Get real-time traffic conditions for a location

Objectives: Retrieve real-time traffic from the HERE Traffic Flow catalog.

Complexity: Beginner

Prerequisites: Get your credentials, Verify Your credentials

Time to complete: 30 min

Source code: Download

This tutorial introduces HERE Traffic Flow catalog and shows how to get information about traffic conditions data using this catalog.

The tutorial covers the following topics:

HERE Traffic Flow catalog overview

HERE Traffic Flow catalog helps drivers reach their destinations efficiently and in a stress-free manner. The catalog delivers up-to-the-minute information about traffic conditions and incidents that could cause delays, including slower-than-normal traffic flow, roadworks and accidents. Moreover, it enables the display of traffic conditions on highways or arterials and is an ingredient to calculating traffic-aware expected time of arrival (ETA).

Real-time traffic data is produced by a sophisticated model that aggregates and analyzes a mix of sources, including high-quality rich vehicle sensor data. The result: best-in-class accuracy in depicting real-world traffic conditions.

HERE Traffic Flow catalog allows to build a better traffic management solution with access to one of the largest aggregated real-time databases.

The following figure shows real-time traffic with information about the average speed and jam factor:

Get catalog information

HERE Traffic Flow is a public catalog that provides a live depiction of conditions on the road. It can identify traffic congestion and deliver live information on road conditions and incidents to the driver.

To get the basic catalog information, you use the platform portal or run the following CLI command:

olp catalog show hrn:here:data::olp-here:here-traffic-flow-v2

The output should contain the following information:

ID                       here-traffic-flow-v2
name                     HERE Traffic Flow (new)
HRN                      hrn:here:data::olp-here:here-traffic-flow-v2
summary                  "HERE RealTime Traffic Flow" provides live information on traffic conditions on roadways.
description              "HERE RealTime Traffic Flow" provides a live depiction of conditions on the road. It identifies where traffic congestion occurs, and how bad it is, delivering minute-by-minute information on road conditions that could set a driver back.

Real-time traffic data is produced by a sophisticated model that aggregates and analyzes a mix of sources, including high-quality rich vehicle sensor data.

The result: best-in-class accuracy in depicting real-world traffic conditions.
notifications enabled?   false
tags                     TrafficItem, TrafficItems, flow, traffic, RealtimeTraffic
billing tags             10648TAppsProd
created                  2022-02-11T21:10:59.475863Z
owner                    HERE-e64d84b3-556e-4f69-ac85-e615cc2c2cab, olp-here
config version           4
metadata version         -1
metadata minimum version -1
marketplace ready        false
layers                   
type         ID                                 name
volatile     realtime-traffic-flow-volatile     RealTime Traffic Flow (v2)
replication              
role                ID             
primary             eu-ireland

Based on the output, you can see that the HERE Traffic Flow consists of one layer. The RealTime Traffic Flow (v2) layer provides the current speed of traffic on roads. Powered by HERE Traffic, the speeds are updated every minute.

In the following tutorial, the realtime-traffic-flow-volatile layer is used to get information about real-time traffic. Let's get familiar with the realtime-traffic-flow-volatile layer.

Check out the realtime-traffic-flow-volatile layer in the platform portal or run the following OLP CLI command to get the information about the layer:

olp catalog layer show hrn:here:data::olp-here:here-traffic-flow-v2 realtime-traffic-flow-volatile

The output should contain the following information:

Details of the realtime-traffic-flow-volatile layer:

ID                  realtime-traffic-flow-volatile
name                RealTime Traffic Flow (v2)
summary             RealtimeFlow 3.3
description         The traffic flow layer provides the current speed of traffic on roads. Powered by HERE Traffic, the speeds are updated every minute.

