ENHANCED ROUNDABOUT METERING D.G. Geers 1,3* , P. Tyler 1 , B. Hengst 1,3 E. Huang 1 , D. Quail 2 1. NICTA, Level 4 223 Anzac Parade Kensington NSW Australia 2052, +61 2 83060439 glenn.geers@nicta.com.au 2. Roads and Traffic Authority of NSW, Australia 3. School of Computer Science and Engineering, University of NSW, Australia ABSTRACT Roundabouts are widely used traffic control measures that function particularly well under balanced, light-to-medium approach traffic flows. However, even moderate flow imbalance can cause disruption and lengthy delays. One solution is to meter traffic on one or more of the approaches to increase both the entry capacity of the roundabout and reduce delay. In this paper the early-stages of a joint project between NICTA and the Roads and Traffic Authority of New South Wales (RTA) to develop novel control methodologies for roundabout metering are discussed, some preliminary results presented and future plans outlined. KEYWORDS Roundabout, Traffic, Metering, Control, Signals, Hidden Markov Model INTRODUCTION Modern roundabouts that use the yield (give way) control rule are known to cease operating effectively when there are widely disparate traffic flows on conflicting arms [1]. Even a modest amount of circulating traffic can cause problems. The standard solution is to meter the roundabout so that up-stream detector occupancy on one arm (the control arm) causes a red (stop) signal to be applied to the conflicting (metered) arm thereby allowing the queue on the occluded (control) arm to (partially) discharge. The installed signals usually only display yellow and red and are frequently augmented with illuminated message boards that inform motorists whether the roundabout is operating normally or is being metered. Such signalisation can significantly increase the entry capacity of a roundabout and reduce delay [2]. In this paper we discuss a joint project undertaken by NICTA and the Roads and Traffic Authority of New South Wales Roads (RTA) aimed at developing a more efficient roundabout metering system.