The dangers of TACC with Speed Assist

[North75]

I agree with sentiments that the TACC as implemented is stupid. (it has never surprised me personally because it very obviously tells you what speed setting it is going to use before you engage it)

I just can't see any reason why it wouldn't always be preferable(and safer) to initially set it at your current speed. If for some reason you are not going the actual speed limit when you engage it, it's easy enough to hit the speed limit sign to set it to the current speed limit. You can then adjust your offset from their easily by spinning the wheel.

For the case when you initially set it in slow traffic, you are going slow, so it's easy to then adjust it to a higher setting so the car can speed up when traffic lightens up.

It would be nice (and I would think reasonably easy to program) an option that always initially engages TACC at your current speed.

 

[totteraptor]

It would be very simple for Tesla to fix this but they have not done so for at least a year. Hence I guess is that they feel there is no problem and are not going to change it at any time.
I come from a Mercedes and would exchange my M3 TACC for the cruise control in my old Mercedes any time. The Merc has a 99.9% reliable distance control that works up to 200km/h limit. My model 3 has TACC with all it’s unpredictable quirks - and is limited to 150km/h. In other words rather US centric design.

 

[totteraptor]

I’d say anyone using TACC near a school during those times when kids are around is borderline driving irresponsibly.

I actually sometimes use the cruise control in such low speed zones to make sure I stay at the safe low speed and can focus my attention on the road and not my speedometer. It depends on the specific conditions - if there are regular crossings then it doesnt make sense with cruise control.

 

[arbr2]

@arbr2Perhaps Tesla isn't prioritising this because it is focussing on FSD features, but until FSD is fully integrated, people will have to be in control, and have the control options to do so.

I've heard the same argument made with people complaining about games and other stuff that they feel are 'non-relevant' features are in software updates. And while it may seem like a very valid argument, I don't think it is. Tesla has a huge staff of software engineers working on a wide range of projects. FSD is clearly the most important one, but working on games doesn't mean work on the FSD side gets less attention. Not everybody in the software team will have the skills or qualificaitons to work on the FSD side of things for example.

That said, as TACC with SA is required to enable Autosteer and FSD functionality like NoA, it would make even more sense to make TACC with SA a better design right now. We're still many years away from actual FSD in many regions, so let's make sure the basics are safe and well-designed. Allmost all the basics are just fine or even excellent, TACC with SA is not one of those basics.

TACC with SA has been just fine in Model S/X for years, why make it worse for a newer generation of vehicles?

 

[arbr2]

V10 has brought quite a few impressive improvements to M3, including to the AP suite. Unfortunately the TACC/SA situation has remained exactly as it was in V9: flawed.

I guess it's time to make sure it does get fixed in V11 I might have a few ways to get this on the roadmap without having to start a whole Twitter campaign. Keep you posted...

 

[totteraptor]

V10 has brought quite a few impressive improvements to M3, including to the AP suite. Unfortunately the TACC/SA situation has remained exactly as it was in V9: flawed.

I guess it's time to make sure it does get fixed in V11 I might have a few ways to get this on the roadmap without having to start a whole Twitter campaign. Keep you posted...

Let us know if there is any way the rest of us can help?

 

[richair]

I guess it's time to make sure it does get fixed in V11 I might have a few ways to get this on the roadmap without having to start a whole Twitter campaign. Keep you posted...

Maybe we can mobilize vloggers like Bjorn Nyland to post a video about this? If they agree about this issue of course...

 

[skatefriday]

The last N times I've engaged TACC with v10 it has set the speed at my current speed. With v9 it always set the speed at the speed limit plus my offset. I assumed this had just been fixed in v10. Is that not so?

 

[Ficheh]

Dramatic title, I know. But it’s a fair one: TACC with Speed Assist on Model 3 in its current form can be outright dangerous. I’ve seen more people complain about this for more than a year now, but now that I’ve experienced it myself I really feel it should either be fixed or disabled right away for Model 3.

Make no mistake: I love my Model 3 and am extremely impressed with it. It’s simply the best car I’ve ever owned, nothing comes close. TACC with Speed Assist seems to be one of the few major design flaws of the vehicle.

Here’s an example that actually happened to me. It might seem like an edge case, but it isn’t. It’s a very common situation and will be encountered by many drivers on a daily basis.