Each tile contains Protobuf data, which is a list of all the current traffic flow messages based on the Traffic schema. Any message which spans across multiple tiles will be reported in all tiles where it exists, with the same ID.
layerType           volatile
partitioning        heretile, tile levels: 12
partitioningScheme  heretile
volume              volatile
contentType         application/x-protobuf
schema              hrn:here:schema::olp-here:com.here.traffic.realtime:traffic_v2:2.1.15
tags                TOLP
billingTags         10648TAppsProd
coverage            US
created             2022-02-11T21:35:45.216436Z
volatileProperties  {"dataRedundancy":"multi-instance","storageCapacityMb":21000}
TTL                 3600000

Apparently, the layer is of the volatile type, which means whenever there is new data, the old data is overwritten. The information in the realtime-traffic-flow-volatile layer updates every minute. The layer has the following properties:

  • partitioning and partitioningScheme: : the layer is heretiled at Tile level 12. This sort of tiling makes it easy to perform geo-related tasks such as finding tiles in a bounding box as explained in the tutorial on calculating Tile IDs. For more information on Tiles, see the HereTileResolver [ Java API | Scala API ] class from the the Location Library Developer Guide.
  • contentType: application/x-protobuf - with this content type, the Tiles are encoded using protobuf format.
  • schema: traffic_v2 is used to decode data stored on the platform. For more information on the traffic_v2 schema, see the Use Data Schema chapter.
  • coverage shows that the realtime-traffic-flow-volatile layer covers 61 countries and values are presented as a list of ISO 3166 two-letter codes for countries.

For more information on the above properties, see Data User Guide.

Use data schema

The Real-Time Traffic schema represents a traffic condition on a given road segment.

The data stored in the traffic_v2 layer is encoded using the traffic_v2 Protobuf Schema. The traffic_v2 Protobuf Schema defines the Protocol Buffer messages and enumerations used by the various data layers in HERE Traffic Flow. The message definitions are defined in the corresponding .proto file that describes the structure of a partition in a catalog layer.

Real-time traffic conditions are provided as attributes (for example, average_speed_kph or jam_factor) for a fine-grained location grid. To describe the location, HERE uses its well-defined HERE tiling at level 12.

Let's look more closely at how the data is structured.

The traffic_v2 contains flow, lane, segment, speed, and traversability status items.

The Flow) message contains information about the speed of traffic on one or more road segments. The segments contained by a flow are determined by algorithms in the HERE platform. This message can contain multiple Segment messages. In this case the segments represent connected sections of the roadway and are ordered in the driving direction. The confidence attribute in the Flow message indicates the percentage of real-time data used in the speed calculation, where:

  • a value of 0.75 or greater indicates high confidence real-time information
  • if the value is in the range of 0.5 to 0.7 - historical speeds are used to calculate the traffic speed
  • if the value is in the range of 0.0 to 0.5 - the speed limit is used to calculate the speed of traffic
  • if the value is -1 - the road is closed.

The Segment message contains information about the flow of traffic on a section of roadway. First, let's find out what a Segment is. A Segment is a directed polyline connecting two Nodes with optional intermediate Shape Points. The logical orientation of a Segment is defined as being from its starting Node to its ending Node. This orientation is not related to the direction of travel on the Segment. However, directional attributes, such as direction of travel or speed limit, reference Segments relative to this logical orientation. A given Node may be both a start and end Node for different Segments that adjoin it. For more information about Segments, see the Topology Model.

The following figure demonstrates Segments that are connected by Nodes using the topology-geometry layer from the HERE Map Content catalog:

The Segment message describes the information about the average speed of traffic for this segment using the Speed message.

The jam_factor attribute in the Segment message describes the state of traffic jams and can range from 0.0 to 10.0 indicating how freely traffic is flowing. The start_offset attribute in the Segment message describes the offset ratio from the start of this segment in relation to the entire traffic condition.

The Segment message also describes if segments are open to traffic using the TraversabilityStatus message, which can take the following values: OPEN - if the segment is open for traffic, CLOSED - if the segment is closed for traffic, and ROAD_NOT_ROUTABLE - if the segment is restricted from carrying traffic. This can happen when both directions of the reversible road are closed, for example, for construction or in case of a major accident.

