Accurate state estimation and prediction models strongly rely on the quality and the dissemination of the available traffic data. In complex networks, such as large urban areas, the position of traffic counts (i.e. loop detectors) is of critical importance for such models. Nevertheless, sensor locations are typically thought for different objectives, e.g., for monitoring bottleneck sections, or to obtain optimal information on the trip-generation matrix. As result, link state estimations and predictions are often inaccurate, and sometimes large blank areas in monitoring traffic are observed, which may reflect into bad prediction, sometimes even on the monitored links.This paper proposes a new approach to the sensor location problem, which has the objective of optimizing the position of traffic counts for reliable travel time estimation and prediction at complex road networks. To do so, we reformulate the Maximum Possible Relative Error, used as objective function in classical approaches, to minimize the error in link traffic states. By formulating the problem at the link level we can obtain more reliable predictions of partial as well as whole network travel times.The solution of the new MPRE would require two extra inputs with respect to the classical approach: 1) the specification of a network travel time or a state estimation model and 2) the specification of the network traffic variability, in order to set the boundaries of the solution space. For large complex networks the latter information might be very difficult to be obtained.As alternative, we propose a simple solution algorithm to the problem that uses the link flow and travel time correlations between links to select, in sequence, the most representative links in the network. We tested the algorithm on a toy network showing that it succeeds in catching a substantially larger percentage of link flows than a classical approach.
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SENSOR LOCATIONS FOR RELIABLE TRAVEL TIME PREDICTION AND DYNAMIC MANAGEMENT OF TRAFFIC NETWORKS FOREWORDReliable estimation and prediction of travel times at road networks strongly depends on the quality of information available on the current, as much as on the expectations of future, traffic conditions. A very popular way to obtain this type of information is through traffic counts collected from automatic detection points (e.g., loop detectors). These sensors provide, with some degree of precision, average traffic intensities and speeds within fixed time periods and at specific locations in the network. This information is therefore typically fragmented in time and space. First, not all parts of the network are monitored and often blank areas in the data are completed with interpolated data. Second, traffic counts are sent to the data users (e.g., road authorities, information service providers) after they are aggregated into fixed time intervals, and therefore they may lose information due to averaging (e.g., speeds are usually collected as mean values). Considering that traffic counts contain always a degree of er...