Brenner Base Tunnel. FS Engineering is engaged in the Construction Supervision and PMC (Project Management Consultancy) of two strategic lots: the Periadriatic Exploratory Tunnel and the Isarco River Underpass. The former involves a twin-bore tunnel connected by cross-passages that can be utilised as escape routes; the latter comprises approximately 4 km of running tunnels and 1.6 km of connecting links to Fortezza station, constructed using specialist techniques, including ground freezing during excavation underneath the River Isarco. The structure will connect Italy and Austria, becoming the longest rail tunnel in the world, and will reduce journey times between Fortezza and Innsbruck to the benefit of sustainable mobility along the European North–South axis.

Giovi Pass Base Tunnel (Terzo Valico dei Giovi). FS Engineering is engaged in the High-Level Construction Supervision of the Giovi Base Tunnel, a new rail corridor that integrates and enhances the link system between the Ligurian port basin, the Po Valley and Northern Europe, increasing transport capacity, particularly for freight traffic. The structure extends for 39 km in tunnels and is linked to the existing line via four interconnections—totalling approximately 14 km—located at Voltri, Genova Parco Campasso, Novi Ligure and Tortona. The underground sections mainly consist of twin single-track tunnels connected by cross-passages, designed to guarantee safe evacuation in the event of an emergency.

Turin-Lyon Base Tunnel. The main structure of the Turin–Lyon cross-border section is the 57 km twin-bore single-track base tunnel with cross-passages designed to guarantee safe evacuation for passengers in the event of an emergency, in accordance with the highest safety standards. FS Engineering provides engineering services for the international section of the project and is engaged in preparing the constrution drawings for one of the three Base Tunnel lots on the French side, and preparing the tender documentation and construction supervision of the work completion lot on the Italian side.

Bologna Railway Through-Line (Passante). FS Engineering managed the design process through to the construction drawing phase and the construction supervision of the structure—a strategic infrastructure on the Turin–Salerno HS/HC line—which consists of approximately 10 km of underground sections, including the twin-bore South Approach Tunnel to the high-speed station, roughly 6 km long. Due to the complex geotechnical context, TBMs were adopted – specifically an Earth Pressure Balance (EPB) tunnel boring machine – while innovative active ground consolidation techniques (compensation grouting) were applied for settlement control, marking the first time this methodology has been utilised for tunnelling works in Italy.

Himalaya Tunnel. FS Engineering is engaged in the detailed design and Project Management Consultancy (PMC) services for the construction of 17 tunnels (involving approximately 105 km of tunnelling work) for the new Rishikesh-Karnaprayag rail link in the State of Uttarakhand, India. The project plays a strategic role in improving transport infrastructure in the Himalayan region, contributing to the development of regional mobility and connectivity within a highly complex topographical and geotechnical context.

Bologna-Firenze HS line tunnels. FS Engineering supervised the design and construction of the works for the Bologna–Florence HS/HC line, a 78.5 km long infrastructure, 73.3 km of which runs in tunnels, serving as a "base tunnel" for crossing the Apennines within a complex geological context. The project comprises 9 twin-track bored tunnels—4 of which exceed 10 km in length—excavated using cutting-edge techniques enabling industrialized tunnelling advance rates, including the application of conventional excavation methods. The highest safety standards are guaranteed by intermediate access adits every 4 km and by the Vaglia service and emergency tunnel.

Eurasia Tunnel. The Joint Venture between FS Engineering and Altinok Consulting Engineering Inc. was awarded the tender issued by the Ministry of Transport of Turkey (AYGM) for the delivery of the construction supervision services. The relevant contract covered the development of the detailed design, construction, structural acceptance testing and commissioning of the Eurasia Tunnel— effectively an intercontinental highway link connecting the Kazlıçeşme district on the European side of Istanbul with Göztepe on the Asian side of the city, running underneath the Bosphorus strait and constituting a strategic infrastructure for enhanced urban and metropolitan mobility. FOCUS ON

Cassia-Monte Mario Tunnel. FS Engineering executed the construction drawings and construction supervision activities for the structural strengthening works on the tunnel located within the Rome Hub, comprising the demolition and reconstruction of the invert arch. The works were delivered by successfully adopting a cutting-edge tunnelling technique – artificial ground freezing (AGF) – providing for the introduction of freeze probes in the invert arch and sidewalls of the tunnel, through which a refrigerant fluid was circulated to freeze the ground to a temperature of -10 °C.

Trasandino Tunnel. FS Engineering, in a joint venture with other international engineering companies, is engaged in the feasibility study and detailed design of this rail project in Peru, structured across three primary tunnels: San Bartolomé (5 km), San Miguel de Viso (15 km) and Trasandino (25 km). This is part of the broader development project for the rail link between the city of Lima and the Huancayo region, comprising transport planning studies, economic and financial analyses, and the definition of technological solutions and architectural components for the infrastructure, covering a total length of approximately 45 km.