The last message used in the Segment message is the Lane message that contains information about the speed of traffic in individual lanes in a roadway. This message is only provided if there are different lane speeds along a roadway.

The message definitions can be found in the following flow.proto file:

syntax = "proto3";

package com.here.traffic.realtime.v2;

import "com/here/traffic/realtime/v2/LocationTypes.proto";

/**
The `Flow` message contains information about the speed of traffic on one or
more road segments. The segments contained by a flow are determined by
algorithms in the Open Location Platform.
*/
message Flow {
    /**
    One or more messages containing information about the flow of traffic on
    a section of roadway, or "segment". If a `Flow` message contains multiple
    `segment` messages, the segments represent
    connected sections of the roadway and are ordered in the driving direction.
    Each `segment` contains a start_offset field which defines the ratio of
    this segment to the overall Flow message. The congestion level for this
    segment is of value 1, i.e. CONSERVATIVE.
    */
    repeated Segment segment = 1;

    /**
    A number from 0.0 to 1.0 indicating the percentage of real-time data used
    in the speed calculation.
    You can use this field to identify whether the data for this `Flow` is
    derived from real-time probe sources or historical information only.
    Confidence is only available for the `Flow` message and applies to all
    `Segment` messages.

    - 0.71 to 1.0: Real-time speeds were used to calculate the traffic speed
    for the `Flow`. A value of 0.75 or greater indicates high confidence
    real-time information.

    - 0.5 to 0.7: Historical speeds were used to calculate the traffic
    speed for the `Flow`.

    - 0.0 to 0.5: The speed limit was used to calculate the speed of
    traffic for the `Flow`.

    - -1.0: The road is closed

    */
    double confidence = 2;

    /**
    DEPRECATED. Flow conditions for supplementary location reference,
    one for each applicable location type
    */
    repeated SupplementaryFlowCondition supplementary_flow_condition
        = 3 [deprecated = true];

    /**
    Additional segments for congestion levels 2 and 3.
    */
    repeated CongestionLevelCodedSegments congestion_level_coded_segments_list
        = 4;
}


/**
Congestion level Option specifies the desired level of “aggressiveness”
to represent the traffic condition.
The client can decide which CF element, if encoded, to utilize.
 */
enum CongestionLevelOption {
    UNKNOWN = 0;
    CONSERVATIVE = 1;
    MEDIUM_AGGRESSIVE = 2;
    MOST_AGGRESSIVE = 3;
}

/**
Segments coded according to congestion level option
 */
message CongestionLevelCodedSegments {
    //Congestion level option identifier
    CongestionLevelOption congestion_level_option = 1;
    //One or more segments for the congestion level
    repeated Segment segments = 2;
}

/**
The `Segment` message contains information about the flow of traffic on a
section of roadway.
*/
message Segment {
    /**
    Information about the speed of traffic for this segment.
    */
    Speed speed = 1;

    /**
    A number between 0.0 and 10.0 indicating how freely traffic is flowing.
    A value of 0 means traffic is flowing freely. A value of 10 means
    traffic is stopped.
    A value of -1.0 indicates that `jam_factor` could not be calculated.

    If a road is closed, `jam_factor` is 10.

    If a road is reversible and traffic is flowing opposite the driving direction,
    `jam_factor` is -1. This value is useful when displaying traffic on a map
    and you do not want to display the road as closed.
    */
    double jam_factor = 2;

    /**
    The offset ratio from the start of this segment in relation to the entire
    traffic condition.
    */
    double start_offset = 3;

    /**
    Specifies whether the segment is traversable.
    See `Flow.TraversabilityStatus` for valid values.
    */
    TraversabilityStatus traversability_status = 4;

    /**
    The traffic condition in each lane. The `lanes` field is only provided
    if there are different lane condition along a roadway.
    When there is lane-level traffic along a roadway, there will be two or
    more `Lane` messages in the `Segment`.
    */
    repeated Lane lanes = 5;

