Traffic-Aware Cruise Control (TACC) - Good & Bad Details

Traffic-Aware Cruise Control (TACC) - Good & Bad Details

Let me start off by saying I am so happy Tesla has finally given us Adaptive Cruise Control or what they call TACC. TACC is the ability to set cruise control and have the car automatically keep a safe distance between you and the car in front of you. This feature has existed for years from other car manufactures.
My only comparison of this feature is with Mercedes, Lexus, and Land Rovers. I have to say there are a lot of features I like better with Tesla’s implementation but there are a few that they need to address.

I find it much safer to always drive with TACC on when driving in stop and go traffic or at speed on the highway. When you press the accelerator you can drive seamlessly with TACC on and let it do the breaking for you. I think the is the key word when describing Tesla's TACC. Seemless.

Here are my impressions please share yours:

1) TACC is Limited to 90 MPH - I am told by friends that make long drives in states that don't have speed limits that setting the cruise control above 90 MPH should not be limited by the implementation unless the radar and computers cannot handle it.

2) TACC Does NOT include blind spot side warnings when attempting to change lanes into moving cars - Mercedes, Cadi, and others produce cars that warn if there is a car or motorcycle in the lane you are attempting to turn into or even as the traffic approaches. I believe all cars should ship with this feature.

1) TACC has Smooth braking when approaching cars in front of you at speed or stopped. Mercedes jerks you around like the Indiana Jones ride at Disneyland.

2) TACC has Autostart after coming to a complete stop has clear message to press the accelerator pedal again. Mercedes just sits there and if there are any messages what to do I have not found them.

3) TACC is Easy to set the distance between cars in front of you using by rotating the cruise control stock. Very clear controls.

4) TACC has a lot less front impact collision warnings than with Mercedes when approaching cars in front. I did have distance set to 1 and warning set to Medium and had one instance where the Front Collision warning came on. I was a lot less eventful than when Mercedes warns you and have you to lock up the car. Tesla stops smoother and faster with dual motors.

5) Left turn signal blinker auto acceleration is nice when changing lanes

Redmiata98 | January 11, 2015

How does #5, GOOD, exactly work? When does the acceleration actually start? Does it only work on the left only or also on the right. Until I understand what and when I am reluctant to use it and I would apreciate feedback if you have already used it.

tes-s | January 11, 2015

#1 bad may just be temporary for first release.

shop | January 11, 2015

90mph limit may very well be a technical limit of how far the radar can see.

michelcolman | January 11, 2015

I sure hope that 90 mph speed limit is temporary, otherwise the system will be pretty useless for me. And German drivers are certainly not going to be amused. 90 mph is way too slow on the autobahn.

brian_in_TX | January 11, 2015

I expect #2 on your bad list to be addressed through software "soon" after reading the new autopilot description.

rdalcanto | January 11, 2015

For #2 on bad list, are you saying it doesn't warn you if you put your turn signal on to change lanes and there is a car there? I thought blind spot monitoring did that now. Or are you saying that if you do an illegal lane change with no turn signal that it won't tell you that there is a car?

drsaab | January 11, 2015

#5 only works on left signal and it will start accelerating as soon as you signal assuming you are going slower than your max set speed

jordanrichard | January 11, 2015

what states are you able to do 90, legally?

mrrjm | January 11, 2015

On the plus side something he didn't say is if the car in front of you only stops briefly such is in stop and go traffic or at a stop sign the Tesla will stop and then accelerate and match the car in front. Also you can take turn while following a car and never touch the go pedal. I was on the highway with the cruise set at 65 mph. I followed a car off the highway. Around a turn at a light. Then stopped at a stop sign and turned. Then another stop sign and continued. All this and I never touched the go pedal.

nelsonc | January 11, 2015

1) I agree with the Germans 90 mph is too damn slow. Here are speed limits in USA. Note some are 85 mph. TELSA is smooth at 133 mph. Remove the limitor or up it to 155 Mph.

2) yeah it's coming but it does not work at all. It seems logical TELSA could turn it on.


5) correct only with left lane I believe and it feels like it speeds up 5 pr 10 mph faster.

mrrjm | January 11, 2015

I'm pretty sure when you switch lanes to the left the car accelerates to the speed the cruise was set at. As long as overtake acceleration is on.

drsaab | January 11, 2015

Here are my notes on TACC so far after 30k miles in a mb distronic plus tacc.

