Transportation Engineering - Vol 2 | 12. Traffic Stream Models by Abraham | Learn Smarter
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Knowledge
12. Traffic Stream Models

Traffic stream models are essential for understanding the relationships between traffic parameters such as speed, density, and flow. The chapter discusses various models like Greenshield's model, which assumes a linear relationship between speed and density, and other advanced models that cater to different traffic conditions. It also addresses the implications of shock waves and presents foundational equations governing traffic flow.

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Sections

  • 33

    Traffic Stream Models

    This section discusses various traffic stream models, focusing on Greenshield’s macroscopic model and its calibration, as well as other notable models.

    Learning Practice

  • 33.1

    Overview

    This section provides an overview of traffic stream models, emphasizing the relationship between traffic parameters and introducing key mathematical models.

    Learning Practice

  • 33.2

    Greenshield’s Macroscopic Stream Model

    Greenshield’s macroscopic stream model describes the relationship between traffic speed and density, establishing fundamental equations for understanding traffic flow.

    Learning Practice

  • 33.2.1

    Relationship Between Speed And Density

    This section explores the relationship between traffic speed and density as defined by Greenshield's macroscopic stream model.

    Learning Practice

  • 33.2.2

    Relationship Between Flow And Density

    This section explores the parabolic relationship between traffic flow and density, building upon Greenshield's model.

    Learning Practice

  • 33.2.3

    Boundary Conditions

    This section discusses boundary conditions in traffic stream models, focusing on jam density, free-flow speed, and maximum flow.

    Learning Practice

  • 33.3

    Calibration Of Greenshield’s Model

    In this section, we explore how to calibrate Greenshield's model to accurately represent traffic conditions by determining key parameters such as free flow speed and jam density.

    Learning Practice

  • 33.4

    Other Macroscopic Stream Models

    This section discusses various macroscopic traffic stream models that extend beyond Greenshield's linear approach, addressing the complexities of speed-density relationships in traffic flow.

    Learning Practice

  • 33.4.1

    Greenberg’s Logarithmic Model

    Greenberg's logarithmic model establishes a logarithmic relationship between traffic speed and density, gaining popularity for its analytical derivation despite its limitations at low densities.

    Learning Practice

  • 33.4.2

    Underwood Exponential Model

    The Underwood Exponential Model presents an exponential relationship between traffic speed and density as a means to address limitations within other traffic flow models.

    Learning Practice

  • 33.4.3

    Pipes’ Generalized Model

    The Pipes’ Generalized Model introduces a flexible approach to traffic flow modeling by incorporating a parameter that allows for variations in the speed-density relationship.

    Learning Practice

  • 33.4.4

    Multiregime Models

    Multiregime models address the variability of speed-density relationships in traffic streams, recognizing that driver behavior shifts at different densities.

    Learning Practice

  • 33.5

    Shock Waves

    Shock waves in traffic flow describe rapid changes in speed, density, and flow resulting from sudden disturbances.

    Learning Practice

  • 33.6

    Macroscopic Flow Models

    Macroscopic flow models provide a framework to analyze traffic flow on a large scale, treating it similar to fluid mechanics.

    Learning Practice

  • 33.7

    Summary

    Traffic stream models aim to establish relationships among key traffic parameters, such as speed, flow, and density, with various models proposed to capture these dynamics.

    Learning Practice

  • 33.8

    Problems

    This section presents a practical problem applying the Greenshield's model for traffic flow metrics.

    Learning Practice

References

33.pdf

Class Notes

Memorization

What we have learnt

  • Greenshield's model establi...
  • Other models include Greenb...
  • Shock waves in traffic can ...

Final Test

Revision Tests