At Cumberland, toward Forest Park, between 12:17 am and 12:17 am. The schedule called for a train every 10 min.
Line
Blue Line
Station
Cumberland (station 40230)
Direction
toward Forest Park
Train before
run 238, passed 12:17:19 am
Train after
run 220, passed 12:17:24 am
Gap
0 min (5 s)
Scheduled gap
10 min
Collector
running the whole time
Scheduled against seen
Each tick is a train at Cumberland toward Forest Park. The two runs either side of the bunch are labeled.
What Train Tracker said
Train Tracker reports each train's next stop. A train has passed Cumberland when its next stop moves past it.
Snapshot
Run 238 (before)
Run 220 (after)
12:16:09 am
next stop Cumberland
not in service yet
12:17:09 am
next stop Cumberland
not in service yet
12:18:09 am
next stop Montrose (Blue)
next stop Harlem (Blue - O'Hare Branch)
12:19:09 am
next stop Irving Park (Blue)
next stop Harlem (Blue - O'Hare Branch)
Showing 4 of 4 snapshots in the gap. The full record, every train on the line minute by minute, is in 2026-10-10-blue-bunch-87444.json.
Check it yourself
Scheduled times come from CTA's GTFS schedule for Sat Oct 10. Positions come from Train Tracker, polled once a minute.
The raw records above are exactly what CTA's servers returned. How the numbers are worked out.