Realtime data for the Atlanta Streetcar doesn't seem to be available via an API, and yet this page exists with a realtime map:
https://www.nextbus.com/googleMap/?a=atlanta-sc
I decided that I would reverse-engineer it, for fun.
It seems they utilize a nonce-like concept for validation, although it's not fully baked. They hard-code an initial key in the javascript of the actual pageload, which you can use for all subsequent lookups. On the actual page, they take the response key from each subsequent request and pass the new one each time along with a count variable called cnt
, but in practice it seems that isn't actually required. The only limitation seems to be you have to fake the referer header.
Here's how I got it to work: