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Erstellt / Aktualisiert 20.06.2021 / 04.07.2021
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Capacity drop phenomena

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  • Many studies have revealed that there is a stochastic nature of bottleneck capacities.
  • Banks (1991) first suggested that discharge flow at bottlenecks diminishes once queues start forming upstream of the location
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What is a model?

A set of mathematical equations (or rules) that tries to describe (i.e. replicate) a physical process (e.g. evolution of traffic congestion over time and space)

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Why do we need models?

  • Process analysis and understanding
  • Planning (forecasting)
    - introduction of a new mode (multimode)
    - modification/extension of infrastructure
  • Operations (control)
    - Design of model-based control strategies
    - Estimation/prediction models
    - Testing the control performance
  • Traffic simulation
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Classification of traffic models

  • Microscopic (mainly for simulation):
    car following + lane changing
     
  • Mesoscopic
    vehicle platoons with similar characteristics
     
  • Macroscopic
    macroscopic traffic variables (in analogy to fluid mechanics)
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Car-following model

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Macroscopic traffic flow models

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Traffic flow control - Supply

  • Urban traffic lights
  • Ramp metering
  • Variable speed limits (VSL)
  • Variable message signs (VMS)
  • Route guidance
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Traffic flow control - Demand

  • Car pooling
  • Congestion pricing
  • Mode choice