A woman's died after a collision involving a van on the Heads of the Valleys Road.
The 41 year-old was walking away from a broken down vehicle with a man at around 7:15pm between Pant and Dowlais.
Her family are being supported by specially trained officers.
South Wales Police are appealing for witnesses, especially a motorist who stopped to speak to the van driver at the scene, to contact South Wales Police Roads Policing Unit via 101.
It is one of South Wales' busiest routes but is also known for its accident blackspots.
A project to upgrade the Heads of the Valleys Road (A465) was given the green light on 1999.
Today the latest stage of the £800million dualling scheme will be officially opened
The Welsh Government says section three of the A465 dualling scheme, Brynmawr to Tredegar, costing £158million, will improve safety and journey times, as well as boost the economy of the region.
It says the 7.8km section of road, joint funded by itself and the EU, has been upgraded from a three lane road to a dual carriageway to alleviate the current issues of poor visibility, congestion, lack of overtaking opportunities and accident hotspots.
Tributes have been paid to a pregnant woman who died in a crash on the Heads of the Valley road on Friday night.
20-year-old Sophie Williams and her unborn baby were killed in a two-car collision between Brynmawr and Ebbw Vale.
20-year-old Sophie Williams and her unborn baby died last night, as she travelled home from a Valentines meal with her fiance, 28-year-old Ben Morgan.
She was due to give birth in just two weeks time.
Ben has returned to the scene of the accident to lay flowers for Sophie and his unborn baby girl.
He's due to be interviewed by police about the tragedy.
Her family in Tredegar, Gwent, were too upset to talk of the tragedy yesterday.
A mum-to-be who was killed in a car crash on the Heads of the Valleys Road yesterday, has been named locally as 20-year-old Sophie Williams from Tredegar.
She was due to have her baby in just two weeks time.
Miss Williams died along with her unborn baby girl as she and her fiance Ben Morgan drove home from a Valentine's meal.
The couple were planning to get married after the baby was born.
They'd been told they were expecting a little girl, and had chosen the name Kayleigh.
The crash happened at 11pm on Friday night during a severe storm at an accident blackspot where roadworks were going on, ironically to turn the road into a dual carriageway, after a high number of fatalities.
Firemen and paramedics freed Sophie from the wreckage and she was taken to Neville Hall Hospital in Abergavenny, but police said doctors were unable to save her and her unborn baby.
Ben and Sophie were in their silver Peugeot 307 when it was in a collision with a blue Peugeot 207 coming the other way.The driver of the other car, a man from Basingstoke, Hampshire, was uninjured but treated for shock.Gwent Police are appealing for anyone who saw the accident to come forward.
Ben is due to be interviewed by police about the tragedy.
A pregnant woman and her unborn baby have died in a crash on the Heads of the Valleys Road between Brynmawr and Ebbw Vale.
Emergency services were called to the collision involving two cars at around 11pm last night.
The dead woman was 20 and from Tredegar.
A pregnant woman has died following a crash on the A465 heads of the valleys road. The 20-year-old from the Tredegar area was a passenger. The crash happened last night around 11pm between Brynmawr and Garnlydan. Two cars were involved.
The mother-to-be was taken to Nevill Hall hospital in a critical condition but later died. The male driver of the car she was in was uninjured. Another female passenger suffered minor injuries to her headand legs. The male driver of the other car involved also escaped uninjured.
The family of the deceased are now being supported by Gwent police who are appealing for anyone who may have witnessed the collision to contact them on 101.
One lane is closed for emergency repairs after an accident on the A465 in both directions between the Resolven Roundabout and the Aberdulais Roundabout.
Motorists across the South Wales Valleys and beyond are to benefit from more than £80m of European money. It's due to be spent on dualling several miles of the A465 Heads of the Valleys road between Brynmawr and Tredegar.
There will also be other improvements along the route which is one of the busiest on the Welsh main road network. David Wood reports.
Wales' Transport Minister, Carl Sargeant, told us the Heads of the Valleys road is vital for people to access jobs, and for the economy to function properly.
The Deputy Minister for European Programmes, Alun Davies, said it is 'fundamental' infrastructure, which 'enables us to compete on the Welsh, UK, European and world stage.'