Bus: DEFRA 🇬🇧

💡 High-Level Description:

DEFRA's methodology for calculating the carbon footprint of bus travel is based on standardized emission factors published by the UK government. These factors are derived from extensive national data sources and provide a reliable basis for estimating greenhouse gas emissions from different types of bus transportation.

DEFRA's methodology takes into account various bus categories, including local buses operating within and outside London, as well as long-distance coaches. Emissions are calculated based on factors such as fuel consumption, average occupancy rates, and energy efficiency. Additionally, DEFRA offers flexibility in emissions reporting by supporting two energy scopes: Tank-to-Wheel (TTW) and Well-to-Wheel (WTW), with WTW being the default option for a more comprehensive lifecycle assessment.

By leveraging DEFRA's well-established reporting framework, businesses and policymakers can ensure consistent and transparent carbon accounting for bus travel, aligning with UK environmental reporting regulations and sustainability strategies. Versioning: Use methodology_version to pin the DEFRA Conversion Factors year (e.g., "2024"). If omitted, SQUAKE uses the latest supported year.

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Sample API Requests

A. Without audit mode (for pre-booking/quotes)

{
  "expand": ["items"],
  "items": [
    {
      "audit": false,
      "type": "bus",
      "external_reference": "test_1",
      "origin": "London",
      "destination": "Bristol",
      "bus_type": "coach",
      "number_of_travelers": 3,
      "energy_scope": "wtw",
      "methodology": "DEFRA",
      "methodology_version": "2024"
    }
  ]
}

B. With audit mode (for finalized/post-booking calculations)

{
  "expand": ["items"],
  "audit_for": "<Auditable Entity ID>",
  "items": [
    {
      "audit": true,
      "type": "bus",
      "external_reference": "test_1",
      "origin": "London",
      "destination": "Bristol",
      "bus_type": "coach",
      "number_of_travelers": 3,
      "energy_scope": "wtw",
      "methodology": "DEFRA",
      "methodology_version": "2024"
    }
  ]
}

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

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API Request Items

• type: bus (required)

• methodology: DEFRA (required)

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

• external_reference: Correlate response to request (max 128 chars).

• number_of_travelers: Minimum 1. Default: 1.

• origin / destination: Postal, IATA/ICAO, UN/LOCODE, or lat,lon.

• distance_in_km: If present, overrides origin/destination.

• bus_type (options):

  • local_bus_not_london

  • local_bus_london

  • average_local_bus (default)

  • coach

• energy_scope:

  • wtw (default) — well‑to‑wheel

  • ttw — tank‑to‑wheel

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

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Origin/Destination Formats (Enriched)

SQUAKE will try to resolve the origin/destination regardless of its format. Ideally:

• Addresses: Use the Post standard.

• Airports: Use IATA/ICAO code (regex: ^[A-Z]{3,4}$, e.g., MUC).

• Ports/Trade locations: Use UN/LOCODE (regex: ^[A-Z]{2}\W?[A-Z2-9]{3}$, e.g., DEHAM).

• Coordinates: Pass latitude/longitude (regex: ^[-+]?\d{1,3}\.\d{1,10}\s?,\s?[-+]?\d{1,3}\.\d{1,10}$, e.g., +40.712,-74.006).

Provider/Stop Codes for Buses

• You can also reference bus stops or stations using provider-prefixed stop IDs:

  • Format: <provider>:<stop_id> (e.g., flixbus:2006).

• Common provider prefixes: flixbus, distribusion, busbud.

If a value cannot be resolved, SQUAKE will fallback to generic (non‑journey‑specific) DEFRA bus factors.

Examples

// Using provider stop codes
{
  "type": "bus",
  "methodology": "DEFRA",
  "origin": "flixbus:london_victoria",
  "destination": "flixbus:bristol_bond_st",
  "bus_type": "coach",
  "number_of_travelers": 1,
  "energy_scope": "wtw",
  "methodology_version": "2024"
}

// Using UN/LOCODEs
{
  "type": "bus",
  "methodology": "DEFRA",
  "origin": "GBLON",
  "destination": "GBBRS",
  "bus_type": "coach",
  "number_of_travelers": 1
}

// Using coordinates
{
  "type": "bus",
  "methodology": "DEFRA",
  "origin": "+51.495,-0.144",
  "destination": "+51.455,-2.597",
  "bus_type": "coach",
  "number_of_travelers": 1
}

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Default Values

• bus_type: average_local_bus

• energy_scope: wtw

• methodology_version: latest supported DEFRA year

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Sample API Response

{
  "carbon_quantity": 15240,
  "carbon_unit": "gram",
  "items": [
    {
      "carbon_quantity": 15240,
      "carbon_unit": "gram",
      "external_reference": "test_1",
      "type": "bus",
      "methodology": "DEFRA",
      "methodology_version": "2024",
      "bus_type": "coach",
      "energy_scope": "wtw",
      "distance": 190.0,
      "distance_unit": "kilometer"
    }
  ]
}

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Versions

• Behavior: If methodology_version is omitted, SQUAKE automatically applies the latest supported DEFRA Conversion Factors year. Pin a specific year for reproducibility and auditability.

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Bibliography

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