Up to 700 morning bus trips in Auckland tomorrow could be affected by industrial action that has been organised on short notice.
In a statement, Auckland Transport said bus users should check the journey planner and think about when they would travel on Monday morning.
The affected bus routes, operated by NZ Bus, include morning peak times.
North Shore express buses are run by a different operator and will not be impacted.
Executive general manager of public transport services Stacey van der Putten said AT had been told that NZ Bus and union representatives would enter mediation on Monday morning.
"It is deeply disappointing Auckland's bus users will have their morning travel disrupted by this industrial action at a time when the reliability of services and our passenger numbers have been improving," van der Putten said.
"Tomorrow's industrial action has the potential to disrupt tens of thousands of Aucklanders and we appreciate how deeply frustrating this is for our customers who have been incredibly patient over the past year while we worked to overcome the driver shortage.
"We're urging our bus passengers to use the AT Mobile App or Journey Planner before they travel tomorrow morning to find out whether their usual bus trip is affected and to see options for alternative services they can travel on."
Van der Putten said she hoped the unions and NZ Bus could work quickly to resolve the dispute so that "tens of thousands" of Aucklanders are not "unnecessarily inconvenienced" further into the week over issues that "could have been dealt with in mediation".
RNZ