Tesla Model 3 Performance
Software 2019.32.2.1 9b8d6cd

Expected and safe behaviour
Germany, Autobahn A3, Speed Limit: none
Speed Assist presets TACC to 150 kmh
On TACC engagement, M3 will try to accelerate to and maintain 150 kmh

Unexpected and dangerous behaviour
Germany, Autobahn A3, Speed Limit: none, Temporary Speed Limit: 80 kmh
Speed Assist presets TACC to 150 kmh
On TACC engagement, M3 will try to accelerate to and maintain 150 kmh

Drivers will not expect the sudden and unintended acceleration resulting in possible dangerous situations. Even if drivers are aware, cruise control is effectively rendered useless in these situations.

The main design flaw is that the driver cannot set TACC to the current speed. It will always preset speed to what Speed Assist thinks is the current speed limit (plus/minus offset), this behaviour cannot be overridden. It is impossible for the driver to select current speed, nor is it possible for the driver to overrule the set speed by Speed Assist before TACC is engaged. This would be reasonable behaviour if Speed Assist would recognise the actual speed limit. However, all speed information is currently based on a database. This data is often outdated or incorrect for many roads, does not take into account time of day nor any temporary restrictions.

The only way to operate TACC with SA would be to engage TACC at 150 kmh, but keep the current speed by keeping the accelerator depressed. Only then can the speed be reduced by turning the right scroll wheel. However, reducing the set speed from 150 to 80 kmh takes 14 ‘fast scrolls’. Furthermore, once TACC is disabled and re-enabled, the speed will be set back to 150 kmh, requiring the same procedure again to safely use TACC.

Model S/X does have a very simply way to set the current speed, even with Speed Assist enabled. This is how it should work on Model 3, there is absolutely no reason to have the current design in production vehicles on public roads. It’s a dangerous feature that can result in unexpected behaviour at high speeds.

I have already filed a report with Tesla. This thread is mainly meant to attract as much attention from Tesla and other Model 3 drivers as possible, this needs to be fixed. A fix should be relatively simple: make it possible for the driver to overrule Speed Assist before TACC engagement and/or enable a way to set TACC to the current speed.

Please feel free to share your experiences. Am I missing something? Is there a magic hidden way to overrule Speed Assist with TACC?



TL/DR
SpeedAssist presets speed for TACC based on incorrect speed limits. The driver cannot overrule this prior to TACC engagement, possibly resulting in unexpected acceleration, speeding fines or serious accidents. This behaviour is dangerous and should be fixed as soon as possible.

Being in the US this doesn't seem to be a problem since there is always a speed limit here. There is also very little reason in the US to be driving so far below the speed limit (unless there's traffic in which case the TACC will not shoot the speed of the car up). I do think TACC should have a resume function like older cruise controls since you may want to go back to the speed that you previously driving at. The bigger concern I have is the car strenuo usly braking hard for reasons I disagree with.

 

[arbr2]

The last N times I've engaged TACC with v10 it has set the speed at my current speed. With v9 it always set the speed at the speed limit plus my offset. I assumed this had just been fixed in v10. Is that not so?

The only way you can achieve what you're saying is by setting the offset to -20 mph, which we have already established is a silly workaround that won't even work outside the US.

Would you mind sharing more details on what vehicle you have, what version you're on and what AP you have?

 

[arbr2]

Being in the US this doesn't seem to be a problem since there is always a speed limit here. There is also very little reason in the US to be driving so far below the speed limit (unless there's traffic in which case the TACC will not shoot the speed of the car up).

I agree that the situation won't be as extreme in the US, but even in the US there are situations where the actual speed limit will not correspond to what the vehicle thinks it should be. There might be roadworks, accidents or other situations where the speed limit will be significantly lower than the normal speed limit. In that case you would still have to enable TACC and scroll down several times to avoid acceleration. And this has to happen every single time you reengage TACC.

Setting the current speed and resetting at previous speed should be quite simple to implement and would solve this whole matter.

 

[N5329K]

One criterion designers of man/machine interfaces should always have uppermost in mind is to never, ever create a situation where the user has to ask, “What’s it doing now?”
Current speed default would go a long way to solving what seems like a pretty serious problem. Want to go faster? Go faster. Or slower. But let the operator decide. Not the machine.
Robin

 

[skatefriday]

The only way you can achieve what you're saying is by setting the offset to -20 mph, which we have already established is a silly workaround that won't even work outside the US.

Would you mind sharing more details on what vehicle you have, what version you're on and what AP you have?

