Weird Speed Limit Assist Behavior
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Member
Joined: Jul 2022
Posts: 159
Likes: 46
GLS 450 (2022), EQE SUV 350 (2025). GLS 450 (2007)
Weird Speed Limit Assist Behavior
Hey folks, here's a question that I'm wondering if someone can answer. I use the speed limit assist all the time, and I find it to be almost flawless. It is so convenient to have the car automatically adjust itself to the current speed limit. Now, here is a little situation that I found interesting that perhaps someone can shed light upon. Occasionally at the same exact point, I drive past a particular speed limit sign, and the car correctly accelerates from the previous 40 mph limit to the new 50 mph limit. The car speeds up just fine as you would expect. However, the little white speed limit sign in the dash (and in the MBUX screen) remains fixed at 40 mph. It is almost as if the data controlling the car and the data shown in the dashboard come from two separate sources. I'm wondering how this can be. This is such an inconsistency and I find it very puzzling. If anyone can shed some light on this behavior, I would certainly appreciate it. Thanks.
Member
Joined: Jan 2023
Posts: 235
Likes: 91
2012 E Cabrio, 2015 GL , 2017 B ED & 2024 GLS
Hey folks, here's a question that I'm wondering if someone can answer. I use the speed limit assist all the time, and I find it to be almost flawless. It is so convenient to have the car automatically adjust itself to the current speed limit. Now, here is a little situation that I found interesting that perhaps someone can shed light upon. Occasionally at the same exact point, I drive past a particular speed limit sign, and the car correctly accelerates from the previous 40 mph limit to the new 50 mph limit. The car speeds up just fine as you would expect. However, the little white speed limit sign in the dash (and in the MBUX screen) remains fixed at 40 mph. It is almost as if the data controlling the car and the data shown in the dashboard come from two separate sources. I'm wondering how this can be. This is such an inconsistency and I find it very puzzling. If anyone can shed some light on this behavior, I would certainly appreciate it. Thanks.
Newbie
Joined: Oct 2023
Posts: 8
Likes: 4
'24 GLS 450
I had a different but similar type of issue occur on our drive down to Florida last November. Cruising at 70 mph, and while passing an off-ramp, the MBUX picks up the yellow offramp speed, say 40 mph, and then slows down abruptly in an unsafe manner. On one occasion a transport truck had to swerve around our GLS. So now I'm cautious passing off-ramps that have have yellow speed limit signs close to the highway.
MBWorld Fanatic!
Joined: May 2023
Posts: 1,125
Likes: 310
'23 GLS450
I had a different but similar type of issue occur on our drive down to Florida last November. Cruising at 70 mph, and while passing an off-ramp, the MBUX picks up the yellow offramp speed, say 40 mph, and then slows down abruptly in an unsafe manner. On one occasion a transport truck had to swerve around our GLS. So now I'm cautious passing off-ramps that have have yellow speed limit signs close to the highway.
Super Member
Joined: Apr 2011
Posts: 542
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2021 GLS580 | 2011 ML350 BlueTec | 2009 Pontiac G8 GXP
I turned it off halfway through the first road trip. I don't go excessively fast, but I do drive with traffic regardless of the posted limit. I would have to correct it after every sign. At one point it even mistook a highway 80 sign for an 80mph limit. My wife was asking what I was doing. Shortly thereafter I found the option to turn off speed limit adoption. I also watched it be repeatedly confused by sequential signs saying one limit for cars and another for trucks & busses. It would initially pickup the car limit, and then pickup the truck/bus limit. Good idea in theory, doesn't work well in the real world. Even if we were talking about fully automated driving it wouldn't be safe to blindly and aggressively adopt a new limit without taking into account the surrounding traffic speed.
