# Is this expected highway autopilot behavior?



## Hendrixx007 (Aug 4, 2017)

There’s an area that I drive maybe once a week that causes me to disable autopilot but its not tricky at all and I dont really understand whats happening. It happens when I’m on i66 in Virginia crossing above 495. The car knows the speed limit is 55 and I’ll have AP set to 67 and as I approach 495 the car will suddenly brake and I see that AP has lowered its max speed to 50. I then scroll the speed back up to 60 and a second or two later it brakes again and goes back to 50. Once I finish passing over 495 its back to smooth sailing on i66. My first thought was that there may be an error in the maps that reports the three lanes of i66 in this overpassas exit ramps and that is why speed reduces dramatically even below the speed limit? This occurs eastbound and westbound and its above the overpass so not like some of the other issues with shadows underneath overpasses. Any ideas?


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## 3V Pilot (Sep 15, 2017)

Sounds like a database speed limit error. I'd submit a bug report and hope they fix it soon. If it happens every time at the same place I can't imagine it being something the car is picking up externally from the radar or camera.


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## MelindaV (Apr 2, 2016)

does it happen both directions, or just east or west?
for those wanting a visual


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## ahagge (May 6, 2017)

IMHO it's a mapping error. I have the same issue with heading southbound on I-5 in the San Fernando Valley here in California - if I'm in the outermost lane, the car will abruptly slow to 45 just before the transition to the 170 southbound. I think it's because the freeway passes under an onramp where the speed limit is likely 45 MPH. Now that I know it will happen, I just keep my foot on the accelerator and press down as soon as it happens, to avoid getting rear-ended, keeping it down until I see the Speed Limit 65 return to the display.


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## Perlman (Mar 9, 2018)

I’ve had a similar issue taking the toll road past 495 to get on to I-66. In my case it was dropping to 35mph and I think the car was seeing an exit ramp speed limit sign. Could the drop to 50mph be the same thing?


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## Hendrixx007 (Aug 4, 2017)

MelindaV said:


> does it happen both directions, or just east or west?
> for those wanting a visual
> View attachment 11931


Happens in both directions and doesnt seem to matter which lane. I have my AP speed offset set to +10 so even it was a basic speed limit database issue I wouldnt think it be slowing down that much. I can even see the little speed limit icon stays at 55mph but the car sets max AP speed down to 50 or maybe even 45. Almost like it thinks I'm transitioning highways or taking an exit.


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## Hendrixx007 (Aug 4, 2017)

Perlman said:


> I've had a similar issue taking the toll road past 495 to get on to I-66. In my case it was dropping to 35mph and I think the car was seeing an exit ramp speed limit sign. Could the drop to 50mph be the same thing?


Sounds like it. In my case the car may be trying to slow down even further but I always disable AP after the initial sudden braking for fear of getting rear ended.


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## Ed Woodrick (May 26, 2018)

Hendrixx007 said:


> There's an area that I drive maybe once a week that causes me to disable autopilot but its not tricky at all and I dont really understand whats happening. It happens when I'm on i66 in Virginia crossing above 495. The car knows the speed limit is 55 and I'll have AP set to 67 and as I approach 495 the car will suddenly brake and I see that AP has lowered its max speed to 50. I then scroll the speed back up to 60 and a second or two later it brakes again and goes back to 50. Once I finish passing over 495 its back to smooth sailing on i66. My first thought was that there may be an error in the maps that reports the three lanes of i66 in this overpassas exit ramps and that is why speed reduces dramatically even below the speed limit? This occurs eastbound and westbound and its above the overpass so not like some of the other issues with shadows underneath overpasses. Any ideas?


Right now, I'd say that map speed limits are only about 50% correct. It is pretty pathetic.


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## GDN (Oct 30, 2017)

Hendrixx007 said:


> There's an area that I drive maybe once a week that causes me to disable autopilot but its not tricky at all and I dont really understand whats happening. It happens when I'm on i66 in Virginia crossing above 495. The car knows the speed limit is 55 and I'll have AP set to 67 and as I approach 495 the car will suddenly brake and I see that AP has lowered its max speed to 50. I then scroll the speed back up to 60 and a second or two later it brakes again and goes back to 50. Once I finish passing over 495 its back to smooth sailing on i66. My first thought was that there may be an error in the maps that reports the three lanes of i66 in this overpassas exit ramps and that is why speed reduces dramatically even below the speed limit? This occurs eastbound and westbound and its above the overpass so not like some of the other issues with shadows underneath overpasses. Any ideas?


