TRANSWA is reducing the size of coaches it runs between Collie and Bunbury and providing extra drop-off points.
The service’s 56-seat coach will be replaced by a coaster with a capacity of 13 seats plus two wheelchairs on July 10.
TransWA spokesman David Hynes said the service had averaged two passengers a trip in the period up to the end of March.
Mr Hynes said the full-sized coach could not be justified.
The smaller bus will stop at Bunbury Central Station, meaning travellers will not need to catch a connecting service into the town centre.
Two additional stops have been added at Bunbury Bus Station and the Activ Foundation.
This follows feedback from Activ employees who said they would use the service to travel to and from work.
Mr Hynes said a targeted marketing campaign, including community engagement and advertisements in local media, will be undertaken in a bid to improve patronage.
Collie-Preston MLA Jodie Hanns said getting the trial extended to January 2024 was a positive outcome.
“The best way to make sure the service remains beyond then is to make your next trip to Bunbury via the Collie-to-Bunbury bus service,” Mrs Hanns said.
TransWA launched the 12-month road coach trial last October following the closure of the privately run South West Coach Lines service.
It provides an early morning departure from Collie and return from Bunbury in the late afternoon on weekdays.