Confirmed Tacc can activate at 17 mph and over.

When stopped without any memory speed in Tacc. Pulling leaver to go forward activates Tacc to default of 17 mph.

There is no normal cruise... TACC is on by default and no way to switch to normal cruise.

Cutting in Lane into slower cars the tesla will warn you of impending collision but continue to stop in time. The mb would warn you. Activate brake assist for max braking but turn off distronic plus so you brake manually. This is better. Not full Collison prevention assist "yet" but close. It is quite reactive vs mb system. The collision sign will come up. Radio will mute so you pay attention. Be prepared but the car will slow if you let it. It will not apply maximum Brakes as if your fully slamming the abs pulsating brakes though "yet".

Coming up on a car stopped fully will not work well yet. If that car in front is even moving at 5 mph, the Tacc will lock on and react. Same as mb distronic plus. It's the same as driving going behind a parked car. It won't stop. My guess it disregards fully stopped objects like parked cars.

My speed up to pass feature works as soon as you put the signal on but only on the left signal. And remember it won't pass the set speed on the cruise. Meaning if you have it set for 70 and are going 50 it will work. 70 and 65 you won't see much effect.

The blue tracking on vs grey no tracking is very useful. The mb I would be guessing if it's locked on. This let's me know.

Lastly. On turns this tacc slows based on g force. I don't think my Mb did this as well. So I can set to 70. Take an on ramp circle and it will limit to 50 mph etc till the straight highway road is reached .

I got so used to mb distronic plus. I used it 90% of driving, city and highway in 30k miles. Once you trust and understand the limits, it can do so much of the driving for you.

The bad:

Wish it displayed speed your setting cruise at vs the little triangle tick. Hard to tell 75 from 74 or 73 etc. Should show set number for a brief second.

This TACC has a high failure rate so far. My Mb distronic plus did not work only couple times in over 30k miles and that was in very heavy rain or snow where cruise was dangerous anyways.

My Tesla acc failed to turn on already today for about three segments of 15 on my driving last few days. It says Cruise not available. I tried stopping and turning power off, no fix. Tried to leave car for a few minutes... fixed. Tried soft reset with wheel scroll buttons.. fixed. It randomly does not work. My sensor, windshield, and radar were clean all 3 times.

I am trying to debug this, my first hypothesis is that possibly setting cruise to early when entering vehicle before it sees any speed signs and the speed limit indicator is a dash mark vs solid line cause it to fail. Still working on figuring if that's the reason.

I do not think i am able to turn on TACC to the speed limit setting. It always just goes to the speed I am traveling. In theory you should be able to drive at 40 and the car sees a speed limit of 55, it your threshold is +9mph then the tick mark is at 64 and pulling for 1/2 sec should turn TACC to 64mph, but i seem to always get it setting at my current 40mph speed. Maybe operator error, if anyone has this work properly please report back method used.

The New videogame autopilot display with all the autopilot features on the new website seem "insane". Can't wait!

Redmiata98 | January 11, 2015

Thanks for the detailed feedback!

drsaab | January 11, 2015

By autopilot video game display I mean the one on the Tesla Autopilot option on the order page... not that there is some video game out.

tezzla.SoCal | January 11, 2015

@drsaab - Maybe operator error, if anyone has this work properly please report back method used.

This works for me, I think the key is to hold (pull back) for over 2 seconds.

nelsonc | January 11, 2015

I have to test coming up to a stopped car. I thought I did that in traffic yesterday. I will test and post results.

I do like turning on Tacc when stopped. It's great around town. I don't know why they don't recommed it.

drsaab | January 11, 2015

@drsaab - Maybe operator error, if anyone has this work properly please report back method used.

This works for me, I think the key is to hold (pull back) for over 2 seconds.

Ok, will try. I believe the release notes said 1/2 second which is what I was doing.


drsaab | January 11, 2015

oops. meant

yeah they need to bring edit back to forums :)

garygid | January 11, 2015

When following a car in traffic, when that car stops briefly at a stop sign, looks for
cross traffic, and proceeds safely, does your car just follow that car, essentially
"running" the stop sign?

nelsonc | January 11, 2015

Yes it runs stop signs today. With autopilot it will stop supposedly.

