The US main transportation safety regulator said on Friday it was seeking information from Tesla about a new driver assistance mode dubbed “Mad Max” that operates at higher speeds than other versions.

Some drivers on social media report that Tesla vehicles using the more aggressive version of its full self-driving (FSD) system could operate above posted speed limits.

“We are going 75 in a 50, I feel like we are racing down the street right now,” one YouTuber said.

“NHTSA is in contact with the manufacturer to gather additional information,” the National Highway Traffic Safety Administration (NHTSA) said in a statement. “The human behind the wheel is fully responsible for driving the vehicle and complying with all traffic safety laws.”

The NHTSA earlier this month opened an investigation into 2.9m Tesla vehicles equipped with its full self-driving system due to the dozens of reports of traffic-safety violations and crashes.

The NHTSA said in opening the investigation it was reviewing 58 reports of issues involving traffic safety violations when using FSD, including 14 crashes and 23 injuries.

Tesla did not immediately respond to a request for comment, but last week reposted a social media post that described Mad Max mode as accelerating and weaving “through traffic at an incredible pace, all while still being super smooth. It drives your car like a sports car. If you are running late, this is the mode for you.”

The NHTSA said earlier this month that FSD – an assistance system that requires drivers to pay attention and intervene if needed – has “induced vehicle behavior that violated traffic safety laws”.

The agency said it had six reports in which a Tesla vehicle, operating with full self-driving engaged, “approached an intersection with a red traffic signal, continued to travel into the intersection against the red light and was subsequently involved in a crash with other motor vehicles”.

Tesla says FSD “will drive you almost anywhere with your active supervision, requiring minimal intervention” but does not make the car self-driving.

Autonomous driving is a crucial aspect of the electric auto behemoth’s business plan. Musk emphasized these efforts after a third-quarter report that saw record vehicle sales but a 37% drop in profits.

Tesla’s full self-driving, which is more advanced than its autopilot system, has been under investigation by the NHTSA for a year. In October 2024, the NHTSA opened an investigation into 2.4m Tesla vehicles with FSD after four collisions in conditions of reduced roadway visibility. The Washington Post had previously reported the agency’s interest in the Mad Max mode.

The NHTSA investigation is one component of wider friction between Musk and the Trump administration, where the tech billionaire used to play a central role. Musk’s ire is often directed towards heads of the agencies tasked with regulating his companies. Most recently, Musk criticized Sean Duffy, Trump’s transportation secretary and acting Nasa administrator, as knowing “absolutely ZERO about rockets & spacecraft”.

Musk’s comments came on the heels of Duffy announcing that Musk’s rocket company, Space X, had “fallen behind”, and that Nasa was opening up contracts for its crewed lunar Artemis program.