FHWA Annual Average Daily Traffic API

What you can build

Annual reported roadway traffic with source route measures, facility codes and linework. Includes only sections with a reported non-null AADT; absent segments do not mean zero traffic. HPMS has coverage gaps and overlapping/concurrent route geometry. Preserve facility direction and collection dates; never sum nearby or overlapping AADT into customer counts or halve bidirectional values. No live traffic, verified driveway access, navigation accuracy or universal street coverage. Source zero/negative markers remain explicit. Use this dataset as a sourced input to an application, analytical model or retrieval tool. Retain its native dimensions when joining it with your own records.

Query FHWA Annual Average Daily Traffic

The example below is a real bounded request against the available release. Replace the environment variable with your server-side API credential. Review endpoint parameters and response schemas before changing selectors.

curl --fail --get "https://api.geoamcan.com/v1/transportation/traffic?state=01&source_id=82&limit=1" \
  -H "Authorization: Bearer $GEOAMCAN_API_KEY"

Saved response excerpt

{
  "requested_area": {
    "state": "01",
    "county": null,
    "source_id": 82,
    "year": null,
    "lat": null,
    "lon": null,
    "radius_m": 1000,
    "bbox": null,
    "min_aadt": null,
    "include_geometry": true
  },
  "data": [
    {
      "state_fips": "01",
      "source_id": 82,
      "year": 2025,
      "route_id": "RP0109700015",
      "begin_point": 0.2955,
      "end_point": 0.298,
      "aadt": 370,
      "county_geoid": null,
      "attributes": {
        "aadt_vd": "2025-01-01",
        "aadt_vt": "A",
        "f_system": null,
        "route_name": null,
        "aadt_status": "published_positive",
        "speed_limit": null,
        "route_number": null,
        "facility_type": null,
        "is_restricted": null,
        "through_lanes": null,
        "access_control": null,
        "section_length": 0.0025
      },
      "located": true,
      "distance_m": null
    }
  ],
  "availability": {
    "status": "available",
    "year": 2025,
    "coverage": [
      {
        "state": "01",
        "year": 2025,
        "reported_aadt_sections": 178265,
        "source_sections_without_reported_aadt": 179430
      }
    ],
    "county_selection": null,
    "county_boundary_vintage": null,
    "sort": "state_then_native_id"
  },
  "snapshot": {
    "fhwa-aadt": {
      "release_id": 115,
      "release": "FHWA HPMS 2025 reported AADT revision f33dde7c28c3",
      "fingerprint": "3e83061d412af68449344ec9361443f6"
    }
  },
  "returned_count": 1,
  "complete": true,
  "next_offset": null,
  "limitations": [
    "Annual reported roadway traffic with source route measures, facility codes and linework. Includes only sections with a reported non-null AADT; absent segments do not mean zero traffic. HPMS has coverage gaps and overlapping/concurrent route geometry. Preserve facility direction and collection dates; never sum nearby or overlapping AADT into customer counts or halve bidirectional values. No live traffic, verified driveway access, navigation accuracy or universal street coverage. Source zero/negative markers remain explicit."
  ],
  "source_attribution": {
    "fhwa-aadt": "US DOT / FHWA, public HPMS Full Join state services — https://www.fhwa.dot.gov/policyinformation/hpms.cfm"
  },
  "metric_definitions": {
    "aadt": "Reported annual average daily traffic, vehicles/day; not live traffic, unique visitors or a guaranteed physical station count",
    "direction": "For two-way facilities, AADT is bidirectional; one-way facilities and ramps are directional. Preserve source facility_type and unknown codes; never halve or double automatically.",
    "distance_m": "Geodesic distance to source roadway line, not driveway access or a road-network travel distance",
    "native_id": "State plus source object ID within this version; retain release snapshot to identify a segment",
    "county_geoid": "Source county where supplied. County selection uses a separately identified display boundary, not an imputed source county.",
    "linear_reference": "Published route begin/end measures retained; 2D geometry omits source M coordinates"
  }
}

Captured 2026-11-05. Excerpt omits pagination credentials and may shorten nested records. Download verified source responses.

Coverage and interpretation

HPMS AADT describes annual reported vehicle traffic on source roadway sections, rather than live traffic or unique customer visits. Only sections with a non-null source AADT are loaded; absent roads indicate unavailable coverage. Preserve source collection dates, facility codes, unknown values and route measures. Two-way facilities report bidirectional AADT; one-way facilities and ramps report directional values. Overlapping routes and repeated section-level values must not be summed or automatically halved. Distances are to source lines and do not establish driveway access. County selection intersects a separately identified installed display boundary; native source county identifiers remain distinct. Source linework is not certified for navigation.

The active release shown here is a catalog snapshot. Check the live catalog and response provenance for current readiness. The underlying public source and Geoamcan access terms are separate; consult the source’s licensing and attribution requirements.

Source and methodology

Source: US DOT / Federal Highway Administration. Geoamcan is an independent API provider, with no agency affiliation or endorsement. Read our data methodology for source handling, geographic joins and update practices.

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