The accident happened at midnight when Vinay, a 22-year-old resident of Bihar's Siwan district, was returning to Delhi with his 20-year-old brother Abhay, a 30-year-old woman, two children aged five and six months, and the car's driver, a police officer said.
The car collided with the divider near the NCC plot in Talgram, 152 kilometres Lucknow, and caught fire.
Mr Vinay, who works in Delhi, was found dead outside the car, while the rest of the passengers were found dead with burns, said Keshav Chandra Goswami, Additional Superintendent of Police.
Mr Vinay's relatives have been told about the accident after police got phone numbers from his mobile phone, Mr Goswami added.
The bodies have been sent for post-mortem, police said.