Interesting TACC behavior

[NovemberXray]

Today I was using TACC around town to maintain speed limit in traffic on surface streets, and I observed two interesting things:

First, I was driving down a street at 30mph, no cars in front of me, and ahead there were cars stopped at a stop sign. I was about to apply the brakes, since TACC is not supposed to be able to distinguish stopped vehicles from road, however the car started slowing and came to a stop by itself!

Second, after coming to a stop behind cars stopped at a stop light with TACC enabled, a "HOLD" indicator appeared above the speedometer, and when the cars in front of me moved when the light changed green, the car did not move and an alert appeared at the bottom of the IC (where the "keep your hands on the wheel" usually appears) saying "Press accelerator to reactivate TACC" (approximately). I tapped the accelerator and the car then proceeded to accelerate on its own and resume TACC.

Anyone else seen that before? I thought perhaps it was after sitting without moving for a certain period, but that doesn't make sense since it happily sits for long periods in freeway stopped traffic and then continues moving when traffic moves.

 

[Saghost]

Today I was using TACC around town to maintain speed limit in traffic on surface streets, and I observed two interesting things:

First, I was driving down a street at 30mph, no cars in front of me, and ahead there were cars stopped at a stop sign. I was about to apply the brakes, since TACC is not supposed to be able to distinguish stopped vehicles from road, however the car started slowing and came to a stop by itself!

Second, after coming to a stop behind cars stopped at a stop light with TACC enabled, a "HOLD" indicator appeared above the speedometer, and when the cars in front of me moved when the light changed green, the car did not move and an alert appeared at the bottom of the IC (where the "keep your hands on the wheel" usually appears) saying "Press accelerator to reactivate TACC" (approximately). I tapped the accelerator and the car then proceeded to accelerate on its own and resume TACC.

Anyone else seen that before? I thought perhaps it was after sitting without moving for a certain period, but that doesn't make sense since it happily sits for long periods in freeway stopped traffic and then continues moving when traffic moves.

The Hold part is normal - the car has a timeout for engaging Hold on a complete stop, and has different thresholds on freeways and surface streets.

The first part is good to hear, and I've heard that some other folks have had that experience in the past - it just isn't 100% reliable in detecting those stopped cars yet...

 

[Tam]

...TACC is not supposed to be able to distinguish stopped vehicles from road, however the car started slowing and came to a stop by itself!...

The car can stop by itself as demonstrated by Elon during Autopilot unveiling video. However, owners have reported that the car would crash on a stopped vehicles as well. The manual does mention that Autopilot may not brake for stationary vehicles.

Thus, the goal is to perfect the car's braking for stationary vehicles but be vigilant and you should brake as would normally do and don't risk relying on the system consistency for now.

...Second, after coming to a stop behind cars stopped at a stop light with TACC enabled, a "HOLD" indicator appeared above the speedometer, and when the cars in front of me moved when the light changed green, the car did not move and an alert appeared at the bottom of the IC (where the "keep your hands on the wheel" usually appears) saying "Press accelerator to reactivate TACC" (approximately). I tapped the accelerator and the car then proceeded to accelerate on its own and resume TACC.

Anyone else seen that before? I thought perhaps it was after sitting without moving for a certain period, but that doesn't make sense since it happily sits for long periods in freeway stopped traffic and then continues moving when traffic moves.

"Hold" function is described in the manual.

In your case, your car has not identified a leader car in front to lock on.

Once it locks on a leader car, it would blindly move with the leader independent of traffic lights or signs.

 

[RossRAllen]

Thanks for the insight about TACC approaching stationary vehicles. Of course I've read the manual, but missed this.

You might have saved me from an accident. I use TACC all the time, AP only to impress/frighten pax.

 

[chillaban]

Note that TACC (and AP) can recognize a lot of stationary vehicles when they are about 10 car distances away. That is, however, way too short of a distance to react if you are driving fast, which is why the manual specifically mentions encountering stopped vehicles while going over 50mph is especially dangerous.

Note that this doesn't mean it'll recognize every vehicle. Weirdly shaped vehicles (like the Ford Transit Connect boxy vans) and weirdly painted vehicles tend to confuse it, as do cars with a bunch of bikes mounted over the rear that covers the brake lights / license plate area.


Bottom line, if you see a stopped vehicle and you're going relatively slowly, you can probably just keep an eye on your instrument cluster to see if the car in front gets recognized. You'll have plenty of reaction time to take over for the 5% of times when it doesn't.

 

[Tam]

Note that TACC (and AP) can recognize a lot of stationary vehicles when they are about 10 car distances away...Note that this doesn't mean it'll recognize every vehicle. Weirdly shaped vehicles (like the Ford Transit Connect boxy vans) and weirdly painted vehicles tend to confuse it, as do cars with a bunch of bikes mounted over the rear that covers the brake lights / license plate area....

And especially, the one mentioned by Tesla blog: "white side of the tractor trailer against a brightly lit sky"

 

[dwebb66]

And especially, the one mentioned by Tesla blog: "white side of the tractor trailer against a brightly lit sky"

It was not the white side of the tractor trailer as much as the 'clear' space under the tractor trailer that lead the car to assume that it was an open road.

 

[Tam]

One often misconception about Autopilot and future perfected Driverless Autonomous vehicles is that the crashes should go down to zero as the system will get better and better to prepare for all possible scenarios.

The truth is: There is no such expectation from US Department of Transportation Secretary:

US government: 'it's not a surprise Google's car crashed'

"Foxx said that he expected the autonomous technology not to be perfect, but that it could prevent up to 80% of crashes in the US."

No matter how much the technology will be advanced in the near future, even with a very best scenario, you still have to be ready for the rest of 20% crashes and fatalities.