Companies like Google have been testing self-driving cars for years, but there's one major hurdle standing in the way of this technology ever making its way into your garage (besides the fact that it could still use some work): government regulations.

On that last point, Google sent a letter Friday to federal transportation officials, urging them to pave the way for the company's self-driving technology to be sold in the U.S., the Associated Press reported. The letter advocates a "tight but realistic" timeframe for ensuring cars meet federal safety standards.

It currently takes several years for new designs to be approved by federal regulators. The main safety roadblock is simple: cars that do not allow a driver to maintain control are not currently legal in the US, according to the AP. That affects the design of any self-driving car that, like Google's, is fully automatic and requires no amount of human intervention.

The fact that Google is advocating regulatory shifts now is not unexpected: its technology is nearing mainstream readiness. The company has already tested its prototypes on public roads in California and elsewhere, though those tests have sometimes involved crashes and other incidents.

Fortunately for Google, there are signs that government regulators are willing to evolve. The U.K. government has welcomed the technology, saying it specifically wants to test Google's self-driving cars. And today's letter to U.S. lawmakers comes as a response to the Department of Transportation's invitation for industry input on speeding up regulatory approval.

In fact, the DOT is willing to spend money of its own on self-driving cars. It could soon embark on a $4 billion, 10-year plan, earmarked in the President's proposed 2017 federal budget, to "accelerate the development and adoption of safe vehicle automation through real-world pilot projects."

Google did not immediately respond to a request for comment, but a spokesperson told the AP that its letter was "the beginning of a process" to create "the right framework that will allow deployment in a safe and timely manner."