The speed data was collected from four-tube counters in George St between the Octagon and Frederick St by council contractor Fulton Hogan.
When asked if the council was happy with motorists travelling at more than twice the posted speed limit, Ms Benson replied: "Motorists should always travel at the posted speed limit".
Southern police district road policing manager Inspector Amelia Steel said the council made her aware of the reduced speed limit and to "support their intent".
No road policing staff had been deployed to the area, Insp Steel said.
Road policing staff were primarily interested in the speeds motorists were travelling on highways, she said.
"We deploy to risk and the risk still remains on our open roads."