Tesla Inc. is releasing a software update to practically all the vehicles it has sold in the U.S. to address a safety issue affecting its Autopilot partly autonomous driving system.

The patch will become available for 2,031,220 vehicles, according to a filing released today by the National Highway Traffic Safety Administration. Tesla began distributing the update on Tuesday at no charge. 

The development follows a two-year NHTSA investigation into Tesla’s Autopilot partially autonomous driving system. The probe focused on an Autopilot feature called Autosteer that automatically detects road edges and ensures the vehicle in which it’s running stays within its driving lane. Autosteer also helps drivers maintain a safe speed and keep an adequate distance from nearby cars.

Drivers are expected to keep their hands on the wheel and pay attention to the road when Autosteer is running. Moreover, they must be ready to take over manually if the software encounters technical issues. As part of its investigation, the NHTSA determined that “there may be an increased risk of a collision” when drivers don’t meet those requirements.

Autosteer includes safeguards meant to prevent it from being used in an unsafe manner. Should a driver attempt to use the feature on a type of road that it’s not equipped to navigate, the software will not activate. If Autosteer is activated on a suitable road but environmental conditions later change to such an extent that its ability to drive is diminished, the software can generate alerts or limit the maximum vehicle speed.

The NHTSA determined that those safeguards don’t always prevent safety risks. “In certain circumstances when Autosteer is engaged, the prominence and scope of the feature’s controls may not be sufficient to prevent driver misuse,” the regulator stated in today’s filing. 

The software update that Tesla began rolling out this week aims to address the issue. According to the company, Autosteer will receive additional controls designed to ensure drivers use the system in the intended manner. The way the controls are implemented will vary depending on what hardware is installed in a given Tesla vehicle. 

Going forward, Autosteer will display more prominent visual alerts to ensure drivers comply with safety requirements. Moreover, a newly added set of safeguards will automatically activate when the feature is used outside controlled-access highways. Tesla has also added a software mechanism that can disable Autosteer if a driver “repeatedly fails to demonstrate continuous and sustained driving responsibility.”

The NHTSA has concluded its safety investigation into Autosteer, but will keep the case open to evaluate the effectiveness of the Autosteer update. The regulator will require Tesla to submit eight quarterly updates about the system’s reliability and then another three annual reports. 

Photo: Tesla