    //The junction traversability status.
    JunctionTraversabilityStatus junction_traversability_status = 6;

    //Length of the segment in km
    double segment_length_in_km = 7;

    //The lane type for this road segment
    BasicLaneType basic_lane_type = 8;

    //Trend of jam factor
    JamFactorTrend jam_factor_trend = 9;

    //Flow conditions and causes based on TFP
    TFPCode tfp_code = 10;

    /**
    Flow conditions and causes codes based on specification of TISA TPEG2-TFP_1.1
     */
    message TFPCode {
        //The tfp006 cause of the traffic flow.
        int32 cause_code = 1;

        //Status parameters per TFP specification.
        StatusParameters status_parameters = 2;

        //Statistical parameters per TFP specification.
        StatisticalParameters statistical_parameters = 3;

        //The vehicle restriction per TFP specification.
        Restrictions restriction = 4;
    }

    //At-grade junction traversability status. Used for road
    //closures to indicate if the closure can be crossed.
    enum JunctionTraversabilityStatus {
        UNKNOWN = 0;
        ALL_JUNCTIONS_CLOSED = 1;
        INTERMEDIATE_CLOSED_EDGE_OPEN = 2;
        ALL_JUNCTIONS_OPEN = 3;
    }

    /**
    The basic type of the lane.
    */
    enum BasicLaneType {
        //Regular traffic lane
        TRAFFIC_LANE = 0;
        //Express lane
        EXPRESS = 1;
        //Ramp lane
        RAMP = 2;
        //Entry lane;
        ENTRY = 3;
        //EXIT lane
        EXIT = 4;
    }

    /**
    The flow status parameters.
    */
    message StatusParameters {
        //The tfp003 Level Of Service code.
        int32 level_of_service = 1;
        //The achievable average speed in km/h.
        int32 average_speed_in_kmh = 2;
        //The time in seconds it takes to traverse the affected
        //road segment under free flow traffic conditions.
        int32 free_flow_travel_time_in_seconds = 3;
        //The delay on the road segment in seconds.
        int32 delay_in_seconds= 4;
    }

    /**
    The statistical parameters based on TISA TPEG2-TFP_1.1.
    */
    message StatisticalParameters {
        //The risk (%) that a congestion
        // (LOS level 'stationary traffic' or 'blocked') will occur
        // at this road section.
        int32 congestion_probability = 1;
        //TFP based value Used to determine the risk that the travel time
        // may exceed the expected travel time considerably.
        int32 t90_relative = 2;
        //The tfp008 flow data quality
        int32 flow_data_quality = 3;
        //This parameter may be used to link to a LOS prediction pattern.
        int32 prediction = 4;
    }

    /**
    tfp based information on restrictions related to the reported traffic flow
    */
    message Restrictions {
        //The tfp001 Vehicle class
        int32 vehicle_class_assignment = 1;
        //The tfp002 vehicle Credentials
        int32 vehicle_credentials = 2;
        //The tfp005 lane restrictions
        int32 lane_restriction = 3;
        //Angle of an entry/exit to the road stretch in 360/255 degree steps
        // clockwise to the direction of the road stretch at the entry/exit point
        int32 angle = 4;
        //Length affected in 10 meter steps
        int32 length_in_ten_meters_steps = 5;
    }

}

/**
   The `Speed` message contains information about the velocity of traffic
   traveling along the segment.
   */
message Speed {

    /**
    The average speed that traffic is traveling, in Kilometers per hour.
    A value of -1.0 indicates that the average speed could not be calculated.
    */
    double average_speed_kph = 1;

    /**
    The average speed that traffic is traveling, but limited to the speed limit.
    If the traffic speed is greater than the speed limit, the value of this
    field will be the speed limit instead of the actual
    traffic speed. The speed is in in Kilometers per hour.

