The 34-year-old man, who voluntarily went to police and was arrested on Sunday (January 28), was released from custody the following day, a spokesman for Metropolitan Police said.
Another man, Jaynesh Chudasama, 28, of Hayes, has been charged with three counts of causing death by dangerous driving.
He appeared at Uxbridge Magistrates' Court on Monday (January 29) and was remanded in custody until a hearing at the Old Bailey scheduled for February 26.
Three teenagers - Harry Rice, 17, and 16-year-olds Josh McGuinness and George Wilkinson - all died after being being struck by a black Audi A5 at around 8.40pm on Friday (January 26).
They were all students of The Harefield Academy in Uxbridge and were walking to a 16th birthday party when they were struck near a bus stop.
Speaking to getwestlondon, Josh's sister Melissa Blackwell said the teenagers, who had known each other since starting school, were "so kind and caring for others".
Melissa, from West Drayton, said: "Everyone keeps saying the same thing about Josh, that he was just hilarious and wouldn't fail to put smiles on people's faces.
"It's the same with George and Harry, all three of them were so funny, kind and caring for others.
"All such mummies' boys as well, Josh and my mum were extremely close."
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