KiwiRail has formally apologised for the disruption expected this week on Wellington train services.

A 70 kilometre per hour speed limit is in place on the Hutt Valley, Kapiti and Wairarapa lines after a specialist track evaluation car which was set to inspect the infrastructure broke down.

Track assessments will get underway today but aren't expected to be complete till Friday -- meaning reduced services will be in place till then.

KiwiRail Executive General Manager of Operations, Paul Ashton says the situation is solely their making.

He says they take full responsibility for the reduction in train services.

KiwiRail will be undertaking an internal investigation into the incident.

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