SCOTLAND'S first compulsory 20mph zone will be created in Edinburgh under plans being devised by the city council.
The 100,000 pilot scheme would cover 25 miles of streets across a swathe of the south side of the city, including Marchmont, Grange and Newington.
Councillors hope cutting speeds will reduce crashes and casualties following the success of a similar scheme at Portsmouth in Hampshire.
Glasgow City Council is considering similar plans after a report into improving health identified it as a "key priority".
However, motoring groups said blanket speed cuts risked alienating drivers.
Edinburgh's new 20mph zone would stretch between the Meadows and Blackford Hill, and between Bruntsfield Place/Morningside Road and Holyrood Park. It will be considered by councillors this month and could be introduced next year, but would not involve new traffic-slowing measures such as speed bumps, or speed cameras. However, 12 miles of through routes would remain 30mph, such as Melville Drive, Marchmont Road, Grange Road, Charterhall Road, Causewayside, Newington Road and Dalkeith Road. If successful, it could be extended across the city.
The move follows 20mph limits being introduced around all Edinburgh's primary schools, some secondary schools, and advisory 20mph limits in many residential areas.
There are already such advisory limits in several parts of the proposed compulsory 20mph zone, such as in Marchmont.
The council said the police backed the scheme in principle following initial discussions.
However, the Institute of Advanced Motorists urged caution.Neil Greig, its director of policy and research, said: "Edinburgh roads have never been safer and this success has been due to a partnership between those who design the roads, those who enforce the law and the vast majority of law-abiding drivers.
"20mph in the right place can be a real road safety and environmental improvement, but blanket bans may risk losing that public support.
"Many roads in central Edinburgh are perfectly capable of safely allowing traffic to travel at 30mph, particularly outside the peak hours.
"We support 20mph limits outside people's homes and schools, where only local traffic is involved, as they reinforce safety messages and can encourage more walking and cycling journeys."
However, Mr Greig added: "The City of Edinburgh Council must be very open about the costs and benefits of spending limited resources on 20mph limits when other road safety issues may end up being neglected."
Council transport convener Gordon Mackenzie said: "In Portsmouth, there was a 15 per cent reduction in accidents resulting in injuries.The evidence is that it's largely self-policing and it appears to be a lot more cost-effective because instead of putting speed bumps on every street, you can target them where there is a pattern of problems."
"We've seen what's happened in Portsmouth and we know other English cities, such as Bristol, are looking to introduce 20mph zones. The results are encouraging in terms of the reduction in accidents."
The Scottish Government welcomed the plan. Its road safety blueprint includes a commitment to encourage local authorities to consider 20mph limits in all residential areas.
A spokesman for its Transport Scotland agency said: "Following the successful implementation of 20mph speed limits around schools in Scotland, we would welcome any plans by local authorities which will help towards the reduction in pedestrian, cyclist and particularly child fatalities and casualties that we are committed to in Scotland."
However, he stressed it was up to councils to decide what form the 20mph limit should take.