Bibliography
  1. Vision Zero Program web site http://www1.nyc.gov/site/visionzero/index.page
  2. Vision Zero Investment article https://www.transalt.org/getinvolved/vision-zero-investment
  3. Vision Zero Data Feeds http://www.nyc.gov/html/dot/html/about/vz_datafeeds.shtml#crash  
  4. Citi Bike program official web site https://www.citibikenyc.com/
  5. Statistical data by the U.S. zip code http://www.unitedstateszipcodes.org/ 
  6. NYC Open Data, NYPD motor vehicle collision data https://data.cityofnewyork.us/Public-Safety/NYPD-Motor-Vehicle-Collisions/h9gi-nx95 
  7. Geopandas heatmap instruction http://nbviewer.jupyter.org/gist/perrygeo/c426355e40037c452434