Coordinated Ramp Metering Based on On-Ramp Saturation Time Synchronization

Abstract

In this paper, a coordinated ramp-metering approach is proposed; the approach is based on the synchronization of the time it takes for an on-ramp to run out of space. The time that congestion and the associated capacity drop can be prevented at a freeway bottleneck by means of ramp metering depends on the available ramp space for temporarily storing the vehicles. For a single on-ramp, the available space and thus the metering time at the bottleneck are often limited. By means of coordination, upstream storage space can be used to prevent a breakdown for a longer period of time. To accomplish that aim, upstream ramps need to reduce their inflow into the mainstream with respect to their own metering task. The extent to which upstream inflow reductions are effectively used to extend the metering time at the bottleneck is determined by the order and timing at which the coordinated ramps run out of space. The proposed approach aims at always saturating the more upstream-located ramps before more downstream-located ones; that is, the ramps run out of space in the downstream direction to make sure that all realized assistance is used by the ramp that is metering at the bottleneck. By means of a simulation test case, the functioning of the algorithm is demonstrated and compared with a no-control scenario, local ramp metering, and an alternative coordination algorithm that aims at filling the ramps equally. Both coordination approaches strongly improve the network performance with respect to local ramp metering, but the proposed coordination approach is able to postpone the breakdown for a longer period of time.

Coordinated Ramp Metering Based on Real-Time OD Information

“…It can take into account the whole system compared with local ramp metering. Present studies have indicated CRM solutions are more efficient than isolated ones [16]- [18].…”

An integrated control method based on the priority of ways in a freeway network

“…Traffic-responsive RM is based on the real-time traffic conditions in a freeway network. Several field and laboratory experiments have shown the effectiveness of traffic-responsive RM (Hourdakis and Michalopoulos, 2002; Khoo, 2011; Kotsialos and Papageorgiou, 2004; Landman, 2015). Although traffic-responsive RM offers potentially strong results to manage the motorway traffic at merging regions, the strictly limited space of ramps makes it difficult to reach satisfactory results (Papamichail et al, 2010).…”

“…In some cases (Carlson et al, 2014; Hegyi et al, 2005a), in order to mitigate the interference of the on-ramp and mainline traffic flows, the benefits of the on-ramp outflow are greatly sacrificed, where the on-ramp queue length is simply considered a constraint condition. Other methods of integrating the RM and VSL are not suitable in certain conditions (Carlson et al, 2012; Gomes and Horowitz, 2006; Khoo, 2011; Kotsialos and Papageorgiou, 2004; Kotsialos et al, 2002; Landman, 2015; Ma et al, 2015). For example, when the merging region is congested, on-ramp vehicles are not allowed to flow into the merging region and the right of way of on-ramp vehicles is deprived.…”

Urban Storage Space Selection Method for Integrated Control on a Freeway Bottleneck

“…Their effectiveness might, however, be suboptimal because full utilization of the coordinated ramp storage spaces is not explicitly targeted. Hence, by doing so, some of the more recently proposed algorithms-such as HERO (9) and the algorithm proposed in Landman et al (10) based on ramp saturation time synchronization-do have the potential to maximize the metering duration on a freeway bottleneck. However, none of the above mentioned methods address which ramps to coordinate to further decrease the total system delay, given the prevailing network characteristics.…”