# TACC and Speed Limit Changes



## C141medic (Aug 31, 2017)

Has anyone experienced this?

Had this happen today (I’m on FW 39.7). 
Only TACC enabled without auto steer. Traveling at 50MPH (with gps indicating 50 on the top right of the display). No one in front of me. Posted speed limit of the road drops to 35MPH (gps also picked up the change and reflected 35MPH on the right side of display) however; the TACC did not adjust and car remained at 50MPH until I had to brake to slow down to the posted speed limit. 

Also when going around curves with only TACC enabled the car is not slowing down whatsoever as the manual indicates that that’s what should occur. 
“Traffic-Aware Cruise Control also adjusts the speed as appropriate when entering and exiting curves.”


----------



## 3V Pilot (Sep 15, 2017)

C141medic said:


> Has anyone experienced this?
> 
> Had this happen today (I'm on FW 39.7).
> Only TACC enabled without auto steer. Traveling at 50MPH (with gps indicating 50 on the top right of the display). No one in front of me. Posted speed limit of the road drops to 35MPH (gps also picked up the change and reflected 35MPH on the right side of display) however; the TACC did not adjust and car remained at 50MPH until I had to brake to slow down to the posted speed limit.
> ...


If the road is marked as a highway, like a state route in some places, the speed limit is not restricted or auto adjusted. Look on a map and see how the road is labeled.

For the issue of slowing around a turn I'm not sure as I haven't attemtped that on V9 yet. It used to work just fine, I'll try it tomorrow.


----------



## C141medic (Aug 31, 2017)

3V Pilot said:


> If the road is marked as a highway, like a state route in some places, the speed limit is not restricted or auto adjusted. Look on a map and see how the road is labeled.
> 
> For the issue of slowing around a turn I'm not sure as I haven't attemtped that on V9 yet. It used to work just fine, I'll try it tomorrow.


Interesting. I'll check it out. Is there any way to enable this in the settings for TACC to auto adjust to the posted speed limit regardless of the type of road?
Regarding the issue with the curve, the posted speed limit was 45MPH on the stretch of road prior to the curve and the posted speed limit by the approach to the curve was 25MPH. TACC definitely did not slow down anywhere near the curve and began to enter the curve at 45MPH until I took over and started braking.


----------



## Bernard (Aug 3, 2017)

C141medic said:


> Has anyone experienced this?
> 
> Had this happen today (I'm on FW 39.7).
> Only TACC enabled without auto steer. Traveling at 50MPH (with gps indicating 50 on the top right of the display). No one in front of me. Posted speed limit of the road drops to 35MPH (gps also picked up the change and reflected 35MPH on the right side of display) however; the TACC did not adjust and car remained at 50MPH until I had to brake to slow down to the posted speed limit.
> ...


I don't get speed limits here on the Big Island (something to do with Tom-Tom, the GPS provider, I am told), so I cannot comment on the speed reduction.
But as for curves, I stopped counting on TACC to do anything about them long ago -- I have yet to see TACC slow down for *any* curve, so I simply disengage it on winding roads or use the wheel to reduce its set speed prior to a known slow-speed curve. I'll try with 39.7, as I tried in the past with each firmware, but am not optimistic. Of course, this could still be related to the GPS issue with speed limits -- GPS tracks the car very accurately, but something in the connection between GPS position and road position is not working around these parts.


----------



## 3V Pilot (Sep 15, 2017)

C141medic said:


> Interesting. I'll check it out. Is there any way to enable this in the settings for TACC to auto adjust to the posted speed limit regardless of the type of road?
> Regarding the issue with the curve, the posted speed limit was 45MPH on the stretch of road prior to the curve and the posted speed limit by the approach to the curve was 25MPH. TACC definitely did not slow down anywhere near the curve and began to enter the curve at 45MPH until I took over and started braking.


There is no setting for what you are looking for, only max speed settings for Autopilot. Currently the cameras do not read speed limit signs so being posted doesn't always mean it's in the database that the car is using. I use autopilot on my daily drive to work and it slows for a curve where the speed doesn't change at all. I'll give it a try using only TACC and see what happens. Maybe you could try using autosteer on that curve and see if the car slows at all. That would be interesting to know.


