Cycling cities: Measuring urban mobility mixing in bikeshare networks

To promote low-carbon transit, cities are increasingly adopting public-private partnerships to offer bikeshare services. But some neighborhoods use bikeshare services more than others, raising questions about how equitable these public programs' rollout has been. We examined the entire temporal directed network of individual rides from Boston's Bluebikes program, tracking bikers' starting and ending stations from 2011 to 2021. We hypothesized that ridership levels are lower between neighborhoods of color than white neighborhoods, and greater between wealthier neighborhoods than working class neighborhoods. We designed edgewise block permutation tests to measure the statistical significance of mobility between similar neighborhoods, while controlling through permutation blocks for population density, program geography, distance, and the distribution of race, wealth, education, and age. The network is deeply stratified by race and income, with more homophilous movement between neighborhoods from similar income brackets than expected due to chance. Race is linked to considerable homophily, but with low statistical significance. However, homophilous mobility by income and race has dropped sharply from 2011 to 2021, suggesting that Bluebikes is gradually reaching a broader range of neighborhoods. This presents signs of hope for a transition to equitable transit options in other major US cities as well.