Car: DEFRA 🇬🇧
Calculate car emissions with the UK DEFRA methodology, across vehicle types from compact cars to SUVs, and pin the Conversion Factors year you report against.
The UK Department for Environment, Food & Rural Affairs (DEFRA) publishes carbon metrics for the car sector that cover the diverse range of vehicles on UK roads. The methodology accounts for direct emissions from fuel combustion and also considers the broader life-cycle emissions of vehicles, including manufacturing, maintenance and disposal. It's backed by research and consultation with automotive industry experts and underpins UK policy-making.
Versioning
Use methodology_version to pin a specific Conversion Factors year, such as "2024". If you leave it out, SQUAKE uses the latest supported year.
Sample requests
Send a route-based quote with origin and destination (or an explicit distance_in_km), then repeat the call with audit set to true once the booking is final. If you don't know the distance, send number_of_days instead.
{
"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"
}]
}audit_for is optional
Pass the ID of an auditable entity when you calculate on behalf of that entity. Otherwise, leave it out.
Distance precedence
distance_in_km takes priority over both origin/destination and number_of_days. The order is distance_in_km > origin/destination > number_of_days.
Defaults
When a field is missing, SQUAKE fills it in before calculating.
| Field | Default | Applies when |
|---|---|---|
fuel_type | average | No fuel_type is sent |
car_type | average | No car_type is sent |
energy_scope | wtw | No energy_scope is sent |
methodology_version | Latest supported DEFRA year | No methodology_version is sent |
How it's calculated
Distance from trip duration
When the trip distance is unknown, SQUAKE estimates it from number_of_days.
number_of_days × 60If you send neither distance_in_km nor origin and destination, SQUAKE uses number_of_days (if provided) to estimate the distance. Otherwise, the request may not contain enough to calculate trip emissions.
Tips
- The actual
distance_in_kmgives the most accurate result.number_of_daysis a convenience fallback and a coarse approximation. - Pin
methodology_versionfor reproducibility and auditability in long-lived reports.
Request fields
typestringrequiredcar
methodologystringrequiredDEFRA
methodology_versionstringDEFRA Conversion Factors year, such as "2024". If you leave it out, SQUAKE uses the latest supported year.
originstringPostal address, IATA/ICAO code, UN/LOCODE, or "lat,lon". SQUAKE resolves the distance.
destinationstringSame formats as origin.
distance_in_kmnumberOverrides origin/destination resolution and number_of_days.
number_of_daysintegerAt least 1. Use it when the trip distance is unknown: SQUAKE estimates the distance as number_of_days * 60. It's the fallback after distance_in_km and origin/destination.
fuel_typeenumOne of petrol, diesel, hev, phev, electricity, average. Defaults to average.
acriss_car_typeenumACRISS segment letter, such as C, D, E, F, G, H, I, J, L, M, N, P, R, S, U, W, X. Mutually exclusive with car_type.
sipp_car_typestringIf you don't send acriss_car_type, SQUAKE can use it to infer the class. Mutually exclusive with car_type.
car_typeenumOne of mini, supermini, lower_medium, upper_medium, executive, luxury, sports, dual_purpose_4x4, mpv, small, medium, large, average. Defaults to average.
energy_scopeenumwtw (default) or ttw.
external_referencestringYour identifier for the item, up to 128 characters, so you can match results to requests.
auditbooleanSet to true to create immutable audit records for finalised calculations. Must be enabled for your account.
POST /v2/calculations in the API referenceSample 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"
}]
}Bibliography
- UK Government. Greenhouse gas emissions: research and statistics. Read on GOV.UK.
- Bramwell, R., et al. (2024). Government Greenhouse Gas Conversion Factors for Company Reporting: Methodology. Methodology paper (PDF).