----------



## C141medic (Aug 31, 2017)

3V Pilot said:


> There is no setting for what you are looking for, only max speed settings for Autopilot. Currently the cameras do not read speed limit signs so being posted doesn't always mean it's in the database that the car is using. I use autopilot on my daily drive to work and it slows for a curve where the speed doesn't change at all. I'll give it a try using only TACC and see what happens. Maybe you could try using autosteer on that curve and see if the car slows at all. That would be interesting to know.


I'll give it a shot with autosteer and see what happens.


----------



## garsh (Apr 4, 2016)

C141medic said:


> Interesting. I'll check it out. Is there any way to enable this in the settings for TACC to auto adjust to the posted speed limit regardless of the type of road?


According to the owner's guide, page 63:
_"Note: When you adjust the cruising speed based on the speed limit, the set speed does not change when the speed limit changes. You must move the gear lever fully down once then release to cruise at the new speed limit."_


----------



## Sandy (Jun 3, 2017)

Probably common knowledge but today I figured out when in TACC and adjusting set speed with the right side wheel ‘spinning’ it up or down changes the speed by 5 kph (didn’t try in mph). Beats clicking it 5 times.


----------



## FRC (Aug 4, 2018)

Sandy said:


> Probably common knowledge but today I figured out when in TACC and adjusting set speed with the right side wheel 'spinning' it up or down changes the speed by 5 kph (didn't try in mph). Beats clicking it 5 times.


same for MPH...very handy.


----------



## Emerald AP (Sep 10, 2018)

garsh said:


> According to the owner's guide, page 63:
> _"Note: When you adjust the cruising speed based on the speed limit, the set speed does not change when the speed limit changes. You must move the gear lever fully down once then release to cruise at the new speed limit."_


I find touching the speed limit display (white rectangle in the left panel) easier than pressing down on the stalk a second time whenever the car switches to a higher/lower speed zone. This also auto-adjusts for your prespecified offset to the speed limit just as the cruise stalk does.

Unlikely to be a realistic concern in any perceivable future (read before your warranty expires), but should also help minimize wear and tear from repeatedly depressing the cruise stalk on every street while on TACC.


----------



## 3V Pilot (Sep 15, 2017)

Okay, so I've used TACC on V9 to go around a turn and did slow the car down prior to the turn. No posted speed limit change and it waits until the last second but it does slow down before the turn. I'd say the computer takes a corner faster than most people would but I personally prefer this to going too slow.

I've also noticed that if I take the same turn with Autopilot engaged it seems to slow down just a hair sooner. Still takes the corner about the same speed but it seems like it slows just a few feet sooner.


----------



## JP White (Jul 4, 2016)

C141medic said:


> Has anyone experienced this?
> 
> Had this happen today (I'm on FW 39.7).
> Only TACC enabled without auto steer. Traveling at 50MPH (with gps indicating 50 on the top right of the display). No one in front of me. Posted speed limit of the road drops to 35MPH (gps also picked up the change and reflected 35MPH on the right side of display) however; the TACC did not adjust and car remained at 50MPH until I had to brake to slow down to the posted speed limit.
> ...


Maybe things changed with V9.

If I am travelling at 70 and enter a 55 zone the car slows down to 64 automatically. Why 64? because I have the audible speed alert set to 9 miles over the posted speed limit. Try setting the audible chime for say 3 miles over and see if the TAC slows down for you then.


----------



## garsh (Apr 4, 2016)

I cannot for the life of me figure out how TACC/Autopilot determine when to change the speed. I have my Autopilot limits set to relative and 0 mph, IIRC.

This morning, I'm driving on interstates. Speed limit starts off at 65 mph, then drops to 55 mph. Here's what happens:

I start off setting my speed to 75 mph (in the 65 zone)
Speed limit drops to 55. EAP keeps my speed at 75 mph.
Right after taking a split, EAP changes my speed to 70 mph. Speed limit is still 55. *Why the change?*
Several miles later, EAP tries to change my speed to 65 mph. Speed limit is still 55. *Why????!?!?!?*


----------



## Emerald AP (Sep 10, 2018)

Pretty big guess here, but do the real speed limit and the speed limit as seen by the car (per car display) match, when this happens?

