Sudden Decelleration on Highway - NOA

[loscosmos]

This has occured twice to me this week where I was driving a tad over the speed limit where the highway transitions from 65mpg to 55mpg.

My car goes into a very hard brake and decellerated. If someone was behind me, they would have definitely hit me.

Has anyone had this happen to them? I took it out of AP immediately and hit the camera button.

Nothing was around me either time. Any explanations or things to watch out for? Gave me a scare.

 

[3antar]

This has occured twice to me this week where I was driving a tad over the speed limit where the highway transitions from 65mpg to 55mpg.

My car goes into a very hard brake and decellerated. If someone was behind me, they would have definitely hit me.

Has anyone had this happen to them? I took it out of AP immediately and hit the camera button.

Nothing was around me either time. Any explanations or things to watch out for? Gave me a scare.

Usually Highways don't have an enforced speed limit within Tesla's AP and you can go 20 or 30 above the legal speed limit. What I do notice is sometimes by GPS may think I'm not on the highway anymore and now enforce the speed limit (With an offset of +5mph) and now the decceleration occurs. The only issue is that Tesla doesn't deccelerate smoothly and I've noticed this a few times.

 

[loscosmos]

Usually Highways don't have an enforced speed limit within Tesla's AP and you can go 20 or 30 above the legal speed limit. What I do notice is sometimes by GPS may think I'm not on the highway anymore and now enforce the speed limit (With an offset of +5mph) and now the decceleration occurs. The only issue is that Tesla doesn't deccelerate smoothly and I've noticed this a few times.

Thanks for your response. It was a pretty shocking hard decceleration and may have even been the car trying to do a hard stop. Not sure what happened or how to avoid it.

 

[ewoodrick]

This has occured twice to me this week where I was driving a tad over the speed limit where the highway transitions from 65mpg to 55mpg.

My car goes into a very hard brake and decellerated. If someone was behind me, they would have definitely hit me.

Has anyone had this happen to them? I took it out of AP immediately and hit the camera button.

Nothing was around me either time. Any explanations or things to watch out for? Gave me a scare.

It's common, for a speed limit change, it's pretty much what it is supposed to do.

Remember, if you are a passenger and the drivers goes from speed to removing foot off accelerator, it feels like hard braking, but it really isn't.
If someone is following that close to you, then they are too close. A 10 mph deceleration isn't that big of a thing.

 

[raptor5244]

The phantom has made an appearance.

 

[jsmay311]

If it's a road/highway that does not have a "Speed Limit +5mph" limit on the Autopilot set speed, then the set speed should not drop automatically when the speed limit goes down.

But when on a road with such a limit on the set speed (usually one with no middle divider or median), then the "Speed Limit +5mph" rule stays intact and your set speed can drop automatically along with a drop in the speed limit.

What I do notice is sometimes by GPS may think I'm not on the highway anymore and now enforce the speed limit (With an offset of +5mph) and now the decceleration occurs.

This is also a good point. There's a section of expressway that I sometimes drive through where Tesla's navigation system is buggy and, for a brief moment, the car doesn't know what the speed limit is (it disappears from the screen) and/or forgets that I'm on a limited-access expressway. As soon as this happens, my set speed will suddenly drop to 50mph (if I recall correctly). Soon after, the car quickly remembers that the speed limit is 60mph and I'm on an expressway, but I have to manually raise the set speed back up to what it was before.

 

[neurocutie]

perhaps not as sudden but my M3 out of the blue decided it couldn't do cruise control anymore (visibility/radar) and started to slow down quickly.... annoying

 

[RichNot]

Several times my car has braked hard at 65 mph on a busy Interstate while in cruise control or auto pilot. Cruise control or auto pilot stays engaged. No change in speed limit. I think it could be that there were marks on the road surface that the car could not understand. Once it happened where construction had taken place and there were long black lines in the surface. Other times I don't know what caused it. Only way I know to correct it is to quickly hit the accelerator. I sure would like to hear more about this.

 

[Marcos02720]

This has occurred

This has occured twice to me this week where I was driving a tad over the speed limit where the highway transitions from 65mpg to 55mpg.

My car goes into a very hard brake and decellerated. If someone was behind me, they would have definitely hit me.

Has anyone had this happen to them? I took it out of AP immediately and hit the camera button.

Nothing was around me either time. Any explanations or things to watch out for? Gave me a scare.

twice to me this week where I was driving a tad over the speed limit where the highway transitions from 65mpg to 55mpg.

My car goes into a very hard brake and decellerated. If someone was behind me, they would have definitely hit me.

Has anyone had this happen to them? I took it out of AP immediately and hit the camera button.

Nothing was around me either time. Any explanations or things to watch out for? Gave me a scare.

I have had my Model 3 for one month now and have had 4 or 5 episodes of sudden braking. This has occurred on the highway on an open road and for no apparent reason.

 

[ewoodrick]

I have had my Model 3 for one month now and have had 4 or 5 episodes of sudden braking. This has occurred on the highway on an open road and for no apparent reason.

You'll have more. It's just the state of the software today. With software updates, all you can say is that it may change next time.

 

[neurocutie]

Several times my car has braked hard at 65 mph on a busy Interstate while in cruise control or auto pilot.

I wish Tesla would offer a pure, dumb cruise control -- just go at the set speed, don't try to out-think the driver. It sometimes tries to be smart enough to be dangerous...

 

[ElectricIAC]

I wish Tesla would offer a pure, dumb cruise control -- just go at the set speed, don't try to out-think the driver. It sometimes tries to be smart enough to be dangerous...

They do. In the SR.

 

[raptor5244]

I wish Tesla would offer a pure, dumb cruise control -- just go at the set speed, don't try to out-think the driver. It sometimes tries to be smart enough to be dangerous...

Good point. They should have an option under settings where you can set it to standard cruise control or AutoPilot mode. That should be easy enough to program into an update.

 

[loscosmos]

Glad my car's not the only one. Hope for the next update to do better.

 

[Knightshade]

Good point. They should have an option under settings where you can set it to standard cruise control or AutoPilot mode. That should be easy enough to program into an update.

It would be, but Tesla already has issues with mode confusion "I wasn't sure if it was on AP or just TACC!' "I didn't realize TACC was on!" "I didn't realize TACC was off!"

Adding yet another mode doesn't seem like something Tesla has ever been interested in.

 

[PianoAl]

My car goes into a very hard brake and decelerated. If someone was behind me, they would have definitely hit me.

Here's a question: If someone had been behind you and the car detected him/her, would it not have decelerated so fast?