Passengers on the Wellington - Johnsonville suburban railway line are facing delays this week. Several trains are out of service due to a series of mechanical problems.
Trans Metro says it needs six trains on the route for a normal service but it has only three available due to a compressor fault, electrical faults, wheel replacements and compulsory service.
It says two trains should be in service on the rails by Friday.
Tranz Metro Manager Scott Brooks says the present English electric trains, which are 60 years old, are due to be replaced by new Matangi trains in March, which should improve the service.
The Wellington - Johnsonville line was originally the main trunk railway line. It was electrified in the 1930s for commuter use.