> For the complete documentation index, see [llms.txt](https://docs-integration.squake.earth/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs-integration.squake.earth/api-calculations-request-response/travel/train.md).

# 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 operator- and country-aware methodology for train items on the Calculation API when you set `methodology` to **`REM`**. If you omit `methodology`, the API uses your client's configured train default. 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.).

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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