U.S. asks Tesla why it didn't recall Autopilot driving system

According to the agency, Tesla did an over-the-internet software update in late September that was intended to improve detection of emergency vehicle lights in low-light conditions.

U.S. highway safety investigators want to know why Tesla didn't file recall paperwork when it updated its Autopilot software to better identify parked emergency vehicles.

In a letter to Tesla, the National Highway Traffic Safety Administration told the electric car maker Tuesday that it must recall vehicles if an over-the-internet update mitigates a safety defect.

“Any manufacturer issuing an over-the-air update that mitigates a defect that poses an unreasonable risk to motor vehicle safety is required to timely file an accompanying recall notice to NHTSA,” the agency said in a letter to Eddie Gates, Tesla’s director of field quality.