The study, published in Frontiers in Sustainable Cities, tackles a question that has long frustrated transport planners and climate policymakers: do massive railway investments actually pull people out of their cars? The transport sector accounts for roughly 30 percent of Europe’s greenhouse gas emissions and nearly 40 percent in Switzerland, with private motorized transport the dominant contributor. Governments across the continent have poured resources into rail infrastructure on the assumption that faster, more frequent, and better-integrated services will induce a modal shift toward sustainable mobility. Yet rigorous empirical evidence on whether such interventions genuinely change individual travel behavior has remained scattered and often inconclusive.

The Ceneri Base Tunnel offered the researchers an unusually clean natural experiment. Opened in December 2020, the roughly 15-kilometer tunnel bypasses the mountainous Ceneri range and, together with the Gotthard Base Tunnel that entered service in 2016, forms part of Switzerland’s New Rail Link through the Alps. Within Ticino, the tunnel halved travel times along the region’s north-south axis: the journey between Lugano and Bellinzona now takes about 15 minutes, while Lugano to Locarno takes roughly 30 minutes. Alongside the physical infrastructure, the canton introduced the TP21 public transport offer in 2021, a comprehensive timetable overhaul that added more frequent trains, new early-morning and late-night services, and tighter network integration across the region.

To isolate the tunnel’s causal effect, the research team turned to the INDMOB travel survey, administered between September and December 2023 to a random sample of 50,000 Ticino residents drawn from the canton’s population register. A total of 24,577 individuals completed at least part of the questionnaire, which included a retrospective module asking respondents to recall their travel behavior in fall 2019, before the tunnel opened. Because no pre-tunnel travel data existed, this recalled information was essential for constructing a before-and-after comparison. After restricting the sample to commuters who provided both home and work or study locations, and excluding those using active modes such as walking or cycling, the final analytical sample comprised 12,683 individuals.

The methodological centerpiece of the study is a Difference-in-Differences design, an econometric approach widely regarded as a gold standard for establishing causality from observational data. The technique traces its origins to John Snow’s famous 1854 investigation of a cholera outbreak in London and underpinned research recognized with the 2021 Nobel Prize in Economic Sciences. The logic is straightforward: compare how the outcome of interest changed over time for a group exposed to an intervention against how it changed for a comparable group that was not exposed. Here, the treatment group consisted of 1,734 commuters whose home-to-work or home-to-school journeys crossed the Ceneri axis, traveling between northern Ticino, including Bellinzona, Locarno, and the Tre Valli area, and southern Ticino, including Lugano, Mendrisio, Vedeggio, and Malcantone. The control group of 10,949 individuals lived and worked or studied within the same zone and therefore benefited from the broader regional service improvements but not directly from the tunnel’s shortened travel times.

The results were striking in their consistency. In the base model without control variables, the tunnel opening was associated with a 6.7 percentage point increase in the probability of choosing public transport as the main commuting mode, relative to the control group, with very high statistical significance. When the researchers added covariates capturing socio-demographics, mobility equipment, and the local level of public transport service, the estimated effect settled at 4.2 percentage points, still statistically significant. The inclusion of these covariates raised the model’s explanatory power from an R-squared of about 0.02 to 0.43, indicating that individual and contextual characteristics account for a substantial share of the variation in mode choice. The persistence of a significant positive effect across specifications suggests the tunnel genuinely shifted commuting behavior rather than merely reflecting pre-existing differences between groups.

Who responded to the new infrastructure? The analysis revealed a familiar pattern of heterogeneous effects. Women showed a 5.7 percentage point higher probability of choosing public transport over the car, while older commuters showed a 9.5 percentage point lower probability, conditional on other factors. The single strongest predictor was possession of a public transport subscription, which was associated with a 48 percentage point higher likelihood of using transit, echoing the sociological literature on motility, which holds that successful modal shift depends on individuals’ access, competences, and appropriation of mobility options. Living in areas with higher public transport service levels, such as the urban centers of Lugano, Bellinzona, and Locarno, added 2.4 percentage points to the probability of choosing transit. These findings align with decades of research showing that younger, female, and transit-engaged populations respond most readily to supply-side improvements, while car-dependent, suburban, and older groups are often left behind.

The context makes these numbers all the more remarkable. Ticino has the highest vehicle ownership rate of any Swiss canton, at 635 cars per 1,000 people, well above the national average of 535 and far exceeding Zurich, Geneva, and Basel. Against this backdrop of entrenched car dependence, a 13 percent relative increase in transit use among exposed commuters suggests that even in car-oriented regions, well-designed rail infrastructure can meaningfully reconfigure travel habits. The findings also complement earlier descriptive evidence from the canton, which documented a 3.2 percent increase in public transport use and a 5 percent decline in car use after the tunnel opened, with even larger changes along the Bellinzona-Lugano corridor.

The authors are careful about the limits of their design. The retrospective survey format introduces potential recall bias, and the study period overlaps with the COVID-19 pandemic, which disrupted travel patterns worldwide and may have affected the treatment and control groups differently, for instance through unequal adoption of remote working. The researchers also note that their sample excludes leisure travelers, cross-border commuters from Italy, and long-distance travelers passing through the tunnel, so the findings speak most directly to daily work and study commuting within the canton. They call on transport authorities to embed evaluation designs into future policy measures from the outset, which would reduce these biases and strengthen causal inference.

For policymakers weighing whether billion-franc tunnel projects can deliver on their climate promises, the study offers a qualified but encouraging answer. Rail infrastructure investments can indeed produce measurable, statistically robust shifts in mode choice, even in highly car-dependent regions, but their effects are concentrated among groups already somewhat engaged with public transport and shaped by the surrounding service environment. The authors argue that major interventions should be embedded within broader strategies, including fare subsidies, behavioral nudges, and continued improvements in accessibility, to amplify and extend their reach. In regions like Ticino, where public transport use remains below the national average, the Ceneri Base Tunnel may serve as a flagship demonstration that infrastructure, when paired with service reform, can begin to bend the curve of car dependence toward a more sustainable mobility future.

Subject of Research: Causal evaluation of the Ceneri Base Tunnel's impact on commuting mode choice in Ticino, Switzerland

Article Title: Railway infrastructure breakthrough and mode choice: evidence from the Ceneri Base Tunnel in Switzerland

Article References: Conte, L., Grandvillemin, J., Rames, C., & Koenga, O. S. (2026). Railway infrastructure breakthrough and mode choice: evidence from the Ceneri Base Tunnel in Switzerland. Frontiers in Sustainable Cities, 8, Article 1938839. https://doi.org/10.3389/frsc.2026.1938839

Image Credits: AI Generated

DOI: 10.3389/frsc.2026.1938839

Keywords: Ceneri Base Tunnel, public transport, modal shift, difference-in-differences, Ticino, railway infrastructure, commuting behavior, sustainable mobility, Switzerland, travel survey, transport policy, car dependence