Only a small part of the 10,000 cities in the world can be considered as cities within a 15-minute walking distance, according to the results of a research published in the journal Nature Cities. The researchers used open data to calculate the average distance people have to walk or cycle to access essential services—including supermarkets, schools, hospitals, and parks—and calculated the proportion of residents who have everything they need close at hand. The researchers selected 54 cities for a detailed study and found that mid-sized European cities—namely Zurich, Milan, Copenhagen, and Dublin—were the most accessible, with more than 95% of residents reaching key service locations within 15 minutes. At the bottom of this ranking are the major North American cities—namely San Antonio, Dallas, Atlanta, and Detroit—with high dependence on cars. Smaller cities have higher rates, but researchers have found that in some large metropolises, particularly Berlin and Paris, more than 90% of residents can reach the service they want within a 15-minute walk. The study's authors developed an algorithm to determine how much these cities would need to change to become more accessible. As a result, they found that Atlanta would need to relocate 80% of its facilities to achieve an even distribution per resident, while Paris would only need to relocate 10% of its facilities. But researchers warn that making a city more accessible is not enough to wean residents off private cars. The Netherlands boasts one of the best cycling infrastructures in Europe, while having more cars per capita than rural countries like Ireland and Hungary. In Zurich, where 71% of residents voted in favor of a proposal to build 50 km of cycling infrastructure by 2020, local residents have long complained about the lack of bike lanes and the dangers to cyclists.