Traffic Signal Optimization Using Cyclically Expanded Networks

Abstract

Traditionally, the coordination of multiple traffic signals and the
traffic assignment problem in an urban street network are considered
as two separate optimization problems.  However, it is easy to see
that the traffic assignment has an influence on the optimal signal
coordination and, vice versa, a change in the signal coordination
changes the optimal traffic assignment.  In this paper we present a
cyclically time-expanded network and a corresponding mixed integer
linear programming formulation for simultaneously optimizing both
the coordination of traffic signals and the traffic assignment in an
urban street network.  Although the new cyclically time-expanded
network provides a model of both traffic and signals close to
reality, it still has the advantage of a linear objective function.
Using this model we compute optimized signal coordinations and
traffic assignment on real-world street networks.  To evaluate the
practical relevance of the computed solutions we conduct extensive
simulation experiments using two established traffic simulation
tools that reveal the advantages of our model.