Regardless of a known issue with speed limits or a true speed limit change, these are not handled well. I've seen something similar, I think Tesla needs to work on speed transitions. This one is a noted and legal speed change, but about 30 minutes up the road on Hwy 75 N of Dallas there is a speed limit change from 75 down to 65. It is a legal and noted change, posted on the road and the car has it in the database, but the car literally decelrates with full regen or braking or both. 10 MPH isn't much, but when you are rolling down the road at 75 MPH or even a few over in heavy traffic and you decide you want to drop 10 MPH in a matter of a couple of seconds, it doesn't bode well for the people behind you. Just not the actual safest way it can be handled for transitions.


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## MelindaV (Apr 2, 2016)

Ed Woodrick said:


> Right now, I'd say that map speed limits are only about 50% correct. It is pretty pathetic.


I think it's really quite remarkable, even with the glitches.


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## garsh (Apr 4, 2016)

MelindaV said:


> I think it's really quite remarkable, even with the glitches.


Autopilot itself is very good. But there's little excuse for Tesla to not have much more accurate speed limit maps for interstates and other major divided highways.

This is a solved problem by just about every other auto manufacturer. I know a Lincoln I test drove displayed the current speed limit on the dash. Even if Tesla doesn't want to pay a third party for the information, they could solve this problem in an automated manner using random samplings of still images from autopilot-equipped cars to find and read speed limit signs.

Or even simpler, have some sort of error-detecting algorithm that goes through their speed-limit database looking for small stretches of divided highways where the speed limit differs from the rest of the road.


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## Perlman (Mar 9, 2018)

Instead of disabling autopilot, you should be able to just push on accelerator pedal and power through until it sees the proper speed limit again. This doesn't disable AP and I have found to be more convenient and comfortable.


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## Twiglett (Feb 8, 2017)

Ed Woodrick said:


> Right now, I'd say that map speed limits are only about 50% correct. It is pretty pathetic.


Are you reporting the errors?
Speed limits change all the time, if nobody reports them they will stay wrong. 
It's a constant problem for all navigation systems.


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## BayAreaModel3Owner (Sep 19, 2017)

I had the exact same problem on I-5 in LA, CA yesterday. The car would suddenly brake to a speed of 40mph, despite the speed limit in the display showing as 55mph. It seemed to be happening mostly when I was driving under an overpass. I reported it through email.


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## GOMCE62 (Aug 13, 2018)

I have the same problem on on Hwy 237 HOV ramp onto I880 North where in the middle of the ramp the Model 3 wants to drop down to 45 MPH. I thought it was also a mapping error until I had a Model S loaner car why my M3 was in for service and the MS stays at 65 MPH with auto-pilot engaged. Isn't the M3 and MS use the same auto-pilot H/W and S/W?.


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## BayAreaModel3Owner (Sep 19, 2017)

GOMCE62 said:


> I have the same problem on on Hwy 237 HOV ramp onto I880 North where in the middle of the ramp the Model 3 wants to drop down to 45 MPH. I thought it was also a mapping error until I had a Model S loaner car why my M3 was in for service and the MS stays at 65 MPH with auto-pilot engaged. Isn't the M3 and MS use the same auto-pilot H/W and S/W?.


Which firmware version do you have? I had 26.1 when I had that issue. Tesla asked me to update to 28.2 and thought it would fix it. I haven't experienced it since, but I also haven't driven the same route.


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## John (Apr 16, 2016)

One thing to remember is that EAP doesn't mind if you press the accelerator to speed up.

This is very useful during EAP lane changes. Frequently a little speed-up makes things go smoother for traffic around you.

This is also useful when traffic is merging and EAP is blissfully unaware that someone is about to merge into the side of your car. Well, that's not what ends up happening, but they get pissed and slam on their brakes. You don't get a chance to explain that it was your autopilot, not you, that wouldn't speed up or slow down to let them merge.

Next time when someone is merging, keep EAP on and just press the accelerator to speed up out of the way. If you have to hit the brakes instead you'll cancel EAP, so try speeding up whenever you safely can.


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## Hendrixx007 (Aug 4, 2017)

Update. Just noticed for the first time today that the map issue is fixed in the spot I mentioned in the original post. I havent updated my software in about a month so I guess the map data is updated externally?


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## GDN (Oct 30, 2017)

Hendrixx007 said:


> Update. Just noticed for the first time today that the map issue is fixed in the spot I mentioned in the original post. I havent updated my software in about a month so I guess the map data is updated externally?