    A value of -1.0 indicates that the average speed could not be calculated.
    */
    double average_speed_capped_kph = 2;

    /**
    The speed at which vehicles can travel the segment when there is no traffic
    congestion or other impediments such as a road closure.
    This speed is calculated as the 80th percentile of observed speeds
    during non-rush hour periods.

    Free flow is useful for understanding the level of congestion.
    When the average speed is greater than or equal to the free flow speed,
    it can be assumed that there is no traffic congestion.
    */
    double free_flow_speed_kph = 3;
}

/**
The `TraversablityStatus` field indicates whether a segment is open to traffic.

- `OPEN`: The segment is open for traffic. This includes reversible roads
that are open.
- `CLOSED`: The segment is closed to traffic. No `Speed` messages will be
provided for this segment.
- `ROAD_NOT_ROUTABLE`: The segment is restricted from carrying traffic.
In some situations, portions of a reversible road will be marked as CLOSED
rather than ROAD_NOT_ROUTABLE. This can happen when both directions of the
reversible road are closed, such as for construction or major accidents.
In a map display, we recommend that you use ROAD_NOT_ROUTABLE to indicate that
the road is not routable, the road segment is not drivable, and not to show
traffic on this roadway.
*/
enum TraversabilityStatus {
    OPEN = 0;
    CLOSED = 1;
    ROAD_NOT_ROUTABLE = 2;
}

/**
Trend of Jam Factor
 */
enum JamFactorTrend {
    CONSTANT_CONGESTION = 0;
    DECREASING_CONGESTION = 1;
    RAPIDLY_DECREASING_CONGESTION = 2;
    INCREASING_CONGESTION = 3;
    RAPIDLY_INCREASING_CONGESTION = 4;
}

/**
The `Lane` message contains information about the speed of traffic in individual
lanes in a roadway.  A `Lane` message is only provided if there are different
lane speeds along a roadway.

The number of lanes along a roadway can be determined by looking at the maximum
lane number in all `Lane` messages in the segment.
*/
message Lane {

    /**
    A list of lanes associated with the traffic. Lane numbers use the HERE Map
    method of lane numbering where the left lane is 1 and each lane to the
    right of the left lane is numbered sequentially. For example, in a
    three-lane road, the left lane is 1, the center lane is 2, and the right
    lane is 3. Lane 1 is always the left lane, regardless of the driving side.
    If multiple lane numbers are presented, all lanes will have the traffic
    condition. Lane numbers will always be sequential.
    */
    repeated int32 lane_number = 1;

    /**
    A Flow.Speed message containing the traffic speed for this lane.
    */
    Speed speed = 2;

    /**
    The jam factor for this `Lane`. See `jam_factor` field in `Segment` message
    for definition.
    */
    double jam_factor = 3;

    //Additional lane type information
    SpecialtyLaneType lane_type = 4;

    //More granular trend information of jam factor
    JamFactorTrend jam_factor_trend = 5;

    //Zero or more arterial turn lane information
    repeated ArterialTurnLane arterial_turn_lanes = 6;

    /**
    Specialty lane types
    */
    enum SpecialtyLaneType {
        REGULAR = 0;
        HOV = 1;
        ARTERIAL_TURN = 2;
    }

    /**
    ArterialTurnLane message is provided if there are one or more Arterial Turn Lane
    events associated with this lane.
     */
    message ArterialTurnLane {

        //To Bearing is the bearing associated with the Arterial Turn
        //Lane maneuver. Bearing is the relative angle (degrees 0-359)
        //based on the link prior to intersection and the successor link
        //after the maneuver. For example, a right turn is represented
        //by TB=90, straight is TB=0, and left turn is TB=270.
        int32 to_bearing = 1;

        //To LinkID is the successor linkID associated with the
        //maneuver. The linkID will be in driving direction order; “F”
        //represents travel direction FROM reference node, “T”
        //represents travel direction TO reference node.
        string to_here_map_link_id = 2;

