1. Introduction
Over the past decade, rail infrastructure has re-emerged as a strategic policy priority in Europe, driven by three converging drivers: economic development, decarbonisation and security. Rail (alongside other realms of public policy) is no longer framed solely as a transport mode, but as a systemic enabler of stable transnational supply chains. This shift is reflected in the evolution of EU transport policy, particularly the Trans-European Transport Network (TEN-T) framework and its funding arm, the Connecting Europe Facility (CEF), which increasingly target cross-border bottlenecks of transnational corridors rather than single national projects.
Within this framework, North-South connectivity has gained renewed importance. While East-West corridors benefited from significant post-2004 EU investment, North-South rail links – especially those crossing the Alps and connecting Central Europe to seaports – have remained structurally weaker. The Baltic-Adriatic (or Adriatic-Baltic) rail corridor exemplifies this. Formally, the Baltic-Adriatic Rail Freight Corridor (RFC5) is a cooperation platform established under EU Regulation 913/2010. RFC5 operates as a European Economic Interest Grouping (EEIG) composed of the infrastructure managers of Poland, the Czech Republic, Slovakia, Austria, Slovenia, and Italy, with its permanent management office based in Venice-Mestre. Despite its designation as a TEN-T Core Network Corridor (CNC) and now as European Transport Corridor (ETC) – linking Baltic and Adriatic ports to Central European industrial regions – the corridor has long suffered from uneven implementation and persistent bottlenecks.
Figure 1. Map of key railways of the RFC5 (Klagenfurt-Graz not shown).
Source: RFC5 (2026c).
A central geographical constraint has been the Eastern Alpine crossing in Austria, specifically the lack of a high-capacity, high-performance rail link between Graz and Klagenfurt. This section effectively acted as a choke point for the entire corridor, delaying returns on investments made elsewhere along the axis. EU corridor documentation has repeatedly identified the Semmering and Koralm projects as ‘missing links’ whose resolution was critical for corridor functionality.
The inauguration of the Graz-Klagenfurt (Koralm) railway in December 2025 marks a structural shift. After decades of planning and construction and an investment of approximately €5.9 billion, the project dramatically reduces travel times across southern Austria and provides a modern, double-track Alpine crossing designed for both passenger and freight traffic. And, while being rightfully reported in national terms – as a major Austrian infrastructure achievement – the Koralm line has far broader implications.
2. The new TEN-T policy context for RFC5
In EU transport policy, rail corridors are increasingly treated as strategic systems rather than standalone infrastructure projects, with appropriate governance. EU experience shows that infrastructure alone is insufficient: coordination and capacity management during works are decisive for achieving cross-border objectives. This systemic logic underpins the EU’s move toward integrated European transport corridors and explains why the Baltic-Adriatic axis must be assessed at corridor level rather than through national project lenses.
The adoption of the revised TEN-T regulation in 2024 – Regulation (EU) 2024/1679 – marked an attempt to address these shortcomings by strengthening the corridor logic of EU transport policy. The reform integrates former CNCs and RFCs into ETCs, overseen by European coordinators and tied more explicitly to staged completion deadlines. For the Baltic-Adriatic axis, this institutional shift matters because it elevates corridor performance – rather than national project delivery – as the primary policy metric.
Figure 2. RFC5 coordination mechanism.
Source: RFC5 (2026a).
Under this framework, member states are no longer assessed solely on whether individual projects are completed, but on whether the corridor as a whole meets requirements related to capacity and interoperability. This creates a stronger incentive to prioritise high-impact bottlenecks and to coordinate works schedules, particularly on sections where temporary capacity restrictions can disrupt international traffic.
Within this policy architecture, RFC5 plays a central role. Now aligned with the ETC framework, RFC5 provides the institutional mechanisms through which infrastructure managers can better coordinate and monitor rail transport. For the Baltic-Adriatic axis, RFC5 is particularly significant because freight traffic is both the corridor’s main growth opportunity and its main stress test. Freight services are more sensitive than passenger traffic to delays and, as a result, the corridor’s ability to attract and retain freight flows depends not only on flagship investments like the Koralm railway, but also on the effectiveness of RFC-level coordination during periods of intensive infrastructure renewal.
3. The new Graz-Klagenfurt (Koralm) railway
For decades, the rail connection between Graz (Styria) and Klagenfurt (Carinthia) represented one of the most significant structural constraints on the Baltic-Adriatic rail axis. Despite Austria’s high-quality rail infrastructure, this east-west link across the Eastern Alps lacked the capacity and speed for competitive long-distance passenger services and modern rail freight. The existing route imposed long travel times as well as limited train lengths.
