A bill that would have helped to put more self driving cars on U.S. roads has stalled in the Senate, where Democratic representatives are holding on to doubts about the safety of the technology.

For lawmakers like Senator Dianne Feinstein of California (whose state is a hotbed of testing for companies like Google, Tesla, and Uber), AI driven cars are just not at the point where they’re safe enough for major roads and they’ve yet to prove they’re safe from cyber attack. And until those points are remedied, they’re blocking the bill.

Late last year, Feinstein publicly opposed the bill, saying she was apprehensive about sharing the road with computer driven cars. “It seems to me,” she said, “that you have to have a period of time where these cars are put on roads, but not necessarily heavily impacted California freeways that are going 65 to 75 miles an hour. I’m a driver, and I know I wouldn’t feel very comfortable.”

Feinstein argued that a change to people’s perception of autonomous cars would take time. “People need to be assured over time,” she stated in an interview with Recode. “You can’t just dump something on a freeway and have people looking over saying, ‘My God, there’s no driver.’”

Lawmakers are no strangers to passing legislation about this technology though. A recent bill called the Self-Drive Act, which was quickly approved, lets tech companies and automakers gain exemptions so they can test experimental vehicles without abiding by the same safety standards that traditional cars face.

More recent actions though, saw more opposition, with representatives calling the technology “unproven” and saying it hasn’t shown that passengers and other drivers are adequately protected.

Authors of the legislation are hopeful still, and plan to address any concerns while still holding on to the basic framework of the newest proposed bill.