It is shown that the probabilistic feature of traffic breakdown at an on-ramp bottleneck leads to great limitations for reliable applications of a free flow control approach in which free flow should be maintained at the bottleneck. Based on these measured features of traffic breakdown at the bottleneck as well as on the Kerner-Klenov microscopic traffic model in the context of the author's three-phase traffic theory, critical discussions of earlier traffic flow models for freeway control simulations and of ALINEA methods of Papageorgiou for feedback on-ramp metering are made. An alternative congested pattern control approach to feedback on-ramp metering ANCONA introduced by the author in 2004 is numerically studied. In ANCONA, congestion at the bottleneck is allowed to set in. However, ANCONA maintains speeds within a congested pattern higher than about 60 km/h and prevents upstream propagation of the pattern. To reach these goals, after traffic breakdown has occurred spontaneously at the bottleneck, ANCONA tries to return to free flow via reduction of on-ramp inflow. A critical comparison of ANCONA with ALINEA and UP-ALINEA is made. (Author/publisher)
Samenvatting