When does TACC switch to HOLD After 5 Seconds

Todd Burch · Apr 21, 2015

When does TACC switch to HOLD After 5 Seconds vs 30 seconds?

All,

Does anyone know the criteria for when TACC uses a 5 second hold vs. a 30 second hold? Sometimes my car uses 30s, sometimes 5s--I'm not sure what the criteria is. The 30 second hold is much nicer, and I wish it were used all the time.

It doesn't seem to have to do with the set speed (something like 60mph or faster). Maybe it's using GPS to determine if you're on a large road or not?

LetsGoFast · Apr 21, 2015

I've noticed that it doesn't seem to switch to 30 seconds on surface streets, but I don't have good data. On my way back from Salisbury, it was doing it on a limitied access highway that isn't an interstate which was the first time I'd seen it on a non-interstate.

Torpedo Ted · Apr 21, 2015

It's 30 seconds on highways.

I don't understand the point of the hold feature at all. It's extremely annoying - TACC would be fantastic in stop and go traffic, but the hold thing ruins everything

LetsGoFast · Apr 21, 2015

Torpedo Ted said:
It's 30 seconds on highways.

I don't understand the point of the hold feature at all. It's extremely annoying - TACC would be fantastic in stop and go traffic, but the hold thing ruins everything

Something I learned in one of these threads that helped a great deal is to restart the car by bumping the cruise switch instead of goosing the gas pedal. It somehow seems much less annoying that way.

Todd Burch · Apr 21, 2015

LetsGoFast said:
Something I learned in one of these threads that helped a great deal is to restart the car by bumping the cruise switch instead of goosing the gas pedal. It somehow seems much less annoying that way.

I agree. I saw that same tip and it helps quite a bit.

Having said that, in the past I think I've seen the 30seconds on both Interstates and surface streets at times, which prompted the question...and also the question as to why the 5 second one exists at all.

Maybe they're just testing the waters and will switch everything to 60 seconds with the Autopilot software update. Please, Tesla?

wk057 · Apr 21, 2015

The hold feature makes a lot of sense, especially while people insist on using TACC for full stops on surface streets.

Imagine TACC stopping behind a car at a light, then while stopped, the driver gets distracted and is looking for something in the car, dealing with a rear seat bratty child, or something equally taking attention away from the road. Now the other car moves to make a right on red. If the Model S *isn't* on "hold" it starts driving into the intersection... and bam.

There are too many people who don't pay attention. I vote hold remains how it is (quick to hold on surface streets, longer on highway). It is effortless to flick the cruise stalk to continue. Don't be lazy.

The only thing I would change is to add a mild audible tone when it does go into hold so I'm not sitting like a fool thinking it's going to start going again only to look down and see "Hold."

MrClown · Apr 21, 2015

^^^ Exactly this. I hope they don't change it. A quick pull on the stalk is simple enough to let the car know I'm paying attention.

Todd Burch · Apr 21, 2015

I understand the argument, but there could be some simple software rules for that situation, no? For instance, the TACC should be able to identify if the target vehicle in front of it turns off to the left or right and disappears from the radar's field of view. in that case, it should switch to HOLD. If the current radar target remains in front, I'm not sure there's a reason why the car can't just continue in the "CRUISE" state (of course still stopped).

MrClown · Apr 21, 2015

Todd Burch said:
I understand the argument, but there could be some simple software rules for that situation, no? For instance, the TACC should be able to identify if the target vehicle in front of it turns off to the left or right and disappears from the radar's field of view. in that case, it should switch to HOLD. If the current radar target remains in front, I'm not sure there's a reason why the car can't just continue in the "CRUISE" state (of course still stopped).

How about a 2-way stop sign at a busy street? The car in front of you finds a gap to go straight and you inadvertently follow suit into traffic and get t-boned.

Todd Burch · Apr 21, 2015

MrClown said:
How about a 2-way stop sign at a busy street? The car in front of you finds a gap to go straight and you inadvertently follow suit into traffic and get t-boned.

That could easily happen with current software. When was the last time you saw a car stop and remain motionless for a full 5 seconds at a stop sign? It only happens if there's traffic in the other direction. If not, most people slowly glide through, or stop for 1 or 2 seconds at most. Heck, even the law (if you're patient enough to follow it to the letter) typically says 3 seconds for stopping at a stop sign. I'm sure you know that sitting with your car at a complete stop at an empty stop sign intersection with no traffic coming for 5 seconds feels like an eternity. If you have TACC on following a car coming up to a stop sign and don't intervene, TACC is going to blow that stop sign in many cases either way, whether the wait is 5 seconds or 30.

