Union advocate John Kerr told the Herald Transdev was refusing to back down on its proposal, despite mediated negotiations.

The proposal would mean train drivers had the responsibility for monitoring door operation as well as passengers, Kerr said. He believed the division of attention would significantly increase the risk of an accident and compromise passengers' safety.

Kerr said he regretted the inconvenience the strike would cause, but workers would not stand back and watch what he called "an attack on the safety culture of our railway".

Buses and ferries would continue to run as usual but Auckland Transport's chief transport services officer, Mark Lambert, anticipated every mode of transport would be busier due to the lack of trains.

"People need to plan ahead, plan their journey and look at what alternatives they can do.

"So if they can travel outside of peak times that would be fantastic, or if there are scheduled bus services that's great, but really just allow extra time for your travel."

Commuters attempting to plan a route through the chaos were being encouraged to use the AT Metro Journey Planner - employing the 'advanced' setting to select bus and ferry services exclusively.

A silver lining for Aucklanders waiting for buses or ferries was the forecast for a fine, warm day. A cloud was expected in the morning and evening and temperatures would peak at 24C.

The Public Transport Users Association was throwing its weight behind the strike, which it said was caused by Auckland Transport and Transdev attempting to cut costs.

Co-ordinator Jon Reeves said they wanted train users to be safe on every trip they took - and this wouldn't be the case with AT and Transdev's plans.

However, the managing director of Transdev Auckland said he found it hard to understand the reasoning behind the strike, which he slammed as "disappointing" and "premature".

Michel Ladral said the proposed changes had worked in busy metros overseas, including London, Melbourne and Hong Kong.

"We call it 'driver-door operations', because 'driver-only operations' suggests there's only one person on board that train. That's not the case."

"We have up to 230 transport officers roving the network and going to those trains we know are causing trouble."

Ladral said Transdev was working alongside NZTA on a safety case and had invited the union to work with them through the testing process. This was still under way.

"We're halfway through and they're already calling the strike. It's just not right in my opinion."