We've known since May that serious flaws in Uber's self-driving software contributed to the fatal crash that killed pedestrian Elaine Herzberg in Tempe, Arizona, back in March. For example, Uber had disabled emergency braking on its vehicles to make its cars' driving behavior less erratic. A new report from Business Insider's Julie Bort sheds light on why Uber's software may have been so flawed at the time of the March crash.

In early 2018, Uber's Advanced Technology Group—the team developing self-driving cars—was focused on getting ready for a forthcoming demo ride with Uber's recently hired CEO, Dara Khosrowshahi. Business Insider reports that in November 2017, Uber circulated a document asking engineers on the self-driving car team to think about "rider experience metrics." Engineers were encouraged to try to limit the number of "bad experiences" to one per ride.

Two days later, another email went out announcing that Uber was "turning off the car's ability to make emergency decisions on its own like slamming on the brakes or swerving hard."

Uber bosses insisted that this was a safety measure. If a self-driving car slammed on the brakes or swerved at the wrong time, it could startle and confuse other cars on the road, they claimed. Instead, their plan was to rely on safety drivers to intervene in situations where the car is about to make a mistake. Of course, disabling these emergency maneuvers could also improve the rider experience metrics.

"A few weeks later, they gave the car back more of its ability to swerve but did not return its ability to brake hard," Business Insider reports.

Hard braking was still disabled in March when Elaine Herzberg stepped into the Tempe roadway ahead of an Uber vehicle. According to the NTSB's report, "at 1.3 seconds before impact, the self-driving system determined that an emergency braking maneuver was needed to mitigate a collision." However, "emergency braking maneuvers" were "not enabled." Even worse, "the system is not designed to alert" the safety driver about an imminent collision.

The Business Insider report sheds some light on how this might have happened. Uber insiders complained to the reporters about poor communication among the various teams inside Uber's self-driving car team.

"One group doesn't know what the other is doing," an engineer told BI. "This engineer said one team would not know the other had disabled a feature, or that a feature didn't pass on the track test, or that drivers were saying a car performed badly."

That might be how Uber wound up with a car that relies on the safety driver to intervene in the case of an imminent crash but doesn't alert the driver when a crash is imminent.

Such communications problems were exacerbated by the fact that Uber's self-driving car team is split among multiple locations. Uber has a team of mostly hardware engineers in Pittsburgh drawn from Carnegie Mellon's National Robotics Engineering Center. The company has a more software-focused team at Uber's headquarters in San Francisco.

According to BI, "the San Francisco people complained that the NREC folks were a bunch of academics with no real-world, product-building experience." Meanwhile, "the NREC team saw the San Francisco engineers as whiny and ungrateful."

Uber's self-driving cars have been essentially grounded since the March crash. Uber pulled out of Arizona entirely , laying off most of its safety drivers and other personnel there. The company is preparing to resume testing—initially on a much more limited basis—in Pittsburgh.

Reached by email, an Uber spokeswoman didn't dispute the details in the BI report.

"Right now the entire team is focused on safely and responsibly returning to the road in self-driving mode," she wrote. "We have every confidence in the work the ATG team is doing to get us there. Our team remains committed to implementing key safety improvements, and we intend to resume on-the-road self-driving testing only when these improvements have been implemented and we have received authorization from the Pennsylvania Department of Transportation.”