A manager at Uber sent an email to senior executives raising concerns about the risks of self-driving vehicle programme - just five days before an Uber vehicle struck and killed a pedestrian in Arizona in March this year.
The email has now been brought into public domain by The Information after conducting interviews with some of Uber's former and current employees.
According to The Information, the email was sent on 13 March by Robbie Miller, a testing-operations manager at Uber.
In his email, Miller complained about athe number of near misses by Uber's autonomous vehicles, which were not properly investigated and had even been ignored. Miller also raised concerns about the "poor behaviour of the operators", who lacked proper training.
An Uber vehicle veered onto the pavement and continued to drive along the pavement
Miller claimed that Uber's autonomous cars were "hitting things nearly every 15,000 miles", and added that some of them were even being damaged in scrapes almost every other day in February 2018.
In one particular incident, an Uber vehicle veered onto the pavement and continued to drive along the pavement until its operator belatedly intervened, but the incident was completely ignored by senior officials for several days.
"This is not how we should be operating," Miller wrote in the email.
Miller urged senior management to start using two backup drivers in each autonomous test vehicle.
The email was sent to seven senior executives and attorneys in the company, including Eric Meyhofer, who leads Uber's autonomous vehicle division.
The crash in Arizona happened on 18 March and resulted in the death of Elaine Herzberg, a 49-year-old woman. The accident led to the suspension of all testing activities. Later, an investigation revealed that the backup safety driver of the vehicle was watching The Voice on her phone when the fatal crash occurred.
Miller resigned from Uber three days after sending the email, according to a colleague of his at the company, who also revealed that none of the executives and attorneys responded to Miller's email.
Uber declined to comment on the email sent by The Information.
"The entire team is focused on safely and responsibly returning to the road in self-driving mode," the company claimed in a general statement.
"We have every confidence in the work that the team is doing to get us there."
Cotton seedling freezes to death as Chang'e-4 shuts down for the Moon's 14-day lunar night
Fortnite easily out-earns PUBG, Assassin's Creed Odyssey and Red Dead Redemption 2 in 2018
Meteor showers as a service will be visible for about 100 kilometres in all directions
Saturn's rings only formed in the past 100 million years, suggests analysis of Cassini space probe data
New findings contradict conventional belief that Saturn's rings were formed along with the planet about 4.5 billion years ago