The Multi-Traffic Lane widget enables configuration and monitoring of multiple traffic lanes, allowing precise lane-level traffic analysis. It is exclusively available through the OPC UA interface. Data generated by this widget is not accessible via other communication methods.
OPC UA Protocol
OPC UA is a platform-independent communication protocol that allows different systems to share data securely and reliably, making it a good choice for connecting FLOW with automated traffic control systems (ATMS).
FLOW communicates traffic data to ATMS through two core OPC UA data structures: TrafficData and TrafficEvents. These can be independently configured and are transmitted at regular intervals over the OPC UA protocol.
TrafficData
Captures statistical summaries (e.g. speed, occupancy, counts) aggregated over fixed time blocks for each traffic lane.TrafficEvents
Reports incident-based alarms (e.g. wrong-way driving) within the same time block structure. Events are logged if they occur at any point during a block, even if they have resolved by its end.
You can read more about the OPC UA protocol here. For integration with FLOW using the public API refer to the FLOW Public API documentation: API Documentation.
Traffic Lane Spatial Filter
The Traffic Lane spatial filter is a core UI element used to define specific traffic lanes. Similar to standard zone filters, it is represented by a polygon drawn over the lane area in the camera view, where vehicle trajectories are detected and evaluated.
Key attributes and components of the TrafficLane spatial filter include:
Section Gates: Two orange lines used to calculate vehicle speed and level of service. Their placement and angle define the expected direction of movement.
Decision Gate: A green line that validates which trajectories are counted toward the lane’s data. Only vehicles passing through this gate are included in TrafficData.
Name
OPC UA Lane Identifier: Assigns an ATMS identifier to the lane name.
Lane Coloring
Reversibility Support: Enables direction switching of the lane, which affects how right-way and wrong-way movements are interpreted.
Section length: Used to calculate the speed and level of service statistics.
Directional Widget: Defines the expected movement direction (Pass Angle) and allowed deviation (Angle Tolerance). By default, pass angles are derived from the section gates; tolerance is ±90°.
Defining a Traffic Lane – Tips
Define Control Points: Draw the polygonal shape of the lane in the camera view. Use the snap-on feature to align adjacent points precisely.
Adjust Gates: Position the section gates across the TL area and place the decision gate within the polygon to capture entering vehicles. Since OPC UA operates on fixed time blocks, it is recommended to place decision gates close together.
Configure Directionality: Set the Pass Angle and Angle Tolerance visually or by entering values, according to the expected traffic flow.
Multi-Traffic Lane Operator
The Multi-Traffic Lane (MTL) operator allows grouping of several traffic lanes to handle intersecting or overlapping trajectory scenarios with clarity. Only one MTL operator can be configured per analytic, but the same traffic lanes may be reused across other analytics.
Traffic Lane Priority and Data Reporting
Users define a list of traffic lanes and assign them priority order. When a vehicle trajectory intersects more than one decision gate, the lane with the highest priority is selected. Each traffic lane can be set to report:
Only TrafficData
Only TrafficEvents
Both
Additional Configuration
Under the OPC UA settings in FLOW (Block -> Interfaces -> OPC UA interfaces), more detailed configuration options are available. These include general interface parameters (such as Name and ID), as well as advanced controls for traffic counting and statistical outputs.
Virtual Detector Length
Defines a virtual detector length used in occupancy calculations. This is not linked to a physical object but is used for formal occupancy metrics.
Time Block Size
Configure the time block duration used for data aggregation. Separate values can be set for TrafficData and TrafficEvents.
Vehicle Category Settings
FLOW offers advanced configuration options for handling different vehicle categories when communicating with ATMS. These options ensure compatibility and allow fine-tuning of statistical calculations:
Category Mapping to ATMS Types:
Since ATMS may define its own vehicle types, FLOW provides a mapping table to match internal categories with external ones. This ensures consistent data interpretation across systems.Virtual Average Length per Category:
Users can assign an average length to each vehicle type. These values are used in calculations such as zone occupancy, without requiring physical measurement.Include/Exclude from Non-Count Statistics:
While all trajectories are included in count-based statistics by default, users may choose to exclude specific categories from selected non-count metrics — namely:Occupancy in a zone
Speed measurement
Level of Service (LoS) Calculation Thresholds
Each Traffic Lane is assigned a Level of Service (LoS) category based on the average speed of vehicles within a time block. According to the OPC UA standard, six service levels are defined. These default thresholds can be adjusted to better match local traffic conditions.
LoS (Level of Service) | Average speed [km/h] |
Breakdown (marked 6-F) | 0 - 12 |
Extremely unstable (marked 5-E) | 12 - 18 |
Borderline unstable (marked 4-D) | 18 - 32 |
Stable operation (marked 3-C) | 32 - 40 |
Reasonably free flow (marked 2-B) | 40 - 64 |
Free flow (marked 1-A) | 64 + |
What Next?
Learn more about widgets and sinks in FLOW, explore time processing, or check out other widget types such as Value and Movement Set Statistics. Use the FLOW Public API to access data from widgets and sinks and integrate it with your external systems.
Make your traffic analytics smarter and more connected with FLOW.