Traffic Management¶

How robots share space and avoid conflicts.

Overview¶

Traffic management ensures robots navigate efficiently without collisions or deadlocks. It's critical for warehouse performance.

Topic	Description
Capacity	Node and edge capacity limits
Congestion	Traffic buildup and measurement
Deadlock	Detection and prevention
Reservations	Space reservation systems

The Traffic Problem¶

Shared Resources¶

Robots share limited space:

Nodes: Discrete locations
Edges: Paths between nodes

Conflicts¶

What happens when resources are contested:

Robot A wants: N1 → N2 → N3
Robot B wants: N4 → N2 → N5
                    ↑
                Conflict at N2

Traffic Model¶

Capacity-Based¶

Each node and edge has maximum occupancy:

traffic:
  node_capacity_default: 1
  edge_capacity_default: 1

Collision Prevention¶

When at capacity:

New robots wait
Or reroute (if configured)

Traffic States¶

Free Flow¶

All robots move without delay:

Resources < Capacity everywhere
Wait time ≈ 0

Congested¶

Some delays occur:

Some resources at capacity
Wait time > 0
Throughput reduced

Gridlock¶

Movement stops:

Circular waiting
Deadlock potential
Intervention needed

Traffic Visualization¶

Light Traffic¶

[N1]     [N2]     [N3]
  ●───────────────●
        R1 →

Moderate Traffic¶

[N1]     [N2]     [N3]
  ●───────●───────●
     R1 →    R2 →

Heavy Traffic¶

[N1]     [N2]     [N3]
  ●───────●───────●
     R1    R2 R3
       ↑
    Waiting

Traffic Management Strategies¶

Reactive¶

Respond to congestion:

Wait when blocked
Reroute when path congested
Queue at destinations

Proactive¶

Prevent congestion:

Reserve paths ahead
Route around busy areas
Coordinate movements

Hybrid¶

Combine approaches:

Reserve critical sections
React to unexpected congestion
Balance efficiency and safety

Configuration Overview¶

traffic:
  # Capacity limits
  node_capacity_default: 1
  edge_capacity_default: 1

  # Congestion handling
  wait_on_blocked: true
  reroute_on_congestion: false
  reroute_threshold: 3.0

  # Deadlock prevention
  deadlock_detection: true
  deadlock_resolution: priority

Performance Impact¶

Throughput vs. Fleet Size¶

Throughput
    │
    │         ┌──── Congestion limit
    │        /│
    │       / │
    │      /  │
    │     /   │
    │    /    │
    │   /     │
    │  /      │
    │ /       │
    │/        │
    └─────────┴─────── Fleet Size
              ↑
        Optimal size

Key Relationships¶

More robots → More congestion
Better traffic management → Higher optimal fleet size
Poor layout → Lower congestion threshold