Car: DEFRA 🇬🇧

💡 High-Level Description

The Department for Environment, Food & Rural Affairs (DEFRA) of the UK has been a stalwart in environmental governance and establishing methodologies across various sectors. Within the car sector, DEFRA's methodology focuses keenly on providing robust and comprehensible metrics for carbon emissions. Recognizing the massive contribution of vehicles to the UK's carbon footprint, DEFRA's guidelines are tailored to encompass the diverse range of vehicles on the roads, from compact cars to SUVs.

DEFRA's approach not only accounts for direct emissions derived from fuel combustion but also considers the broader life-cycle emissions of vehicles, including manufacturing, maintenance, and disposal. Their methodology, backed by extensive research and consultation with automotive industry experts, provides a solid foundation for the UK's policy-making, encouraging sustainable car manufacturing and usage. Through DEFRA's efforts, consumers, manufacturers, and policymakers are better equipped to make environmentally conscious decisions regarding transportation.

Versioning: Use methodology_version to pin a specific Conversion Factors year (e.g., "2024"). If omitted, SQUAKE uses the latest supported year.

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Sample API Requests

A. Route-based request without audit mode (origin/destination or explicit distance)

{
  "expand": ["items"],
  "items": [
    {
      "audit": false,
      "type": "car",
      "methodology": "DEFRA",
      "external_reference": "string",
      "origin": "Frankfurt am Main, Germany",
      "destination": "Berlin, Germany",
      "fuel_type": "hev",
      "car_type": "dual_purpose_4x4",
      "energy_scope": "ttw",
      "methodology_version": "2024"
    }
  ]
}

B. Route-based request with audit mode (for finalized/post-booking calculations)

{
  "expand": ["items"],
  "audit_for": "<Auditable Entity ID>",
  "items": [
    {
      "audit": true,
      "type": "car",
      "methodology": "DEFRA",
      "external_reference": "string",
      "origin": "Frankfurt am Main, Germany",
      "destination": "Berlin, Germany",
      "fuel_type": "hev",
      "car_type": "dual_purpose_4x4",
      "energy_scope": "ttw",
      "methodology_version": "2024"
    }
  ]
}

Note: audit_for is optional. Provide when calculating on behalf of a specific Auditable entity; otherwise omit.

C. Duration-based request (fallback when distance is unknown)

When the trip distance is unknown, you may pass number_of_days. The API will estimate the distance as estimated_distance_in_km = number_of_days * 60.

{
  "expand": ["items"],
  "items": [
    {
      "audit": false,
      "type": "car",
      "methodology": "DEFRA",
      "external_reference": "string",
      "fuel_type": "hev",
      "car_type": "dual_purpose_4x4",
      "energy_scope": "ttw",
      "methodology_version": "2024",
      "number_of_days": 5
    }
  ]
}

Precedence rule: If distance_in_km is provided, it will be used and takes priority over both origin/destination and number_of_days.

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Sample API Response

{
  "carbon_quantity": 10764,
  "carbon_unit": "gram",
  "items": [
    {
      "carbon_quantity": 10764,
      "carbon_unit": "gram",
      "external_reference": "string",
      "type": "car",
      "methodology": "DEFRA",
      "methodology_version": "2024",
      "distance": 110.0,
      "distance_unit": "kilometer"
    }
  ]
}

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API Request Items

• "type": "car" (required)

• "methodology": "DEFRA" (required)

• "methodology_version": DEFRA Conversion Factors year (e.g., "2024"). Optional; if omitted → latest supported year.

• "external_reference": Unique identifier to correlate responses (max 128 chars).

• "origin" / "destination": Postal, IATA/ICAO, UN/LOCODE, or "lat,lon"; SQUAKE resolves distance.

• "distance_in_km": If present, overrides origin/destination resolution and number_of_days.

• "number_of_days": integer (display name: Number-Of-Days), >= 1.

  • Use when trip distance is unknown.

  • Estimated distance formula: estimated_distance_in_km = number_of_days * 60.

  • Precedence: distance_in_km > origin/destination > number_of_days (fallback).

• "fuel_type": "petrol", "diesel", "hev", "phev", "electricity", "average" (default: "average").

• "acriss_car_type": ACRISS segment letters (e.g., C,D,E,F,G,H,I,J,L,M,N,P,R,S,U,W,X,O). Mutually exclusive with "car_type".

• "sipp_car_type": If acriss_car_type not passed, can be used to infer class. Mutually exclusive with "car_type".

• "car_type": "mini", "supermini", "lower_medium", "upper_medium", "executive", "luxury", "sports", "dual_purpose_4x4", "mpv", "small", "medium", "large", "average" (default: "average").

• "energy_scope": "wtw" (default) or "ttw".

• "audit": boolean (optional). Set to true to create immutable audit records for finalized calculations. Must be enabled for your account.

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Default Values

• "fuel_type": "average"

• "car_type": "average"

• "energy_scope": "wtw"

• "methodology_version": latest supported DEFRA year

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Notes

• Data quality tip: whenever possible, pass the actual distance_in_km—it yields the most accurate result. number_of_days is a convenience fallback and a coarse approximation.

• Pin methodology_version for reproducibility and auditability in long-lived reports.

• If neither distance_in_km nor origin/destination are supplied, the API will use number_of_days (if provided) to estimate distance; otherwise the request may be insufficient to compute trip emissions.

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Bibliography

• UK Government — Greenhouse gas emissions: Research & statistics: https://www.gov.uk/environment/greenhouse-gas-emissions#research_and_statistics

• Bramwell, R., et al. (2024). Government Greenhouse Gas Conversion Factors for Company Reporting — Methodology. (Methodology paper PDF).