Geoscience Reference
In-Depth Information
selection due to the fact that in most metropolitan areas where such systems are
planned, several competing modes of transportation (bus, private car) are available.
Rapid transit network design is made up of two intertwined problems: the
determination of alignments and the location of stations. There are other related
location problems such as those of locating park-and-ride facilities and depots, but
usually their corresponding feasible sets are limited to very few possibilities and
thus do not give rise to interesting location problems. The location of stations is a
typical attractive facility location problem for which several criteria can be applied
depending on the goals of the decision maker. However, a station located in a high
density area could be non-efficient because of the direction of the line to which it
belongs. For example, if the line goes north-south but the people located close to the
station work east of the station, this station will not be useful for their working trips.
Therefore, it is crucial to concentrate on the location of the alignments and not only
on that of the stations. Since the facility to be located is a network, and therefore
very large with respect to its environment, the problem under consideration is an
extensive or multi-dimensional facility location problem (Mesa and Boffey
1996
).
Our aim is to review some of the main aspects of rapid transit location. For the
sake of readability, we have avoided the use of lengthy formulations and formulas as
much as possible. These can be found in the original sources. We will first describe
in Sect.
22.2
the main indicators used to assess the quality of a rapid transit network.
Models and algorithms used for rapid transit network design will be described in
Sect.
22.3
. In Sect.
22.4
we focus on the location of stations. Conclusions follow in
Sect.
22.5
.
22.2
Objectives and Network Assessment
The main objective of a collective transit system is to improve the population
mobility. Since rapid transit systems usually have a high capacity, they extensively
reduce traffic congestion, airborne pollution and energy consumption, thus provid-
ing sustainable mobility. Moreover, these systems are among the quickest collective
mode of ground transportation, and therefore they usually provide the shortest travel
times. Another important feature is their structuring influence on cities since they
provide the backbone for the development of residential, business and commercial
areas. Rapid transit systems require high-level investments, both for construction
and maintenance. The initial investment is related to the construction of tunnels,
elevated or at grade right-of-ways, communication systems and the purchase of
rolling stocks. Operating cost include fixed and variable costs on a daily basis.
The agents interested in the planning processes can be broadly classified into
three groups: the society in general, which is represented by transportation agencies
and government sections, the potential riders, and the company offering the service.
The first group is mainly interested in global advantages such as those mentioned
above and they are therefore concerned with the population to be served by the
system. A measure frequently used at the planning stage is the population covered
