But Chief Minister Katy Gallagher has sent officials back to the drawing board after she saw the proposal to slash the speed limit by 20km/h on the whole of London Circuit in Civic by the end of the year.

The NRMA is also worried about the proposal to introduce the zones in central Belconnen, Tuggeranong and Civic, saying elements of the idea were ''problematic''.

The 40km/h zones introduced last year in Woden and Gungahlin have been considered a success and Territory and Municipal Services (TAMS) planners want to extend the lower limit to the other three town centres.

Ms Gallagher told The Canberra Times that dropping the speed limit in Woden and Gungahlin, made permanent this year, had proved a hit with local residents.

''There were two trials and they were very successful, people love them,'' the Chief Minister said.

''They were ambivalent when we went into the 40km/h trial but once they went in there, they realised there was quite a lot of support for them.

''So the decision was to put them into the other town centres, Belconnen and Civic, and Tuggeranong.''

Ms Gallagher said she was worried when officials, who were planning public consultation, showed her maps of the proposed speed zones.

''I saw the maps recently and I've asked TAMS for more information on them,'' she said.

''They've wanted to go out to consultation on those three sites but in say, Civic, it's the whole of London Circuit, pretty much, at 40km/h.

''It wasn't clear from the brief that I got whether the consultation would ask people if they thought it should happen or if they would be asked if they thought 40km/h was a good idea for Civic and I'm going to discuss that with TAMS on Monday [today].''

Ms Gallagher said that significant physical changes would have to be made to London Circuit if the speed limit was dropped.

''When I saw the maps, it was clear that it's definitely more complicated than Woden or Gungahlin,'' she said. ''Corinna Street in Woden is narrow and small and likewise Hibberson Street has quite a lot of traffic calming measures in there anyway.

''But in Civic, you would be looking at quite a lot of traffic calming measures along London Circuit.

''I didn't think the other three looked as straightforward as Woden or Gungahlin in terms of disruption to traffic and TAMS would have a good understanding on what speed people would be going at on those roads and I want a good understanding of that too.''

NRMA director Alan Evans said that Civic, Tuggeranong and Belconnen were less straightforward than Gungahlin and Woden. ''They hold this [40km/h zones] out as a panacea but you've got to look at the crash rates, the numbers of pedestrian incidents and ask yourself is this really going to solve problems or even if there [are] problems to be solved,'' Mr Evans said.

''[London Circuit] would be problematic, because when you're on the lake side of that road and even when you're going past the police station, there's not much traffic and not many pedestrians.

''We would have to be convinced of the arguments for doing it, be convinced that people are doing this to respond to real problems and not just getting on a bandwagon.''