WASHINGTON (Reuters) - Two U.S. senators on Friday urged regulators to bar Tesla from allowing the use of driver assistance system Autopilot on roads where it is not intended.

Democratic Senators Ed Markey and Richard Blumenthal said the National Highway Traffic Safety Administration should "require Tesla to restrict its Autopilot feature to the roads it was designed for. We urge the agency to take all necessary actions to prevent these vehicles from endangering lives."

The auto safety agency said on Friday it is opening an investigation into the adequacy of Tesla's December recall of 2 million vehicles to boost Autopilot safeguards.