Train: Green Travel Pledge

💡 High‑Level Description

Green Travel Pledge (GTP) is an industry initiative led by the UK Rail Delivery Group (RDG) providing recognised, route‑level carbon data for rail journeys in Great Britain. Under the umbrella Green Travel Data (GTD) programme, RDG publishes per‑journey and per‑passenger emissions so businesses can compare rail with car and air and drive modal shift.

GTP focuses on per‑passenger CO₂e for specific origin–destination pairs and, where available, seat class. When a journey‑specific figure is not provided, the dataset offers fallback factors per passenger‑kilometre. SQUAKE implements both layers with deterministic fallbacks and preserves comparison values for diesel car, plug‑in hybrid, battery electric car, and air for auditability.

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Sample API Requests

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

{
  "expand": ["items"],
  "items": [
    {
      "audit": false,
      "type": "train",
      "external_reference": "test_1",
      "origin": "GRF",
      "destination": "MBR",
      "number_of_travelers": 1,
      "seat_type": "second_class",
      "methodology": "GREEN-TRAVEL-PLEDGE",
      "departure_date": "2025-05-03"
    }
  ]
}

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

{
  "expand": ["items"],
  "audit_for": "<Auditable Entity ID>",
  "items": [
    {
      "audit": true,
      "type": "train",
      "external_reference": "test_1",
      "origin": "GRF",
      "destination": "MBR",
      "number_of_travelers": 1,
      "seat_type": "second_class",
      "methodology": "GREEN-TRAVEL-PLEDGE",
      "departure_date": "2025-05-03"
    }
  ]
}

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": "train" (required)

• "methodology": "GREEN-TRAVEL-PLEDGE" (required)

• "external_reference": Correlates request/response (max 128 chars).

• "number_of_travelers": Minimum 1. Default: 1.

• "origin" / "destination": Stations per GTD (GB rail). Standard resolvers (CRS/3‑letter, TIPLOC, name) supported.

• "departure_date": ISO date YYYY-MM-DD. Used to select the latest dataset published on or before this date. If omitted, SQUAKE uses the latest available dataset at calculation time (captured in metadata as dataset_date).

• "distance_in_km" (optional): If provided, used only for fallback when per‑journey emissions are not available and per‑pax‑km factors must be applied.

• "seat_type" (optional): One of "first_class", "second_class", "average" (default: "average"). See mapping below.

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

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Seat Type Mapping

• Client → GTP:

  • "second_class" → "standard"

  • "first_class" → "first"

  • "average" → use dataset "average" (where available) or computed average if class values are missing.

Zero‑value guardrails

• If the class value (standard/first) is present but equals 0, SQUAKE uses the average value for that journey.

• If class and average are missing or zero, SQUAKE enters fallback mode (see below).

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Calculation & Fallbacks

1. Primary (per‑journey CSV) – gtd-emissions-output-by-journey.csv

   • Use the exact O–D row for the specified departure_date dataset.

   • Choose class‑specific value (first or standard) or average per the mapping/guards above.

   • Multiply by number_of_travelers. Result is grams CO₂e if dataset is already per journey; otherwise convert as per dataset units.

2. Fallback (per‑passenger‑km CSV) – gtd-emissions-output-by-passenger.csv

   • Take factor kgCO₂e/pax/km; compute:

     grams = factor_kg_per_pax_km × distance_in_km × number_of_travelers × 1000

   • distance_in_km is required for fallback. If not provided, SQUAKE attempts to resolve rail distance; on failure, returns distance_required error.

Comparison Modes (saved for audit)

• Alongside train emissions, SQUAKE stores comparison values (if provided by GTP dataset) for:

  • Diesel Car, Plug‑in Hybrid Electric Car, Battery Electric Car, Air.

• If a comparison value equals 0, SQUAKE records "N/A" meaning Not Comparable.

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Default Values

• "seat_type": "average"

• Dataset selection: latest published on/ before departure_date; otherwise latest available (metadata includes dataset_date).

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Sample API Response

{
  "carbon_quantity": 1580,
  "carbon_unit": "gram",
  "items": [
    {
      "carbon_quantity": 1580,
      "carbon_unit": "gram",
      "external_reference": "test_1",
      "type": "train",
      "methodology": "GREEN-TRAVEL-PLEDGE",
      "origin": "GRF",
      "destination": "MBR",
      "seat_type": "second_class",
      "dataset_date": "2025-05-01",
      "data_source": "journey",
      "distance": 0.0,
      "distance_unit": "kilometer",
      "metadata": {
        "comparison": {
          "diesel_car_g": 4860,
          "phev_car_g": 3140,
          "bev_car_g": 1430,
          "air_g": "N/A"
        }
      }
    }
  ]
}

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Versions / Dataset Updates

• GTP datasets are periodically refreshed. SQUAKE selects the latest dataset at or before departure_date (or latest available if departure_date is omitted) and returns dataset_date for traceability.

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Bibliography

• Rail Delivery Group — Green Travel Data / Green Travel Pledge (programme overview & calculator). https://www.raildeliverygroup.com/uk-rail-industry/green-travel-data.html