Tesla Autopilot

The National Highway Traffic Safety Administration (NHTSA) said it was acting following 11 Tesla crashes since 2018 involving emergency vehicles.

In some cases, the Tesla vehicles "crashed directly into the vehicles of first responders", it said.

The investigation will cover roughly 765,000 Tesla cars made since 2014.

That includes those in the Model Y, Model X, Model S and Model 3, the NHTSA said - the entire current range.

The vehicles' Autopilot system generates a speed limit warning on the dashboard display and sends a notification if the car is sitting still at a green traffic light.

The features were released in the latest update of Tesla's "full self-driving" version of Autopilot.

Tesla vehicles can already slow down at red lights and stop signs.

In July 2019, Tesla's website advertised the "full potential for autonomous driving" including automatic driving on motorways - although it has always maintained that its Autopilot is not designed to be a substitute for a human driver.

It follows at least two crashes, one fatal, in which the system was active.

Consumer Reports accused Tesla of an "aggressive rollout of self-driving technology".

Tesla described it as "well-meaning advice", adding: "We make our decisions on the basis of real-world data."

In a statement, the firm said: "Tesla is constantly introducing enhancements proven over millions of miles of internal testing to ensure that drivers supported by Autopilot remain safer than those operating without assistance.