Haggy | January 11, 2015

When you rotate the knob, what does the car show you? Other cars I've had showed me 1-2-3 second following distances.

tezzla.SoCal | January 11, 2015

@Haggy - Just the number 1 thru 7

tezzla.SoCal | January 11, 2015

Question, do the numbers (1-7) really relate to SECONDS?

garygid | January 11, 2015

With stop sign running, I will need to disable this auto-follow for my wife.

Can one disable TACC and just use CC?
Can one disable Resume Auto-Follow after stop.

Around here, many cars do not actually stop at stop-signs.
It happens so often that it is called a "California Stop".

If the followed car makes a quick stop, or no-stop, but turns abruptly
right (or left) and disappears from your car's line of sight, would your
car abruptly accelerate through the stop sign and the intersection?

In a driver Profile, can one disable TACC completely, for that driver?

As is normal with CC, a novice, or untrained-in-autopilot driver would
expect that any tap of the brake pedal would disengage CC. Does
any use of the brake pedal also disengage the TACC function?

nelsonc | January 11, 2015

No cc just tacc. I like that personally.

It does show a cool graphic when you rotate the tacc knob at the end of the stock. You see a pic of two cars getting further apart.

I cannot stress to check your settings for frontal impact warning. It defaults to medium. I reset mine to early.

Haggy | January 11, 2015

With normal CC, if you get to a stop sign, you need to use the brakes. With TACC, you will need to do the same. I can't see why it would ever be an advantage to use CC over TACC. I've had ACC before and I never found myself wishing that the car wouldn't slow down when there was a vehicle in front of me.

drsaab | January 11, 2015

Autopilot is created for use on highways.

Using it for "stop" signs is not what is intended, so do not complain if it won't do what you would normally do. You can use it, but do not expect the car to drive for you 100% of the time.

They never advertised it as such. Elon said "on ramp to off ramp" not stop signs in the neighborhood dropping your kid off to school.

Solarguy01 | January 11, 2015

TACC worked flawlessly for me yesterday, even when getting prepared to exit freeway at 75mph and moved into slow lane it automatically slowed from 75 to 60 to meet slow lane speed applying brakes as necessary to rapidly slow down.

geekdad.604 | January 11, 2015

I had a loud click (almost cracking) sound when I engaged cruise control for the first time today. Not sure if the stalk was just sticky from the factory. May have the SC look at it next time I'm in. Anyone else have that experience?

Still playing with TACC, take a bit of time to get used to... It was strange to have the car come to a complete stop behind another car in front. I had my foot covering the brake the whole time.

Just had a thought during the drive though... Legalities and public policy/safety aside, I can see a day when I can have my MS drive itself to the SC for checkup and come back clean and serviced. Exciting!

garygid | January 11, 2015

My questions above are safety concerns and operation details
about the 6.1 firmware operational functions, not questions
about what the software was intended to do, or what it might
do in the future. Thanks. If you know the answers, I would
like to be educated, please. If not, speculations usually do
not help me very much, but Thanks anyway.

will | January 11, 2015

Used TACC for the majority of a 285 mile road trip yesterday and it worked great. For stop and go traffic it is absolutely invaluable. I used it without major problems both on freeways and major surface street routes.

One of the things I did notice is when the road opens up in front of you because the car in front changes lanes or turns off, the acceleration up to cruise speed is quite aggressive and beyond what I would do myself when driving in an energy efficient manner (when I'm so inclined). On more than one occasion I consciously canceled the TACC to avoid this burst of acceleration and manually brought the car back up to cruise in a more sedate manner before resuming the TACC.

Even with a following distance set to max you will occasionally come up on traffic stopped at a light at a rate that is not scary, but concerning enough to warrant getting ready with your brake foot. Often this occurs when (as above) someone coming up to a red light pulls right into a turn lane and the car accelerates into the new open space only to have to brake harder than necessary for the rest of the stopped traffic at the light. This requires the car to engage the friction brakes fairly often where I would normally only use regen braking.

