Introduction¶

The data service speeds and flows contain minute data about speeds, flows (flows often are subdivided by vehicle category) and queue information. This data is determined with point measurements and/or VRI’s. The delivery will take place no later than 60 seconds after the measurement minute. The data service contains the sum of the number of measured vehicles per lane per measuring point. The measurement period is one minute and the delivered value is a conversion of this minute data to one hour. Depending on the provisions of the road authority concerned, the output will show a distribution over vehicle categories.

The files are made available as open data on opendata.ndw.nu as trafficspeed.xml (periodic data regarding speeds, intensity and queues) and measurement_current.xml (configuration data of the measurement sites).

For more information about the structure of the MeasurementSiteTablePublication (measurement_current.xml) you can click here.

Structure and content¶

General¶

The data service Speeds and flows is part of the real-time traffic data (AVG). The specialization (xsi: type) MeasuredDataPublication from PayloadPublication is used for this purpose in the Datex II structure.

The main structure is shown in the figure below.

In the example below the use of the most important elements in this data service is explained.

Example¶

The file/soap message with the periodic data of travel times starts with the standard DatexII elements for delivery (see example XML below). The exchange element is used to exchange parameters related to the delivery, in this case the details of the supplier.

<d2LogicalModel xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" modelBaseVersion="2" xmlns="http://datex2.eu/schema/2/2_0">
  <exchange>
   <supplierIdentification>
     <country>nl</country>
     <nationalIdentifier>NLNDW</nationalIdentifier>
   </supplierIdentification>
  </exchange>
  <payloadPublication lang="nl" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:type="MeasuredDataPublication">
    <publicationTime>2017-08-09T08:52:40.008Z</publicationTime>
    <publicationCreator>
      <country>nl</country>
          <nationalIdentifier>NLNDW</nationalIdentifier>
    </publicationCreator>
    <measurementSiteTableReference targetClass="MeasurementSiteTable" version="960" id="NDW01_MT"/>
    <headerInformation>
      <confidentiality>noRestriction</confidentiality>
      <informationStatus>real</informationStatus>
    </headerInformation>
  ..
  </payloadPublication>
</d2LogicalModel>

In the above example, the attribute xsi: type of the PayloadPublication indicates that the specialization “MeasuredDataPublication” has been used. In addition, the following elements were used to provide extra information about the data delivery.

The actual travel time data can be found in the siteMeasurements element (see XML example below). The reference to the measurement location within the measurementSiteTable is done by means of the attributes of the measurementSiteReference element. In addition, the start time of the measurement minute is indicated in measurementTimeDefault.

<siteMeasurements xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
<measurementSiteReference id="PZH01_MST_0661_01" version="3" targetClass="MeasurementSiteRecord" />
<measurementTimeDefault>2017-11-15T14:11:00Z</measurementTimeDefault>
  <measuredValue index="1">
    <measuredValue>
      <basicData xsi:type="TrafficFlow">
        <vehicleFlow supplierCalculatedDataQuality="0">
          <dataError>true</dataError>
          <vehicleFlowRate>0</vehicleFlowRate>
        </vehicleFlow>
      </basicData>
    </measuredValue>
  </measuredValue>
</siteMeasurements>

The traffic data for a measuring point is recorded in one or more measuredValue (main) elements. Each element refers (using the mandatory attribute index) to the corresponding measurementSpecificCharacteristics. The element itself has one mandatory element, measuredValue (subelement), and one optional element measuredValueExtension (not used in the example).

The measured value and the typing of the value itself is recorded in the specializations of the basicData element. In the case of the data service speeds and flows, the following specializations are used:

In the code example above it concerns the specialization “TrafficFlow” for code examples and the relevant elements of the other two specializations you can click through on the specialization names below.

   <measuredValue index="5">
 <measuredValue>
    <basicData xsi:type="TrafficSpeed">
      <averageVehicleSpeed numberOfInputValuesUsed="11" standardDeviation="3">
      <speed>48</speed>
      </averageVehicleSpeed>
    </basicData>
  </measuredValue>
</measuredValue>

<measuredValue index="5">
  <measuredValue>
    <basicData xsi:type="TrafficStatus">
      <trafficStatus>
      <trafficStatusValue>freeFlow</trafficStatusValue>
      <trafficStatusValueExtension>
        <trafficStatusValueExtension>
          <queueInformation>
            <distanceToHeadOfQueue>0</distanceToHeadOfQueue>
            <queuingDuration>26.0794277</queuingDuration>
          </queueInformation>
        <multipleStopsInformationAtIntersection>
          <nStopsMinimum>1</nStopsMinimum>
          <numberOfStopsN>0</numberOfStopsN>
        </multipleStopsInformationAtIntersection>
      </trafficStatusValueExtension>
      </trafficStatusValueExtension>
      </trafficStatus>
    </basicData>
  </measuredValue>
</measuredValue>

Within the basicData element, the vehicleFlow element is used to report the intensity of a measurement site. The vehicleFlow element inherits the attributes from VehicleFlowValue and DataValue. The vehicleFlow element expands its attributes with the vehicleFlowRate attribute. The attributes numberOfInputValuesUsed and standardDeviation are not used in this specialization.

In the event of a faulty measurement, the dataError subelement is used to indicate this. About how this is done click here. In addition, the reference value is included within the basicDataReferenceValue element in the measuredValueExtension. A typing of the reference value takes place using the referenceValueType element. In addition, the structure of basicData has been included under travelTimeData to indicate the reference value.

Below is an overview of the sub-elements of the measuredValue element with “TrafficFlow” as a specialization of the basicData subelement.

De opbouw van de specialisatie “TrafficSpeed” (snelheid) van basicData kent de volgende elementen:

The structure of the specialization “TrafficStatus” (queues) of basicData has the following elements: