Expanding high-capacity rail infrastructure in Austria has always been one of the most demanding engineering challenges in Europe. The Alps have a major influence on routing and design, making large structures like tunnels and bridges essential to a modern rail network. The Koralm Railway is an excellent example of this development. As one of the country’s most significant rail engineering projects, it is the first rail connection between Graz and Klagenfurt, the two largest metropolitan areas in southern Austria. The project represented an infrastructure milestone, with far-reaching significance at both the national and international level.

The central element of the new line is the Koralm Tunnel, which, together with the rest of the newly constructed line, forms a high-capacity transport artery crossing the Alps. The new railway not only closes an infrastructure gap that had existed for decades, but also is a major element in strengthening the Trans-European Transport Network (TEN-T). As a result, the Koralm Railway is not just a national project, but also a strategic link in the European rail network.

An overview of the Koralm Railway

The Koralm Railway covers a total distance of around 130 kilometres, with around 50 kilometres of that running through tunnels. The heart of the line is the 33-kilometre Koralm Tunnel between the Styria and Carinthia regions. With a maximum uphill gradient of 5.4‰, it sets new benchmarks in transalpine rail engineering. The Koralm Tunnel is the sixth-longest railway tunnel in the world. It consists of two parallel tunnels running at a depth of up to 1.2 kilometres under the Koralm mountain range. The line is designed for trains travelling at up to 250 km/h, underlining the ambition of creating a high-capacity line that is ready for the future.

A major part of the project is the consistent integration of modern signalling and safety technology. The European Train Control System (ETCS) is a uniform standard that is compatible across borders. The electrification and construction of the overhead contact line system, particularly in the tunnels, used a highly specialized catenary installation machine with hybrid drive: the HTW 100 E³ from Plasser & Theurer. Its quiet, low-emission, battery-powered operating mode offers major advantages, especially when working in large tunnels.

One of the central principles of railway engineering is that large projects need to be thought of in long cycles. The Koralm Railway is the perfect example of this. The planning and construction work took several decades, while the infrastructure itself will last for generations. This meant very demanding requirements in terms of quality, precision, and technological foresight.

A project with national and international relevance

With its location at the heart of Europe, Austria plays a key role in international rail transport. A total of four TEN-T corridors run through the country. The Koralm Railway represents a long-term reinforcement of the Baltic-Adriatic corridor in particular, connecting the industrial hubs of northern and central Europe with the Adriatic ports in the south. It will result in faster, simpler, and higher-capacity connections for both freight and passengers across national borders, helping to connect Europe even further and shift more transport to rail.

The gains in efficiency are especially striking in freight transport. The new flat section enables much greater loads to be transported, with up to 250 tonnes of additional cargo per train. According to projections, shorter transit times and optimized cycles will reduce the amount of necessary rail journeys by up to 300,000 kilometres per year. At the same time, lower uphill gradients will reduce energy consumption, making a measurable contribution to greater sustainability in rail freight transport.

Economic and social benefits

As well as its significance to the transport network, the Koralm Railway will deliver major economic and social benefits. It will create a continuous economic zone with around 1.8 million inhabitants and 770,000 workers, making it the second-largest metropolitan area in Austria. The new transport options will strengthen labour markets, encourage investment, and make the entire region more attractive.

The Koralm Railway is an excellent example of rail policy that thinks long term and delivers benefits across Europe. It connects regions, improves life for people and businesses alike, and represents a major step forward towards sustainable, high-capacity rail transport.

Foto: © ÖBB/Harald Eisenberger