Reliability of Stockholm Subway - Index of

Passengers, thousand
1.2 Problem Description
Subway network is one of the most efficient modes of mass transit systems in big
cities. It has high capacity and it is independent of road traffic. Statistics shows that
the amount of passengers in agglomerations constantly increases. To deal with the
growing transportation demand transit operators may construct new infrastructure,
which is usually extremely expensive, or enhance capacity of the current network by
more effective operating. Intensive use of the capacity may cause problems of service
reliability which brings about less attraction of customers. That is why operators
maximizing the capacity should guarantee the service reliability.
Stockholm subway running by city-owned public transit company SL, AB
Storstockholm Lokaltrafik, is not an exception. The number of passengers gradually
but constantly grows. The tendency during last several years is presented on figure
1.1. The histogram shows the number of Stockholm subway passengers per one
winter day (SL, 2009).
1200
1000
800
600
400
200
0
1012 1016 1016 1073 1094 1117 1117
2003 2004 2005 2006 2007 2008 2009
Figure 1.1 Number of passengers in Stockholm subway
Green line
Red line
Blue line
Total
At peak hours subway experiences difficulties with increasing passenger flows on
some segments of the network. To cope with the challenge the operator runs the
service with the shortest possible headways. The minimal designed time difference
between the pair of consecutive trains allowed by the system is 90 seconds.
Theoretically it lets operating with up to 40 trains per hour. However in reality the
11