I can relate to unexpected braking feeling unnerving while on AP. I’ve reported two such bug reports on specific roads where this has happened for me. At least it’s consistently wrong (happens all the time on the specific section of that road) so imagine fixable!


----------



## garsh (Apr 4, 2016)

Emerald AP said:


> Pretty big guess here, but do the real speed limit and the speed limit as seen by the car (per car display) match, when this happens?


Yes they do. Sorry, I had actually thought to check that and should have included that in my post above.
That's what's really strange. The car sees no change in the speed limit, yet decides to change speeds. It makes no sense to me.

And this was on an interstate - no sharp curves to worry about either.


----------



## Mayhem (May 25, 2018)

So when (if ever) will TACC/Autopilot slow down/speed up to adapt to speed limit changes? It _has_ to for FSD, because the dang thing has to know how fast to drive for the location it's in. Seems like low hanging fruit.


----------



## 3V Pilot (Sep 15, 2017)

Mayhem said:


> So when (if ever) will TACC/Autopilot slow down/speed up to adapt to speed limit changes? It _has_ to for FSD, because the dang thing has to know how fast to drive for the location it's in. Seems like low hanging fruit.


Mine already does, it's not perfect and doesn't yet "see" the speed limit signs in real time (like a construction zone). But for established roads where the speed limit is already mapped the car will speed up/slow down, right at the sign most of the time.


----------



## Mayhem (May 25, 2018)

3V Pilot said:


> Mine already does, it's not perfect and doesn't yet "see" the speed limit signs in real time (like a construction zone). But for established roads where the speed limit is already mapped the car will speed up/slow down, right at the sign most of the time.


You must have a 'special' car. From the most updated Model 3 Manual pg 68:

"*Warning*: When cruising at the speed limit, the cruising speed does not change when the speed limit changes. If your driving speed is at or below the new speed limit, move the lever up to cancelTraffic-Aware Cruise Control, then move it back down again to re-initiate and cruise at the new speed limit."


----------



## Mayhem (May 25, 2018)

Actually reading the manual further (pg 89), it is obvious that this speed up/ slow down functionality probably won't be included _until sign reading is implemented_ -- because the wording of the manual is such that Tesla is concerned the driver must agree and initiate cruising speed due to inaccuracies of the GPS localization or confusion of the GPS (e.g. being on a frontage road immediately next to the interstate and having the GPS mistake the frontage limit for the interstate). They simply don't want the liability nor hear whining about tickets because the car changed speed "without my authorization!" and therefore the "speeding ticket is not my fault!"


----------



## 3V Pilot (Sep 15, 2017)

Mayhem said:


> You must have a 'special' car. From the most updated Model 3 Manual pg 68:
> 
> "*Warning*: When cruising at the speed limit, the cruising speed does not change when the speed limit changes. If your driving speed is at or below the new speed limit, move the lever up to cancelTraffic-Aware Cruise Control, then move it back down again to re-initiate and cruise at the new speed limit."


On my daily commute to work I have a stretch of road where the speed limit drops from 55 to 45 and the car slows automatically every time. I could of swore that it has increased speed automatically in past but maybe that was an earlier firmware version. Usually I'm well on the "go-pedal" before any increase so I probably would not notice that as much. I'll have to give that a try one of these days, almost positive it would increase speed in the past.


----------



## Mayhem (May 25, 2018)

3V Pilot said:


> On my daily commute to work I have a stretch of road where the speed limit drops from 55 to 45 and the car slows automatically every time. I could of swore that it has increased speed automatically in past but maybe that was an earlier firmware version. Usually I'm well on the "go-pedal" before any increase so I probably would not notice that as much. I'll have to give that a try one of these days, almost positive it would increase speed in the past.


On some surface streets and smaller state roads the AP will cap speed at 5 over the GPS determined speed limit. Also, the AP may decrease the speed to take turns/ curves in the road. To give it a fair test use TACC only, not AP, and see if you get the same results.