SR+, v10, standard AP. I do not recall setting the offset to -20, but I'm sure going to check next time I get in the car.

 

[Nostromo]

One criterion designers of man/machine interfaces should always have uppermost in mind is to never, ever create a situation where the user has to ask, “What’s it doing now?”

The very first time I activated TACC on my new 3 was on the freeway at night in the rain (I know probably not the best choice of situations to try a new thing). But I expected it to work like a regular cruise control and set my current speed when activated. Unaware of the nuances, I was surprised when the car accelerated from my current 45 mph or so to 65 when all other traffic was doing 45. There wasn’t a car in front of me, that’s why. So my answer to “What’s it doing now?” at that point was, it’s trying to kill me! So I decided to name my car Christine after that. Now I understand the car’s behaviors a lot better but the name stuck.

 

[arbr2]

Unaware of the nuances, I was surprised when the car accelerated from my current 45 mph or so to 65 when all other traffic was doing 45. There wasn’t a car in front of me, that’s why. So my answer to “What’s it doing now?” at that point was, it’s trying to kill me!

This is exactly why I started this thread. The acceleration in itself is not that dangerous, you've got quite a few systems protecting you as well. However, the feeling that your car is doing something that's not within your control is not great to say the least. Most people might react properly to remedy the situation, but there will be others that react instinctively by braking or steering which will result in very dangerous situations.

 

[totteraptor]

This is exactly why I started this thread.

I have provided this issue to Tesla on [email protected] but not heard back from them. If anyone else would consider to also make the suggestion to implement a "current speed" option in model 3 it might eventually be implemented.

 

[Nostromo]

I have provided this issue to Tesla on [email protected] but not heard back from them. If anyone else would consider to also make the suggestion to implement a "current speed" option in model 3 it might eventually be implemented.

Setting speed to current speed makes a lot more sense to me, although I can think of one scenario where you would not want this - say you were not using TACC and the traffic slowed to a crawl. You enable TACC because it it makes it so much easier to deal with stop and go traffic. Then traffic speeds up but you do not.

Maybe a "target" or goal speed could be displayed which would show you the TACC limit speed, in addition to the speed limit already displayed. Pressing that image on the screen would set the target to the current speed, and pressing the speed limit display would set the target to the current speed limit (from map data). Whenever you enable TACC and it was disabled before, it would set the TACC limit to current speed. This way you could change speed with the accelerator or brake and quickly update TACC top speed by either pressing the TACC limit display or disabling and re-enabling TACC. No need to use scroll wheel at all.

 

[DopeGhoti]

Setting speed to current speed makes a lot more sense to me, although I can think of one scenario where you would not want this - say you were not using TACC and the traffic slowed to a crawl. You enable TACC because it it makes it so much easier to deal with stop and go traffic. Then traffic speeds up but you do not.

As much as I like TACC as currently designed, I have to say that scroll-wheeling the set speed up from formerly bumper-to-bumper traffic would be a lot less frenetic -- and indeed a lot less emergent -- than panic-scroll-wheeling the set speed down when the car "unexpectedly" accelerates as is currently implemented.

"The car isn't going as fast as I expect it to" is a lot less unsettling of a situation than "the car is going a lot faster than I expect it to", all other factors being equal.

 

[totteraptor]

Setting speed to current speed makes a lot more sense to me, although I can think of one scenario where you would not want this - say you were not using TACC and the traffic slowed to a crawl. You enable TACC because it it makes it so much easier to deal with stop and go traffic. Then traffic speeds up but you do not.

Maybe a "target" or goal speed could be displayed which would show you the TACC limit speed, in addition to the speed limit already displayed. Pressing that image on the screen would set the target to the current speed, and pressing the speed limit display would set the target to the current speed limit (from map data). Whenever you enable TACC and it was disabled before, it would set the TACC limit to current speed. This way you could change speed with the accelerator or brake and quickly update TACC top speed by either pressing the TACC limit display or disabling and re-enabling TACC. No need to use scroll wheel at all.

I see your point but in that scenario I would simply press the speed limit sign on the screen and the car changes its set TACC value (works already today).
Anyway, the suggestion in the thread is merely to add an option to be able to select "current speed" instead of the existing way TACC works. It can only make more users happy (especially in Europe) - no-one should be forced to start using a new TACC modus.

 

[DopeGhoti]

How about "Tap current speed" to set current speed, or a "long-hold-down" of the driving mode lever?