Construction of the electrification of 19km of southern rail line connecting Papakura and Pukekohe will begin by late 2020, but the details of the project remain obscure.

The $315 million upgrade will come as part of the $6.8 billion dollar investment in transport infrastructure announced by the government on January 29.

Franklin Local Board chair Andy Baker says he was "relieved" to hear the news.

"It's been a long time coming."

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SUPPLIED Chair of the Franklin Local Board, Andy Baker, says local government have been kept in the dark on the electrification the southern rail line.

He says council members like deputy Mayor Bill Cashmore have pushed central government to integrate the southern line since the electrification of Auckland's railway service in 2015.

The work will see the existing fleet of diesel ADL class DMU trains removed from service, cutting 1234 tonnes of C02e released into the atmosphere each year. They will be replaced with Auckland's existing AM class three-carriage shuttles.

According to Auckland Transport the upgrade is expected to increase the number of hourly train services to six, however while the speed of the new trains will be faster, the extra stops means the average commute time will stay roughly the same.

The electrification of the southern line has been planned since 2018 as part of Auckland Transport Alignment Project.

Supplied The over bridge access to the Pukekohe Train Station which was constructed in 2018.

However, at the time the enterprise lacked a start date or a set construction timeline and was delayed by months in 2019 due to issues raised by NZTA.

"The frustration was that ATAP was pretty apolitical so to see it get.... delayed was disappointing," said Baker.

"It's really good to see it finally there."

However, Baker says local government have been kept in the dark about key facts such as the exact date when construction begins.

"We've had no information at all as to what happens now, other than what's been in the news.

"It's just frustrating because with all the building there is going to be considerable disruption for people."

Baker says commuters can expect some periods of slower train times during construction and traffic disruption due to road works.

"We got some pain coming... I just hope people can look at that very, very small light at the end of the tunnel."

There's also still been no official construction timeline released to the public, however Baker says he understands the project is expected to take at least two to three years.

"We've always been told...we can expect that at a minimum."

John Brown Former Suburan Auckland train carriages sit in the Pukekohe Station.

Even this, he says, is ambitious given the number of potential issues.

"Because of the bridges and the issues with the motorway near Drury.

"Knowing what I know all I can think is 'crikey there's going to be some people working hard'."

Two new stations will also be built in Drury costing $247 million.

Baker said it was concerning that a future station for Paerata Rise was missing from the announcement.

"That's a significant station and it hopefully will have a significant Park and Ride facility," says Baker.

The 300-hectare housing development situated between Karaka and Pukekohe, is Auckland's largest urban project currently under construction, and is set to bring 4500 homes to the region.

Paerata Rise Executive Director Chris Johnston says they were led to believe station would be coming.

"We were advised that we were getting a train station at Paerata Rise and have not been advised otherwise... we are currently seeking clarification," he said.

Port Waikato MP Andrew Bayley says he's also "trying to understand is why there is no mention of a new station at Paerata".

"I’ll certainly be asking where that is," he said

Ministry of Transport Manager of System Strategy and Investment Helen White says they're short on details as both Kiwirail and NZTA are still in the planning stages.

"It is expected that they will report to Ministers in coming months."