Pollaczek contour integrals for the fixed-cycle traffic-light queue

TL;DR

This paper derives Pollaczek contour integrals for the fixed-cycle traffic-light queue, enabling efficient computation of queue-length distributions and moments without complex root-finding, extending to generalized models.

Contribution

It introduces a contour-integral representation for the FCTL queue's generating function, simplifying analysis and extending to generalized models.

Findings

Contour integrals facilitate computation of queue-length distribution.

Method avoids complex root-finding procedures.

Results extend to generalized FCTL queue models.

Abstract

The fixed-cycle traffic-light (FCTL) queue is the standard model for intersections with static signaling, where vehicles arrive, form a queue and depart during cycles controlled by a traffic light. Classical analysis of the FCTL queue based on transform methods requires a computationally challenging step of finding the complex-valued roots of some characteristic equation. Building on the recent work of Oblakova et al. (Exact expected delay and distribution for the fixed-cycle traffic-light model and similar systems in explicit form, 2016), we obtain a contour-integral expression, reminiscent of Pollaczek integrals for bulk-service queues, for the probability generating function of the steady-state FCTL queue. We also show that similar contour integrals arise for generalizations of the FCTL queue introduced in Oblakova et al. (2016) that relax some of the classical assumptions. Our results allow to compute the queue-length distribution and all its moments using algorithms that rely on contour integrals and avoid root-finding procedures.