Use new powers on 20mph zone, Welsh Government urged
Campaigners are urging the Welsh Government to use new powers to reduce speed limits from 30mph to 20mph in built-up areas.
The government gained control over setting national speed limits this month.
Research by Public Health Wales has suggested the health benefits of such a move would be significant in reducing emissions and accidents.
The Welsh Government said the wider research remained "inconclusive".
Campaign group 20's Plenty For Us said the Welsh Government was "incorrect" and they "need to get on with it".
Anna Semlyen, campaigns manager, said there was a "huge number of reasons" for cutting from 30mph to 20mph (48km/h to 32km/h) in built-up areas.
She said the Welsh Government needed to "listen to their own public health directors".
She added: "The health economics are absolutely clear. It's recommended by the World Health Organisation... by the Association of Public Directors of Public Health.
"Anybody in health says it's a good idea so, Wales, you need to get on with it."
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Councils are able to alter speed limits after a public consultation.
A report by Public Health Wales in 2016 found there would be "significant" public health benefits from dropping the limit.
It said transport emissions would drop by 12% in residential areas and would result in about 2,000 fewer road traffic casualties each year, saving about £92m.
Sarah Jones, a consultant who wrote the study, said: "Actually we struggled to find negative health effects [to lowering the limits].
"In almost everything we look at - road traffic injuries, air pollution, noise pollution, social cohesion, active travel, physical activity generally, loneliness and benefits to reducing isolation - they are all seen as a result of increased use of 20mph."
Last month, a global think tank for transport policy at the Organisation of Economic and Co-operation and Development called for a standard speed limit of 20mph in urban areas around the world.
A Welsh Government spokeswoman said: "We continue to support local authorities' decision making to reduce 30mph speed limits in their area where there are local circumstances.
"While the wider research remains inconclusive we continue to consider research in this area including working closely with colleagues in the Department for Transport who have commissioned a three-year research project to consider the benefits of lowering the speed limits in 30mph zones.
"That work is due for completion later in the year."