Faults have caused disruptions on the Wellington and Auckland rail networks on Monday afternoon.
Buses replaced trains for the last two stops on the line between Trentham and Upper Hutt after points and signals in the area failed.
KiwiRail says the problem affected hundreds of passengers but the company had enough buses to transport them without significant delays.
The Wairarapa line was also disrupted for a time on Monday.
There were signal failures and a breakdown on the Paraparaumu line last week and passengers took several hours to get home.
Commuter trains between Wellington and Wairarapa were also disrupted for three days last month after a train was partially derailed by a landslip due to bad weather.
In Auckland, there were 10-minute delays on the Western line on Monday due to a signal failure between Swanson and Waitakere.
Trains between Henderson and Britomart are operating on the line, while buses were used between Henderson and Waitakere.