Railway Transport for France
SNCF public API

Irish Rail planned engineering works: affected stations, DART closures, change log and ICS feeds.
Railworks API is a free Transportation API that requires no API key, is served over HTTPS and supports CORS, so it can be called from the browser.
Irish Rail planned engineering works as JSON, station days, a change log and calendar feeds. OpenAPI 3.1, no API key.
Details from railworks.paddez.com.

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SNCF public API
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The Railworks API is provided by railworks (railworks.paddez.com). Irish Rail planned engineering works as JSON, station days, a change log and calendar feeds. OpenAPI 3.1, no API key.
Yes. The Railworks API is listed in the Transportation category of the public-apis directory, which only includes APIs that are free or have a free tier. Check its documentation for rate limits and paid plans.
No. The Railworks API requires no authentication, so you can start making requests without signing up.
Yes. The Railworks API supports CORS, so front-end JavaScript can call it directly.
Yes. The Railworks API is served over HTTPS, so it's safe to use in production.