BBC News, photo: Google
Google has criticised the Department of Motor Vehicles (DMV) in California for insisting driverless cars must have a fully licensed driver behind the wheel.
On Wednesday, the DMV published draft regulations which outline how the technology could be used on the roads.
The regulations say truly driverless cars would be "initially excluded" from operation.
Google's director of self-driving cars, Chris Urmson, said the move was "perplexing".
"This maintains the same old status quo and falls short on allowing this technology to reach its full potential, while excluding those who need to get around but cannot drive," he wrote in his blog.
"We've heard countless stories from people who need a fully self-driving car today. People with health conditions ranging from vision problems to multiple sclerosis to autism to epilepsy who are frustrated with their dependence on others for even simple errands."
Google argues that driverless cars are much safer than manually driven cars, because they eliminate the human error that causes a majority of collisions.
The technology has inspired a web game by Made With Monster Love which demonstrates the effectiveness of computer control over human intervention.