It's not clear exactly what the rules it uses are, but there are definitely some roads where the set speed is limited to 0 above the speed limit when autopilot is engaged.

This is consistent with my experience:

> - On highways: Autosteer and Traffic Aware Cruise Control have speed limits of 90 mph.

> - Off highways: Autosteer is no longer restricted to 35 mph. Autosteer has a speed limit of 5 mph faster than the detected speed limit, unless you’ve specified a lower speed limit offset.

> - If Model S does not detect a limit, then the maximum speed the vehicle can drive is 45 mph.

https://insideevs.com/news/332446/tesla-autopilot-update-bum...

We know it wasn't a divided highway. Even if they were on a 2 lane highway the speed limit would have been limited to 60MPH. They wrapped the car around a tree, destroyed the integrity of the battery, and both passengers were disabled enough they couldn't escape the car.

The car doesn't peg the accelerator under autopilot so even getting to 60MPH in "A couple hundred yards" seems unlikely unless there was someone applying the gas pedal.

I suppose the alternative explanation is there was a malfunction which caused uncontrolled acceleration and ejected the driver into the back seat?

Ahh, that explains it, my "speed limit offset" is set to zero.

One could speculate that maybe the guy 'driving' from the passenger seat tried to plant his boot on the brake and got the accelerator instead?

In my Model Y, there is no way the passenger could reach across to put his foot on the brake or gas unless they were straddling the console.

This was a Model S, though: https://cdn.carbuzz.com/gallery-images/2015-tesla-model-s-da...

The linked article didn't say what model it was other than the fact that it was a 2019. Even so, that console only looks marginally easier to get your foot over. Definitely not a maneuver you could pull off in the heat of the moment.

When auto steer is engaged, it limits the speed to 5MPH over the speed limit unless you are holding the gas pedal down. If you hold the gas pedal down, the automatic braking and speed controls are not active. At that point, the car isn't in control.

If you are on the highway, it is different. But this car was in a residential area.