Background:
The constructions of the Vasco da
Gama Bridge, in Lisboa , Portugal Europe with its length of 17,2 km . The two goals of
the bridge - clearly declared before this project - were accepted.
1. First, it aimed for the
decongestion of the other bridge
of Lisbon
2. Second, it meant to create the
north-south connection around the capital city.
After the first bridge went into
use, many inhabitants and firms moved to the other side of the river Tejo
opting for a further location. However, it led to an increased congestion cost
for those who traveled from Spain
Theory: What is expected according to the theory?
As the Vasco da Gama Bridge is not
the first connection between the north and the south side of the river Tejo (Tagus ), the main goal was the reduction of congestion on
the 25th of April Bridge. In our analysis we should ignore the impacts of the
first bridge and focus on the second one. According to the theory, the bigger
the city is (that means a larger number of firms), the higher the congestion
costs are. If there are many companies in the city, congestion acts as a
spreading force that stimulates firms to move from the central business
district to the periphery zone, where traffic is lower.
The core model of new economic
geography (congestion is not included) says that if transport costs are low
then agglomeration is the stable equilibrium. Adding congestion to the theory,
spreading equilibrium becomes more general and agglomeration is only an
exception. According to the two-region core model (Brakman et al.), even a
small change in congestion can easily lead to a new long-run equilibrium. As
transport costs start to decrease, first partial then total agglomeration will
develop. The further shrinking of costs result in spreading as a stable
equilibrium again.
Although in Lisbon Lisbon
Reality: What had happened?
As for the decongestion of the 25th
of April, traffic experts agreed that this aim can be reached without building
a new bridge. Another, even better solution could have been achieved with
focusing on the significant improvements of the railways and public transport
connections between the two banks of the river. However, the Vasco da Gama
Bridge was built.
According to a document from 1994 it
had been estimated in advance that the new bridge would stimulate traffic above
the annual transport growth rates without having too much impact on the other
bridge. As we see on the table below, the expectations came true.
Source:
Melo, J.
As data shows, after opening the
Vasco da Gama Bridge the total amount of vehicles grew dramatically while the
traffic of the 25th of April Bridge did not represent significant
decrease. Why? A new bridge always generates urban and traffic growth, as we
can see in our case.
So, can we explain these empirical
evidences with the transport coming from the East in order to trade with the
Centrum of Portugal? As they do not have to either be in the traffic jam or
bypass the whole river in order to get into the city, it should be the
appropriate solution to reduce transport costs. Interestingly, according to a
paper (Melo, J.), these traders prefer to use the bridge in Carregado that is
about 30 km
from Lisbon to the North and was built after the
Vasco da Gama Bridge
To sum it up, decreasing
this level of congestion theoretically drives agglomeration forces. As the
bridge did not stimulate so far development in the south, the theory seems to
be confirmed on this side. However, we cannot observe any significant reduction
in congestion on the 25th of April Bridge either. So, the Vasco da
Gama Bridge does not seem to reach its initial goals, although it has clearly
positive effects in other areas.
Noémi Szabó
References
Brakman et al. (2009). The New Introduction to
Geographical Economics. Cambridge University Press, New York
Melo, J. (2000). The Vasco da Gama Bridge on the
Tagus Estuary: A paradigm of bad decision making, but good post-evaluation. World Transport Policy & Practice, 6(2). 20-30. p.
