Density is an important macroscopic parameter of traffic flow. A number of studies have based estimations of the density on a section of roadway on speed and flow measurements at the section entrance and exit. This paper views density as a continuous-time, stochastic process and considers the characteristics of the process itself. The study relied on freeway traffic data previously obtained by sequential aerial photography. Position data were smoothed and interpolated to construct individual trafectories, which were aggregated to obtain continuous vehicle counts in roadway sections of various lengths. Autocorrelation functions and power spectra were calcualted for these records. It was found that for the traffic flow under consideration, correlation time was proportional to freeway section length. The power in the process was concentrated below a cut off frequency that was inversely related to section length. The implications these results have for sampling real traffic processes are discussed. /Author/

Media Info

  • Media Type: Print
  • Features: Figures; References;
  • Pagination: pp 79-83
  • Monograph Title: Highway capacity, measures of effectiveness, and flow theory
  • Serial:

Subject/Index Terms

Filing Info

  • Accession Number: 00189855
  • Record Type: Publication
  • Report/Paper Numbers: HS-025 846
  • Files: TRIS, TRB
  • Created Date: Apr 12 1979 12:00AM