KiwiRail says major disruptions predicted across the region in May could be over within a week, as Wellington trains set to slow speeds could soon get the green light.
The rail operator earlier said services in May would be reduced as trains had to travel at slow speeds because equipment used to checks the rail lines were safe was being repaired.
But on Saturday the company made another announcement to say the repairs to the equipment were just about done, and it was now hoped the restrictions could be over in a week - this Friday night, 5 May - rather than the weeks that had been expected.
KiwiRail spokesperson Siva Sivapakkiam apologised for the disruptions.
He said the wheels of its Track Evaluation Car (TEC) had now been re-lathed and monitoring equipment was being re-attached to the wheels.
The car would leave the Auckland workshop early on Sunday.
"This means the TEC can ... travel down the North Island Main Trunk Line to Palmerston North by Sunday night.
"On Monday evening we will begin track assessments on the Kāpiti Line as it travels from Palmerston North to Wellington, with infrastructure teams ready address any track issues found.
"We are focussed on repairing any track as quickly as possible, so are bringing in additional infrastructure teams from Palmerston North to support our Wellington crews."
A 70kmh blanket speed restriction was already in place on the Kāpiti line, but by Saturday all other lines were still running at normal speeds.