Tesla FSD v14.3.5 Brakes Suddenly at Green Light for Non-Emergency Ambulance, Phantom Braking Complaints

A US Tesla owner recently reported on social media that their vehicle, with the Full Self-Driving (FSD) system engaged, suddenly braked at a fully green-lit intersection, causing a bag and lunch on the passenger seat to be thrown forward. The car was traveling at about 80 km/h at the time, and the FSD system triggered the hard brake without prior indication. After reviewing dashcam footage, the owner found that the system had identified an ambulance approaching the intersection, but the ambulance had not activated its lights or siren and was not on an emergency call. The FSD version used was v14.3.5.

The FSD v14 series has previously exhibited similar "overreaction" issues. The system has been known to misinterpret other vehicles' turn signals as emergency vehicle lights and subsequently pull over. Complaints related to sudden braking have also increased noticeably. "Phantom braking" is a long-standing problem with Tesla's driver-assistance systems. In 2022, the US National Highway Traffic Safety Administration (NHTSA) received hundreds of complaints from owners whose vehicles had braked suddenly on highways without cause.

From FSD v13 to v14, Tesla released a major update after a one-year gap. Crowdsourced data indicates that the average distance between critical disengagements for the system is about 732 miles. While this represents an improvement over previous versions, it remains significantly short of the roughly 10,000 miles required for unsupervised operation.