Councillor Allison Duncan has made an impassioned plea for the SIC to follow through with plans to widen the Levenwick road.
Concerns had been raised after the council pledged to explore a 50mph speed limit and crash barriers as an interim solution.
But a post by bus driver Jacklyn Smith on social media said that would not go far enough, and large vehicles would still be put at risk.
Mr Duncan said at Wednesday’s full council meeting the proposed measures were unacceptable.
“Nobody is interested in the speed or smaller temporary safety barriers,” he said.
“It’s all about the widening this road. Speed limits and crash barriers would not address the situation.”
The South Mainland councillor said the SIC had “a duty to ensure the safety of those using this road”.
Council convener Andrea Manson repeatedly told him the SIC was not looking to dismiss the widening project – just to potentially pursue a cheaper option as a temporary solution.
She said reports about the road would come to the full council early next year.
But Mr Duncan was not appeased, and said any scaled-back plans would still put large vehicle drivers at risk.
Fellow South Mainland councillor Alex Armitage agreed more needed to be done to protect these drivers.
He said he had been taken out onto the road by a truck driver recently, and had seen first-hand how narrow the road was for these vehicles.
“I crossed my fingers as we went past a bus,” he said.
However, he said the crash barriers and speed limits would help protect other drivers, pedestrians and cyclists – and encouraged the council to follow this up.
Council leader Emma Macdonald reminded them that the Cullivoe road – which has been hit by a delay, members heard – was their number one priority project.
And she said that staff capacity, as well as budget restrictions, affected how much work they were able to do.