These should both be addressable in software by limiting or providing control over TACC aggressiveness on acceleration. Right now it seems to be prioritized on getting you back up to cruise speed (or following distance) rather than energy conservation. It would also be nice to have some speed "slack" on uphill sections rather than it trying to maintain the set speed regardless of energy use. I'm willing to drop from 65 back to say, 60, on an uphill when I'm trying to conserve energy and I will find myself canceling TACC in these situations and resuming once I crest the hill.

The other thing I noticed is that I _seem_ to be achieving better range with my P85D without having to use nearly as much effort in hyper-miling as I have used in previous range runs. When I was cruising on TACC on flat straight flat freeway at 65 it was staying at or below the rated range line most of the time.

P85D, 19" cyclones, 450lb payload, sport+range mode, temp 55-65 degrees, trip mostly highway varying from 55-65mph with some city. Trip was from San Jose to Napa/Calistoga via 680-N/29-N over to the Vacaville SC and Winters via 80-E and then back to San Jose via 80-W/880-S. Used TACC pretty much all the time with some occasional manual intervention as decribed previously. Trip meter:

Distance: 284.4 miles
Total energy: 89.1 kWh
Avg Energy: 313 Wh/mi

nelsonc | January 11, 2015

The Safety concerns are the same with any other Manufacturer which is why I am a bit disappointed in tesla just playing catchup. I am ready for them to take the lead a and shut up more nah sayers.

So what are your concerns.
New safety concerns? Ha ha

Now with 6.1 the car can warn you early, medium or late of an impending front end crash. Good for us. Your concern is you need to listen to a beep and watch your dash and not panic but hit your brakes.

Also with 6.1with TACC your car can now apply acceleration and braking automatically at speeds above 17 MPH and keep a safe distance between you and anything in front of you. If an idiot jumps in front of you the front collision warning may sound. What does this mean to you. It means you don't have to accurate or brake in normal traffic or stop and go. You only have to steer the while and watch your mirrors and maybe check stock prices.

Other safety concerns might include auto high beam. I am old so I need high beam to be less sensitive to street lights and turn on more easily. What does this mean to you is you might have to use your high beams as you do today.

Keep in mind all of these features are slow play to auto pilot and only work on newer teslas that have the hardware, cameras, radar, and computers to support this.

nelsonc | January 11, 2015

I love the acceleration with TACC. I would accelerate a lot faster. Don't change it tesla or make it configurable.

Hart | January 11, 2015

@will: I like the way it speeds up back to full cruising speed when lane opens up. Don't want it any less. If you do, just kick out TACC as you did. Not everyone (in fact I would venture to say very few) who drives a PD likes to go at, much less below speed limit!
@nelsonc: +1

tezzla.SoCal | January 11, 2015

@will - today I did a comparison 60 mile trip without tacc then repeated the same trip with 100% tacc. No difference in the Wh/mile usage.

Here are my screen shots:

will | January 11, 2015


I actually do like the way it accelerates back up to speed in the vast majority of situations. It works well and I would not want change the rate of acceleration except in the case where I am trying to conserve energy where acceleration back up to the set speed could be moderated.

This was purely an energy conserving test run to see whether there were any range improvements and to play with the new features. When driving manually, I am generally more aggressive than the TACC on the go petal (grin mode... that's why I forked out for the P85D), but there were definitely situations where the TACC made a decision to accelerate towards stopped cars down the road and then jam the friction brakes that most drivers would not have done with good situational awareness. It always stopped in time, but my wife as a passenger had a few white knuckle moments where she asked what the hell I was doing ("it's not me... it's the new TACC!").

I have no idea whether the TACC affected mileage, whether it's something with the 6.1 firmware or whether I was just so enthralled and engaged with the new features that everything just seemed better and brighter. I'll leave it to others to perform more objective tests... your experience makes it pretty definitive that there is nothing special going on with the TACC to affect mileage. Thanks for doing that experiment.

will | January 11, 2015

"go petal" -> "go pedal" :-)

Pbfoot | January 11, 2015

I was following a cyclist today on a one-lane road for about a mile (we were leaving a nature preserve). Since the MS is wide, there wasn't enough room to pass him. I set the TACC and it followed him at ~16-18 mph with about a 60-70 foot distance. There was one time where the blue indicator showing the little car graphic above the speed disappeared, so I'm guessing it didn't sense him there for a few seconds, but then it came back on. I'm not sure why that happened briefly as there was no significant change in his position or of the topography.

