Bus: DEFRA 🇬🇧

Calculate bus and coach travel emissions with the UK government's DEFRA conversion factors, by bus category and energy scope, pinned to a Conversion Factors year if you need to.

About the methodologyCopy Anchor Link

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

The methodology covers several bus categories, including local buses inside and outside London and long-distance coaches. Emissions are calculated from factors such as fuel consumption, average occupancy and energy efficiency. DEFRA supports two energy scopes: tank-to-wheel (TTW) and well-to-wheel (WTW). WTW is the default, for a more comprehensive lifecycle assessment.

Building on DEFRA's established reporting framework, businesses and policymakers get consistent, transparent carbon accounting for bus travel, aligned with UK environmental reporting regulations and sustainability strategies.

VersionsCopy Anchor Link

Use methodology_version to pin the DEFRA Conversion Factors year (for example "2024"). If you omit it, SQUAKE automatically applies the latest supported year. Pin a specific year for reproducibility and auditability.

Sample requestsCopy Anchor Link

Send a quote before booking, then repeat the call with audit set to true once the booking is final. The body is otherwise identical.

{
  "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"
  }]
}

DefaultsCopy Anchor Link

Request fieldsCopy Anchor Link

Origin and destination formatsCopy Anchor Link

SQUAKE tries to resolve origin and destination whatever their format. Ideally, use:

• Addresses: the Post standard.
• Airports: an IATA/ICAO code (regex ^[A-Z]{3,4}$, for example MUC).
• Ports and trade locations: a UN/LOCODE (regex ^[A-Z]{2}\W?[A-Z2-9]{3}$, for example DEHAM).
• Coordinates: latitude and longitude (regex ^[-+]?\d{1,3}\.\d{1,10}\s?,\s?[-+]?\d{1,3}\.\d{1,10}$, for example +40.712,-74.006).

Provider and stop codes for busesCopy Anchor Link

You can also reference bus stops or stations with provider-prefixed stop IDs, in the format <provider>:<stop_id> (for example flixbus:2006). Common provider prefixes: flixbus, distribusion, busbud.

{
  "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"
}

Sample responseCopy Anchor Link

{
  "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"
  }]
}

BibliographyCopy Anchor Link

UK Government: Greenhouse Gas Emissions: Research & Statistics.