A Dynamic-Zone-Based Coordinated Ramp-Metering Algorithm With Queue Constraints for Minnesota's Freeways

Abstract

Abstract-Following about 40 years of successful deployment of coordinated traffic-responsive ramp control, a new generation is being developed for Minnesota's freeways based on density measurements, rather than flow rates. This was motivated from recent research indicating that the critical value of density at which capacity is observed is less sensitive and more stable than capacity, thereby allowing the opportunity for more effective control. The main goals of the new approach are to delay the onset of the breakdown and accelerate system recovery when ramp metering is disabled due to the violation of maximum allowable ramp waiting times. This is obtained by a dynamic zone partitioning of the freeway network to identify critical bottleneck locations and coordinated balancing of ramp delays, which aims to avoid mainline breakdown. The effectiveness of the new control strategy is assessed by comparison with the currently deployed version of the stratified zone metering algorithm through microscopic simulation of a real 12-mi 17-ramp freeway section. Simulations show a decrease in delays of mainline and ramp traffic and an improvement of 8% in overall system delays while avoiding maximum ramp delay violations.

Empirical observations of capacity drop in freeway merges with ramp control and integration in a first-order model

“…The main reason for this high drop is the extremely high values of ramp flows a few minutes before the occurrence of the breakdown, due to the overreaction of the existing ramp metering strategy once long queues occur at the on ramps. Our recent findings (Geroliminis et al, 2011) show that a ramp metering strategy with a smoother reaction to long queues can significantly improve total travel times.…”

Optimizing Coordinated Ramp Metering: A Preemptive Hierarchical Control Approach

“…The models’ reliability is checked by comparing simulation outputs with observed field data at each loop station along the freeway corridor and ramps. Our simulation model was calibrated following a similar approach introduced in Gomes et al (2004), Sarvi et al (2004), and Zhang et al (2009). The traffic inputs, routing decisions, and driver behavior parameters are adjusted to minimize the difference between simulation outputs and ground‐truth data.…”

“…Coordinated ramp metering strategies address the insufficient response capability issue with the local ramp metering systems, but require extensive coverage of traffic detection and communication infrastructure to implement and operate. Representative coordinated ramp metering strategies include the multivariable control strategy developed by Papageorgiou et al (1990), the METALINE algorithm proposed by Diakaki and Papageorgiou (1994), the Helper algorithm developed by the Colorado Department of Transportation and evaluated by Saito et al (2003), and the optimal control strategies developed by Zhang et al (1996), Chen et al (1997), Zhang and Recker (1999), Bellemans et al (2002), Zhang and Levinson (2004), Papamichail and Papageorgiou (2011), Geroliminis et al (2011), and Gomes and Horowitz (2006). For example, the METALINE algorithm is an extension of ALINEA and Papageorgiou and Kotsialos (2002) reported that METALINE performed better than ALINEA against nonrecurrent congestion but showed no advantage over ALINEA under recurrent congestion.…”

Improved bottleneck approach for heuristic systemwide responsive ramp metering on congested freeways

“…With the ability of adjusting the metering rate with respect to different traffic conditions, the Zone method is flexible and can be implemented in a real time fashion. In recent years, the Zone system in Minnesota has been significantly improved to enhance its robustness and efficiency considering system dynamics and traffic stochasticity (Geroliminis et al, 2011;Zhang and Levinson, 2010;Wu et al, 2010;Zhang and Levinson, 2004).…”