Control of spatiotemporal congested traffic patterns at highway bottlenecks

Abstract

The physics of congested traffic pattern formation at an on-ramp bottleneck under on-ramp metering is studied. Various congested pattern nucleation effects at the bottleneck under different control rules are found. Based on the author's three-phase traffic theory, a congested pattern feedback on-ramp inflow control approach is proposed and investigated. In this congested pattern control approach (ANCONA approach for short), congestion at an on-ramp bottleneck is allowed to set in. The basis idea of the ANCONA approach is to keep congestion conditions at the minimum possible level at the bottleneck. In particular, the congested pattern should not propagate upstream, i.e., the congested pattern should be localized on the main road in a small neighborhood of the bottleneck. It is used in the ANCONA approach that in accordance with empirical congested pattern features, congested patterns are of various types some more favorable than others in terms of the discharge volume from the congested pattern and of the vehicle delay time due to congestion. Based on a microscopic traffic flow model of Kerner and Klenov in the context of three-phase traffic theory, a comparison of the ANCONA approach with a well-known free flow control approach in which free flow is maintained at the bottleneck is made. In particular, a ramp metering ALINEA method based on the free flow control approach that is used in many real installations is studied and compared with the ANCONA approach. Benefits of the ANCONA approach are (i) higher throughputs on the main road downstream of the bottleneck, (ii) considerably lower vehicle waiting times at the light signal on the on-ramp, (ii) the upstream propagation of congestion does not occur even if large amplitude perturbations appear in traffic flow.