The Welsh Government has announced plans to reduce the national default speed limit in Wales from 30mph to 20mph on residential roads and busy pedestrian streets.
It forms part of its legislative priorities for this year and will run as a pilot scheme in eight areas of the country.
If passed, Wales will be the first UK nation to introduce the speed limit, which the Welsh Government said will reduce the number of road-related deaths.
The Welsh Government said the move will also have a positive impact on wellbeing and the environment.
The risk of being killed is almost five times higher in collisions between a car and a pedestrian at 31mph compared to the same type of collisions at 18.6mph, according to the Welsh Government.
Lee Waters, Deputy Minister for Climate Change, said: "Making 20mph the default speed limit on busy pedestrian streets and in residential areas across Wales is a bold step that brings about significant benefits.
"Not only does it save lives, but it also helps to make our streets a safer and more welcoming place for cyclists and pedestrians, has a positive outcome for our physical and mental wellbeing and with fewer vehicles on the road helps create a positive impact on the environment.
"We know this move won't be easy - it's as much about changing hearts and minds as it is about hard enforcement - but over time 20mph will become the norm, just like the restrictions we've introduced before on carrier bag change, smoking inside businesses and organ donation."
The village of St Brides Major in the Vale of Glamorgan is one of the first areas to see the 20mph speed limit introduced as part of the pilot.
The headteacher of St Brides Major Church in Wales Primary School welcomed the move.
Duncan Mottram said: "Both the school and local community are delighted to be playing such a prominent role in this exciting initiative.
"Reducing the speed limit on our roads will make them safer and also help to promote alternative, greener forms of transport like walking and cycling.
"Pupils have been involved in this project from the start, taking part in a competition to design road signs that appear around the village, while a local residents' group has also made their support clear from the outset.
"We are proud to be one of the pilot schemes for this new lower speed limit and we look forward to it being rolled out across the country."
The eight areas involved in the pilot scheme
St Brides Major, Vale of Glamorgan - already launched
St Dogmaels, Pembrokeshire - already launched
Llanelli North, Carmarthenshire - launching in mid-July
North West Cardiff - launching in September
Cilfrew Village, Neath Port Talbot - launching in September
Abergavenny and Severnside, Monmouthshire - launching in early 2022
Buckley, Flintshire - launch date unconfirmed
The Welsh Government has already introduced a permanent 50mph speed limit on a stretch of the M4 motorway in a bid to reduce nitrogen dioxide levels and the risk of accidents.
Approximately seven miles of motorway between junctions 24 and 28 near Newport became subject to average speed limit checks in March.