Latest data from the end of March shows 24.7 per cent of services were late compared with 16.24 per cent in the first week of January.

A service is considered on time when departing a nominated point within one minute early and four minutes later than scheduled.

Each weekday almost 22,000 times are noted and in 2015-16 there were more than six million records made.

"While a bus may start and end a route on time, some of the timing points in between may not be met, affecting our on-time measurements," a Transport Canberra spokesman said.

"A few factors have contributed to the network punctuality outcome, including roadworks under way throughout Canberra and the way we measure on-time running.

"Transport Canberra is monitoring network delays due to roadworks, and where possible will recalibrate its timetable to reflect actual bus travel times.

"Early running is now at its lowest point of 5.78 per cent. This is important because for our customers it is generally worse that a bus leaves early than slightly late.

"If a bus leaves early there is an increased chance our passengers might miss that bus."

Other performance indicators were mostly positive. More people were using MyWay cards, new routes were attracting strong patronage and overall passenger numbers climbed.

"Investment in new buses and services, such as the new airport service, will help to attract more people to public transport in Canberra," the spokesman said.

"MyWay cards provide a discount compared to paying for a cash ticket. The cards also provide a very useful source of passenger movement data to Transport Canberra, allowing us to plan our network more effectively.

"In 2017 we are seeing close to 90 per cent of all passenger boardings being made with a MyWay card."

Overall fare revenue showed annual growth of between 3.5 and 4 per cent, reaching $23.118 million in 2015-16.

The spokesman said patronage on the new Weston line had doubled since it was introduced in August 2016.

The Free City Loop service introduced in July 2016 has recorded more than 70,000 boardings.

The Red Rapid series carried more than 190,000 passengers in March 2017, an increase from 156,000 in March 2016.

Public transport advocate David Johnston said the latest performance data was encouraging.

"The high use of MyWay combined with the well-overdue change to allow rear door exit at all stops on all services will increase the efficiency of bus services and should be good for ridership," he said.

"These numbers show that improvements can be made to our public transport to increase ridership without spending billions on light rail.

"However it is very disappointing to see the latest numbers on punctuality, with less than 70 per cent of services running on time and nearly 25 per cent of services running late.

"These numbers need to be addressed by Transport Canberra if it is serious about reliability and increasing passenger numbers."

Mr Johnston welcomed the recent introduction of an airport bus service.

"However, more improvements to the network are needed to make public transport attractive to more people," he said.

"Better planning is needed to have good connecting services and key services such as the Blue Rapid should run later especially on Friday and Saturday nights."