CBTC Migration Checklist
The cutover does not create problems. It reveals them. Everything before it is an opportunity to surface a design or integration defect while there is still an exit path; the cutover itself is the one irreversible moment, with the traveling public aboard. This sheet is the sequence of things that have to be true beforehand.
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What's inside
- Six stages from feasibility to burn-in, as printable sign-off items.
- The four cutover strategies — big bang, segment-phased, fleet-phased, function-phased — with shutdown length, mixed-mode duration, rollback risk and real US examples.
- Mixed-mode capacity arithmetic: why a 30 tph line runs at ~20 tph until conversion completes.
- What belongs in a Method of Procedure, and why a 15-page MOP is worse than none.
- War-room roles for the cutover window, including who holds authority to stop it.
- The first-90-day burn-in regime.
Choosing the cutover strategy is the decision that shapes everything else
Segment-phased is the most common approach in US brownfield deployments, and for good reason: risk is distributed, and what segment one teaches gets applied to segment two. The L Line converted in three geographic segments between 2006 and 2009, each with a three-to-four-day closure. Big bang concentrates all the risk into one 3–7 day window and makes rollback largely impractical — defensible on greenfield with simple topology, hard to justify on an operating urban line. Fleet-phased stages the capital but stretches mixed running to 18–36 months. Function-phased separates ATP from ATO and deploys them years apart.
The parts people skip
A Method of Procedure is a minute-by-minute choreography of the shutdown window, with flowcharts, a responsibility matrix and explicit escalation criteria. A good one runs 60–100 pages; a 15-page MOP is worse than useless because it manufactures confidence. A full cutover rehearsal four to six weeks out — same procedures, same staff, same equipment, same timeline — surfaces the procedural gaps, the communication breakdowns and the staff-fatigue factors that a paper walkthrough never will. The L Line rehearsed each of its three segment cutovers, and each rehearsal improved the next.
And someone in the war room must hold explicit authority to stop the cutover on safety grounds, named in the MOP before the window opens. If that authority is not written down, it does not exist at 03:00.
Sources & method
Adapted from Communications-Based Train Control, Volume 1, Chapter 12, by Chunjun (Francisco) Wang. The cutover decision matrix is Table 12.7; strategy examples reflect documented US brownfield practice. Durations assume a mid-size urban line and compress substantially on greenfield.