"All of the legislation encompasses how long people driving buses can work and what breaks they should take.
"Not all of the driver's shifts are breaching the legislation but certainly the long ones are."
O'Sullivan said drivers had told him that some at the company are being rostered on for 70 hours a week.
"It's unacceptable in this day and age that people should be asked to work those types of hours. It's a significant safety risk.
"If rosters exceed 13 hours a day then there's requirements for paid breaks and the rest break regulations specify when breaks should be taken.
"But shifts we've seen have long periods of work with unpaid breaks in the middle of the day and our advice is that those rosters breach that legislation."
O'Sullivan said some members at NZ Bus work close to those hours, but the difference is that they get compensated with penal rates and rest breaks.
"In the Tranzit shifts that we've seen there's no provisions like that and people are still expected to work them."
Tranzit and Police have been contacted for comment.
Police have confirmed they received a complaint about bus drivers' working hours yesterday and said they were looking into it.
Meanwhile the teething problems continue for the network itself, with two buses getting stuck on their new routes last night.
A local contacted NZME around 6.30pm yesterday to report two buses grounded near the Grenada North bus depot.
A got stuck on the driveway of the depot itself, and then another bus found itself jammed after trying to enter the nearby Metro Glass driveway.
Both buses were left jutting out across one lane of the road until they could be freed.
Metlink said it was aware of the situation and was in the process of establishing how it happened.
