Flow

Flow data provides information about how traffic is moving along specific roadways. For each segment of the road network which is covered, flow provides speed values together with additional information characterizing the traffic conditions.

Note

While flow information indicates closed roads via the jamFactor field, for use cases where closures are of specific interest, Incidents should be used instead.

Request Parameters

There are two mandatory request parameters when getting flow or incident data. For details, see the respective concept pages:

  • in - geospatial filter
  • locationReferencing - location references

For more details about how to use these parameters, see Geospatial Filters and Location Referencing.

Additionally, there are three further filter parameters:

  • minJamFactor and maxJamFactor filter the response based on the currentFlow.jamFactor value. For further details, see the flow use case Filter by Jam Factor.
  • functionalClasses filters the locations in the response by the Functional Road Class of the roadway that is represented. For further details, see the flow use case Filter FLow by Functional Class.

Finally, the advancedFeatures parameter is used to request that advanced traffic features are included in the response. For more information, see Deep Coverage Flow and Lane Level Flow.

Note

Requests which include the advancedFeatures parameter will fall into the transaction category based on the Advanced Traffic. Refer to HERE Platform Terms for details.

Response Data Model

The response from the flow endpoint provides a list of flow objects together with the last updated time of the source data.

Each flow object consists of a location field containing a location reference and a currentFlow field describing the current traffic conditions.

The location reference object is described under Location Referencing.

Speeds

A current flow object contains 3 speed values:

  • freeFlow - the reference speed along the roadway when no traffic is present
  • speed - the expected speed along the roadway; will not exceed the legal speed limit
  • speedUncapped - the expected speed along the roadway; may exceed the legal speed limit

Jam Factor

The jamFactor field provides a value for the amount of traffic on the roadway. The value is between 0.0 and 10.0.

A value of 0.0 indicates that there is no congestion on the roadway. As the value approaches 10.0, it indicates increasing congestion. A value of 10.0 is reserved to represent a blocked roadway (closure).

Jam Tendency

The jamTendency field denotes whether the congestion is increasing, decreasing, or constant. The congestion tendency may take the following values.

  • +2 - rapidly increasing congestion
  • +1 - increasing congestion
  • 0 - constant congestion
  • -1 - decreasing congestion
  • -2 - rapidly decreasing congestion

Traversability

The traversability describes whether the roadway can be driven. This parameter can take one of three values:

  • open - the roadway can be driven
  • closed - the roadway cannot be driven (jamFactor is 10.0)
  • reversibleNotRoutable - the roadway is reversible and currently not routable

This traversability status is the best source of information when routing through reversible lanes. This data will be more accurate than any other source, including the base map data, as published reversible information can be changed based on daily traffic flow or special events.

The application can deal with reversibleNotRoutable in any way, but it is recommended that it is used to indicate "not routable" and to not show traffic on this roadway in map display.

For reversible roads, both directions will not be routable for portions of the day when the road direction is being switched. There is a possibility that portions of a reversible road will be marked as closed rather than reversibleNotRoutable; when this happens, both directions of the reversible roadway will be closed, which can happen for construction or major accidents.

Junction Traversability

This parameter indicates junction traversability and is used for road closures to indicate if the junctions along the closure can be crossed.

  • allOpen - all junctions are open
  • allClosed - all junctions are closed
  • intermediateClosedEdgeOpen - junctions at the beginning and end of the roadway are open, intermediate junctions are closed
  • startOpenOthersClosed - first edge junction is open, all others are closed
  • endOpenOthersClosed - last edge junction is open, all others are closed

The default value is allOpen and the field will only be present if the value differs from this default.

Confidence

The value of the confidence field indicates the proportion of real time data included in the speed calculation. It is a normalized value between 0.0 and 1.0 with the following meaning:

  • 0.7 < confidence <= 1.0 indicates real time speeds
  • 0.5 < confidence <= 0.7 indicates historical speeds
  • 0.0 < confidence <= 0.5 indicates speed limit

This field can be used to identify whether the data for a location is derived from real time probe sources or historical information only. All confidence data 0.71 and above is based on real-time information, where a confidence value of 0.75 or greater indicates high confidence real-time information. A confidence value equal to 0.70 means that the data is derived from historical data only.

Lanes

The lanes field will be present only when there is lane level flow data for the current flow roadway and the advancedFeatures parameter contains lanes.

Note

Requests which include the advancedFeatures parameter will fall into the transaction category based on the Advanced Traffic. Refer to HERE Platform Terms for details.

For more details on the contents of the lanes field, see Lane-Level Flow.

Sub-Segments

In many cases, there is flow data available on a more granular scale than the location referencing scheme used. In these cases, the subSegments field will contain two or more sub-segment objects.

The sub-segments are ordered in the direction of travel and together sum up to the entire roadway described in the current flow object they appear on. Each sub-segment has a length field which determines the portion of the roadway that it covers.

In addition to the length field, the sub-segment object contains all the fields that appear on a current flow object, except the subSegments field itself.

Advanced Features

Note

Requests which include the advancedFeatures parameter will fall into the transaction category based on the Advanced Traffic. For details, refer to HERE Platform Terms.

Deep Coverage Flow

Deep coverage for flow can be requested by including the deepCoverage option in the advancedFeatures parameter.

Deep Coverage provides a major traffic coverage increase focused on urban roads in cities.

Lane Level Flow

In some cases, there is flow information available for specific lanes of a multilane roadway, mostly motorways/freeways and major roads.

Lane level for flow can be requested by including the lanes option in the advancedFeatures parameter.

The lanes parameter will enable flow defined per separate lanes heading in the same direction, this includes standard split lanes as well as HOV lanes.

Lane level traffic can be represented for a whole roadway in the CurrentFlow object or for a sub-segment under a SubSegment object. When lane level flow is provided, the non-lane-level speed is also provided so that even when lane level traffic is requested, the client can opt to not use the lane level information.

Each lane object has the following fields:

  • laneNumbers - list of lanes associated with this traffic, left most lane = 1, right most lane = n (lane 1 will always be the left most lane, independent of the driving side)
  • laneType - populated to indicate special lane type hov, see below for details
  • speedUncapped - uncapped speed as described for flow
  • jamFactor - jamFactor as describe for flow <!--
  • laneType - populated to indicate special lane types hov and atl, see below for details
  • speedUncapped - uncapped speed as described for flow, will not be filled for laneType=atl and will instead be within arterialLanes
  • jamFactor - jamFactor as describe for flow, will not be filled for laneType=atl and will instead be within arterialLanes
  • arterialLanes - only populated when laneType is atl, see Arterial Turn Lane (ATL) for details -->

High-Occupancy Vehicle (HOV) Lane

Lanes with laneType of hov are designated High-Occupancy Vehicle lanes. Their use is restricted depending on local road regulations. HOV lanes are not present in all countries.

HOV lanes will only be provided when the advancedFeatures parameter contains lanes.

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