An Analytical Formulation of Dynamic Multi-Stage Merging Process with Tight Integration of Efficiency and Safety Objectives and Flexible Merging Point Selection

Vehicle merging maneuver at freeway on-ramps is a significant trigger for traffic congestion, accidents, and oscillation. While many individual vehicle-based or cooperative driving automation-based merging control algorithms have been developed in the literature, a few notable issues remain unaddressed. First, a key parameter to analytically describe traffic flow dynamics at the merging area, effective discharge rate, has not been well formulated even though evidence from the field suggested discounts in capacity due to the lane-changing and merging behaviors. Next, most research assumed a predefined merging point, which simplifies the modeling process and solution, however, is not consistent with real-world driving behavior. Last but not the least, an analytical formulation that tightly integrates traffic flow efficiency and safety, as the two main objectives in freeway merging, have not been fully explored in the literature.

To fill these research gaps, this manuscript proposes an analytical formulation approach to model the dynamic multi-stage merging process, with a tight integration of traffic flow efficiency and merging safety, as well as flexible merging point selection strategies. We start by characterizing the multi-stage dynamic merging process and the underlying traffic dynamics with Newell’s simplified car-following model and triangle fundamental diagram, as well as defining the state of the merging vehicles and the dynamic state transition of the merging process. The effective charge rate at the merging point location is analytically derived with a mathematically simple expression, in a closed form, based on which we then derive the dynamic traffic flow performance measurements including the length of the queue and the traffic delay. A crash risk function is also defined to quantitatively measure the risks of crashes during this multi-stage merging process. A dynamic programming problem is then formulated to jointly minimize the delay and crash risk. The derived effective discharge rate is validated using the NGSIM dataset. Numerical experiments are conducted, and the results show that the proposed model with a flexible merging point outperforms the benchmark algorithm, achieving a more efficient and safer merging process.

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Work Title An Analytical Formulation of Dynamic Multi-Stage Merging Process with Tight Integration of Efficiency and Safety Objectives and Flexible Merging Point Selection
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Open Access
Creators
  1. Qing Tang
  2. Xianbiao Hu
Keyword
  1. Freeway merging
  2. Capacity drop
  3. Effective discharge rate
  4. Dynamic programming
  5. Connected and automated vehicles
License In Copyright (Rights Reserved)
Work Type Research Paper
Publication Date 2022
Deposited February 20, 2023

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Version 1
published

  • Created
  • Updated
  • Added Creator Qing Tang
  • Added Creator Xianbiao Hu
  • Added CAV freeway ramp merging control_TRB.pdf
  • Updated License Show Changes
    License
    • https://rightsstatements.org/page/InC/1.0/
  • Published
  • Updated Keyword Show Changes
    Keyword
    • Freeway merging, Capacity drop, Effective discharge rate , Dynamic programming, Connected and automated vehicles
  • Updated