The Brilliant Cut-Off (or Brilliant Branch) was opened in 1904 to alleviate congestion on the Pennsylvania Railroad Mainline through Pittsburgh. It was closed from 1976-1995, then closed again for good in 2019. Currently, its fate is in the hands of Allegheny County. For now, its just a nice walk in the woods.
http://bridgestunnels.com/location/brilliant-branch-railroad-bridge/
http://pghbridges.com/pittsburghE/0592-4479/brilliantsilver.htm
https://www.brooklineconnection.com/history/Facts/Brilliant.html
https://www.unionprogress.com/2024/05/05/allegheny-county-rail-developer-pushing-different-directions-for-scenic-route-from-aspinwall-to-homestead/
https://nextpittsburgh.com/features/brilliant-plan-bikes-pittsburgh-designers-vision-defunct-brilliant-branch-railroad/?fullarticle=true
https://books.google.com/books?id=5VBBAQAAMAAJ&pg=PA463#v=onepage&q&f=false
https://www.newspapers.com/article/the-pittsburgh-press/113522185/