Ryan Kelley, a former safety driver for Uber's autonomous vehicle program, told Business Insider he felt as if he wasn't allowed to take bathroom breaks the month before he was fired.

"They made it clear you probably should hold it," he said.

Stopping a test vehicle for a bathroom break could disturb it and ultimately require up to an hour of rebooting or troubleshooting, Kelley said, which would decrease the number of miles it would drive.

Read the full story about Uber's self-driving car program here.

Ryan Kelley, a former safety driver for Uber's autonomous vehicle program, told Business Insider he felt as if he wasn't allowed to take bathroom breaks the month before he was fired.

Kelley described December, 2017, as a stressful month for Uber's autonomous driving team, which was under pressure to log as many test miles as possible. Stopping a test vehicle for a bathroom break could disturb it and ultimately require up to an hour of rebooting or troubleshooting, Kelley said, which would decrease the number of miles it would drive.

"They made it clear you probably should hold it," he said.

Read more: Uber employees describe a stressful and 'ridiculous' culture at the self-driving car unit under its current leader Eric Meyhofer

Uber's autonomous driving software was prone to overly aggressive braking on one day that month, leaving Kelley's vision blurred and stomach upset, he said. He described the experience of operating the vehicle that day as similar to "being in a series of low-end collisions for three hours, with my head slamming against the headrest constantly."

Kelley and other drivers told their supervisors about the headaches they experienced that day. After the manager responsible for safety, Rob Shoup, heard about the drivers' complaints, he accused the drivers of faking their symptoms.

"They are just faking it, trying to shirk work," Shoup said, according to Kelley (although Uber denies that Shoup accused anyone of faking their complaints).

Kelley left work early that day and was diagnosed with a mild concussion "consistent with symptoms for a low-speed car accident," after his wife made him go the emergency room, he said.

He said he brought his ER diagnosis to work the next day as evidence of his and the other safety drivers' headaches and reported Shoup's comment to Uber's human resources department.

About a month later, on January 26, Kelley was fired.

Uber's HR told him he had let the car roll through a stop sign on January 3 and failed to report it. Kelley denied that this incident occurred to Business Insider and told us he was never shown the car's video of the incident. Uber says that after initially denying it, Kelley later admitted fault and apologized. His apology did not get him reinstated to his job.

"I truly believe I was let go because I was a squeaky wheel. I made safety concerns," he said.

In an emailed statement, Eric Meyhofer, the current leader of Uber's self-driving car unit, acknowledged that the team made "missteps" in the past but said it had done some soul-searching in the nine months since the fatal accident.

"Our team continues to demonstrate a strong commitment to building a culture rooted in safety, transparency, and continuous improvement across every facet of our self-driving development," he said. "While we have made some missteps in the past, we are optimistic that the changes we've made over the last 9 months reflect the kind of culture we want to foster at ATG."

Uber received permission on December 18 to resume testing its self-driving vehicles on public roads in Pittsburgh, nine months after a fatal accident in Arizona.

Have you worked for Uber? Do you have a story to share? Email this reporter at mmatousek@businessinsider.com.

Read the full story about Uber's self-driving car program here.