Under a government rating system, the Dunedin City Council is required to use, some sections of narrow, winding road near the city are assessed as being appropriate for speed limits that are up to double those posted.
Dunedin City Council senior traffic engineer Bruce Conaghan said speed limits were reviewed every three years, as nearby developments meant limits could become inappropriate.
Community boards had also requested a review of some areas.
The council is legally required to use "speed limits New Zealand" (SLNZ), a procedure for calculating the speed limit.
It takes into account development, the extent of frontage and roadside development, and road features, including footpaths, cycleways, and curves and crests on the road.
An example of differences between the posted limit and the SLNZ rating is North Rd, running up the hill to Mt Cargill Rd, where the SLNZ rating is 100kmh, compared with the 50kmh limit in place.
Mt Grand Rd, a 50kmh area where excessive speed has resulted in crackdowns in the past by police, also has a rating of 100kmh.
Mr Conaghan, who is dealing with the review, said on a road like Mt Grand Rd, a high percentage of drivers drove about 70kmh, as they viewed the road as rural.
It was important to get the limits closer to the speed that seemed natural to the driver, as motorists were less likely to comply with arbitrarily imposed limits that were too low.
"Realistic and credible" limits were voluntarily observed by the majority of drivers, and were more effective in regulating traffic flow and reducing crashes.
"The fundamental thing is the speed limit is not a target."
He said, in a report to this week's infrastructure services committee, development was the primary determinant of speed under SLNZ, and road features secondary.
The system was "not particularly good" at setting limits on some rural roads.
The New Zealand Transport Agency was working on the rating system.
Mr Conaghan said his next job was to consider the speed changes in more detail, and discuss the proposed changes with the agency, before they went out for public consultation.
