Why Europe’s mega-tunnels thrive while HS2 founders

The recent ceremonial breakthrough of the Brenner Base Tunnel (BBT), connecting Italy and Austria 1,400 metres beneath the Alps, was more than a construction milestone - it was a powerful affirmation of Europe’s capacity for sustained, coordinated infrastructure delivery. Attended by Italian Premier Giorgia Meloni and Austrian Chancellor Christian Stocker, this moment signalled the nearing completion of the world’s longest underground rail tunnel and the integration of a critical link in the Scandinavian-Mediterranean (Scan-Med) TEN-T Corridor, writes John Ridgeway.

This achievement stands in stark contrast to the infrastructure narrative playing out across the English Channel. As the BBT and its counterpart, the Turin-Lyon (TAV) high-speed link, forge ahead toward their 2032 operational deadlines - despite costs soaring into the tens of billions of Euros - it prompts a critical question for infrastructure planners in the UK. So how did the United Kingdom, a nation with a proud engineering history, so fundamentally derail High Speed 2 (HS2)?

To understand the success of the European model, one must first appreciate the scale, stability and enduring financial commitment driving these cross-border leviathans and compare that to the political volatility that plagued the UK's rail project.

The European mega-projects have been defined by their clear strategic mandate - to shift millions of tonnes of freight off roads to meet aggressive EU decarbonization goals and enhance pan-European connectivity for both passengers and commerce. The costs are immense, but the funding mechanisms and delivery structure has been robust.

The Brenner Base Tunnel (BBT)

The BBT, which will reduce travel time between Verona and Munich by over half to approximately two and a half hours, is the ultimate example of geopolitical cooperation overcoming geological challenge. Planning began decades ago, with construction commencing in 2007/2008. After nearly 25 years of continuous effort, the tunnel is scheduled for commissioning in 2032.

The original estimates were high, but the latest forecast for the total project cost is around €10.5 billion (at 2023 prices). The project is co-funded by Austria and Italy, but crucially, the European Union provided substantial co-financing (up to 40-50%) through the Connecting Europe Facility (CEF). This guaranteed, cross-border funding pipeline insulates the project from the annual budget fluctuations of any single member state.

The Turin-Lyon High-Speed Rail (TAV)

The TAV project is equally vital, featuring the Mont d’Ambin Base Tunnel, another massive underground bore connecting the rail networks of Italy and France. This link is essential for integrating the Mediterranean Corridor and slashing the Milan-Paris journey time by 30% to just 4.5 hours.

The total cost for the entire line is estimated between €25 billion and €27 billion, with the core international section costing around €11 billion. Similar to the BBT, the TAV relies heavily on the EU commitment, covering up to 40-55% of the international section’s costs, locking Italy and France into a unified delivery strategy.

HS2 - the Anatomy of a fiasco

In contrast - the narrative surrounding the UK's High Speed 2 (HS2) programme is marked - not by a stable upward curve of cost inflation (as seen with the BBT), but by constant political instability, dramatic changes in scope and catastrophic cost escalation. It represents a casebook example of governance failure in complex infrastructure delivery.

When the full Y-shaped network - connecting London, Birmingham, Manchester and Leeds -was first envisioned over a decade ago, the estimated cost was approximately £32.7 billion. This initial optimism quickly dissolved, with the latest estimates for the severely curtailed Phase 1 (London to Birmingham, largely excluding the contentious Euston terminus) now range from £54 billion to £66 billion (2019 prices), with overall programme costs trending toward £80 billion+ when adjusted for inflation and full contingency.

In a stunning reversal, the eastern leg (to Leeds) was scrapped, followed by the complete cancellation of the northern leg (from Birmingham to Manchester) in October 2023. The final delivered product is now a fraction of the original vision, yet the cost has tripled.

The full network was originally targeted for completion by 2033. The current, shortened Phase 1 is still projected to open between 2029 and 2033, demonstrating that the decades-long European projects have maintained a more reliable delivery forecast despite being geometrically and geologically more challenging.

The irony is that European nations are driving monumental tunnels through the heart of the Alps to connect distant economic zones, while the UK failed to build a domestic network link across its own relatively benign geography.

How did the UK get It wrong?

The divergent fates of the TEN-T projects and HS2 can be traced directly to fundamental differences in governance, political commitment and project sequencing. The core flaw of HS2 was its failure to secure enduring, cross-party political consensus. Every five-year electoral cycle brought fresh reviews, new ministers and scope creep - or, worse, scope cancellation.

The constant threat of cancellation or modification (such as the costly political decision to lengthen tunnels through the Chilterns) led to massive sunk costs, stop-start procurement and a demoralised supply chain. As one National Audit Office report put it, HS2 became a "casebook example of how not to run a major project."

Early estimates were also wildly optimistic, providing insufficient contingency for poor ground conditions, detailed design changes and inevitable inflation. The UK government failed to apply lessons learned from previous mega-projects like Crossrail.

Furthermore, while the BBT and TAV possess a dual passenger/freight mandate tied directly to a binding EU environmental directive, HS2’s purpose frequently shifted. Was it purely about speed? Capacity? Regional rebalancing? The lack of a clear, enduring priority made it vulnerable to political attack.

In contrast, the EU's ability to mandate and co-finance cross-border freight infrastructure provides a critical anchor that domestic projects often lack. This focus shifts the project’s benefit calculation from merely passenger time savings (an often-contested metric) to undeniable economic and environmental necessity.

Sequencing and sunk costs

The cancellation of the northern legs after billions had already been spent on land acquisition and early works also created billions in wasted expenditure. The decision to prioritise the southern leg first meant that when the political will faltered, the area’s most reliant on the "rebalancing" benefits (the North) were abandoned, leaving the project highly unbalanced in its economic return.

In stark contrast, the European tunnels, by focusing on a singular, massive cross-border bore, defined the single hardest and most essential part of the project early on, locking in commitment through sheer scale and multinational dependency.

The breakthrough beneath the Brenner Pass is a testament to the power of sustained, cooperative, and strategically funded infrastructure development. The European model—driven by TEN-T corridors, underwritten by shared EU capital, and focused on defined economic and environmental goals, has delivered unprecedented connectivity despite tackling the world's most challenging geology.

The HS2 debacle, however, serves as a harsh lesson. In a major project, political volatility is the highest-cost risk. When government oversight is weak and commitment is fragile, the inevitable complexity of building a high-speed line becomes unmanageable, leading to spiralling costs and a drastically diminished product. The BBT confirms that projects are too big to be tackled, only if they are shackled by political indecision.