I can't say I had complete confidence in the system detecting him, so I was very attentive the whole time, but at least it appears the system does register cyclists/motorcyclists most of the time.

Hart | January 11, 2015

@will: thanks for your explanation. I understand now. I was puzzled that you seemed to want only gentle acceleration to increase range...
@Pbfoot: great to know! Thanks for sharing this info.

graham.simmonds | January 12, 2015

I realise you are all playing with it but I am not sure TACC was designed for round town driving! Whilst it may be able to detect what is in front of you it cannot detect cars pulling out of side turns when you least expect them to or pedestrians walking across the road. I am not looking forward to the first thread entitled "My First TACC Accident!".

will | January 12, 2015


Yep. Fully aware of the potential pitfalls and I am now careful about how I utilize the TACC for non-freeway driving. You'll have to pry it from my cold dead hands for stop and go along large multilane urban streets where it really makes a huge difference, but as I learned you still have to be vigilant for scenarios where TACC is not suitable. I worry a little more about unexpected braking that someone else reported when the TACC mistakenly thought it saw an obstacle/car in its path when cornering... I always disable it when taking any kind of turns.

Disclaimers notwithstanding in the manual, having a TACC that operates really well in slow stop and go traffic means it is going to be used in non-freeway driving by many owners. For me, as long as the traffic flow I'm in looks just like slow freeway traffic I feel comfortable using the TACC, but as soon as things get squirelly with corners, parked cars, cars entering from side streets, etc. I will be taking the controls.

RonaldA | January 12, 2015

Will Tacc work on "older" Model S from 2013 or will hardware be missing (front directed sensors for example)? If this is the case I expect then that most 6.1 updates will not apply to my vehicle.

ParklandFLMike | January 12, 2015

I have not used it enough to be certain but it seems the following distance is increased at night?

Has anyone noticed this or am I mistaken?

Even with 7 car length settings, the car slows down and brakes much later than my personal driving habits and doesn't leave much reaction time left if I needed to brake the car myself.

I would like there to be "earlier" braking setting to keep me a little less on edge.

Overall I love it. Tesla keep the updates coming!

nelsonc | January 12, 2015

TACC requires a hardware update to newer Tesla with equipped hardware. I believe late summer / fall 2014

Think of it as upgrading a expensive iPhone.

Hart | January 12, 2015

@Ronald: TACC will not work on older Model S cars like yours. Would need major hardware upgrades. Some of the other 6.1 features should work, though (e.g. %charge, energy graph prediction, etc.).

Haggy | January 12, 2015

I was surprised how long it takes CC to get up to speed when it's reengaged, so this is interesting. Pre-6.1 takes way too long, and 6.1 with TACC is aggressive, while I would have expected something in the middle. I don't have 6.1 yet, but I'd take something more aggressive over what CC offers. I hardly use CC but use ACC regularly on other vehicles.

I found that my other cars do a remarkably good job of working around curves, and have even had no problem following cars on off ramps from one freeway to another just letting the car adjust its speed. So I would be disappointed it the MS didn't do the same. That being said, when I did that with other cars I always had my foot hovering over the brake pedal just in case.

Brian H | January 12, 2015

braking and seamlessly are better words. Can't quite imagine what seemless would mean if it were a word! ;p

I wonder if TACC could include an option to choose California or real stops! When in Los Angeles ...

drsaab | January 14, 2015

btw....TACC will only work with your seatbelt on.

Cruise not available otherwise

garygid | January 14, 2015

I think that these features are important, and not difficult go implement:

1. normal CC should be available for inexperienced drivers.
2. the resume acceleration should be adjustable, from low to high.
3. the following distance maximum should allow for gentle regen and economy.
4. any autopilot car should be configurable to drive like a non-autopilot car.

vlad22 | January 14, 2015

Driving in heavy traffic today I got my first collision warning when the car started braking. It stopped itself without an issue. This was in wet but above freezing conditions. Had the roads been icy by the time the car recognized it had to brake it would have been way too late. I am not aware of any feature that disables autopilot when roads become slick. The car was coming towards the vehicle in front at a pace that I would not be comfortable with. Perhaps I will answer my own question by saying that had the car In front of me had the same tires, surface to grip, traction control systems etc then the buffer zone is sufficient??? Jmho