next, each value is multiplied by the corresponding criterion weight:

$$d_{ij}=\widetilde{x_{ij}} ·w_j.$$

(8)

Then, two sums are calculated: S_+i, which contains all normalized values weighted for stimulants in the i variant, and S_−i, which contains all normalized values weighted for destimulants in the i variant.

The algorithm concludes with determining the relative weights of variants according to the following formula:

$$Q_i=S_{+i}+{\displaystyle \frac{mi{n}_i\left(S_{-i}\right)·{{\displaystyle \sum }}_{i=1}^n{S}_{-i}}{S_{-i}·{{\displaystyle \sum }}_{i=1}^n\frac{mi{n}_i\left(S_{-i}\right)}{S_{-i}}}}$$

(9)

In the COPRAS method, the variant with the highest Q value is considered the most favorable.

A beneficial aspect of comparing the results obtained by the AHP and COPRAS methods is that the results for all variants in both methods sum to a value of 1.

10. COPRAS Method—Results

In the approach using simplified evaluation, all criteria are stimulants, significantly simplifying the calculations. The obtained results are presented in a bar chart (Figure 6).

Although the ranking order remains unchanged, the Poznań PKM clearly achieves a better score. Interestingly, this phenomenon also occurs when assuming that all criteria are equally important (i.e., without the influence of the weight vector).

Using numerical values instead of simplified evaluations slightly complicates the calculations, as the presence of destimulants affects Formula (9). However, the results obtained using the COPRAS method remain at a similar level, as illustrated in the chart below (Figure 7).

Regardless of the approach used, an improvement in the evaluation of the Poznań Metropolitan Railway network is noticeable, at the expense of a decline in the Pomeranian Metropolitan Railway’s score. However, this does not change the final assessment—Gdańsk’s PKM maintains the highest position in the rankings.

11. Conclusions

The paper may contribute to the development of sustainable transport by analyzing the impact of individual factors, emphasizing those aspects of creating agglomeration railways that ensure their actual use by residents of metropolitan areas. In further steps, it can be the beginning of developing a new approach to the development of agglomeration railways.

In order to achieve more sustainable transport, people responsible for planning railway and urban investments should take into account several key points at the pre-design stage, which will enable a change in the habits of passengers themselves.

