Off-peak trains on most Wellington region lines will soon be arriving every 20 minutes.

Sweeping changes have been proposed for the Wellington region's commuter rail services, with passengers who use the Wairarapa's notoriously late-running trains set to be the main beneficiaries.

Sometime after Easter 2018, off-peak trains are set to begin running every 20 minutes, rather than every half hour, on the Johnsonville, Kapiti and Hutt Valley lines.

Peak-time services will also be adjusted to improve spacing between trains.

ILLYA MCLELLAN/STUFF Extra trains could be brought in from Auckland to provide more peak-time services for Wairarapa.

Greater Wellington Regional Council is also pondering increasing the premium that Hutt Valley commuters pay to use Wairarapa-bound trains instead of Hutt trains, which share the same track. The aim would be to have fewer Wairarapa trains stopping in the Hutt Valley.

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The Wairarapa line, which runs between Wellington and Masterton, has become so bad that only 64 per cent of trains arrived on time between July and May, a decrease of 18 percentage points over the previous 12 months.

STUFF Changes are finally on the way for the ailing Wairarapa rail line, which has been dogged by lateness for years.

While the track will ultimately need an estimated $60 million upgrade to fix its problems, a number of short-term solutions have been proposed by to reduce delays and disruptions in the meantime.

They include running extra trains during peak times, possibly by bringing in surplus diesel trains from Auckland, as well as adjusting capacity to meet demand.

Timetable changes are also being considered to prevent Wairarapa trains, with few scheduled stops in the Hutt Valley, getting stuck behind frequently-stopping Hutt trains. Low-cost track improvements are also being looked at.

STUFF Greater Wellington Regional Council public transport general manager Wayne Hastie.

The suggestions for the Wairarapa line come after regional councillors requested an explanation for the line's poor performance, and that subsequent urgent improvements be made.

The ageing track mean Wairarapa trains are subject to speed restrictions, and the council is hoping that funding for repairs will be allocated in next year's Budget.

Public transport general manager Wayne Hastie said it was unclear when the proposed changes would come into effect, with details still to be ironed out.

PIERS FULLER/STUFF Masterton Mayor Lyn Patterson says people want the rural Wairarapa lifestyle, but still want to be able to commute to Wellington.

"Any additional service will have a cost associated with it."

Hastie said Hutt Valley commuters had several trains to choose from, while Wairarapa commuters just had one, so charging Hutt commuters more would encourage them off the Wairarapa trains to help to ease pressure.

Wairarapa trains depart from Wellington five times a day, Monday to Thursday, with an extra late service on Fridays, and twice a day on weekends.

Masterton Mayor Lyn Patterson welcomed the proposed changes, but said the line's ailing track remained the main problem.

"We've been pushing for this for many years, and I'm delighted GWRC has taken our concerns on board," she said.

"What we urgently need, though, is an investment in the rail line. We need a lot of money spent to bring it up to speed because it's lacked maintenance over quite a number of years."

Carterton Mayor John Booth said the proposed improvements were a positive sign.

"It's high time that all these things were looked at and these options explored," he said.

"That train service is a critical service for us, but there's a huge upgrade of track maintenance that's got to be done here as well." ​