The train meltdown could not have come at a worse time - both for passengers, because it happened on the cusp of peak hour, and for Metro, because the Andrews government is believed to be on the verge of announcing it will hand Metro a seven-year contract extension.

For political reasons, it might be less likely to come out and announce this so soon after the system has let commuters down so badly.

Metro's automatic train control centre failed at 4pm, leaving the operator scrambling and at a loss to identify what caused the system failure.

With the system down, train controllers were staring at blank screens and literally did not know where in the network Melbourne's trains were, so all trains were brought to a halt for safety's sake.