Dense cities where public transit was already popular generally saw the largest increases. In cities with lower density, more cars per capita and higher traffic speeds, the increase in cycling was more modest. Paris, which implemented its bike lane program early and had the largest pop-up bike lane program of any of the cities in the study, had one of the largest increases in riders.
“It almost seems like a natural law that the more infrastructure you have, the more cycling you will have,” said Sebastian Kraus, the study’s lead author.
But in public transit research, the effect of adding bike lanes is a matter of debate.
“It’s like a chicken and egg problem,” said Mr. Kraus, a doctoral candidate in economics at the Mercator Research Institute on Global Commons and Climate Change in Berlin. “There can be this reverse causality that, actually, if you have a lot of cyclists, they will demand better infrastructure, and it’s not really the infrastructure that creates more cycling.”
The researchers collected data, including the lengths of new bike lanes and data from bike counters, from 106 cities across Europe. The bike counters allowed the researchers to measure the number of cyclists citywide, not just on the new bike paths. They analyzed the number of cyclists from March through July and found that in cities that had added bike lanes, cycling increased 11 percent to 48 percent more than in cities that had not added bike lanes.
The researchers found that the increase held when controlling for weather and changes in public transit supply and demand.