An 890-word email was sent to Uber’s executives that raised safety concerns about the company’s autonomous vehicle program just days before an Uber vehicle killed a pedestrian in Arizona last March. The email was sent to the head of Uber’s autonomous vehicle division and other top executives and lawyers by a manager in the group. It was made public by The Information, which validated the assertions through interviews with current and former employees. The email complained about near misses that frequently weren’t investigated properly or even ignore, and about backup drivers who lacked proper training and vetting.

The email from Robbie Miller, an operations manager from the autonomous group, raised serious concerns about the backup drivers being placed in control of the vehicles. Miller writes that “poor behavior of the operator” was usually the cause of accidents, and he noted that “several of the drivers appear to not have been properly vetted or trained.” He goes on to recommend that Uber reinstate its policy of having two backup drivers in each vehicle. Days later, on March 18th, a self-driving Uber vehicle was involved in a fatal collision. The backup driver was reportedly streaming The Voice on Hulu on her phone at the time of the crash.

Even before the fatal crash, Miller’s email claims that Uber’s vehicles were getting into accidents with alarming regularity. It notes that the company’s fleet was “hitting things every 15,000 miles,” and that a vehicle was damaged “nearly every other day” in February 2018. Near misses reportedly occurred as frequently as every 100 miles, while backup drivers had to take control once every one to three miles. The more miles the fleet drove, the more likely incidents were to arise.

At the core of many of Miller’s complaints is the suggestion that Uber’s self-driving fleet had expanded far too quickly for the company to safely handle. The email says it took two weeks for one near collision to be properly investigated and that another incident where a car mounted the sidewalk was ignored before Miller raised it personally. It goes on to claim that Uber’s fleet could be reduced by as much as 85 percent without slowing the development of the self-driving software since the company’s cars were already collecting “more than enough data.”

Although Miller did not receive a direct response to his email beyond an assurance from his manager that the issues he raised would be looked into, Uber said that his concerns were later included in the top-to-bottom safety review that it conducted as a result of the fatal collision.

It’s unclear what within Uber initially led to these failings, but The Information speculates that Eric Meyhofer, who leads Uber’s autonomous vehicle division and was one of the seven recipients of the email, was placing too much emphasis on the number of miles driven as a metric for how advanced its software was getting. In December 2017, Uber proudly boasted that its self-driving cars had already driven 2 million miles, after reaching the 1 million milestone just 100 days before.

Uber is not alone in touting this metric. Waymo recently announced that its cars have driven over 10 million miles, while Tesla owners have reportedly driven as many as 1 billion. The assumption is that the more miles a fleet has driven, the better the software must be. But in the case of Uber, it appears that the fleet was generating more data than it could analyze, and diminishing returns had set in.

Uber’s self-driving car program resumed testing back in July. It did so with a driver in manual control of each vehicle and with new safety features, such as a monitoring system to ensure that the drivers are paying adequate attention. Each vehicle is now helmed by two drivers, just as Miller’s original email recommended.

Responding to the report, a spokesperson from Uber said that “the entire team is focused on safely and responsibly returning to the road in self-driving mode,” and that it was committed to implementing key safety improvements. The company intends to eventually resume on-the-road self-driving testing, but it will do so “only when these improvements have been implemented and we have received authorization from the Pennsylvania Department of Transportation.”

Gaining this authorization will be of critical importance as Uber moves into 2019, a year in which it intends to file an IPO.