THE ACCESS CONTROL PROBLEM ON CAPACITATED FIFO NETWORKS
WITH UNIQUE ORIGIN-DESTINATION PATHS IS HARD

Alan L. Erera
Department of Industrial Engineering and Operations Research,
University of California, Berkeley CA 94720, U.S.A.

and

Carlos F. Daganzo
Institute of Transportation Studies
University of California, Berkeley CA 94720, U.S.A.

and

David J. Lovell
Department of Civil Engineering,
University of Maryland, College Park, MD 20742, U.S.A.


ABSTRACT

This paper is concerned with the performance of multi-commodity capacitated networks with continuous flows in a determinsistic but time-dependent environment. For a given time-dependent origin-destination (O-D) table, it asks if it is easy to find a way of regulating the input flows into the network so as to avoid queues from growing in it. It is shown that even if the network structure is very simple (unique O-D paths) finding a feasible regulation scheme is a 'hard' problem. More specifically, it is shown that even if all input functions are smooth, there are instances of the problem with finite but possibly very large number of solutions. Furthermore, finding whether a particular instance of the problem has one feasible solution is an NP-hard problem because it is related to the Directed Hamiltonian Path problem of graph theory by a polynomial transformation. It is also shown that the discrete-time version of the problem is NP-complete.


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Last update 11/30/99