This document discusses the aspects of network design.First a brief introduction of network design will be
given.Then various types of assignment techniques will be discussed including the mathematical
formulation and numerical illustration of the important ones.Then the concept of bilevel programming
and few examples will be presented.Finally one such example, namely the network capacity expansion
will be formulated as a bilevel optimization problem and will be illustrated using a numerical example.
Transportation network design in a broad sense deeds with the configuration of network to achieve
specified objectives.There are two variations to the problem, the continuous network design and the
discrete network design. Examples of the form include
a
The determination of road width.
Transportation Network Design
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b
The calculation of signal timings.
c
The setting of road user charges.
Although this document covers the continous network design in detailed, basis underlinig principles are
some form the discrete case. Conventional network design has been concerned with minimization of total
system cost.However, this may be unrealistic in the sense that how the user will respond to the proposed
changes is not considered. Therefore, currently the network designis thought of as supply demand
problem or leader-follower game.The system designer leads, taking into account how the user follow.
The core of all network design problems is how a user chooses his route of travel. The class of traffic
assignment problem tries to model these behaviour. Therefore, the traffic assignment will be discussed
before adressing bi-level formulation of the network design problems.