Millions of drivers are facing the prospect of reduced speed limits in towns and cities across England and Wales, according to new research.
Figures obtained by The Independent show more than a third of local authorities have introduced measures to stop motorists exceeding 20mph on at least some roads, or are planning to do so.
Of the 75 local authorities that responded to a survey by the newspaper, 27 said they had introduced or were in the process of considering default 20mph zones, while six were awaiting new guidelines from the Department for Transport (DfT).
A separate poll for the newspaper found public backing for a blanket 20mph limit in built-up areas has reached more than 60%, with support particularly strong among women, younger people and pensioners.
Eight million people are already living in authorities where 20mph limits are in operation such as Liverpool, Bristol, York, Newcastle-upon-Tyne and parts of London.
The move comes after official figures released in August showed road casualties in 20mph zones increased by almost a quarter in 2011.
The number of people killed or injured on roads in built-up areas with a speed limit of 20mph totalled 2,262 in 2011, up by 24% from 2010.
Meanwhile casualties on 30mph roads were down by 1% from 2010, recorded at 125,494 in 2011, according to data from the DfT.
Transport minister Norman Baker said at the time that local authorities were best placed to make the decision on whether or not to impose 20mph limits in certain areas.
"British Medical Journal research has shown a reduction in casualties and collision of around 40%, a reduction in children killed or seriously injured of 50% and reduction in casualties among cyclists by 17%," he said. "That is why we believe 20mph speed limits are useful in certain residential areas and support their introduction where it can be shown that they benefit road safety and quality of life."