        //The extra delay in seconds that corresponds to the maneuver.
        //This delay time is extra delay in addition to the the time of
        //the speed reported at segment level.
        int32 extra_delay_in_seconds = 3;

        //The average speed, not capped by speed limit, on these lanes
        //of traffic that current traffic is travelling.
        double average_speed_in_kph = 4;

        //The number between 0.0 and 10.0 indicating the expected
        //quality of travel.
        double jam_factor = 5;

    }

}

Set up the Maven project

In order to get real-time traffic conditions, you may download the source code at the beginning of the tutorial and store it in a folder of your choice, or create a folder structure for your project from scratch as follows:

here-realtime-traffic
└── src
    └── main
        ├── java
        └── resources
        └── scala

You can do this with a single bash command:

mkdir -p here-realtime-traffic/src/main/{java,resources,scala}

The Maven POM file is similar to the one in the Verify Maven Settings tutorial, with the parent POM and dependencies sections updated:

The Parent POM is sdk-standalone-bom_2.12 as this tutorial is designed to run locally for the sake of simplicity.

<parent>
    <groupId>com.here.platform</groupId>
    <artifactId>sdk-standalone-bom_2.12</artifactId>
    <version>2.51.5</version>
    <relativePath/>
</parent>

The following dependencies are used:

  • hrn_2.12 to initialize Real Time Traffic catalog hrn.
  • traffic_v2_java to decode Partitions data.
  • data-client_2.12 and data-engine_2.12 to download partition data.

Dependencies:

<dependencies>
    <dependency>
        <groupId>com.here.platform.data.client</groupId>
        <artifactId>data-client_${scala.compat.version}</artifactId>
    </dependency>
    <dependency>
        <groupId>com.here.platform.data.client</groupId>
        <artifactId>data-engine_${scala.compat.version}</artifactId>
    </dependency>
    <dependency>
        <groupId>com.here.hrn</groupId>
        <artifactId>hrn_2.12</artifactId>
    </dependency>
    <dependency>
        <groupId>com.here.traffic.realtime</groupId>
        <artifactId>traffic_v2_java</artifactId>
    </dependency>

</dependencies>

Get real-time conditions for a specific location

This tutorial demonstrates how to fetch the real-time traffic data from the HERE Traffic Flow catalog at a given location described with road segments - in this case the Brandenburg Gate.

The input to this tutorial is a Tile ID 23618402 on zoom level 12 that covers the Brandenburg Gate and segment IDs 202981252, 203203107 82419435 covering a small part of Unter der Linden street near Brandenburg Gate) and Pariser Platz square.

Road segments near Brandenburg Gate and Pariser Platz square
Figure 1. Road segments near Brandenburg Gate and Pariser Platz square

The code snippet below does the following:

Step 1:

Retrieve Partition metadata for the obtained Tile ID on zoom level 12 using the getVolatilePartitions() method from the Data Client Library.

Step 2:

Download partition for the given Brandenburg Gate Tile ID on zoom level 12 using the getDataAsBytes() method from the Data Client library.

Step 3:

Using the downloaded partition in Step 2, parse data with the traffic_v2 Protobuf Schema.

Step 4:

Fetch speed item list that contains information about topology segment IDs and then get all segments with information about traffic by filtering results by given segments IDs: 202981252, 203203107 82419435.

