Geoscience Reference
In-Depth Information
technical literature, rapid transit usually covers not only metro, but also commuter
train, light metro, light rail, monorail and others urban mass rapid public transport
systems. A metro system is independent from other traffic, even though some light
metros or German
stadtbahn
are underground in city centers, but at grade with
preference level crossings in suburban areas. According with the World Metro
Database (Rhode
2014
), 49 out of 191 cities with a metro system have inaugurated
it in the twenty-first century. The latter figure can be compared with that of 1991
(Gendreau et al.
1995
), when there existed fewer than 90 metro systems. Even
though the list is not exhaustive, in July 2014 Wikipedia reported that 36 such
systems were under construction (Wikipedia
2014
). Bus rapid transit (BRT) systems
are sometimes considered as rapid transit systems. They share several characteristics
with those using rails but they exhibit several differences, such as slower vehicles,
level crossings, and less capacity. They are usually treated separately in planning
processes and in academic research.
In practice, rapid transit planning is a very complex task involving agents with
different backgrounds and loyalties (politicians, urban planners, transit agencies,
engineers, construction companies, citizen groups, etc.). These players may there-
fore have different and sometimes conflicting goals. The planning process usually
starts by analyzing the area under consideration and the main travel patterns. Then,
based on travel patterns codified by origin-destination flow matrices, some broad
traffic corridors are identified and combined, giving rise to several network scenarios
which can be evaluated from different points of view, often using finite multi-criteria
analysis. Since, the problem is inherently strategic, this process usually takes a long
time.
Rapid transit planning can be broadly classified depending on whether the
network is to be constructed from scratch or whether it is to be extended by adding
new lines or extending some existing ones. Rail rapid transit planning lies within
the broader field of rail network planning. The sequential process of rail planning
is based on the knowledge of the travel patterns and starts with network design.
Line planning, timetabling and resource scheduling are the subsequent stages in
this process. Other related important issues are reliability, robustness, timetabling
information, shunting, platforming, etc. However, due to their special characteristics
rapid transit planning deserves a particular study. Usually, the tracks of metro lines
are not interconnected. There are exceptions to this rule, for example the cases
where there is a common trunk for several lines (Los Angeles, Brussels and Bilbao
metros), or the case of a line working as a set of lines but most of the lines work
independently. This is the case of the London Underground Northern line with three
northern termini and two different routes in the city center, see Fig.
22.1
. Some lines
in commuter systems also share the railway system in the city centre. This implies
that network design and line planning (except frequency setting) are considered
together in the modeling process. A second specific characteristic of metros is that
they carry a large number of passengers traveling over short distances compared
with medium and long distance railways. This implies that headways are very short
(with the new telecommunication technologies, in some cases these are reduced to
one minute and a half). Another distinguishing feature is the importance of mode
