Copenhagen is known as a cyclist paradise, a place where the bike is treated equally, if not preferentially, to the car. There are long-running cultural reasons for this–the Danes are into bikes, period–but also more structural factors as well. One of those is how the city justifies its cycling investments relative to other modes of transport.

In a new paper, Stefan Gössling from Lund University and Andy Choi from the University of Queensland take a look at Copenhagen’s approach and argue that it explains how the city has built out so much dedicated cycling infrastructure, including miles of uninterrupted and separated bike lanes, and even dedicated bike tunnels, bridges, and traffic lights.

Flickr user Boegh

When the city decides on a cycling project, it compares the cost to that of a road for cars, and it includes not only the upfront amount, but also things like the cost of road accidents to society, the impact of car pollution on health, and the cost of carbon emitted to the atmosphere. After including these factors, it comes to a rather startling calculation. One kilometer driven by car costs society about 17 cents (15 euro cents), whereas society gains 18 cents (16 euro cents) for each kilometer cycled, the paper finds. That’s because of factors like the health benefits of cycling and the avoided ill-effects of cars.

“What we learn here is that society profits from people cycling. It’s better for society if people cycle from many different angles, from resource intensity to people’s health,” says Gössling, in an interview.

As well as costs and benefits to society, there are also personal costs and benefits, including the time lost or gained from taking a bike or car, and the impact of noise and pollution on quality of life. When these are included in the analysis, cars cost 57 cents per kilometer while bikes come in at 9 cents per kilometer, the paper finds.

Gössling says Copenhagen’s costing approach helps illuminate cycling full advantages, as well as the value of good infrastructure in encouraging cycling among different social groups.

“If we want people to cycle, then we have to change our approach towards urban infrastructure. Cyclists will only cycle [in large numbers] when they feel physically safe and when it’s fast, which means they need to be physically separated from cars,” he says.