Metro networks linked to major drops in car traffic, study finds

A new study shows a clear link between the presence of a subway system and significantly lower levels of car use in cities. According to the research:

• In cities with a subway, 37% of commuting trips are made by car.
• In cities with trams but no subway, that figure is 50%.
• In cities with neither trams nor subways, it climbs to 54%.

Vienna is a notable example. As Austria’s only city with a subway, it records the lowest car share nationwide: on the routes analysed, around 25% of commutes are made by car. This outcome follows decades of investment, beginning with the politically contested decision to build a subway in 1968, through protracted construction phases, and culminating in the first line opening in 1978.

The study by researcher Rafael Prieto-Curiel examined 47 cities with subways, 46 with trams but no subways, and 285 metropolitan areas without either mode. The findings point to a pronounced “subway effect”, where subways make it significantly easier for residents to leave their car at home. For large cities with more than one million inhabitants, the difference is especially striking. A big city with a subway sees around 370 million car trips per year, compared with almost 700 million in a similarly sized city served only by trams.

While subways offer high capacity and rapid transit, the study acknowledges their substantial construction costs. There are also notable exceptions, such as Rome and Toulouse that have subway systems yet still register more than 60% of trips by car. However, for large metropolitan areas aiming to reduce car dependency and congestion, investing in a subway network remains one of the most effective long-term strategies.

Author: Anna Vasilenka

Views and opinions expressed are those of the author(s) and do not reflect those of the European Commission.