# Train

Train travel, often celebrated for its comparatively lower carbon footprint, still contributes to environmental emissions. From the energy source powering the locomotives to the infrastructure maintenance, every journey has its carbon tale.

**REM (Rail Emission Model)** is the default operator- and country-aware methodology for train items on the Calculation API when you omit `methodology` or set it to **`REM`**. See [**Train: REM**](/api-calculations-request-response/travel/train/train-rem.md) for tiered factor resolution, distance and `route_coords` behavior, and auditable request fields (`departure_date`, ISO country codes, `energy_scope`, etc.). The legacy name **`SQUAKE`** is still accepted as an alias for **`REM`**.

Other national and framework methodologies (ADEME, DEFRA, US EPA, and others) are listed in the table of contents for this section.

With SQUAKE’s precise carbon calculation tools, rail operators can detail these emissions with unwavering accuracy. Integrating SQUAKE ensures that train journeys aren’t just scenic but also transparently green, allowing passengers to ride the rails with a clear environmental conscience.


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