by Nolan Phillips
The Boston Area Research Initiative (BARI) is excited to announce a new data set that is publicly available as part of our annual geographical infrastructure data release! The new data provides measurements of distances and travel durations (using several modes of travel) between Boston’s census block groups and tracts. The dataset and documentation can be downloaded from the Boston Data Library.
The first part of the new data set contains population-weighted centroids of Boston’s census block groups and tracts. These improve upon the census estimates by using the populations of census blocks nested within each type of areal unit. The population-weighted centroids minimize the error of how far residents must travel and how long it will take them to travel between block groups and tracts.The second part of the new data set uses the population-weighted centroids to quantify several distance and travel duration metrics between block groups and tracts, respectively. These include:
Practitioners, policy makers, advocacy groups, researchers or the general public can use these files to examine inequities in travel durations relative to their Euclidean distances. Bostonians know that it can take a long time to travel to particular parts of Boston (just try to get to Logan Airport during rush hour!), but those durations are unequal burdens to residents of Boston. Residents of Brighton, Alston or East Boston have longer travel durations not simply because they are on the outskirts of the city, but due to a lack of infrastructure (particularly public transit) that connects them to the rest of the city.
The figure below shows the total distance and travel time that residents of each block group must travel to reach all other block groups in Boston. Blocks groups that are equidistant but vary dramatically on travel durations highlight the travel inequities.
While this may seem obvious to many, there are serious consequences for assuming that residents can travel distances equally. For example, Boston Public Schools (BPS) uses Euclidean distances rather than driving or public transit distances when assigning kids to schools (see BARI’s report on BPS’s school assignment here). This new data set can be used to examine these inequities, and it is our sincere hope that it will be used to rectify them.