Services are resuming on the Wellington line but commuters are warned to expect "major" delays.
All trains on the Hutt Valley line - including Wairarapa services - had been suspended this morning after an excavator derailed near Taita during scheduled maintenance overnight.
Metlink said while services have now resumed some will not be running to timetable and there will be delays.
However, Melling services were still running to schedule, it said.
The delays to train services has caused traffic to build up on both State Highway 1 and 2 coming into the capital.