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Is TACC/AP supposed to detect stopped cars in your lane?

caps04

Member
Aug 14, 2014
282
110
NJ USA
Since buying my car, I have never once had my car detect, slow down or stop for a car stopped at a traffic light or traffic jam in my lane. Maybe it might have but I never waited that long. Just to be sure, I have tested it to the point where I had to brake so hard, things flew forward - so even if it works after that point, it's not practical for me.

Btw, it works perfectly if the car is moving in front me - just never gets a lock on a stationary car if I am approaching it at a non-trivial speed (40 MPH or more).

Is my front facing radar somehow busted? I wouldn't think so because in all other situations it works perfectly. Or is this how it's supposed to work?
 

Stoneymonster

Active Member
Jan 8, 2013
1,787
1,064
Aptos, Ca
Since buying my car, I have never once had my car detect, slow down or stop for a car stopped at a traffic light or traffic jam in my lane. Maybe it might have but I never waited that long. Just to be sure, I have tested it to the point where I had to brake so hard, things flew forward - so even if it works after that point, it's not practical for me.

Btw, it works perfectly if the car is moving in front me - just never gets a lock on a stationary car if I am approaching it at a non-trivial speed (40 MPH or more).

Is my front facing radar somehow busted? I wouldn't think so because in all other situations it works perfectly. Or is this how it's supposed to work?

TACC did not claim to and most of the time would not. I don't know if that's changed with AP, but probably not. For what it's worth, on my car it often does stop reasonably, but I don't think that means there's anything wrong with your car.
 

FlasherZ

Sig Model S + Sig Model X + Model 3 Resv
Jun 21, 2012
7,024
1,013
Unless the car previously saw the object moving, it will not, and that's to prevent the car from seeing another stationary object (say, on the side of the road) as another car and suddenly stopping you.
 

CHG-ON

Still in love after all these miles
Jun 24, 2014
3,079
636
Santa Cruz Mountains, USA
Mine always stops. Even when I am rolling up behind somebody and engage it maybe 10 ft back. It locks on instantly and stops, then follows. I use it every day and practically never have to touch the brake myself. I think I might be misunderstanding the question.
 

FlasherZ

Sig Model S + Sig Model X + Model 3 Resv
Jun 21, 2012
7,024
1,013
Mine always stops. Even when I am rolling up behind somebody and engage it maybe 10 ft back. It locks on instantly and stops, then follows. I use it every day and practically never have to touch the brake myself. I think I might be misunderstanding the question.

I read it as he was travelling up the road and there was a stationary car ahead that hadn't been seen as moving by the car previously. So you come around a slight curve to find a car stopped at a red light ahead (that the car hadn't locked onto previously). I don't think Model S TACC has ever slowed down for that (although it's likely to engage emergency braking when you get really really close).
 

yoyo

Member
Nov 14, 2014
103
6
IL, USA
I think it changed with AP. when auto steering is active and it goes into red light with stopped cars which was not detected before, it would slow down and stop
but do not try this with curve as it will detect it too late and slam on brake.
 

FlasherZ

Sig Model S + Sig Model X + Model 3 Resv
Jun 21, 2012
7,024
1,013
I think it changed with AP. when auto steering is active and it goes into red light with stopped cars which was not detected before, it would slow down and stop
but do not try this with curve as it will detect it too late and slam on brake.

Ah, yes, I would expect it changes with later AP... My experience with TACC is limited to loaner use until I get the X.
 

CHG-ON

Still in love after all these miles
Jun 24, 2014
3,079
636
Santa Cruz Mountains, USA
I just tested it on my way home. A car was stopped at a light about 15ft ahead of me. I engaged just TACC and the car stopped as always. Though I can certainly see if I were travelling at speed and came around a tight curve upon a stopped car, it could have a problem. But so far, even when driving with nobody ahead of me, when I encounter another car, moving, from around a curve, TACC locks on immediately and tracks. I've only had one real issue where it slammed the brakes on when it shouldn't have. Scared the crap out of me. I reported to Tesla right away. That was back when it was first released. No problems since. I'm actually surprised at just how well it works. I'm still figuring out AutoSteer. It can do some funky stuff on surface streets, which I would expect. The highway has been great so far.

I read it as he was travelling up the road and there was a stationary car ahead that hadn't been seen as moving by the car previously. So you come around a slight curve to find a car stopped at a red light ahead (that the car hadn't locked onto previously). I don't think Model S TACC has ever slowed down for that (although it's likely to engage emergency braking when you get really really close).
 

RDoc

S85D
Aug 24, 2012
2,736
1,588
Boston North Shore
Since buying my car, I have never once had my car detect, slow down or stop for a car stopped at a traffic light or traffic jam in my lane. Maybe it might have but I never waited that long. Just to be sure, I have tested it to the point where I had to brake so hard, things flew forward - so even if it works after that point, it's not practical for me.

Btw, it works perfectly if the car is moving in front me - just never gets a lock on a stationary car if I am approaching it at a non-trivial speed (40 MPH or more).

