The last train of the night clears the tunnel at 1:12 a.m. By 1:20, a work train carrying rail-grinding equipment, ballast, and a fourteen-person crew is already moving into the same section of track, and from that point, the crew has until roughly 4:40 a.m., when power has to be restored and the tunnel cleared for the first test run ahead of morning service, to complete whatever maintenance is scheduled for that night. The math leaves under three and a half hours of actual working time once safety checks, equipment staging, and evacuation procedures are accounted for.
“People think we have all night,” said Priscilla Nowak, a maintenance supervisor with the transit authority. “We have a window, and the window is smaller than it looks on paper, because getting equipment in and getting everyone safely out both eat into it before any actual work starts.”
What fits into a single night’s window
The work assigned to any given night depends on what that specific section of track needs, determined by inspection data collected during regular service using sensor-equipped trains that measure rail wear, gauge, and alignment continuously. A single overnight window typically accommodates one of the following, rarely more than one:
- Rail grinding, using a specialized train that removes surface irregularities from the rail head to reduce wear and noise, covering roughly one to two kilometres of track in a full window.
- Tie replacement, swapping out degraded wooden or concrete rail ties, which is slower and more labor-intensive, typically covering a few hundred metres per night depending on crew size.
- Signal and switch maintenance, calibrating and testing the equipment that controls train routing and spacing, work that often requires the track to be fully de-energized rather than simply closed to trains.
- Third rail or overhead power repair, addressing the electrified infrastructure that actually powers the trains, which carries its own additional lockout procedures before anyone can approach it.
Whichever task is scheduled, the crew works against a hard deadline that doesn’t bend for a job running behind. If work isn’t finished by the point where restoring power and clearing the tunnel becomes non-negotiable, ahead of the first scheduled test train, the site is secured in whatever state it’s in and the remaining work is rescheduled for a future night, a fact that means genuinely large jobs, replacing a long run of track entirely, can take weeks of scattered overnight sessions to complete.
The part that can’t be rushed
Every overnight work session begins with a safety process called track possession, in which the section being worked is formally isolated, power cut, signals set to prevent any train from entering, and a designated safety officer confirms the isolation before any crew member is permitted onto the track. Nowak says this process alone typically consumes twenty to thirty minutes at both the start and end of a shift, time that isn’t available for actual maintenance but that nobody on her crew has ever suggested shortening.
“You cannot rush the possession process, ever, for any reason,” she said. “I have told crews we’re behind schedule and we still take the full time to confirm the track is isolated properly, because the alternative is someone standing on a live track, and there’s no maintenance task in this system worth that risk.”
The crews themselves work exclusively overnight by assignment, a schedule the transit authority staffs through a mix of dedicated night-shift maintenance workers and rotating assignments from the broader workforce. Nowak has worked nights for eleven years and says the adjustment that never fully happens is temporal, not physical: even after a decade, her body still registers 3 a.m. as the middle of the night, not the middle of a workday, no matter how many years she’s spent proving otherwise to it.