A woman is appealing for help to find a lorry driver who she says crashed into her car when she was driving with her two-year-old daughter.
Amy Wickland, 28, said she was driving along Newport Road, in Cardiff, with her child in the back when a lorry hit her car, forcing her off the road.
"I didn't know if my daughter was alive or not in that moment," she said.
South Wales Police said it was investigating the "distressing incident".
The mother-of-three said she was driving home from a hospital appointment at about 12:30 GMT on Friday when she saw the lorry being driven "irresponsibly".
Seconds later, she said, her Audi A3 was shunted off the road.
"It was like a bang and we ended up spinning across the three lanes and we ended up facing the opposite direction in the middle of the road," she said.
The nursery nurse said her daughter Layla would normally have been sitting in her child seat on the side the lorry hit, but she had put her on the other side that afternoon.
"I've never sat her on that side before, but it's so lucky I did because it could potentially have crushed her in her sleep," she said.
"She's ok, but she was in absolute shock, she was crying so much. Luckily neither of us have serious injuries."
Ms Wickland said the driver failed to stop and police later told her he stopped down the road, got out and checked his vehicle before driving off.
Two men in a van pulled over to help the family and allowed them to sit in the back of their van, at a distance, while she called 999.
But she claimed a call handler for South Wales Police said because no-one was seriously injured, officers would not attend because of a new policy.
She said after being advised to move the car - if it was drivable - as it was obstructing traffic, she had no choice but to drive the damaged car home.
"It was really traumatising to be left in that situation," she said.
"The car is a write-off, but I don't care about the car at all. There's a driver out there who knows he's hit someone or something and he hasn't even stopped to check," Ms Wickland said.
"We could have been dead in that car, or maybe next week a family could die on the motorway - that's 70mph, this was 30 - I do not want this to be dropped, the next person might not be so lucky."
A spokesman for South Wales Police said officers were investigating and were appealing for dash cam and CCTV footage.
"Due to the distance and other vehicles on the road blocking a clear view, neither the collision nor the registration plate of the lorry involved can be seen on CCTV that has so far been recovered," he said.
"This was a distressing incident for the driver who was with her young child and we would appeal for the lorry driver to come forward."