• In light of research on public transport [32], it can be seen that for passengers, one of the most important criteria used in making a decision about traveling by agglomeration railway is the frequency of public transport, hence this aspect should be treated as a priority. The current departures every 30 min during peak traffic hours are insufficient in the perspective of future years; we should strive to achieve the performance of Western cities, i.e., departures every 15 min (e.g., agglomeration lines in Madrid during rush hours run every 10–15 min [33]).
• In terms of trade, it is necessary to create subscription offers targeted at specific recipients (pupils/students, commuters, seniors). The existence of permanent groups of passengers will provide a foundation for further expansion of stops and the agglomeration railway system.
• The stops themselves do not have to be created in richly equipped versions. Using a modular approach, you can initially propose only the necessary elements at a new stop (necessary from the passenger’s point of view, and not only from a technical point of view), and as time passes and the number of passengers using the stop gradually increases, add more modules. As shown by survey research, the basic equipment of an elementary agglomeration railway stop is a bus shelter and a toilet.
• Changing the way residents think about sustainable transport will certainly require promotional campaigns that will increase the awareness of potential passengers about alternative ways of moving around the Poznań agglomeration. This applies especially to transfer options, in the future in particular, the bicycle-train/bus connection.
• Despite the significant cost, including the Poznań Freight Bypass in the PKM network is certainly necessary in order to ensure the future development of sustainable transport in the Poznań agglomeration. The new stops that will be built along this long-awaited investment will enable a large number of Poznań residents to use alternative transport solutions, and will also significantly shorten the time needed to travel between the two districts located on opposite sides of the city. It is worth noting that the stops that are to be created along with this investment will also provide access to other means of transport in their close vicinity thanks to the planned transfer hubs. Creating such new hubs or rebuilding existing solutions will certainly have a positive impact on passengers’ opinions about the possibilities of public transport using rail transport.
• In the future, other concepts of expanding the railway network in the agglomeration area will also probably be revived, such as the construction of connecting roads in the vicinity of the Poznań Wschód or Luboń stations. These stations may in the future relieve the Poznań Główny station as a transfer hub.
• It will also be necessary to change the way of thinking about railway stops, as their functions change along with changes in the approach and habits of the passengers themselves.
• A dynamic metropolitan railway will also require other investments that will increase its capacity. One example is the railway line 354 from Poznań to Piła, which is served by a single track for a significant section (over 50 km). The modernization of this line completed in 2019 did not include the reconstruction of the second track (line 354 was originally double-track for almost its entire length; after World War II, two tracks only operated on a few sections).
• The concept of a fifteen-minute station assumes the possibility of cycling to nearby places, including the destination itself. Unfortunately, the liquidation of the Poznań City Bike in 2022 has pushed this aspect of the idea of sustainable agglomeration transport away from implementation. We should hope that a similar solution will appear in the future, and the agglomeration railway stops themselves must have bicycle parking spaces in their vicinity. A solution that is occurring in an increasing number of Polish cities is the introduction of shared electric scooters, the simplicity of which and their availability fit very well into the idea of sustainable transport. However, this also involves a number of problems that will require solutions. Data on electric scooters collected in Gdańsk [34] indicate an urgent need to create clear regulations that will define the methods of using this type of device (currently existing regulations do not solve all the problems related to this means of transport). These studies have shown that many people still do not feel safe when encountering a scooter traveling relatively fast.
• The most difficult challenge related to the development of agglomeration railways will definitely be changing the approach of potential passengers themselves. It should be remembered that the ongoing expansion of access networks around Polish cities began relatively recently, while large cities in Western and Northern Europe began this process decades ago, during which time residents were accustomed to the presence of railways in their daily commute to work, schools, or shopping and cultural centers. The gradual electrification of car traffic, caused by the EU’s efforts to reduce the share of cars with combustion engines, will most likely reduce the number of cars on Polish roads, and the growing number of people wishing to work in large cities will increase the demand for efficient and accessible public transport.
• The conclusions drawn from the comparison of agglomeration railways in Poznań, Szczecin, and Gdańsk may be optimistic, but should also arouse the vigilance of engineers and representatives of the bodies managing such investments. Projects to expand integrated communication networks around an increasing number of Polish cities constitute a major step towards creating modern, environmentally friendly, and efficient agglomeration transport systems. At the same time, potential problems can be seen, which are often economically based. First of all, the first stages of the project should be mentioned here, such as the subsequent stages of feasibility studies, which only slightly focus on the needs of residents, and often promote the cheapest option for further implementation. There is also a frequent lack of a well-thought-out connection between rail traffic and bus or tram traffic. While the agglomeration railway network around Szczecin is currently only being formed, the system for the city of Poznań allows for further expansion, especially using the existing infrastructure of the Poznań Freight Bypass. However, no technical and urban solutions will be enough if the residents themselves are not encouraged in an appropriate way, by constructing an appropriate offer, advantageous in terms of travel time and price, which will allow the metropolitan railway to play a significant role in changing the habits of passengers. These changes will also be driven by legal factors, which will force people to use the public transport network more often (bans on combustion vehicles entering city centers, taxation of registration of combustion cars, etc.). Looking at the future from this perspective, the decision to eliminate the city bicycle network may raise concerns. On the other hand, the picture of the Poznań Metropolitan Railway is slightly more pessimistic, taking into account a very important factor limiting its development, namely the capacity of the Poznań Główny station. This factor should be particularly taken into account in any future plans for the reconstruction of the most important of Poznań’s railway stations.