On November 24, 2022, a Tesla Model S caused an eight-vehicle crash in San Francisco. Let's clarify what happened.
Where the accident took place
The accident occurred inside the San Francisco Bay Bridge, exactly here.
What do websites say about a Tesla rear-end collision in San Francisco?
Articles like this one immediately appeared on the internet , where they complain about "Full Self Driving Mode " and " phantom braking".
Other articles reports (like this one from abc7news.com) that Tesla was "abruptly braking":
Video from security cameras
This is the first instant where the Tesla Model S is seen (9 seconds and 336 milliseconds):
At 10.951 seconds the blinker is still off.
In the next frame (11.025 seconds) the turn signal is on.
Was FSD actually switched on?
The fact that the car was in "Full Self Driving" mode is a driver statement. The driver told the police that he had been using Tesla’s new “Full Self-Driving” feature, before the Tesla’s “left signal activated” and its “brakes activated,” and it moved into the left lane, “slowing to a stop directly in [the second vehicle’s] path of travel.”
The driver might have lied trying to escape his responsibilities.
In any case, the driver demonstrates that he does not know the various Tesla assisted driving modes, which, as explained here , are as follows:
- Autopilot
- Traffic-Aware Cruise Control
- Autosteer
- Enhanced Autopilot
- Navigate on Autopilot
- Auto Lane Change
- Car park
- Summon
- Smart Summon
- Full Self-Driving Capability
- Traffic and Stop Sign Control (Beta)
The Full Self-Driving Capability is active inside the city, not on multi-lane roads or freeways. It is more probable that Enhanced Autopilot with the "Navigate on Autopilot" functionality was active, rather than the "Full Self Driving".
Was it a Phantom Brake phenomenon?
The "phantom brake" occurs when, during normal travel following the lane, the autopilot system sees an obstacle that does not actually exist and therefore brakes violently. Here the car turn on blinker, change lane and stops, so I exclude that it braked due to the "phantom brake" phenomenon.
Was Tesla abruptly braking?
I also exclude that this was an abrupt braking. Now I'll tell you why. Below is the instant in which the turn signal lights up (11 sec and 87 msecs). I highlighted the distance between this instant and the point where the car stopped.
We can count four horizontal dashed lines. What is the distance between one line and another? Google Earth helps us, with the measure function. It's 14 meters (the length of the white stripe alone is 4 meters).
We can estimate how many meters separate the car from the moment the turn signal is on to the moment it stops.
We have 56 meters, covered in about 4.7 seconds (15.813 sec – 11.087 sec). The speed limit on this road is 50 mph, which corresponds to about 80 km/h.
Look at the car pointed by the red arrow. It traveled 14 meters between the two frames:
Doing the math, this car is traveling within the speed limits of 50 mph (14 meters in 0.668 seconds = 20.95 metres/sec = 75 km/h).
And how long does it take to stop a Tesla Model S? At 100 km/h he needs 41 meters to stop in an emergency (source: quattroruote ). I wouldn't really define it an "abrupt braking", given that the Model S stopped in 56 meters starting from less than 80 km/h.
So what really happened during the Tesla pileup in San Francisco?
There are ongoing investigations. Tesla will probably make the logs available and they will clarify what actually happened. I don't know exactly what happened. I think the driver wasn't vigilant when the car was braking: he had almost 5 seconds to accelerate and avoid a rear-end collision. And if driver assistance systems were actually active? In any case it is driver's responsibility to take control of the vehicle in case the automatic systems make mistakes. I blame also the drivers behind the Model S: they did not keep a safe distance.
Hope that you liked this article, see you next time!
Leonardo
