Carjacking incident at Risca and Pontymister railway car park
A woman has been left in "considerable distress" after an attempted carjacking incident in Caerphilly county, say British Transport Police.
The offender threatened to stab his victim and demanded she get out of her vehicle at Risca and Pontymister railway station car park.
But he ran off as a train pulled into the station on Saturday at 14:00 GMT.
Officers have issued a CCTV image of a man they want to question in connection with the "terrifying incident".
He is described as around 6ft (1.83m) tall, aged 20 to 25, with bleached blonde hair.
He was wearing a blue puffer jacket and dark trousers. He was also carrying a white carrier bag.