This map visualizes the median household income by station along Washington DC’s Metro system. It is inspired by The New Yorker's Inequality and New York's Subway Project.
The New Yorker map showed that transit networks are powerful orientation features. Because they are so familiar, they form a nice backbone over which we can communicate data in an intuitive way.
To build on the work of The New Yorker map, we are in the process of developing an open-source library by which any census data for any city can be visualized over a transit network. This is the first usage of this library.
Using median household income data from the census at the blockgroup level, we mapped the changes in income across each metro line. In Washington DC, the stops along the green line show lower median income than other lines. The westernmost stations show higher income than those on the other end of the line.
Station, line and route information was constructed from a GTFS (General Transit Feed Specification) feed. A station neighborhood around each station was defined as a circle with radius of 0.5 mile was constructed. All block groups that intersect a station neighborhood were identified and the proportion of the intersection area to the block group area was used to weight the population for each block group. A weighted average of median incomes was calculated for each station neighborhood across the intersecting block groups.
Data sources for DC:
American Community Survey 2009 to 2013 (5-Year Estimates): www.socialexplorer.com