123-4_together 5-6_together     REFERENCE_LINKS:

http://www.bcn.cat/estadistica/angles/index.htm

( for vehicular data )

http://en.wikipedia.org/wiki/Districts_of_Barcelona(

for population and area of districts)

http://opendata.bcn.cat/opendata/cataleg/TRANSPORT/antiguitat-veh/

( for downloading files)

Nus de la Trinitat

(image source)