Very likely all of those 5GB downloads discussed in a few threads. Seems they update the maps often.


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## IPv6Freely (Aug 8, 2017)

You'd think that if you're cruising along at well over the speed limit anyway it wouldn't matter if the map has a glitch... Come on Tesla, CLEARLY I don't care about what the signs are saying!


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## Mike (Apr 4, 2016)

Hendrixx007 said:


> Update. Just noticed for the first time today that the map issue is fixed in the spot I mentioned in the original post. I havent updated my software in about a month so I guess the map data is updated externally?


I know way out here in the sticks of eastern Ontario, this morning all my local 2 lane roads suddenly have the correct speed limits now showing. Finally I can use the TACC system to drive locally.


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## TBM3 (Aug 24, 2018)

Twiglett said:


> Are you reporting the errors?
> Speed limits change all the time, if nobody reports them they will stay wrong.
> It's a constant problem for all navigation systems.


How do you report the errors to Tesla? I'm a new M3 owner and I have the same problem where the car slows dramatically on a 4 lane freeway on my way to work. I was wondering who/how to report these issues to.


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## Bokonon (Apr 13, 2017)

TBM3 said:


> How do you report the errors to Tesla? I'm a new M3 owner and I have the same problem where the car slows dramatically on a 4 lane freeway on my way to work. I was wondering who/how to report these issues to.


Right after the slowdown happens, hold down the right scroll wheel on the steering wheel to engage the voice-recognition system, and say, "Bug report" followed by a description of what happened (e.g. "car slowed down unexpectedly to 40 mph on a 65-mph highway"). This will file a bug report with Tesla that includes your car's current status and position, and they will investigate from there.

Most likely it's a map issue where a slower speed limit from an adjacent / above / below road is erroneously being applied to the freeway you're on, which causes the car to brake suddenly.


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## Love (Sep 13, 2017)

Going to bump this for a quick question.
Are you all reporting wrong speeds using the Bug Report as well? Or is there another way?

A road I use daily for work has a 40MPH limit. It used to be 45 and both mine and my wife’s cars showed it as 45. I use EAP on this road every day. Just recently this same road started showing as 25MPH, so turning on EAP causes my car to brake and go to that.


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## Mike (Apr 4, 2016)

Lovesword said:


> Going to bump this for a quick question.
> Are you all reporting wrong speeds using the Bug Report as well? Or is there another way?
> 
> A road I use daily for work has a 40MPH limit. It used to be 45 and both mine and my wife's cars showed it as 45. I use EAP on this road every day. Just recently this same road started showing as 25MPH, so turning on EAP causes my car to brake and go to that.


I always use bug report for every error I see.

And if it is the same error every day, well I just bug report it every. single. day.


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## SoCalWine (Oct 1, 2018)

John said:


> One thing to remember is that EAP doesn't mind if you press the accelerator to speed up.
> 
> This is very useful during EAP lane changes. Frequently a little speed-up makes things go smoother for traffic around you.
> 
> ...


I understand courtesy and all but I have never understood why it is my responsibility to speed up or slow down to allow a car to merge into my lane. Why can't they speed up or slow down?


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## John (Apr 16, 2016)

SoCalWine said:


> I understand courtesy and all but I have never understood why it is my responsibility to speed up or slow down to allow a car to merge into my lane. Why can't they speed up or slow down?


Strictly speaking, you don't have to do anything if the other lane is supposed to yield.

But in practice, the world is a nicer place when people help each other. And sometimes there are pushy people, who demand that other people get out of their way. And sometimes there are timid people, who don't speed up enough to merge properly when they get on the freeway.

All of us have days where we end up being the boneheaded one. So the same thing we shake our head at today is the thing we end up doing tomorrow when we are distracted, or in a hurry, or upset about something. Karma is about being understanding, and hoping someone will be understanding with you, later.


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## SoCalWine (Oct 1, 2018)

John said:


> Strictly speaking, you don't have to do anything if the other lane is supposed to yield.
> 
> But in practice, the world is a nicer place when people help each other. And sometimes there are pushy people, who demand that other people get out of their way. And sometimes there are timid people, who don't speed up enough to merge properly when they get on the freeway.
> 
> All of us have days where we end up being the boneheaded one. So the same thing we shake our head at today is the thing we end up doing tomorrow when we are distracted, or in a hurry, or upset about something. Karma is about being understanding, and hoping someone will be understanding with you, later.


Well said.


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