Work to resolve Wairarapa vibration issues begins this month

KiwiRail and Greater Wellington Regional Council are taking a two phased approach to fix carriage vibration issues in the Wairarapa, following the completion of an independent investigation.

KiwiRail General Manager Metro’s Jon Knight says that with the Wairarapa fire ban now lifted, grinding the tracks will be the first phase of work.

“I appreciate how frustrating it has been for Wairarapa locals since we put speed restrictions in place last year to manage these vibration issues, which resulted in longer journey times. Now that we have a good understanding of the factors contributing to the situation, we are moving as quickly as we can to resolve them and lift the speed restrictions north of the Remutaka Tunnel.

“The vibration in the Wairarapa are caused by issues with how carriage wheels are interacting with the rail. Grinding the new rail with our specialist machine is our first step to fix the problem. We will have our grinder in Wellington to start work on 26 May.

Grinding the 40km of track between Featherston and Masterton will be done at night, when passenger trains aren’t running. We will start in the areas where there are vibration issues, and the total distance should take about eight weeks to complete.”

“Grinding is a standard maintenance practice and it should help the track and carriage wheels fit better together. It’s something we have been planning to do for months but, given the amount of sparks grinding generates, the summer fire ban in the Wairarapa made that impossible. With the ban lifted, we can now get our grinder down to Wellington and get the work done.

“We will then be able to re-test for carriage vibrations at a range of train speeds. If this is not enough to resolve the vibration issues, we will move to the second phase and work closely with the Council to have the wheels of their 18 Wairarapa carriages reprofiled. KiwiRail will make our facilities available, if they are needed.

“KiwiRail is in the middle of a $870 million upgrade of the Wellington rail network, to enable more reliable and frequent trains. $375m is being spent in the Wairarapa alone, including work to prepare it for the council’s new hybrid trains. In the coming years, as work is completed, we will be able to remove more speed restrictions and further reduce journey times for passengers.”

The investigation into the Wairarapa vibration issues, undertaken by Beca, recommended rail grinding and reprofiling the wheels of the Wairarapa carriages as the key steps to resolve the vibration issues. Reprofiling of the carriage wheels requires each wheel to be placed on the lathe machine and the shape of the wheel changed. Reprofiling of all wheels is currently being planned, but will likely take place over several months. The carriages will have to undergo strict testing to make sure no further issues are introduced.

Metlink Group Manager Samantha Gain says a plan is in place to ensure a long-term solution for the Wairarapa vibration problems and improve reliability for commuters.

“We acknowledge our Wairarapa passengers are inconvenienced by the speed restrictions and we’re working hard to improve their services,” Ms Gain says.
“We’re confident we can fix the vibration issues.

“The track is new and made of modern materials. Grinding will reduce the risk of track faults in the future, help reduce wear and tear on the Wairarapa carriages, and we hope will reduce the vibrations.

“Several of the Wairarapa carriages’ wheels will have been reprofiled by the time the rail grinding is finished.

“It will mean further testing can begin straight away and we will quickly know if the remaining carriages need to have their wheels reprofiled, or whether grinding will be enough to lift the speed restrictions. If we do need to continue reprofiling we will do this as fast as possible.”

The report also found:

• The new Wairarapa track was installed correctly to KiwiRail’s national standard and was within its acceptable engineering tolerances. The report also found that the tolerances on the new Wairarapa track is a significant improvement on the old track, which was many decades old. The tolerances are a lot more consistent and within the correct range, compared to the older track which varied widely between being too loose and too tight.
• The Wairarapa carriages were maintained to a strict schedule and within expected tolerances by Metlink/Transdev. The carriages are of an older design which, unknowingly could be prone to “hunting” (vibration issues) on the new track, as they do not have the levels of vibration absorption that other carriages used around Wellington do.
• Integrated planning between Metlink, Transdev, and KiwiRail is required to ensure the track and wheel interface continue to operate efficiently when changes are made to either track or wheels (inter-operability).

Work will also be done to ensure long-term inter-operability in Wellington.

“We need to make sure that KiwiRail and Transdev are all informed about any track or carriage changes to ensure our services operate smoothly and any risk of disruption for passengers is reduced,” Ms Gain says.

“The investigation highlights there is work to be done in this area. The good thing is we have discovered these inter-operability issues now. We will be working with KiwiRail and Transdev to ensure we are aligned on any changes proposed to be made by the three organisations.

“With this issue on track to being resolved, Metlink and KiwiRail will soon be able to lift one of the main speed restrictions impacting our Wairarapa line services – with more promising work to come as we work to futureproof our rail network ahead of the new hybrid trains arriving in 2028/29.”

The independent report into Wairarapa vibration issues is available here.
ENDS