Properties of a Well-Defined Macroscopic Fundamental Diagram for Urban Systems

A field experiment in Yokohama (Japan) revealed that a macroscopic fundamental diagram (MFD) linking space-mean flow, density and speed exists on a large urban area. It was observed that when the somewhat chaotic scatter-plots of flow vs. density from individual fixed detectors were aggregated the scatter nearly disappeared and points grouped neatly along a well defined curve. Despite these and other recent findings for the existence of well defined MFDs for urban areas, these MFDs should not be universally expected. In this paper the authors investigate what are the properties that a network should satisfy, so that an MFD with low scatter exists. The authors show that the spatial distribution of density/occupancy in the network is one of the key components that affect the scatter of an MFD and its shape. The authors also propose an analytical derivation of the spatial distribution that considers correlation between adjacent links. The authors investigate the scatter of an MFD in terms of errors in probability density function of spatial occupancy and errors of individual links’ fundamental diagram (FD). Later, using real data from detectors for an urban arterial and a freeway network the authors validate the proposed derivations and the authors show that an MFD is not well defined in freeway networks as hysteresis effects are present. The datasets in this paper consist of flow and occupancy measures from 500 fixed sensors in the Yokohama downtown area and 600 loop detectors in the Twin Cities Metropolitan Area Freeway network (Minnesota, USA).

Language

  • English

Media Info

  • Media Type: DVD
  • Features: Figures; Maps; References; Tables;
  • Pagination: 21p
  • Monograph Title: TRB 89th Annual Meeting Compendium of Papers DVD

Subject/Index Terms

Filing Info

  • Accession Number: 01152268
  • Record Type: Publication
  • Report/Paper Numbers: 10-3521
  • Files: TRIS, TRB
  • Created Date: Jan 25 2010 11:47AM