Abstract
This paper introduces a novel approach to the online short-term prediction of point-to-point freeway travel time, combining statistical forecasting techniques with traffic simulation. At every freeway entrance point, a time series analysis model based on traffic detector counts is used to predict traffic demands, whose flow through the freeway segment is simulated by a cell transmission model. This procedure, applied within a rolling-horizon framework, generates online travel time predictions consistent with traffic flow theory. Experimental results obtained from synthetic data strongly suggest that the estimates obtained with this methodology are robust and accurate. For a wide range of congestion conditions and freeway segment lengths, more than half of the predictions errors were found to be smaller than 15%. Moreover, 80% of these errors fell below 40 s when the actual travel times ranged between 3 and 10 min. Further analyses of the model sensitivity to traffic detector coverage revealed that detector separations of approximately 1 mi resulted in the most precise travel time estimates. In addition to its satisfactory performance, the proposed framework is flexible, and it can make use of additional online data and easily incorporate different forecasting and simulation techniques. Therefore, this work provides a powerful tool for online travel time prediction, suitable for a variety of practical implementation conditions and requirements.
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