Scala
Java

/*
 * Copyright (c) 2018-2023 HERE Europe B.V.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

import akka.NotUsed
import akka.actor.{ActorSystem, CoordinatedShutdown}
import akka.stream.ActorMaterializer
import akka.stream.javadsl.{Sink, Source}
import com.here.hrn.HRN
import com.here.platform.data.client.common.VolatilePartitionsFilter.byIds
import com.here.platform.data.client.engine.javadsl.{DataEngine, ReadEngine}
import com.here.platform.data.client.javadsl.{DataClient, Partition, QueryApi}
import com.here.platform.data.client.model.AdditionalFields
import com.here.traffic.realtime.v2.Traffic.TrafficItems

import scala.collection.convert.ImplicitConversions.`collection AsScalaIterable`
import scala.concurrent.ExecutionContext.Implicits.global

object RealTimeTrafficTutorialScala {

  private val FLOW_CATALOG = HRN.fromString("hrn:here:data::olp-here:here-traffic-flow-v2")
  private val FLOW_LAYER = "realtime-traffic-flow-volatile"

  def main(args: Array[String]): Unit = {

    val actorSystem: ActorSystem = ActorSystem.create("flow")
    val actorMaterializer: ActorMaterializer = ActorMaterializer.create(actorSystem)
    val queryApi: QueryApi = DataClient.get(actorSystem).queryApi(FLOW_CATALOG)
    val readEngine: ReadEngine = DataEngine.get(actorSystem).readEngine(FLOW_CATALOG)

    val berlinCityCenterTileId = "23618402"

    val segmentsIdForStreet = List(202981252, 203203107, 82419435)

    // Step 1: Retrieve Partition metadata for the given Brandenburg Gate Tile ID on zoom level 8
    val partition = queryApi
      .getVolatilePartitions(FLOW_LAYER,
                             byIds(Set(berlinCityCenterTileId)),
                             AdditionalFields.AllFields)
      .thenCompose((partitionsSource: Source[Partition, NotUsed]) =>
        partitionsSource.runWith(Sink.head(), actorMaterializer))
      .toCompletableFuture
      .join()

    // Step 2: Download partition for the given `Brandenburg Gate` Tile ID on zoom level `12`
    val partDownloadedTraffic = readEngine.getDataAsBytes(partition).toCompletableFuture.join()

    // Step 3: Parse real-time traffic data
    val speedsTrafficItems = TrafficItems.parseFrom(partDownloadedTraffic)

    // Step 4: Fetch speed item list that contains information about topology segment IDs
    // and then get all segments with information about traffic
    // by filtering results by given segments IDs: `202981252, 203203107 82419435`.
    val realTimeTraffic = speedsTrafficItems.getItemsList
      .filter(item =>
        item.getTopologySegment.getTopologySegmentIdList.exists(segmentsIdForStreet.contains))
      .flatMap(traffic => traffic.getFlow.getSegmentList)

    printf(
      s"The real-time traffic data for the given segments Ids [${segmentsIdForStreet.map(_.longValue()).mkString(", ")}] is: $realTimeTraffic")

    CoordinatedShutdown
      .get(actorSystem)
      .run(CoordinatedShutdown.unknownReason)
      .onComplete(print)

  }

}




/*
 * Copyright (c) 2018-2023 HERE Europe B.V.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

import akka.actor.ActorSystem;
import akka.actor.CoordinatedShutdown;
import akka.stream.ActorMaterializer;
import akka.stream.javadsl.Sink;
import com.google.protobuf.InvalidProtocolBufferException;
import com.here.hrn.HRN;
import com.here.platform.data.client.common.VolatilePartitionsFilter;
import com.here.platform.data.client.engine.javadsl.DataEngine;
import com.here.platform.data.client.engine.javadsl.ReadEngine;
import com.here.platform.data.client.javadsl.DataClient;
import com.here.platform.data.client.javadsl.Partition;
import com.here.platform.data.client.javadsl.QueryApi;
import com.here.traffic.realtime.v2.*;
import java.util.*;
import java.util.concurrent.ExecutionException;
import java.util.stream.Collectors;

public class RealTimeTrafficTutorial {

  private static final HRN FLOW_CATALOG =
      HRN.fromString("hrn:here:data::olp-here:here-traffic-flow-v2");
  private static final String FLOW_LAYER = "realtime-traffic-flow-volatile";

  public static void main(String[] args)
      throws ExecutionException, InterruptedException, InvalidProtocolBufferException {
    ActorSystem actorSystem = ActorSystem.create("flow");
    ActorMaterializer actorMaterializer = ActorMaterializer.create(actorSystem);
    QueryApi queryApi = DataClient.get(actorSystem).queryApi(FLOW_CATALOG);
    ReadEngine readEngine = DataEngine.get(actorSystem).readEngine(FLOW_CATALOG);

