Using wireless mesh network for traffic control

Wireless mesh networks (WMN) have attracted considerable interest in recent years as a convenient, flexible and low-cost alternative to wired communication infrastructures in many contexts. However, the great majority of research on metropolitan-scale WMN has been centered around maximization of available bandwidth, suitable for non-real-time applications such as Internet access for the general public. On the other hand, the suitability of WMN for missioncritical infrastructure applications remains by and large unknown, as protocols typically employed in WMN are, for the most part, not designed for realtime communications. In this chapter, we describe a real-world testbed, which sets a goal of designing a wireless mesh network architecture to solve the communication needs of the traffic control system in Sydney, Australia. This system, known as SCATS (Sydney Coordinated Adaptive Traffic System) and used in over 100 cities around the world, connects a hierarchy of several thousand devices -- from individual traffic light controllers to regional computers and the central Traffic Management Centre (TMC) - and places stringent requirements on the reliability and latency of the data exchanges. We discuss some issues in the deployment of this testbed consisting of 7 mesh nodes placed at intersections with traffic lights, and show some results from the testbed measurements.