Uber has reportedly said that it will push back against demands made to take its self-driving cars off the roads in San Francisco, California. The firm began testing its vehicles earlier this week; however, unlike other firms trying out self-driving vehicles, Uber has not obtained a test permit.

The California Department of Motor Vehicles (DMV) slammed Uber after one of its self-driving vehicles was spotted breezing through a red light on 14 December. The DMV has threatened legal action against Uber unless it stops its launch and obtains a test permit for any future on-the-road testing.

Uber VP of advanced technologies Anthony Levandowski said in a conference call with media on 16 December that he had "respect" for the authorities. He added that the test permit only applies to vehicles that can be operated "without the active physical control or monitoring of a human operator".

The permit requires firms performing trials of autonomous vehicles to cover insurance costs as well as issue public reports of any collisions or incidents when the human driver is required to take the wheel.

Other firms such as Google and Tesla have applied for and been granted permits. "It is illegal for the company to operate its self-driving vehicles on public roads until it receives an autonomous vehicle testing permit," said Brian Soublet from the California DMV in a letter to Uber this week, BBC reported.

Uber indicated that it would reveal details about the performance of the cars but refrained from specifying how it intended to do so. As of Friday (16 December) afternoon, several of Uber's self-driving cars were seen running on San Francisco's streets.