The Subte in Buenos Aires

The underground subway system in Buenos Aires is known as the subtel, short for subterráneo (underground).  It is the first underground subway system built in Latin America.  It also has the reputation of being the first subway system in the world to be privatized during that binge of privatizations that took place in Argentina during the 1990s.  

Organizationally, this system contains five separate lines (named easily Line A, Line B, Line C, Line D and Line D) that were constructed one after another.  Line A is the oldest and still carries the original subway cars with the antique wood-framed interiors.  Physically, the system design is in the form of a fork.  To get from one station on one line to another station on another line means going down to the center and coming back.  A map is shown below:

We will now cite some suvery data from the 2003 TGI Argentina survey.  Within this study, there were 2,570 persons beween the ages of 12 to 75 years old who live in the the Federal District/Gran Buenos Aires area.  Over the course of the week, 12.5% of these people say that they used the subte to go to work or school.  Now, the cost of a subte ride is about 70 centavos (US 25 cents) and the system accepts fichas (tokens) which can be purchsed from boleterías (ticket booths) located at the stations.  In the following graph, we show the incidences of the usage of the subte and two other popular modes of transportation by socio-economic level.  The profile of subte usage is similar to automobile usage, whereas the buses are used uniformly within the population.

The relationship between subte usage and socio-economic level is not totally related to the cost.  Rather, there is the odd effect that the nearness of a residence or a business to a subte increases the value.  Thus, other things being equal, a home that is 'one minute from a subte station' will be worth more than another one that is 'twenty minutes away.'  And business in the central district will be more prestigious than those in outlying areas due to rent costs.  In turn, other things being equal, subte riders should have higher socio-economic levels.

The TGI Argentina survey also contains detailed information about the usage of the different subte lines.  Within the average week among the subte riders, 74% used just one line, 21% used two lines and 5% used three or more lines.  The following table gives the usage and cross-usage of these lines.  All percentages in this table should be interpreted as horizontal percentages.

  % Used Line A % Used Line B % Used Line C % Used Line D % Used Line E
TOTAL PERSONS 3.6 % 4.5% 2.8% 4.8% 0.9%
TOTAL RIDERS 29% 36% 23% 39% 7%
   Line A Riders 100% 26% 15% 25% 5%
   Line B Riders 20% 100% 13% 15% 3%
   Line C Riders 19% 21% 100% 34% 7%
   Line D Riders 19% 14% 20% 100% 2%
   Line E Riders 19% 18% 23% 13% 100%

If subway ridership of one line were completely independent of another line, those entries of each line in the table would match the entry for total riders.  As it were, the entries are less in all cases.  This indicates that people are more likely to be single line users than chance alone (note:  transfers among lines are free within the system).  Again, there is an odd effect in that people would choose a home or a job that is located close enough to reduce commute time (which is a different kind of cost).  Thus, other things being equal, one would rather choose a job on the same subte line rahter than having to make more than one line.

 (posted by Roland Soong, 9/13/2003)

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