Flow

Flow data provides information about how traffic is moving along specific roadways. For each segment of the road network that is covered, flow provides speed values, along 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:

in - geospatial filter
locationReferencing - location references

For more information about how to use these parameters, see:

Additionally, there are three more filter parameters:

minJamFactor and maxJamFactor filter the response based on the currentFlow.jamFactor value. For more information, see how to filter flow by jam factor.
functionalClasses filters the locations in the response by the functional road class of the roadway that is represented. For more information, see how to filter flow by functional class.
The advancedFeatures parameter is used to request that advanced traffic features are included in the response. For more information, see the Advanced Traffic.

📘
Note
Requests that include the advancedFeatures parameter will fall into the transaction category based on Advanced Traffic. For more information, see the HERE platform terms and conditions.

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.

For more information on the location reference object, see Location referencing.

Speeds

A current flow object contains 3 speed values:

freeFlow - the reference speed (in meters per second) along the roadway when no traffic is present.
speed - the expected speed (in meters per second) along the roadway; will not exceed the legal speed limit.
speedUncapped - the expected speed (in meters per second) 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, between 0.0 and 10.0, indicate the expected quality of travel.

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

The default value is 0 and is used when this attribute is not present.

Traversability

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

open - the roadway is open and can be driven upon.
closed - the roadway is closed (blocked) and cannot be driven (jamFactor is 10.0) upon.
reversibleNotRoutable - the roadway is reversible but is currently not routable. See below for more information.

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 occur due to construction or major accidents.

The default value is open.

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 intermediateClosedEdgeOpen and the field is only present when 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.

For more information, see the Advanced Traffic.

📘
Note
Requests that include the advancedFeatures parameter will fall into the transaction category based on the Advanced Traffic. For more information, see the HERE Platform terms and conditions.

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 (distance in meters between the beginning and end of a roadway or sub-segment).

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.