Fifteen percent of Auckland's peak-hour bus services are late reaching their destination.
On thirteen city bus routes, fewer than half of the buses arrived on time, but Auckland Transport said overall, commuters should be pleased.
It said 90 percent of buses in the region should reach their destination within five minutes of the scheduled time, and 97 percent do.
But figures supplied to RNZ showed that in peak time that falls to 85 percent, and on some routes fewer than three buses in ten end up on time.
Metro operations general manager Brendon Main said the agency investigates problematic runs, and has a longer-term plan to improve bus reliability.
"We're trying to put in more kilometres of bus lanes each and every year.
"We had a three-year programme, of which we are in the third year, to put additional bus priority in which is aiming to speed up those run times by giving buses priority across the network."