Figures collected from the ACTION bus network show the average number of passengers travelling on the arterial road between May and July this year was 7996 a day, significantly fewer than projected patronage used as part of the case for building a $783 million light rail line from the city to Gungahlin.

Minister for Capital Metro Simon Corbell said a direct comparison between the existing bus patronage and projections for trams on the Northbourne Avenue, Federal Highway and Flemington Road line was not representative and did not take into account forecast increases in population growth, increased employment and changed land use.

Figures provided to the Legislative Assembly by Territory and Municipal Services Minister Shane Rattenbury show the afternoon peak period between 3 o'clock and 6 o'clock has an average of 2707 passengers, the highest numbers on weekdays.

An average of 2570 passengers use bus services between 6am and 9am, just 882 between 9am and 12pm and a further 967 between noon and 3pm.

The evening sees an average of 652 passengers between 6pm and 9pm and just 218 between 9pm and midnight.

Across Canberra in July, there was a total of 1,305,304 passengers on ACTION services.

The Canberra-wide patronage delivered ticket revenue of $1,901,361.08.

The Capital Metro Agency expects tram services in the corridor will attract 13,700 passengers each day by 2021, and 20,700 by 2031.

The modelling considers expected population growth and pull factors for tram services including growing road congestion, rising fuel prices and planned increases in density along the Northbourne corridor.

Assumptions released by the agency show plans for 3500 passengers in the morning peak between 7 o'clock and 9 o'clock, nearly 1000 more passengers than current bus patronage from 6am to 9am.

The afternoon peak period between 4 o'clock and 6 o'clock would see 3400 passengers two years into the operation of light rail, 700 more than currently use buses from 3pm to 6pm.

Capital Metro has built its numbers using existing bus patronage as well as travel surveys, traffic counts, simulated household travel and participation rates in activities including work, education, shopping and recreation.

Employment, student enrolments, recreation, public transport fare prices and government policy outcomes are also considered.

Mr Corbell said the new bus passenger figures were not a like-for-like comparison with patronage projections for the future light rail route.

He said they only represented the daily number of passengers on buses on Northbourne Avenue as they departed stops at Macarthur Avenue, while the government's light rail estimates were for the whole route.

He said the road was already changing rapidly and creating growing demand for public transport.

"As a modern and attractive transport mode, light rail attracts more passengers out of cars than is typically achieved by buses. Light rail is also capable of moving more passengers than buses and is best placed to support ongoing growth," he said.

Data from route 956, which runs from the Gungahlin bus station to the City bus station via Northbourne Avenue and Flemington Road, shows an average of 486 passengers on Saturdays since February 1.

Trams on Canberra's light rail line are expected to have a capacity of about 200 passengers and operate every seven minutes in the morning peak in 2021 and every four minutes in 2031.

Australian Bureau of Statistics data shows about 8 per cent of Canberra's population uses public transport for work or study.