I can think of a lot of examples where current software would get you similarly t-boned. Car in front pulls up to a stop sign, a car immediately passes, a gap opens after being stopped for 2 seconds. Car goes, then your car advances forward into the intersection.

Car in front stops, inches forward a few seconds later, stops a few more seconds, inches forward again, then finally goes.

In no case here would the car switch to HOLD.

In the end, the driver must take responsibility.

MrClown · Apr 21, 2015

That's why I specified a _busy_ street. You could be behind the car at the stop sign for a while, at least long enough to forget you still have TACC on. Even 5 seconds is a long time to forget. Also, I think it may be 3 seconds on surface streets rather than 5. Ultimately TACC isn't intended for surface streets as discussed in many threads here but of course people will use it anyway so I think limiting the possible failure cases is a good idea.

In all your cases, the car would have moved on its own relatively recently. The 3 second hold time is about not forgetting you have TACC on.

- - - Updated - - -

Todd Burch said:
In the end, the driver must take responsibility.

Totally agree!

Todd Burch · Apr 21, 2015

If I'm on the highway sitting for 20 seconds (long enough to forget, based on the 3 or 5 second threshold--whichever it is), I could just as easily rear-end a car that tries to squeeze into my lane from the side when the car in front starts to go.

I understand everything you're saying, and it makes sense, but...if we are to assume the driver can forget about TACC after 5 seconds, they probably ought not be using TACC (or perhaps driving at all)!

wk057 · Apr 21, 2015

Todd Burch said:
If I'm on the highway sitting for 20 seconds (long enough to forget, based on the 3 or 5 second threshold--whichever it is), I could just as easily rear-end a car that tries to squeeze into my lane from the side when the car in front starts to go.

I understand everything you're saying, and it makes sense, but...if we are to assume the driver can forget about TACC after 5 seconds, they probably ought not be using TACC (or perhaps driving at all)!

There are a lot of people who should not be driving at all, IMO. So, definitely sticking to the desire to keep things as safe as possible at the expense of a negligible amount of inconvenience (literally moving one finger a few inches...)

Torpedo Ted · Apr 22, 2015

wk057 said:
The hold feature makes a lot of sense, especially while people insist on using TACC for full stops on surface streets

This may be the reason, but it still doesn't make much sense...

1. People are supposed to keep their eyes on the road.

2. Instead of HOLD, it could easily be solved by making an audible alert immediately when it detects the car infront moving, and then wait 1 second before it accelerates.

The alert/waiting time before accelerating could even be automatically adjusted depending on how long the car has been still. E.g:
Less than 5 second stop: No alert, immediate acceleration (like today)
<10 seconds stop: Alert, immediate acceleration
<30 seconds stop: Alert, 2 seconds delay before automatically accelerating
And so on. After more than 1 minute stops it should require manual resuming.

Cyclone · Apr 22, 2015

Just as a side note that an audible alert would do nothing for someone is deaf. I like your idea though, so perhaps tweaking the implementation could expland its applicability to more drivers.

Torpedo Ted · Apr 22, 2015

Cyclone said:
Just as a side note that an audible alert would do nothing for someone is deaf. I like your idea though, so perhaps tweaking the implementation could expland its applicability to more drivers.

Alert with vibration in the steering wheel

CHG-ON · Apr 22, 2015

This happend to me, but I was able to override and stop before a problem. So, while I don't like the 5 sec hold, in the end I am glad it is there. I stopped using TACC with stop signs. Too unsafe.

MrClown said:
How about a 2-way stop sign at a busy street? The car in front of you finds a gap to go straight and you inadvertently follow suit into traffic and get t-boned.

Todd Burch · Apr 23, 2015

OK, so this discussion got sidetracked and the original question was never answered:

Does anyone have definitive evidence as to when the long hold is used instead of the short hold? What's the car using as criteria?

LetsGoFast · Jul 22, 2015

I believe I have an answer to this question now. I was in a traffic jam on a surface street caused by a backup on the interstate. TACC was set for 64 and the speed limit was 55. TACC was operating on the long hold time. At some point, the speed limit on the road I was taking dropped to 45mph and TACC switched to the short hold, even though the cruise target remained set for 64. It sucked, because there was a traffic light far ahead that was only allowing a handful of cars to pass and the long hold was sufficient to work for every restart and the short hold was not.

I therefore conclude that long hold is in effect when the posted speed limit is 55mph or higher and the set speed for your cruise control is not a controlling factor. I do not have sufficient evidence to be sure what would happen at a speed limit of 50, but there is no road I know with such a speed limit for testing.

FWIW, the street in question was a two lane, non-divided street and TACC still was on long hold while the speed limit was 55. This falsifies a few theories that had been floated previously.

When does TACC switch to HOLD After 5 Seconds

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