
Data about positions of Metro vehicles in real time and travel their routes.
Transport for Los Angeles, US API is a free Transportation API that requires no API key, is served over HTTPS and has unconfirmed CORS support.
Details from developer.metro.net.

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Data about buses routes, parking and traffic
The Transport for Los Angeles, US API is provided by Metro Open Data (developer.metro.net).
Yes. The Transport for Los Angeles, US 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 Transport for Los Angeles, US API requires no authentication, so you can start making requests without signing up.
CORS support for the Transport for Los Angeles, US API is unknown. Test a request from the browser, and fall back to a server-side call if it is blocked.
Yes. The Transport for Los Angeles, US API is served over HTTPS, so it's safe to use in production.