SAN FRANCISCO (KRON) — Cruise, the self-driving robotaxi service in San Francisco, has recalled the software on its autonomous cars after a collision that happened in March.

While tech experts tell Nexstar’s KRON the recall is good, what prompted it was alarming.

Last month, a Cruise self-driving robotaxi crashed into a San Francisco city bus.

“Fender benders like this rarely happen to our [autonomous vehicles], but this incident was unique,” founder and CEO Kyle Vogt said Friday. “We do not expect our vehicles to run into the back of a city bus under any conditions, so even a single incident like this was worthy of immediate and careful study.”

He went on to note the “bus’s behavior was reasonable and predictable,” and that the Cruise vehicle “did brake in response” but “too late and rear-ended the bus at about 10 mph.”

“The Muni bus has an unusual shape because it is two sections, so the movement was not something it had in its scenarios,” San Jose State University professor and tech expert Ahmed Banafa explained to KRON.

The cars use a combination of cameras and radar to operate without a driver. Banafa says the companies are still training the software on how to react to different scenarios.

The incident ultimately led Cruise to file a voluntary recall with the National Highway Transportation and Safety Administration, Vogt explained. Engineers and operations teams were able to identify and push out an upgrade to roughly 300 Cruise cars, according to Vogt, who described alerting the NHTSA as a “proactive step.”

“The problem that I see is that the training is happening on real streets,” Banafa said. That’s opposed to training the cars in a controlled environment like a closed track.

Before the crash with a bus, there had been other incidents involving Cruise cars in San Francisco. During a late March storm, two of the self-driving taxis did not detect road closure tape and briefly drove into areas closed for downed trees or power lines.

Principal analyst for Guidehouse Insights Sam Abuelsamid says there should be more regulations around the technology for these vehicles.

“This is another indicator of what I long advocated for which is that we shouldn’t be allowing companies developing the software to essentially self-regulate and decide when these vehicles are safe enough to put on the road,” Abuelsamid said. He says there should be federal motor vehicle safety standards and testing, like human drivers take a test.

“These automated vehicles are operating in much more constrained environments than what humans drive in and if you look at the number of crashes per mile, they’re really not any better and in fact not as good as human drivers yet at this stage,” Abuelsamid said.

No one was injured in the crash that prompted the recall. Cruise says its testing shows this specific issue will not happen again.

The company is now working to get approval for around-the-clock driverless taxis in San Francisco. Currently, the cars are only operating on off-peak hours.