A man suffered serious head injuries and two women were also badly hurt after a teatime road crash on the A71 in Larkhall yesterday.
Paramedics aboard an ambulance that happened to be passing lent immediate assistance.
Now police are appealing for witnesses to the smash, which happened around 5pm - for example from other drivers who were on that stretch of road at the time,
A 19 year old man had been driving his white BMW east on the A71, Ayr Road, Larkhall, when he was involved in a collision with a blue Volkswagen Polo travelling west.
He was initially taken by ambulance to Wishaw General Hospital with serious head injuries, but has since been transferred to the Queen Elizabeth University Hospital in Glasgow where medical staff describe his condition as critical.
There were no other passengers in the BMW.
The two women from the VW Polo, the 58-year-old driverand her 24-year-old daughter, who was a front seat passenger, were also taken to Wishaw General Hospital.
The mum suffered leg and back injuries, while her daughter sustained internal injuries.
Medical staff describe their condition as stable.
Constable Gregg Dick at Motherwell Road Policing Unit said: “Thankfully at the time of the crash an ambulance happened to be passing and the paramedics were able to stop and assist the injured at the scene.
“From our investigations there were other cars on the road when the crash happened and I would appeal to anyone who saw the crash or who may have information that will assist officers with their enquiries to contact officers at Motherwell Trunk Roads Policing Unit via 101.”
The A71 – between Ayr Road and Ashgillhhead Road – was closed for around six hours. It is now fully re-opened.