On Saturday August 25, a Tesla Model S crashed into a stopped firetruck in San Jose, California. The two occupants inside the Tesla sustained minor injuries, and the 37-year-old driver was arrested on suspicion of driving under the influence of alcohol. According to a police report, he told authorities, "I think I had Autopilot on." Tesla has not confirmed the semiautonomous system was in use, but it's at least the third time this year a Tesla has hit a stopped firetruck at highway speeds. We've updated this story, which originally ran on January 25, 2018, about why Autopilot and similar systems have trouble detecting stopped vehicles.

Early Saturday morning, a Tesla Model S driving south on the 101 Freeway slammed into the back of a stopped firetruck in San Jose, California, the latest in a series of crashes that highlight the shortcomings of the increasingly common semiautonomous systems that let cars drive themselves in limited conditions. A Tesla spokesperson says the automaker has not yet received data from the vehicle, so can't confirm if Autopilot mode was running (this typically takes a few days), and that Tesla is "working to establish the facts of the incident.”

Whatever the particulars, there's a serious sense of déjà vu here. In January, a Tesla Model S drove into the back of a stopped firetruck on the 405 freeway in Los Angeles County. The driver apparently told the fire department the car was in Autopilot mode at the time. In May, a Tesla driver in Utah hit a firetruck at highway speeds; she told reporters Autopilot was engaged and she was looking away from the road at the time.

So this latest surprisingly non-deadly debacle—the San Jose Tesla driver and his passenger sustained minor injuries—also raises a technical question: How is it possible that one of the most advanced driving systems on the planet doesn't see a freaking fire truck, dead ahead?

The car's manual does warn that the system is ill-equipped to handle this exact sort of situation: “Traffic-Aware Cruise Control cannot detect all objects and may not brake/decelerate for stationary vehicles, especially in situations when you are driving over 50 mph (80 km/h) and a vehicle you are following moves out of your driving path and a stationary vehicle or object is in front of you instead.”

Volvo's semiautonomous system, Pilot Assist, has the same shortcoming. Say the car in front of the Volvo changes lanes or turns off the road, leaving nothing between the Volvo and a stopped car. "Pilot Assist will ignore the stationary vehicle and instead accelerate to the stored speed," Volvo's manual reads, meaning the cruise speed the driver punched in. "The driver must then intervene and apply the brakes.” In other words, your Volvo won't brake to avoid hitting a stopped car that suddenly appears up ahead. It might even accelerate towards it.