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Historical Traffic Volumes

AADT

Last edit: 2026.09.24

Introduction

This guide covers the Annual Average Daily Traffic (AADT) data accessible via the Map Content Portal. Each release contains AADT volumes for road elements in the specified map version.

Release tags

In the Map Content Portal, each release is labeled with tags that describe its content:

  • Type — one of two main tags:
    • aadt — the data files contain only the aadt volume values.
    • aaht — in addition to the aadt values, the data files also contain the average weekday traffic (d1 - d7) and the average week hour traffic (d1h0 - d7h23).
  • year — the year for which the traffic volumes are calculated.
  • update — the version of the volumes for that year. The changes introduced in each update are described in its Release Notes.

Release Notes

After selecting a release, the Release Notes section at the top lists the changes introduced in that update. We recommend always using the latest update, as it contains the best available version of the AADT data.

Release files

Each region in the release contains the following files:

  • {mapVersion}_{countryCode}_{stateCode}_{year}_shp_aadt.zip a Shapefile archive containing the Annual Average Daily Traffic data for the region for the year.
  • {mapVersion}_{countryCode}_{stateCode}_{year}_pqt_aadt.parquet a Parquet file containing the same data as the Shapefile.
  • {mapVersion}_{countryCode}_{stateCode}_{year}_cvg_aadt.json a JSON file with road network coverage information.

The {stateCode} part is currently present only for the United States, where the data is released per state. The file names always use the aadt suffix — whether the daily (d1 - d7) and hourly (d1h0 - d7h23) fields are included is determined by the release type tag (aadt or aaht), not by the file name.

The release also contains a user-guide.zip file with the product user guide.

Data fields

For each road element, the following fields are provided:

  • id a unique identifier for the road element.
  • frc the Functional Road Class of the road element indicates the importance of the road in the network. This is a value between 0 and 7 where 0 is considered most important and 7 least important. FRC 0 roads are highways and FRC 7 roads are local or residential roads. The values 0, 1, 2, 3, 4, 6 and 7 occur in the data.
  • openlr a base 64 encoded OpenLR binary location reference for the road element. This is a map-agnostic way to identify the road element.
  • osm_id the OpenStreetMap ways the road element lies on, written as way:length:offset, for example 281499617:2493:-859. The first number is the OpenStreetMap Way ID, followed by the length of the way and the offset of the road element along it. Where a road element spans several ways, the triples are separated by commas. Use the first number to join with OpenStreetMap data.
  • gers_id the Overture Maps GERS identifier of the road element, written as id:start:end, for example 086be6ea-7fff-ffff-0461-bd0a07a2bc72:0:500. The first part is the GERS segment ID, followed by the start and end offsets along it.
  • aadt the average number of vehicles that traverse this road element in a day. This is calculated by dividing the total number of vehicles that traverse the road element in the year by the total number of days in the year.
  • d1 - d7 the average daily traffic on the road for each day of the week where d1 is Monday and d7 is Sunday. For example, for Monday, this is calculated by dividing the total number of vehicles that traverse the road element on Mondays during the year by the total number of Mondays in the year. Provided in releases tagged aaht only.
  • d1h0 - d7h23 the average week hour traffic on the road where d1h0 is the hour between midnight and 1am on Monday and d7h23 is the hour between 11pm and midnight on Sunday. For example, for Monday between midnight and 1am, this is calculated by dividing the total number of vehicles that traverse the road element on Mondays between midnight and 1am during the year by the total number of Mondays in the year. Provided in releases tagged aaht only.

Coverage file

In addition to the Shapefile, a {mapVersion}_{countryCode}_{stateCode}_{year}_cvg_aadt.json file is provided with road network coverage information. The coverage information is provided per Functional Road Class. For each Functional Road Class, both the length of the road network covered by the data and the total length of the road network are provided. Both coveredLength and totalLength are expressed in meters.

{
  "FRC0" : {
    "totalLength" : 3522516,
    "coveredLength" : 3446765
  },
  "FRC1" : {
    "totalLength" : 3382940,
    "coveredLength" : 3355337
  },
  "FRC2" : {
    "totalLength" : 8848407,
    "coveredLength" : 8821315
  },
  "FRC3" : {
    "totalLength" : 15286866,
    "coveredLength" : 15232944
  },
  "FRC4" : {
    "totalLength" : 28151126,
    "coveredLength" : 27735947
  },
  "FRC6" : {
    "totalLength" : 59894813,
    "coveredLength" : 27145800
  },
  "FRC7" : {
    "totalLength" : 117411909,
    "coveredLength" : 46201560
  },
  "FRC9" : {
    "totalLength" : 19673700,
    "coveredLength" : 211157
  }
}

Loading the Shapefile

To open the Shapefile for viewing:

  • Install a client that can read and display Shapefile format. We recommend QGIS or ArcGIS.
  • Open QGIS.
  • Add a base map layer to the view, for example OpenStreetMap.
  • Drag and drop the {mapVersion}_{countryCode}_{stateCode}_{year}_shp_aadt.zip Shapefile archive into the Layers panel in the bottom left of the UI. This will add the AADT layer to the view.
QGIS

To view the AADT values for a single road element:

  • Zoom into a road element on the map.
  • In the top menu, select View -> Identify Features.
  • Right click on any road element. This will open the road element properties in the right panel.
QGIS select road