2013 Session: 213

• Feedback Gating Based on Sparse-Measurement Urban Network Fundamental Diagrams
  Abstract: Based on the recently proposed concept of an operational urban NFD (Network Fundamental Diagram) and a feedback gating procedure, it is shown that simple, practicable and efficient gating control may be based on a strongly reduced amount of real-time measurements. The urban network of Chania, Greece, is used as a test-bed for the investigations within a realistic microscopic simulation environment. The results indicate that reduced NFDs, obtained with far less measurements than for a complete NFD, exhibit a critical range of traffic states that is virtually equivalent to its counterpart of the complete NFD; and that the provision of accordingly reduced amounts of real-time measurements for feeding the feedback regulator leads to virtually equivalent gating results as in the full measurement case.
  Authors: Keyvan-Ekbatani, Mehdi; Papageorgiou, Markos; Papamichail, Ioannis
  Authors: Keyvan-Ekbatani, Mehdi; Papageorgiou, Markos; Papamichail, Ioannis
  Year: 2013
  Document Type: Paper
  Subject: Operations and Traffic Management
  Session: 213
  Paper Number: 13-0958
• Using Mobile Probe Data and Macroscopic Fundamental Diagram to Estimate Network Densities: Tests Using Micro-Simulation
  Abstract: Recent advances in urban traffic modeling have led to the proposal of several network-wide control strategies aimed at improving network efficiency. These strategies include limiting vehicle entry through pricing, optimally charging vehicles to enter the network, and optimally allocating limited street space between multiple modes. However, these types of strategies typically rely on accurate predictions of network-wide traffic conditions, and take for granted that these predictions can be obtained in real time. In practice this is not a trivial issue, as measuring traffic conditions across a network typically requires a tremendous amount of data that is usually not available in real time. This paper proposes combining travel speed information from few circulating probe vehicles with a Macroscopic Fundamental Diagram of urban traffic to indirectly estimate network densities in real time. The proposed method is advantageous because it requires little real-time data and involves few calculations. Tests of this methodology on a simulated traffic network show that results are not accurate when the network is uncongested. However, reliable density estimates are obtained when the network is congested or approaching congestion, even if only a small fraction of vehicles serve as probes. This is promising since congested states are the most critical to identify. Thus, this methodology seems particularly useful as a traffic monitoring scheme to complement network-wide traffic control strategies, provided that a well-defined and reproducible macroscopic fundamental diagram exists on the network.
  Authors: Gayah, Vikash V.; Dixit, Vinayak V.
  Authors: Gayah, Vikash V.; Dixit, Vinayak V.
  Year: 2013
  Document Type: Paper
  Subject: Operations and Traffic Management
  Session: 213
  Paper Number: 13-1493
• Figure-Eight Hysteresis Pattern in Macroscopic Fundamental Diagrams for Urban Freeway Network in Beijing, China
  Abstract: This paper presents Macroscopic Fundamental Diagrams (MFDs) for an urban freeway network in Beijing, China. In the diagrams, a figure-eight hysteresis pattern is clearly observed. To understand the causes, analyses are made ranging from spatialtemporal heterogeneity of vehicles to the flow-occupancy relation for individual locations. As a result, we observe at individual locations that free-flow traffic with the same occupancy exhibits different flows in the onset and offset of congestion; it is attributed to the figure-eight hysteresis pattern at the macroscopic level. The formation of the multi-branch flow-occupancy diagram at individual locations is discussed and explained. The paper enriches the knowledge about MFDs and provides some empirical support for the existing theory.
  Authors: He, Zhengbing; He, Shuyan; Guan, Wei
  Authors: He, Zhengbing; He, Shuyan; Guan, Wei
  Year: 2013
  Document Type: Paper
  Subject: Operations and Traffic Management
  Session: 213
  Paper Number: 13-1760
• Information Provision and Network Performance Represented by Macroscopic Fundamental Diagram
  Abstract: The existence of Macroscopic Fundamental Diagram (MFD), which relates space-mean density and flow, has been shown in urban networks under homogeneous traffic conditions. Since MFD represents the area-wide network traffic performances, studies on perimeter control strategies and an area traffic state estimation utilizing the MFD concept has been reported. One of the key requirements for well-defined MFD is the homogeneity of the area-wide traffic condition with links of similar properties, which is not universally expected in real world. For the practical application of MFD concept, several researchers have identified the influencing factors for network homogeneity. However, they did not explicitly take drivers’ behaviour under real time information provision into account, which has a significant impact on simulation outputs. This research aims to demonstrate the effect of drivers’ route choice behaviour on network performance by employing MFD as a measurement. A microscopic simulation is chosen as an experiment platform. By changing the ratio of en-route informed drivers and pre-trip informed drivers, different scenarios are simulated in order to investigate how drivers’ adaptation to the traffic congestion influences the network performance and MFD shape. This study confirmed and addressed the impact of information provision on MFD shape.
  Authors: Tsubota, Takahiro; Bhaskar, Ashish; Chung, Edward; Geroliminis, Nikolas
  Authors: Tsubota, Takahiro; Bhaskar, Ashish; Chung, Edward; Geroliminis, Nikolas
  Year: 2013
  Document Type: Paper
  Subject: Operations and Traffic Management
  Session: 213
  Paper Number: 13-3549
• Feedback Gating Based on Sparse-Measurement Urban Network Fundamental Diagrams
  Authors: Keyvan-Ekbatani, Mehdi
  Authors: Keyvan-Ekbatani, Mehdi
  Year: 2013
  Document Type: Presentation
  Subject: Operations and Traffic Management
  Session: 213
  Paper Number: 13-0958
• Using Mobile Probe Data and the Macroscopic Fundamental Diagram to Estimate Network Densities: Tests Using Micro-Simulation
  Authors: Gayah, Vikash
  Authors: Gayah, Vikash
  Year: 2013
  Document Type: Presentation
  Subject: Operations and Traffic Management
  Session: 213
  Paper Number: 13-1493
• Figure-Eight Hysteresis Pattern in Macroscopic Fundamental Diagrams for Urban Freeway Network in Beijing, China
  Authors: He, Zhengbing
  Authors: He, Zhengbing
  Year: 2013
  Document Type: Presentation
  Subject: Operations and Traffic Management
  Session: 213
  Paper Number: 13-1760
• Information Provision and Network Performance Represented by Macroscopic Fundamental Diagram
  Authors: Tsubota, Takahiro
  Authors: Tsubota, Takahiro
  Year: 2013
  Document Type: Presentation
  Subject: Operations and Traffic Management
  Session: 213
  Paper Number: 13-3549
• Connecting Networkwide Travel Time Reliability and Network Fundamental Diagram of Traffic Flow
  Authors: Mahmassani, Hani
  Authors: Mahmassani, Hani
  Year: 2013
  Document Type: Presentation
  Subject: Operations and Traffic Management
  Session: 213
  Paper Number: 13-5184
• Connecting Networkwide Travel Time Reliability and Network Fundamental Diagram of Traffic Flow
  Abstract:

  The existence of the Network Fundamental Diagram (NFD) has been established at the urban network scale. It relates three traffic descriptors, speed, density and flow; however its deterministic nature does not convey the underlying variability within the network. On the other hand, travel time reliability as a network performance descriptor is of growing concern to both the traveling public as well as traffic managers and policy makers. The objective of this paper is to extend travel time reliability modeling from the link/path level to the network level, and connect overall network variability to the NFD. Robust relations between travel time variability and network density and flow rate are derived, and investigated/validated using both simulated and real word trajectory data. It is observed that the distance-weighted standard deviation of travel time rate, as a measure of travel time variability, increases monotonically with network density. A maximum network flow rate exists, as corresponding to the one in NFD, beyond which network travel time reliability deteriorates at a much faster pace. The results also suggest that these relations are inherent network properties (signature) which are independent of demand level. The effects of en-route information on the proposed relationships are studied, which shows en-route information helps reduce network travel time variability. Analytical approaches are applicable to model these relationships. The findings provide a strong connection between Network Fundamental Diagram and travel time variability, which can be further utilized for network travel time reliability modeling, and assessment of measures intended to improve reliability of travel in a network.

  Authors: Mahmassani, Hani S.; Hou, Tian; Saberi, Meead
  Authors: Mahmassani, Hani S.; Hou, Tian; Saberi, Meead
  Year: 2013
  Document Type: Paper
  Subject: Operations and Traffic Management
  Session: 213
  Paper Number: 13-5184
  Practice-Ready: Yes