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Characterizing Traffic Conditions in Urban Areas

Author

Listed:
  • Robert Herman

    (The University of Texas at Austin, Texas)

  • Siamak Ardekani

    (The University of Texas at Austin, Texas)

Abstract

A series of vehicular traffic experiments conducted in Austin, Texas, shows the reasonableness of the two assumptions in the two-fluid (moving and stopped vehicles) model of town traffic. The observational data support the assumption that the average speed in an urban street network is proportional to the fraction of the vehicles moving raised to a power and is also in agreement with the supposition that during relatively uniform periods the traffic is ergodic. An important consequence is that the average of the fraction of time stopped for a test vehicle circulating in a street network is approximately equal to the average fraction of the vehicles stopped in the system during the same test period. The parameters of the two-fluid model and the observed ranges of trip time and stop time per unit distance have been shown to be effective in assessing or rank ordering the relative quality of traffic service in a number of Texas cities; comparisons are made with various cities around the world. The two-fluid methodology appears to be useful in a preliminary “before”/“after” study during which signal timing changes were made. Finally, a preliminary analysis of aerial photographic data in two cities allows the determination of an additional two-fluid model parameter, p , in the relation stating that the fraction of vehicles stopped is given by the ratio of concentration to the jam or maximum concentration raised to a power, p . It is suggested that this parameter may be useful in describing the relative quality of various traffic systems.

Suggested Citation

  • Robert Herman & Siamak Ardekani, 1984. "Characterizing Traffic Conditions in Urban Areas," Transportation Science, INFORMS, vol. 18(2), pages 101-140, May.
    • Handle: RePEc:inm:ortrsc:v:18:y:1984:i:2:p:101-140
    DOI: 10.1287/trsc.18.2.101
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    Citations

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    Cited by:

    1. Daganzo, Carlos F., 2011. "On the macroscopic stability of freeway traffic," Transportation Research Part B: Methodological, Elsevier, vol. 45(5), pages 782-788, June.
    2. Geroliminis, Nikolaos, 2007. "Increasing mobility in cities by controlling overcrowding," Institute of Transportation Studies, Research Reports, Working Papers, Proceedings qt5wg9j6z7, Institute of Transportation Studies, UC Berkeley.
    3. Geroliminis, Nikolas & Daganzo, Carlos F., 2008. "Existence of urban-scale macroscopic fundamental diagrams: Some experimental findings," Transportation Research Part B: Methodological, Elsevier, vol. 42(9), pages 759-770, November.
    4. Sun, Bin & Zhang, Qijun & Hu, Le & Zou, Chao & Wei, Ning & Jia, Zhenyu & Zhao, Xiaoyang & Peng, Jianfei & Mao, Hongjun & Wu, Zhong, 2023. "A prediction-evaluation method for road network energy consumption: Fusion of vehicle energy flow principle and Two-Fluid theory," Physica A: Statistical Mechanics and its Applications, Elsevier, vol. 626(C).
    5. Daganzo, Carlos F., 2010. "On the Stability of Freeway Traffic," Institute of Transportation Studies, Research Reports, Working Papers, Proceedings qt4vf597r5, Institute of Transportation Studies, UC Berkeley.
    6. Liu, Ronghui & May, Tony & Shepherd, Simon, 2011. "On the fundamental diagram and supply curves for congested urban networks," Transportation Research Part A: Policy and Practice, Elsevier, vol. 45(9), pages 951-965, November.
    7. Jiayu Ding & Yuewei Wang & Chaoyue Li, 2024. "A Dual-Layer Complex Network-Based Quantitative Flood Vulnerability Assessment Method of Transportation Systems," Land, MDPI, vol. 13(6), pages 1-27, May.
    8. Geroliminis, Nikolas & Daganzo, Carlos F., 2007. "Existence of urban-scale macroscopic fundamental diagrams: Some experimental findings," Institute of Transportation Studies, Research Reports, Working Papers, Proceedings qt2rq792j1, Institute of Transportation Studies, UC Berkeley.
    9. Gayah, Vikash V. & Daganzo, Carlos F., 2011. "Clockwise hysteresis loops in the Macroscopic Fundamental Diagram: An effect of network instability," Transportation Research Part B: Methodological, Elsevier, vol. 45(4), pages 643-655, May.
    10. Williams, James C. & Mahmassani, Hani S. & Herman, Robert, 1995. "Sampling strategies for two-fluid model parameter estimation in urban networks," Transportation Research Part A: Policy and Practice, Elsevier, vol. 29(3), pages 229-244, May.
    11. Stamos, Iraklis & Salanova Grau, Josep Maria & Mitsakis, Evangelos, 2013. "Μακροσκοπικά Θεμελιώδη Διαγράμματα: Ευρήματα Μέσω Προσομοίωσης Για Το Οδικό Δίκτυο Της Θεσσαλονίκης [Macroscopic fundamental diagrams: Simulation based findings from the road network of Thessalonik," MPRA Paper 61538, University Library of Munich, Germany.
    12. Aghamohammadi, Rafegh & Laval, Jorge A., 2020. "Dynamic traffic assignment using the macroscopic fundamental diagram: A Review of vehicular and pedestrian flow models," Transportation Research Part B: Methodological, Elsevier, vol. 137(C), pages 99-118.
    13. Amini, Behnam & Shahi, Jalil & Ardekani, Siamak A., 1998. "An observational study of the network-level traffic variables," Transportation Research Part A: Policy and Practice, Elsevier, vol. 32(4), pages 271-278, May.

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