Charlotte EdwardsTechnology reporter, BBC NewsThe U.S. National Highway Traffic Safety Administration (NHTSA) has contacted Tesla after footage shared on social media appeared to show its newly-launched driverless cars breaking traffic laws.The firm's long-awaited robotaxis - which boss Elon Musk says are central to Tesla's future - were tried out on public roads for the first time in Austin, Texas, on Sunday.Videos posted online seem to show instances where the vehicles, which had a safety driv...