Real-time estimation of critical occupancy for maximum motorway throughput

The local ramp metering strategy ALINEA aims at stabilizing downstream motorway occupancy near critical occupancy to achieve maximum motorway throughput. Two previously proposed real-time estimation schemes for the critical occupancy are fine-tuned, modified, and evaluated by use of extensive traffic data from eight locations of the UK M6 motorway. The evaluation results indicate satisfactory estimation accuracy, rapid tracking behavior, and high robustness for measurement noise, detector failures, and different kinds of traffic conditions. The reported investigations open the way to field implementation of the adaptive AD-ALINEA ramp metering, strategy that incorporates real-time estimation of critical occupancy.