Uber has admitted that there is a "problem" with the way autonomous vehicles cross bike lanes, raising serious questions about the safety of cyclists days after the company announced it would openly defy California regulators over self-driving vehicles. An Uber spokeswoman said on Monday that engineers were working to fix a flaw in the programming that advocates feared could have deadly consequences for cyclists. Uber began piloting its self-driving vehicles in its home town of San Francisco last week, despite state officials' declaration that the ride-share company needed special permits to test its technology. On day one, numerous autonomous vehicles – which have a driver in the front seat who can take control – were caught running red lights and committing a range of traffic violations. Self-driving cars: Uber's open defiance of California shines light on brazen tactics Despite threats of legal action from the department of motor vehicles (DMV) and California's attorney general, Kamala Harris, Uber refused to back down on Friday, claiming its rejection of government authority was "an important issue of principle".