Croatia is advancing one of its most significant railway infrastructure programmes: the Zagreb–Rijeka Lowland Railway.
The project is intended to improve rail connectivity between Zagreb, the Croatian capital, and Rijeka, the country's principal Adriatic port, while strengthening freight connections between the Adriatic coast and Central Europe.
According to HŽ Infrastruktura, Croatia's railway infrastructure manager, the key new railway sections between Karlovac and Tijani will extend for approximately 111 km and include a substantial concentration of tunnels, viaducts and other major civil engineering structures.
The programme is also notable for Croatia's planned introduction of an IPP / Alliance delivery model for the future design and construction of these sections.
A New Railway Corridor between Zagreb and Rijeka
The planned lowland railway forms part of the broader modernisation of the Zagreb–Rijeka rail corridor.
Two major new sections are currently under development:
- Karlovac–Oštarije/Skradnik: approximately 39.1 km
- Skradnik–Krasica–Tijani: approximately 72.2 km
Together, these sections represent approximately 111 km of new railway infrastructure.
Once the new alignment is completed, the railway distance between Zagreb and Rijeka is expected to be approximately 175 km, around 56 km shorter than the existing route.
The planned railway will be a double-track electrified line for mixed passenger and freight traffic.
Current design parameters include:
- Passenger train speeds of up to 160 km/h
- Freight train speeds of up to 120 km/h
- Accommodation of freight trains up to 750 m long
- Five new railway stations and one passenger stop
The new alignment will cross challenging mountainous terrain between Karlovac and the Rijeka region, making major civil engineering structures a defining feature of the project.
57 km of Tunnels and Major Structures
The scale of the underground works is one of the most significant engineering characteristics of the planned railway.
Current project information indicates that the Karlovac–Tijani alignment will include:
- 14 tunnels with a combined length of approximately 57 km
- 17 viaducts with a combined length of approximately 10 km
Among the largest structures are the tunnels crossing the Velika Kapela and Mala Kapela mountain massifs.
Current planning information identifies two major Kapela tunnels:
- Kapela 1: approximately 10 km
- Kapela 2: approximately 15 km
These structures will form part of a railway alignment passing through complex mountainous terrain and will represent some of the most substantial underground works within the Croatian railway network.
The project therefore involves a broad range of engineering disciplines, including tunnelling, geotechnical engineering, geological investigation, structural engineering, railway systems, construction monitoring, waterproofing, ground treatment, construction equipment and project logistics.
Detailed excavation methods, construction systems, equipment requirements and individual work packages will be defined as the design and procurement process progresses.
Connecting the Port of Rijeka with Central Europe
The importance of the Zagreb–Rijeka railway extends beyond Croatia's domestic transport network.
Rijeka is one of the principal Adriatic ports serving Central Europe, while Zagreb is an important regional transport node.
The European Commission identifies the new railway line between Rijeka and Zagreb as a key project within the Baltic Sea–Adriatic Sea European Transport Corridor.
The wider corridor connects ports on the Baltic and Adriatic seas with major economic centres including Vienna, Bratislava, Budapest, Ljubljana and Zagreb.
The Rijeka–Zagreb connection is also associated with the Mediterranean transport corridor, which provides another major east-west transport axis linking the Adriatic region with Central Europe.
Improved railway capacity is particularly relevant to the development of freight transport from the Port of Rijeka.
HŽ Infrastruktura has highlighted the relationship between the new railway and the recently developed Rijeka Gateway container terminal, with improved rail connectivity expected to support freight movements from Rijeka towards Hungary and other Central European markets.
The project is therefore part of a wider combination of railway, port and intermodal infrastructure development.
Current Project Status
The Karlovac–Skradnik and Skradnik–Krasica–Tijani sections are currently progressing through the preliminary design and permitting stages.
Environmental approvals for both sections were obtained in 2025.
Design documentation and location permit procedures have subsequently continued, with HŽ Infrastruktura indicating that applications for location permits are expected to be submitted by the end of 2026.
The estimated construction value of the overall Zagreb–Rijeka Lowland Railway has been indicated at approximately EUR 3 billion.
However, HŽ Infrastruktura has stated that the final construction value, financing arrangements and implementation schedule will be determined following completion of the preliminary design and an assessment of market prices at the time the construction procurement is launched.
The project should therefore currently be regarded as a major railway programme progressing through design, permitting and procurement preparation rather than a project already under main construction tender.
Preparing an Alliance Delivery Model
Another important aspect of the programme is the proposed procurement and contractual approach.
In February 2026, HŽ Infrastruktura launched a public procurement procedure for technical assistance related to the preparation and implementation of an IPP / Alliance contract for the design and construction of the Karlovac–Skradnik and Skradnik–Krasica–Tijani sections.
IPP refers to an integrated project approach.
Alliance contracting is generally used for large and technically complex infrastructure programmes where the client and key project participants operate within a more integrated contractual framework.
The model places greater emphasis on collaborative project management, shared objectives and coordinated management of project risks compared with more conventional contractual structures.
HŽ Infrastruktura has stated that the Zagreb–Rijeka Lowland Railway would represent the first application of this type of Alliance model to a major infrastructure project in Croatia.
In July 2026, HŽ Infrastruktura announced that two offers had been received for the technical advisory assignment.
The procurement has an estimated value of EUR 1.5 million, and the advisory contract is planned to run for 60 months.
The scope includes development of the procurement strategy for future Alliance design-and-construction contracts, preparation of contractual documentation and advisory support during implementation.
This procurement relates to the preparation of the future delivery framework and should not be confused with the main construction procurement itself.
A Strategic European Infrastructure Programme
The Zagreb–Rijeka Lowland Railway combines several important infrastructure themes:
- Major railway corridor modernisation
- Extensive tunnelling through mountainous terrain
- Long-span viaduct and structural works
- Port and railway integration
- International freight connectivity
- TEN-T transport corridor development
- Introduction of a new collaborative project delivery model in Croatia
The project is therefore relevant not only from a Croatian railway perspective, but also within the broader development of transport infrastructure connecting the Adriatic region with Central Europe.
Several important project milestones remain ahead, including completion of preliminary design activities, location permitting, development of the Alliance procurement framework and subsequent preparation of the main design-and-construction procurement.
The technical scope, procurement structure, financing arrangements and construction programme may continue to evolve as these activities progress.
Following Global Infrastructure Development
EngiFind follows major infrastructure programmes and engineering market developments across Europe, Central Asia, Southeast Asia and other international markets.
Our coverage includes railways and transit systems, tunnelling and underground works, bridges and structures, geotechnical engineering, construction equipment, engineering materials, monitoring and surveying, digital engineering, design, consulting and specialised professional services.
By combining infrastructure information with an international civil engineering supply-chain platform, EngiFind aims to make engineering capabilities, technologies, products and professional services easier to discover across markets.
EngiFind — Connecting Engineering Capabilities with Global Infrastructure
Sources
This article has been prepared with reference to publicly available project information from:
- HŽ Infrastruktura, Croatia
- European Commission, Directorate-General for Mobility and Transport
- Public information relating to the Zagreb–Rijeka Lowland Railway and the European TEN-T transport corridors
Project scope, technical parameters, procurement arrangements, costs and schedules may be updated as planning, design and procurement activities progress.