From a corridor perspective, this constraint was disproportionately influential. The Graz-Klagenfurt section sits at the interface between Central European rail networks and the southern branches of the corridor leading toward Northern Italy, Slovenia, and Adriatic ports. As a result, its limitations effectively capped the performance of the entire North-South axis. EU corridor documents repeatedly classified the Koralm project as a ‘main missing link’, acknowledging that upgrades elsewhere along the corridor could not fully deliver benefits while Alpine crossings remained unresolved.
The Koralm Railway (Koralmbahn) was conceived to address these structural deficiencies through a new, high-performance alignment. The project comprises approximately 130 km of double-track electrified railway, including the 33-kilometre Koralm base tunnel, designed for mixed passenger and freight traffic and significantly reduced gradients compared to the legacy route. With design speeds of up to 250 km/h for passenger services, the line represents a qualitative shift. After nearly three decades of planning and construction, the Koralm railway entered service in conjunction with the Europe-wide timetable change in December 2025.
The resolution of the Graz-Klagenfurt bottleneck benefits the economics of the Baltic-Adriatic axis. For Adriatic ports such as Trieste, Koper and Venice, improved Alpine connectivity expands their effective hinterland deeper into Central Europe, strengthening their competitive position vis-à-vis Northern European ports. For Central European industrial regions, the new link improves access to southern gateways and diversifies routing options in periods of disruption elsewhere on the network.
At the same time, the Koralm breakthrough raises the stakes for complementary investments, the project functions as a keystone investment: it does not complete the corridor, but it changes where policy attention must focus next.
The Graz-Klagenfurt case illustrates a broader lesson for EU corridor policy. High-impact bottlenecks can suppress corridor performance for decades, but their resolution can rapidly transform network dynamics if aligned with effective governance and follow-up investments. The Koralm railway demonstrates the value of long-term, capital-intensive Alpine projects when they are embedded in a corridor and supported by EU-level prioritisation – thus giving the project a much wider scope than intra-national movement of people and goods.
4. Remaining bottlenecks and ongoing works
As evidenced by the ‘Maps of Main TCRs RFC5 2026-2028’ published on January 12, 2026, the Baltic-Adriatic rail corridor is entering a phase characterised by widespread renewal across its length. Between 2026 and 2028, infrastructure managers along the corridor are carrying out an extensive programme of works aimed at improving capacity, reliability, safety and compliance with TEN-T standards. Rather than focusing on a single missing link, current interventions are distributed across multiple sections and nodes, reflecting a shift from network expansion to system optimisation. The geographic pattern is clear:
- Alpine interfaces in Austria;
- port-hinterland links in Poland and Italy; and
- metropolitan nodes in Vienna, Bratislava, Budapest, and Ljubljana.
Austria
In addition to the Koralm railway, the second Austrian megaproject with corridor-wide implications is the Semmering Base Tunnel (to be completed by 2030), which addresses the long-standing capacity and performance limitations of the Semmering crossing on the southern rail artery between the Vienna region and Styria/Carinthia. Without Semmering, the benefits of Koralm risk being partially ‘stranded’ upstream, as freight and passenger flows would still face constrained capacity on the northern Alpine interface. Taken together, the two base-tunnel projects are therefore essential to upgrading the Austrian section from the corridor.
Nevertheless, in Austria works are heavily concentrated into the existing rail network. These interventions focus on track renewals and node adjustments necessary to accommodate higher traffic volumes.
Poland
On the northern section of the corridor, Poland is undertaking extensive works on port access and mainline connections linking Baltic seaports with Upper Silesia and Central Europe. The longest and most impactful interventions are concentrated on the Gdynia-Maksymilianowo axis, where multi-year renewals and staged closures extend into 2028. These projects are complemented by works on the Wrocław-Katowice corridor, reinforcing Katowice’s role as the principal Polish node connecting the Baltic-Adriatic axis with Warsaw, Kraków, and the wider Polish network.
The geographic spread and duration of these works point to a strategic emphasis on modernising freight corridors serving Polish ports, with the aim of supporting higher volumes and longer trains once works are completed.
Central Europe (Vienna-Bratislava-Ostrava cluster)
The densest concentration of works occurs in the central corridor node cluster spanning Vienna, Bratislava, and Ostrava. Here, multiple projects overlap in time and space. These projects reflect the strategic importance of this area as the corridor’s main switching and distribution zone, where North-South flows intersect with East-West traffic.
Figure 3. Main upgrade operations in Czechia, Slovakia and Northeastern Austria in 2026-2027.
Source: RFC5 (2026a, p. 3).
Hungary
In Hungary, the primary focus is the upgrade of the Danube bridge in Budapest between Ferencváros and Kelenföld, including the construction of a third track. This project is intended to strengthen Budapest’s role as a secondary hub on the extended corridor.
Slovenia and Northern Italy
On the southern section, works are concentrated in Slovenia and northeastern Italy, where relatively short corridor segments carry very high traffic volumes toward Adriatic ports. In Slovenia, long-term station renewals (notably in Ljubljana and Jesenice) and line upgrades aim to modernise an intensively used transit network that connects Austria with Italy and the Balkans.
