The Darfield no.86 will continue running until at least June next year.
The 87 from Leeston to the city will continue operating as it has been until December 20.
An Environment Canterbury spokeswoman said usage of the Leeston service remains below where it needs to be to continue it in its current form long-term.
"Options for the service beyond the end of the year are being considered. This will include looking at introducing a different fare structure to increase viability and assessing whether the extension from Leeston to Southbridge remains viable," she said.
"If a suitable solution can be found, the service will take a break during the holiday period, recommencing for the new school year in late January or early February 2020."
The Darfield service has continued to be well supported by the community with consistent usage, the spokeswoman said.
The bus trials began in January of this year.
In July, ECan confirmed the services would continue until the end of October.
