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Roundabout Setup and Usage

The Roundabout feature helps you model traffic flow on circular intersections by adding a roundabout object and attaching gates directly to the ellipse.

In the Design workflow, this is available in tab:

  • 6. RoundAbount - Manage roundabout and auto movements

When to use Roundabout

Use roundabout setup when:

  • You analyze a circular intersection where vehicles enter and leave through multiple approaches

Before You Start

prepared gates

Prepare the scene first:

  1. Add and position gates in the Gates tab
  2. Set each gate type correctly:
  3. Entry = input to roundabout
  4. Exit = output from roundabout
  5. Bidirectional = both input and output
  6. Verify gates are placed close to each approach lane

The gate type decides how a gate is assigned under a roundabout.

Step 1: Add Roundabout Shape

create create

  1. Open tab 6. RoundAbount - Manage roundabout and auto movements
  2. Click Add
  3. On the video frame:
  4. First click sets the center of the roundabout
  5. Second click sets the ellipse size (radius)
  6. The roundabout appears as an ellipse with direction arrows

Step 2: Attach Gates on the Ellipse

In the editor, right-click on the roundabout ellipse and use attachment actions:

  1. Choose Add attachment here
  2. Select the gate ID from the list
  3. Repeat for all gates connected with the roundabout
  4. Drag attachment points along the ellipse to correct angle positions

The scene tree shows attachments as: GateId @ angle.

Step 3: Classification Uses Synthetic Roundabout Movements

create create create

  1. Roundabout movements are generated internally from attachments
  2. They are used by classification and grouping automatically
  3. They are not added to editable Movements list, so the scene is not cluttered

Step 4: Set Correct Rotation Direction

Roundabout movements depend on rotation direction.

create create 1. Check the roundabout(s) in the tree (top-level checkbox) 2. Click Reverse to switch direction: - Clockwise -> CounterClockwise - CounterClockwise -> Clockwise 3. After changing direction, synthetic trajectories are recalculated automatically

Optional: Draw a Custom Movement Through Roundabout

If needed, you can still draw editable movements manually in Movements mode:

  1. Start on an Entry or Bidirectional gate
  2. Click through the desired path (optional intermediate points)
  3. Pass through the roundabout area
  4. Finish on an Exit or Bidirectional gate

This is useful for non-standard geometry or special traffic patterns. Manual movements and synthetic roundabout movements can work together.

Editing and Cleanup

  • Delete: remove selected roundabout by clicking it in image
  • Clear: remove all roundabouts from the current configuration
  • Removing a gate from the configuration also removes its roundabout assignment

Best Practices

  1. Place gates close to physical entries/exits of the roundabout
  2. Keep one roundabout object per physical roundabout center

Troubleshooting

I cannot create a roundabout

  • Make sure you clicked Add in the RoundAbount tab
  • You must provide two clicks: center and ellipse edge

Generated movements look wrong

  • Verify gate types (Entry/Exit/Bidirectional)
  • Verify attachment positions and angles on the ellipse
  • Use Reverse if traffic circulation direction is opposite

Too many possible exits are classified

  • This can happen when many gates are attached to one roundabout
  • Remove unnecessary attachments or adjust attachment angles