Generating Optimal Signal Positions
Author(s)
E. A. G. Weits & D. van de Weijenberg
Abstract
In The Netherlands railway traffic is growing. As the growth has to be largely
accommodated on existing tracks, short headways are increasingly important.
Headways are mainly determined by signal positions. Since signal positions are
subject to many diverse constraints, finding a good signal positioning scheme by
hand is a time-consuming task and it is nearly impossible to prove optimality.
Therefore, an algorithm that generates an optimal signal positioning scheme,
taking care of all constraints, has been designed and implemented in a computer
program for infrastructure planners. The algorithm calculates the sequence of
signal positions that minimises the weighted sum of headways for a set of trains,
each pair of trains with a common track yielding possibly two headways. The
first step of the algorithm consists of a tree search leading to an enumeration of
groups of similar signal sequences. Secondly, a linear programming problem is
applied to all groups in order to find the best solution within each group. A
validation study showed that the signal positioning scheme produced by the
algorithm slightly outperforms the results found manually, as long as the
computer program is restrained to the same number of signals as used in the
manual solution. In a number of cases, the computer program suggested better
solutions using a larger number of signals. The results of the validation study
have led to adoption of the computer program for use in projects. At the same
time further research to improve the computational speed has started.
Keywords: railway capacity, signalling scheme, signal positions, headways.
1 Introduction
The Dutch railway network is heavily utilised and the number of passengers is
growing by between 3 and 5 percent a year. Therefore, the intention is to
increase the frequency of departures from 4 to 6 times per hour, for intercity
Keywords
railway capacity, signalling scheme, signal positions, headways
Related Book
Other papers in this volume
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