Horizons' bus services have worked on a coverage model - covering as much of town as possible with limited resources. It caters to people without cars, which Tonnon said was admirable.
The trial route would work on a patronage model and will also appeal to people with cars.
The aim was to use frequency to increase passenger numbers.
Buses every 15 minutes are a "turn up and go" proposition, Tonnon said.
The Whanganui council was considering putting $180,000 into the second year of its upcoming Long Term Plan, Mayor Hamish McDouall said at its February 9 meeting.
Horizons has said it will contribute the same amount and Waka Kotahi New Zealand Transport Agency is likely to match that.
Bee Card data will be used to decide which stops should be kept. One stop will be at Whanganui Hospital, where car parking is limited.
It will run longer into weekday evenings, later on Friday and Saturday nights, and connect to the Whanganui River Markets and the beach.
Because it passes all four city bridges and because Whanganui buses have bicycle racks it will add options for walkers and cyclists.
More buses will be needed, and they will need new branding, marketing and livery, Tonnon said.
During the trial remaining routes will continue to operate.
Horizons spends about $600,000 on Whanganui bus services every year and every trip taken by a Whanganui person is subsidised by $5 to $6.
In 1990 Whanganui people made an average 10 bus trips a year. By 2020 that had fallen to three.