----------



## 3V Pilot (Sep 15, 2017)

Mayhem said:


> On some surface streets and smaller state roads the AP will cap speed at 5 over the GPS determined speed limit. Also, the AP may decrease the speed to take turns/ curves in the road. To give it a fair test use TACC only, not AP, and see if you get the same results.


Yes, so I know that AP has a max of 5 over on local roads or to really get into the weeds "non-divided highways and local roads". TACC will never auto adjust speeds and has only the top end limit of 90mph. I was talking about using AP and having the speed auto adjust. I hope they NEVER do that with TACC, love to have the option to set whatever speed I want and no "robo-car-cop-thingy" telling me different! 

Oh, one other side note though, even just using TACC the speed will reduce for a curve. I have one of those on my commute also, seems like AP will lower the speed just a fraction sooner than TACC but both are very similar. I've also noticed that TACC is much smoother when coming to a complete stop and AP can grab the brakes a bit aggressive at times. A simple way to test this is engage TACC and as you approach a stopped car engage AP, the car will stop much sooner.


----------



## MelindaV (Apr 2, 2016)

3V Pilot said:


> On my daily commute to work I have a stretch of road where the speed limit drops from 55 to 45 and the car slows automatically every time. I could of swore that it has increased speed automatically in past but maybe that was an earlier firmware version. Usually I'm well on the "go-pedal" before any increase so I probably would not notice that as much. I'll have to give that a try one of these days, almost positive it would increase speed in the past.


if you are on an off ramp or interchange, it will reduce the speed in mysterious ways. Someone recently mentioned they had confirmation from Tesla that it will reduce it based on other prior driver's reactions to those interchanges.
in my daily commute, I go from a 60MPH freeway to a 55MPH freeway. half way thru the interchange, it drops the speed to 50MPH (EVERY F'ING TIME) while the speed limit sign still shows 60MPH on the screen. For me at this point, it is particularly annoying, because this is just after the traffic gets back up to speed after spending an hour crawling along at less than 20MPH and everyone immediately is going 5+ over the speed limit. So EAP/TACC set between 60-65MPH and hit the spot where it wants to be 50MPH you have to be ready to accelerate or traffic behind will think you are brake checking them.


----------



## garsh (Apr 4, 2016)

I have stretches of highway where autopilot automatically reduces speed for no apparent reason. The speed limit certainly doesn't change at those locations.

I *think* it's because the highway has a sizable curve at those points. Nobody else slows down at all for the curves, but I can't think of any other reason why the car would slow down.


----------



## 3V Pilot (Sep 15, 2017)

MelindaV said:


> if you are on an off ramp or interchange, it will reduce the speed in mysterious ways. Someone recently mentioned they had confirmation from Tesla that it will reduce it based on other prior driver's reactions to those interchanges.
> in my daily commute, I go from a 60MPH freeway to a 55MPH freeway. half way thru the interchange, it drops the speed to 50MPH (EVERY F'ING TIME) while the speed limit sign still shows 60MPH on the screen. For me at this point, it is particularly annoying, because this is just after the traffic gets back up to speed after spending an hour crawling along at less than 20MPH and everyone immediately is going 5+ over the speed limit. So EAP/TACC set between 60-65MPH and hit the spot where it wants to be 50MPH you have to be ready to accelerate or traffic behind will think you are brake checking them.





garsh said:


> I have stretches of highway where autopilot automatically reduces speed for no apparent reason. The speed limit certainly doesn't change at those locations.
> 
> I *think* it's because the highway has a sizable curve at those points. Nobody else slows down at all for the curves, but I can't think of any other reason why the car would slow down.


I agree that there are times it slows down when it doesn't really need to. For the places I drive on a regular basis I just keep my foot on the accelerator until I'm passed that area. If it's an off ramp I'll disengage the system entirely because I can slow down or maintain speed as needed based on what's going on farther down the road. I do have an off ramp I take daily where the car slows down then speeds up again only to slow down once more, it's not as smooth as just turning it off and allowing the regen to do it's thing.


----------

