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OCC-MP: A Max-Pressure framework to prioritize transit and high occupancy vehicles

Tanveer Ahmed, Hao Liu, Vikash V. Gayah

TL;DR

This paper addresses the limitation of Max Pressure (MP) signal control, which treats transit and high-occupancy vehicles like private cars. It introduces OCC-MP, an occupancy-aware MP variant that weights movements by upstream occupancy to implicitly prioritize transit and high-occupancy travel while preserving MP’s stability properties. The authors prove maximum stability for isolated intersections and demonstrate through microsimulation on a grid network that OCC-MP improves transit performance and overall passenger travel time, with robust performance under occupancy errors and partial connected-vehicle penetration. OCC-MP also remains effective in shared-lane networks without dedicated bus lanes, offering a practical, CV-compatible approach to transit signal priority without heavily constraining private-vehicle throughput. The work highlights OCC-MP’s potential to reduce dependence on dedicated lanes while supporting more efficient and reliable multimodal urban traffic.

Abstract

Max-pressure (MP) is a decentralized adaptive traffic signal control approach that has been shown to maximize throughput for private vehicles. However, MP-based signal control algorithms do not differentiate the movement of transit vehicles from private vehicles or between high and single-occupancy private vehicles. Prioritizing the movement of transit or other high occupancy vehicles (HOVs) is vital to reduce congestion and improve the reliability and efficiency of transit operations. This study proposes OCC-MP: a novel MP-based algorithm that considers both vehicle queues and passenger occupancies in computing the weights of movements. By weighing movements with higher passenger occupancies more heavily, transit and other HOVs are implicitly provided with priority, while accounting for any negative impacts of that priority on single occupancy vehicles. And, unlike rule-based transit signal priority (TSP) strategies, OCC-MP more naturally also accommodates conflicting transit routes at a signalized intersection and facilitates their movement, even in mixed traffic without dedicated lanes. Simulations on a grid network under varying demands and transit configurations demonstrate the effectiveness of OCC-MP at providing TSP while simultaneously reducing the negative impact imparted onto lower occupancy private vehicles. Furthermore, OCC-MP is shown to have a larger stable region for demand compared to rule-based TSP strategies integrated into the MP framework. The performance of OCC-MP is also shown to be robust to errors in passenger occupancy information from transit vehicles and can be applied when passenger occupancies of private vehicles are not available. Finally, OCC-MP can be applied in a partially connected vehicle (CV) environment when a subset of vehicles is able to provide information to the signal controller, outperforming baseline methods at low CV penetration rates.

OCC-MP: A Max-Pressure framework to prioritize transit and high occupancy vehicles

TL;DR

This paper addresses the limitation of Max Pressure (MP) signal control, which treats transit and high-occupancy vehicles like private cars. It introduces OCC-MP, an occupancy-aware MP variant that weights movements by upstream occupancy to implicitly prioritize transit and high-occupancy travel while preserving MP’s stability properties. The authors prove maximum stability for isolated intersections and demonstrate through microsimulation on a grid network that OCC-MP improves transit performance and overall passenger travel time, with robust performance under occupancy errors and partial connected-vehicle penetration. OCC-MP also remains effective in shared-lane networks without dedicated bus lanes, offering a practical, CV-compatible approach to transit signal priority without heavily constraining private-vehicle throughput. The work highlights OCC-MP’s potential to reduce dependence on dedicated lanes while supporting more efficient and reliable multimodal urban traffic.

Abstract

Max-pressure (MP) is a decentralized adaptive traffic signal control approach that has been shown to maximize throughput for private vehicles. However, MP-based signal control algorithms do not differentiate the movement of transit vehicles from private vehicles or between high and single-occupancy private vehicles. Prioritizing the movement of transit or other high occupancy vehicles (HOVs) is vital to reduce congestion and improve the reliability and efficiency of transit operations. This study proposes OCC-MP: a novel MP-based algorithm that considers both vehicle queues and passenger occupancies in computing the weights of movements. By weighing movements with higher passenger occupancies more heavily, transit and other HOVs are implicitly provided with priority, while accounting for any negative impacts of that priority on single occupancy vehicles. And, unlike rule-based transit signal priority (TSP) strategies, OCC-MP more naturally also accommodates conflicting transit routes at a signalized intersection and facilitates their movement, even in mixed traffic without dedicated lanes. Simulations on a grid network under varying demands and transit configurations demonstrate the effectiveness of OCC-MP at providing TSP while simultaneously reducing the negative impact imparted onto lower occupancy private vehicles. Furthermore, OCC-MP is shown to have a larger stable region for demand compared to rule-based TSP strategies integrated into the MP framework. The performance of OCC-MP is also shown to be robust to errors in passenger occupancy information from transit vehicles and can be applied when passenger occupancies of private vehicles are not available. Finally, OCC-MP can be applied in a partially connected vehicle (CV) environment when a subset of vehicles is able to provide information to the signal controller, outperforming baseline methods at low CV penetration rates.
Paper Structure (20 sections, 1 theorem, 18 equations, 14 figures, 3 tables, 1 algorithm)

This paper contains 20 sections, 1 theorem, 18 equations, 14 figures, 3 tables, 1 algorithm.

Table of Contents

  1. Introduction
  2. Method
  3. Max Pressure
  4. Proposed OCC-MP policy
  5. Maximum stability for isolated intersections
  6. Simulation Setup
  7. Network setup
  8. Scenario setup
  9. Results
  10. Scenario 1: Non-connected vehicle environment
  11. Vehicle travel time comparison
  12. Passenger travel time comparison
  13. Network stability comparison
  14. Sensitivity to APC errors
  15. Scenario 2: Connected vehicle environment
  16. ...and 5 more sections

Key Result

Theorem 1

Assume the expected value of the average occupancy of a movement is independent of the queue length of that movement, the proposed OCC-MP algorithm stabilizes the queue process for isolated intersections if $\mathbf{d}\in \pazocal{D}^0$.

Figures (14)

  • Figure 1: Example of transit signal priority using OCC-MP.
  • Figure 2: Network configuration.
  • Figure 3: Lane configuration and phases.
  • Figure 4: Time varied demand.
  • Figure 5: Average vehicle speeds under Q-MP across sub-scenarios.
  • ...and 9 more figures

Theorems & Definitions (4)

  • Definition 1
  • Definition 2
  • Theorem 1: Maximum stability
  • proof