I don't know of any operating examples but I envisioned a rail transit line with a single track section at the far end. Depending on train spacing outbound approaching the single tracked section, some trains (maybe every other train) would short turn without going to the far end. Passengers on a short turning train would simply board the next train. There would be provision for ad hoc short turning of trains notably if bunching occurred coming outbound.
Some sites may lend themselves to fewer short turns if, should bunching occur, a train going to the outer end began its inbound run early instead of on schedule. Another possibility is a tail track (could be just one) to store an extra train to fill in inbound for a delay of trains coming outbound.
I thought that such a single track system could work for an extension of Boston's Orange Line past Forest Hills where there isn't room for two new tracks for rapid transit. Even just to Roslindale Village (one mile, one more stop) would eliminate a lot of buses from congested Washington St. although the extension would need land for a bus staging area at the new proposed terminal.
Build something. Anything.