Real-life CRONOS evaluation

CRONOS is a real-time urban traffic control (UTC) algorithm developed at INRETS in France (Boillot et al., 1992). It provides the traffic light states (green, amber, red) of junctions for the next few seconds based on a traffic criterion optimisation and using the rolling horizon concept (Gartner, 1982). Three main features characterise it: its ability to control, in the same optimisation process, a zone of a few junctions (typically 5 or 10 junctions). This feature comes from the good properties of the modified Box algorithm version used for the optimisation purpose; its flexibility in the choice of the traffic light states: CRONOS is acyclic and no stages are defined a priori. Each junction is defined as a set of safety constraints on the traffic light groups which define all the forbidden durations and correlations of the states; and its ability to use video based measurements like the queue lengths along the links or the spatial occupancy in the inner junction storing zones. It was decided to undertake a real-life evaluation of the CRONOS performances. After the building of a complete control chain described in Boillot (1997), an 8 months experience has been undertaken on a single junction. We describe in the paper the main features of this experience and the evaluation results