In Italy, major interventions affect the Villach-Udine line and the Cervignano-Trieste/Venice one, as well as port-related infrastructure in Trieste. These projects focus on renewing ageing infrastructure.
5. Linking the RFC5 with Rail Baltica
A defining feature of the Baltic-Adriatic rail corridor is the high concentration of network nodes in the Central European core, particularly in the triangle formed by Katowice, Wien and Budapest as shown in Figure 4 below. This area functions as the corridor’s principal switching zone, where North-South, East-West, and regional flows intersect and where there is high infrastructure density. Within Poland, Katowice emerges as the key southern hub, anchoring the corridor through Upper Silesia and channelling flows northward toward Warsaw, eastward toward Kraków, and onward to Polish seaports on the Baltic Sea.
Figure 4. Main connections, nodes and stations of RFC5.
Source: RFC5 (2026b, p. 57).
While Katowice is central to the corridor’s industrial and freight logic, Warsaw plays a distinct and increasingly strategic role: as the northern hinge between the Baltic-Adriatic axis, Rail Baltica and westbound connections toward Germany, the Polish capital is positioned to add a genuinely continental dimension to the corridor.
Through Warsaw, the Baltic-Adriatic rail system extends beyond a regional North-South spine to become a core component of Europe’s wider rail network, linking the Baltic States, Central Europe, Western Europe, and the Adriatic basin within a single framework. Rail Baltica, the EU’s flagship rail project connecting Poland with Lithuania, Latvia and Estonia and, indirectly, Finland, plays an important role. Additionally, the strategic relevance of connecting the Baltic-Adriatic corridor to Rail Baltica extends beyond trade and movement of people. Both ‘corridors’ are increasingly framed within the EU’s broader agenda of military mobility. Rail Baltica, in particular, has a pronounced security dimension.
Figure 5. Rail Baltica planned railway system.
Source: Rail Baltica (2026).
Rail Baltica was conceived primarily as a Baltic States integration project, aimed at overcoming rail isolation by eliminating the Soviet-era connections and physically anchoring Estonia, Latvia, and Lithuania into the EU’s standard-gauge rail system via Poland. Its core objective was political and structural: ensuring basic connectivity to the EU rail network rather than optimising long-distance continental freight flows. By contrast, the Baltic-Adriatic corridor evolved as a Central European logistics and industrial corridor. As a result, the two initiatives addressed fundamentally different constraints and progressed on different timelines. At the time Rail Baltica entered planning and early construction phases, the southern half of the Baltic-Adriatic corridor lacked the infrastructure needed to function as a high-performance North-South spine. From a system-planning perspective, anchoring Rail Baltica to a corridor whose southern core was not yet functional offered limited strategic value. A further explanation to why RFC5 and Rail Baltica were not ‘linked’ lies in the way EU corridor policy was structured prior to recent reforms. Under earlier TEN-T frameworks, corridors were planned and governed as largely self-contained entities, each with its own coordinator, work plan and funding. Rail Baltica was embedded in the North Sea-Baltic corridor (RFC NS-B), spanning West-East, while the Baltic-Adriatic corridor followed a separate governance track. There was no strong institutional mechanism to incentivise or require cross-corridor integration.
Figure 6. Map of key railways of RFC NS-B.
Source: RFC NS-B (2026).
6. Policy recommendation
Given that Rail Baltica is institutionally embedded in RFC NS-B, rather than in the Baltic-Adriatic RFC, deeper integration between the two axes cannot be achieved through infrastructure alone. Instead, a logical policy step could be the development of a pilot inter-corridor connection between RFC5 and RFC N-SB. For instance, such a pilot could test coordinated capacity allocation, aligned timetable planning, performance indicators and joint management of disruptions at the key interface nodes in Poland, notably around Warsaw and Upper Silesia.
After three decades from when ‘Pan-European corridors’ were conceived to revolutionise mobility in Central-Eastern Europe, this approach would allow the EU to advance corridor integration incrementally, building practical experience while preserving the existing TEN-T and RFC structures. If successful, the pilot could serve as a template for wider inter-corridor integration under the European Transport Corridor framework, moving EU rail policy beyond parallel corridors toward a genuinely interoperable continental network.
7. Resources
Rail Baltica (2026) Official website. Available at: https://www.railbaltica.org/.
RFC5 (2025) Baltic – Adriatic Rail Freight Corridor Implementation Plan.
RFC5 (2026a) Maps of Main TCRs RFC5 2026-2028.
RFC5 (2026b) Baltic – Adriatic Rail Freight Corridor 5 Corridor Information Document.
RFC5 (2026c) Official website. Available at: https://www.rfc5.eu/.
RFC NS-B (2026) Official website. Available at: https://www.rfc-nsb.eu/.
