Velocity Obstacle Based Conflict Avoidance in Urban Environment with Variable Speed Limit

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Current investigations into urban aerial mobility, as well as the continuing growth of global air transportation, have renewed interest in conflict detection and resolution (CD&R) methods. The use of drones for applications such as package delivery, would result in traffic densities that are orders of magnitude higher than those currently observed in manned aviation. Such densities do not only make automated conflict detection and resolution a necessity, but will also force a re-evaluation of aspects such as coordination vs. priority, or state vs. intent. This paper looks into enabling a safe introduction of drones into urban airspace by setting travelling rules in the operating airspace which benefit tactical conflict resolution. First, conflicts resulting from changes of direction are added to conflict resolution with intent trajectory propagation. Second, the likelihood of aircraft with opposing headings meeting in conflict is reduced by separating traffic into different layers per heading–altitude rules. Guidelines are set in place to make sure aircraft respect the heading ranges allowed at every crossed layer. Finally, we use a reinforcement learning agent to implement variable speed limits towards creating a more homogeneous traffic situation between cruising and climbing/descending aircraft. The effects of all of these variables were tested through fast-time simulations on an open source airspace simulation platform. Results showed that we were able to improve the operational safety of several scenarios
Original languageEnglish
Article number93
Number of pages32
JournalAerospace — Open Access Aeronautics and Astronautics Journal
Issue number4
Publication statusPublished - 2021


  • Air traffic control (ATC)
  • BlueSky ATC Simulator
  • Conflict detection and resolution (CD&R)
  • Deep deterministic policy gradient (DDPG)
  • Reinforcement learning (RL)
  • Self-separation
  • Solution space diagram (SSD)
  • U-space
  • Variable speed limit (VSL)
  • Velocity obstacles (VOs)


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