The Effect of the Gotthard Base Tunnel on Road Traffic: A Synthetic Control Approach

TL;DR

This study evaluates the impact of the Gotthard Base Tunnel on road traffic, finding only a modest short-term decline in car usage despite significant increases in rail demand, using synthetic control methods.

Contribution

It applies synthetic control and difference-in-differences methods to quantify the tunnel's effect on road traffic, a novel causal analysis in this context.

Findings

Modest decline in car traffic after tunnel opening

Strong increase in rail demand due to travel time savings

Induced demand for rail travel observed in short term

Abstract

The opening of the Gotthard Base Tunnel in 2017, the longest railway tunnel in the world, marked a milestone in Swiss transport policy. The tunnel, a part of the New Rail Link through the Alps, serves as a key instrument of the so-called "modal shift policy," which aims to transfer transalpine freight traffic from road to rail. The reduction in travel time by train between northern and southern Switzerland raised expectations that a substantial share of tourist-oriented passenger traffic would also shift from car to rail. In this paper, we conduct a causal analysis of the impact of the Gotthard Base Tunnel's opening at the end of 2016 on the number of cars using the parallel Gotthard motorway section in the subsequent years. To this end, we apply the synthetic control and the synthetic difference-in-differences methods to construct a synthetic Gotthard motorway section based on a weighted combination of other alpine road crossings (a so-called donor pool) that did not experience the construction of a competing rail infrastructure. Our results reveal only a modest but statistically significant decline in the number of cars between the actual and the synthetic Gotthard motorway in the short run. Given the consistently strong and increasing demand for the new rail connection through the Gotthard Base Tunnel, we infer a substantial induced short-run demand effect resulting from the rail travel time savings.