Motorists in Portsmouth will have to limit their speed to 20mph in the city's residential areas as part of a major new road safety initiative.
Portsmouth council will introduce a 20mph speed limit on Friday
The council says the new limit around most homes will protect all users of the city's narrow, congested streets.
However, a spokesman admitted that the scheme will be "self-enforcing", with no additional resources allocated.
Most of Portsmouth's main routes will not be affected by the lower limit which is to be brought in on Friday.
Starting in the south east of Portsmouth, it will be extended across most of the city by the end of 2007.
The government funded scheme follows a period of consultation which, the council says, showed that the majority of residents were in favour.
Traffic surveys will be carried out after six and 12 months to help monitor its success.
If speeds have not dropped, residents will be asked whether they want extra action to be taken.
Councillor Alex Bentley, executive member for traffic, praised the "bold step" and said the new speed limit will help to "change attitudes and make speeding an anti-social way to behave".
He added: "It's a vital safety measure and we make no apology for bringing it in."
Similar low-speed zones are already in place in other towns and cities across the south, such as Salisbury and Bournemouth.
Portsmouth City Council, however, claims that its adoption of the 20mph limit is "a first" in terms of the extent of the area covered.