[b KiwiRail says it expects problems to continue for some time on its Wellington metro lines while it updates the system.
The company says the roll-out of new carriages will improve the situation.
KiwiRail says service performance has lifted, but it has not had its full stock of carriages available.
Chief executive Jim Quinn says there is much work to do to refurbish old trains and update networks, which interferes with its operations.
The problems with the Wellington metro services have been compounded by rising fuel prices, which has meant an increase in the number of people using trains, he says.