Regional councillors asked staff to report on the trends in passenger complaints, which had doubled from 2007-08 to 2009-10.
A staff report said the complaints were mostly the result of a combination of increased services - from 486 in mid-2007 to 718 - and a parallel increase in passenger numbers.
A call centre set up in November 2008 also made it easier for people to lodge complaints and adverse public perception of the council could also have made an impact, the report said.
There was also concern about a recent rise in complaints about Citibus services, partially explained by the "above reasons", and the number of its timetabled services that had not run, it said.
The company had reported 10 missed services in April and had been penalised for those services.
"Further monitoring over the next few months, including close scrutiny of missed services, is needed to see whether or not the number of complaints about Citibus services decline," the report said.
Staff were setting up a system to track the actions bus operators took when receiving a complaint.
They had asked Citibus, and planned to ask Dunedin Passenger Transport, for information on the actions they had taken in response to complaints made this year.
Cr Michael Deaker said at a recent regional council policy and resource committee meeting that May patronage figures of 133,000 were an improvement on the April numbers.
Patronage numbers for April 2010 of 120,000 fell below the 2008 and 2009 April levels, but it was not known why.
However, despite the fall in numbers, revenue for April 2010 of $250,000 was higher than the corresponding months in the previous two years, but down on March's peak of about $310,000.
Cr Stephen Woodhead said it was good to see patronage "climb a bit higher".
Citibus manager Tony Collins said many of the complaints would be solved by "real time" information at bus stops as its new global positioning system units in each bus enabled the company to let people know where buses were when they called to complain.
It was also working on its systems around bus driver sickness to minimise the problems experienced in April, he said.
