KEY POINTS:

• A freight train derailed last night damaging the railway tracks.
• An estimated 20,000 commuters are affected this morning.
• Most Wellington train services are cancelled.
• The Johnsonville line trains are unaffected and still operating.

An estimated 20,000 rail users have to either find alternative travel arrangements - or have been told to stay home - as Wellington is crippled by a major train outage.

Train services in and out of Wellington on the Hutt, Kāpiti, Melling and Wairarapa lines have been cancelled until further notice after a derailment last night damaged the tracks.

Metlink has not been able to source enough replacement buses to transport the roughly 20,000 passengers who travel by train during the weekday peak morning period.

Greater Wellington regional councillor Daran Ponter told Newstalk ZB it was a day for those who live in Hutt Valley and the Kapiti Coast to consider staying home.

UPDATE 8:15AM#WellingtonTraffic should expect SIGNIFICANT SOUTHBOUND DELAYS on SH1 and SH2 this morning. SH1 queues stretch from the Porirua to the Urban Motorway. SH2 Queues stretch from the Haywards Interchange to the Petone Interchange. ^RShttps://t.co/GT2D8jSjNA

— NZTA Wellington (@NZTAWgtn) July 2, 2019

"A freight train has taken out the signalling in the choke point in the Wellington railyard."

It's the place where all the trains are coming into the city, he said.

The work would not be completed until the afternoon at the very earliest, and possibly not completed today, he said.

"I'm afraid for those people who are relying on buses it is going to be a little bit like the Hunger Games out there."

Southbound traffic on SH1 from the Johnsonville Off-ramp about 8.10am. Photo / NZTA Journey Planner

There are just not enough buses to cater for a total shut down, he said

"Bus seats will be tight."

Traffic is already spiking as people have driven to the park and rides along the network, seen the cancellations, and hopped back into the car, he said.

NZTA has warned motorists to expect delays on major highways near the capital, as southbound traffic was heavier than usual as of 6.40am.

While the main highway route in and out of the capital is expected to become heavily congested with extra traffic, a handful of tourists remain at the eerily quiet Wellington Railway Station.

Sally Rose, from Louisiana, was hoping to travel on the Northern Explorer to Auckland.

Rose said they were turning to booking a $500 flight to get up there instead.

"It's a bummer that we don't get to see the route we wanted to see but it's okay."

Greytown Martin Grimshaw is unsure how

He waited up past midnight to find out what was

The eerily empty Wellington Railway Station this morning. Photo / Emme McKay

KiwiRail chief operations officer Todd Moyle said that about 7.40 last night a number of wagons on a freight train leaving Wellington freight yard derailed.

"The wagons remained upright but it took the locomotive engineer 230 metres before he was able to stop the train, leaving damaged tracks and points on the main tracks into Wellington."

KiwiRail brought in two cranes and staff from across the North Island to support local staff in removing the damaged wagons and repairing tracks overnight, he said.

The cause of the derailment is being investigated, he said.

"KiwiRail apologises for the inconvenience and is working as quickly as possible to restore the network to its normal operation.

"Safety is our utmost priority."

The three derailed wagons and the remainder of the train were removed by crane from site by 5am, he said.

"KiwiRail is now focused on repairing the damaged points and track.

Work crews have worked overnight to clear the freight train and repair the damage, but that process is expected to take some time. Photo / Metlink

"The recovery of the derailed wagons was complicated by having to work around the overhead wires.

"The power supply to these wires had to be isolated before the recovery could commence."

Your service:

Kāpiti line:

Reduced train services stopping at all stations will run on a half hourly timetable from 6am between Waikanae and Porirua only. If you are wanting to travel between Porirua and Wellington Metlink recommends alternative transport or avoiding travel.

Hutt Valley line:
Reduced train services stopping at all stations will run on a half hourly timetable from 6am between Upper Hutt and Petone only. If you are wanting to travel between Petone and Wellington Metlink recommends alternative transport or avoiding travel.

Wairarapa line:
Six buses will travel between Masterton and Wellington in the morning, which will be departing at 6.47am only. Metlink recommends alternative transport or avoiding travel.

Melling line:
All Melling line services are cancelled. Metlink has asked commuters to arrange alternative transport or avoid travel.

Johnsonville line:
Train services will continue to run to timetable on the Johnsonville line as it is not affected by the derailment.