Is my front facing radar somehow busted? I wouldn't think so because in all other situations it works perfectly. Or is this how it's supposed to work?
It always stops for me, even at highway speeds and regardless of if it ever saw the car moving. It was very abrupt at first, but each update has noticeable improved the smoothness.
 

lorih

Member
May 12, 2013
709
46
A few things to check:
1) make sure your TACC is set for the proper distance. It might not stop for the distance you like.
2) if it really gets to the point where it is too close to stop it should give you a collision mitigation warning and it should emergency break for you.
3) make sure it seeing the car in front of you. If you have manually engaged TACC then you should see a replica on the dashboard of what it 'sees'. If you turn it on and it doesn't see anything to track it should be pale grey, not white or blue.

If this all working, but still not stopping, I would bring it to the service center to check.

Disclosure: these are the things I learned as a passenger with someone else driving, so I don't know how it "feels", just what the driver tells me.
 

tezzla

Supporting Member
Jul 14, 2013
650
282
SoCal
From the manual:

Warning: Traffic-Aware Cruise Control can not detect all objects and may not brake/decelerate for stationary vehicles, especially in situations when you are driving over 50 mph (80 km/h) and a vehicle you are following moves out of your driving path and a stationary vehicle or object, bicycle, or pedestrian is in front of you instead. Always pay attention to the road ahead and stay prepared to take immediate corrective action. Depending on Traffic-Aware Cruise Control to avoid a collision can result in serious injury or death.
 

Stoneymonster

Active Member
Jan 8, 2013
1,787
1,064
Aptos, Ca
From the manual:

Warning: Traffic-Aware Cruise Control can not detect all objects and may not brake/decelerate for stationary vehicles, especially in situations when you are driving over 50 mph (80 km/h) and a vehicle you are following moves out of your driving path and a stationary vehicle or object, bicycle, or pedestrian is in front of you instead. Always pay attention to the road ahead and stay prepared to take immediate corrective action. Depending on Traffic-Aware Cruise Control to avoid a collision can result in serious injury or death.

That's that one! Thanks for finding this.
 

caps04

Member
Aug 14, 2014
282
110
NJ USA
A few things to check:
1) make sure your TACC is set for the proper distance. It might not stop for the distance you like.

You mean the TACC car length setting? I usually keep it around 3. I'll try to set it to 7 and see if it works better. There is also a setting for Collision warning/Automatic braking in Settings screen which I have played with without seeing any difference.

- - - Updated - - -

From the manual:

Warning: Traffic-Aware Cruise Control can not detect all objects and may not brake/decelerate for stationary vehicles, especially in situations when you are driving over 50 mph (80 km/h) and a vehicle you are following moves out of your driving path and a stationary vehicle or object, bicycle, or pedestrian is in front of you instead. Always pay attention to the road ahead and stay prepared to take immediate corrective action. Depending on Traffic-Aware Cruise Control to avoid a collision can result in serious injury or death.

I remember reading this but I've seen many people claim that it should still work (at least occasionally) and mine never did. Anyway, with this disclaimer, I don't expect service to even look at it because otherwise it works fine.
 

Johan

Ex got M3 in the divorce, waiting for EU Model Y!
Feb 9, 2012
7,495
9,770
Drammen, Norway
To reply to the OP's question: of course it is designed to stop for cars stopped or stopping in front. If not it would be designed to drive through them (highly unlikely). And yes, if the car can see and measure it's differential speed to something in front then I'm confident it won't have an issue measuring the relative speed and distance to something that happens to contribute 0 to the relative equation. The car doing the measuring is moving anyway, so the delta will be even if measured object's speed is 0.
 

Stoneymonster

Active Member
Jan 8, 2013
1,787
1,064
Aptos, Ca
To reply to the OP's question: of course it is designed to stop for cars stopped or stopping in front. If not it would be designed to drive through them (highly unlikely). And yes, if the car can see and measure it's differential speed to something in front then I'm confident it won't have an issue measuring the relative speed and distance to something that happens to contribute 0 to the relative equation. The car doing the measuring is moving anyway, so the delta will be even if measured object's speed is 0.

This is at least historically incorrect, as several early videos and incidents demonstrate.
 

LetsGoFast

Active Member
Oct 13, 2014
1,329
101
Virginia
But what then could explain that technically?

Stationary objects are much more difficult to classify than moving ones. Radar can easily confuse an overhead sign for a parked car (as an example). I think the car's ability to detect stationary objects and be certain that they are cars has gotten steadily better over time, but it remains a much more challenging technical problem than detecting moving cars.
 

Johan

Ex got M3 in the divorce, waiting for EU Model Y!
Feb 9, 2012
7,495
9,770
Drammen, Norway
Stationary objects are much more difficult to classify than moving ones. Radar can easily confuse an overhead sign for a parked car (as an example). I think the car's ability to detect stationary objects and be certain that they are cars has gotten steadily better over time, but it remains a much more challenging technical problem than detecting moving cars.

Of course you're right. I understood it by thinking like this: in the "other object speed" range 0 it's very crowded with objects as opposed to any other speed (faster or slower than 0).
 

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