Picture: Google Maps
The victim, who is in her 20s, was driving in Dunlop Road around 8.50pm on Sunday, 25 November when a car appeared behind her and began flashing its lights.
It then overtook and stopped in front her and a man got out the passenger side.
He walked over to her vehicle, opened the door and held a knife to her face while threatening to take the car.
He then suddenly got back into the car he was travelling in and was driven off.
An 18-year-old man was arrested on Wednesday, 28 November on suspicion of robbery and has been bailed until Friday, 21 December.
Police believe a group of around 20 youths may have seen the incident and would like to speak to them.
They also want to hear from anyone with information or dash cam footage.
Witnesses or anyone with information are asked to call Grays CID on 101 quoting crime reference 42/172630/18.
Alternatively they can contact Crimestoppers anonymously on 0800 555 111.
Tags: Thurrock, Tilbury