    String berlinCityCenterTileId = "23618402";

    List<Integer> segmentsIdForStreet =
        new ArrayList<>(Arrays.asList(202981252, 203203107, 82419435));

    // Step 1: Retrieve Partition metadata for the given Brandenburg Gate Tile ID on zoom level 8
    Partition partition =
        queryApi
            .getVolatilePartitions(
                FLOW_LAYER,
                new VolatilePartitionsFilter.Builder()
                    .withIds(Collections.singleton(berlinCityCenterTileId))
                    .build(),
                Collections.emptySet())
            .thenCompose(
                partitionsSource -> partitionsSource.runWith(Sink.head(), actorMaterializer))
            .toCompletableFuture()
            .join();

    // Step 2: Download partition for the given `Brandenburg Gate` Tile ID on zoom level `12`
    byte[] partDownloadedTraffic = readEngine.getDataAsBytes(partition).toCompletableFuture().get();

    // Step 3: Parse real-time traffic data
    Traffic.TrafficItems speedsTrafficItems = Traffic.TrafficItems.parseFrom(partDownloadedTraffic);

    // Step 4: Fetch speed item list that contains information about topology segment IDs
    // and then get all segments with information about traffic
    // by filtering results by given segments IDs: `202981252, 203203107 82419435`.
    List<FlowOuterClass.Segment> realTimeTraffic =
        speedsTrafficItems
            .getItemsList()
            .stream()
            .filter(
                item ->
                    !Collections.disjoint(
                        item.getTopologySegment().getTopologySegmentIdList(), segmentsIdForStreet))
            .flatMap(t -> t.getFlow().getSegmentList().stream())
            .collect(Collectors.toList());

    System.out.printf(
        "The real-time traffic data for the given segments Ids %s is: %s",
        segmentsIdForStreet, realTimeTraffic);

    CoordinatedShutdown.get(actorSystem)
        .run(CoordinatedShutdown.unknownReason(), Optional.empty())
        .toCompletableFuture()
        .join();
  }
}

To execute the application, run the following command:

Scala
Java

mvn compile exec:java -D"exec.mainClass"="RealTimeTrafficTutorialScala"



mvn compile exec:java -D"exec.mainClass"="RealTimeTrafficTutorial"

According to the results of the program the traffic jam is 1.53047 out of 10.0 possible, the average speeds for 202981252 and 82419435 segments are 10.0 kph, for the 203203107 segment, the average speed is 8.35 kph. The speed at which vehicles can travel the segment, when there is no traffic congestion or other impediments, such as a road closure, is 10.0 for all segments, as indicated by free_flow_speed_kph. The average speed that traffic is traveling, but limited to the speed limit is 10.0 for 202981252 and 82419435 segments and 8.35 for 82419435 segment as indicated by average_speed_capped_kph.

The real-time traffic data for the given segments Ids [202981252, 203203107, 82419435] is: 
[
speed {
  average_speed_kph: 10.0
  average_speed_capped_kph: 10.0
  free_flow_speed_kph: 10.0
}
, speed {
  average_speed_kph: 8.35
  average_speed_capped_kph: 8.35
  free_flow_speed_kph: 10.0
}
jam_factor: 1.53047
, speed {
  average_speed_kph: 10.0
  average_speed_capped_kph: 10.0
  free_flow_speed_kph: 10.0
}
]

Conclusion

In this tutorial, you got acquainted with the HERE Traffic Flow catalog and learned how to get information about traffic conditions data using this catalog.

Further information

For more details on the topics covered in this tutorial, see the following sources:

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