this post was submitted on 18 Oct 2025
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I’m not sure what this system does, but my non-Tesla car can adjust its intelligent cruise control by speed limit signs it sees, and you can tell it to have a buffer. Mine is set for +5, so if the sign says 45 miles per hour, the car drives itself at 50 mph.
If it’s something like that, which you set yourself, it’s probably fine. Just know what the police in your area enforce. Where I live you can generally go five over without an issue, ten over on the freeways. Everyone does this, so if you go the speed limit you end up annoying everyone.
I've driven by a few radar speed indicators in my car, and I'm consistently going 4 km/h less than what my digital speedometer says, regardless of speed. I find it difficult to believe this is an accident. So if I had your vehicle and it behaved like my speedometer does, I would still only be +1 over the limit. Also, I now drive with my speedometer +5 to +9 relative to the speed limit, which keeps me more in line with the traffic around me.
This is kinda dumb. So they have to adjust speed limits below safe levels so you don't get over it?
So dumb that society collectively agreed that 35 means 40, 40 means 45, 45 means 50, etc.
There’s a little more to it than that. They also need to consider that, in cars with an analogue speed dial, the actual speed is not displayed precisely. Plus, there may be minor discrepancies between the speed dial and the actual speed, which can be affected by non-standard tyres etc. So a small “buffer” in acceptable speeds is pretty reasonable.
I recall being told by someone at a Mitsubishi factory that car manufacturers actually intentionally set the speed dials to be slightly higher speed than reality to accommodate for people’s need to break the rules just a little…!
Can confirm the last part.
Almost every car with speed control set to, for examole, 50 kph was metered at 45kph on GPS.
I was also told it's about the calibration of the radar guns. They are calibrated to -7/+0 meaning if you are going 47 mph there is a chance you are picked up as going 40. That said if you are going 41 or 42 there is a good chance the cop picks you up as going less than 40.
That I understand, but as the person I replied to said that I hope you read, people intentionally go 50 in the 45.
So the grace window you mention is irrelevant; you'd be doing 51 in the 45.
In Germany there are speedtraps everywhere.
No bs cop on-site decides, that today you have chosen a bad day.
It makes us feel like we’re speedy little rebels. 🤣
But then why don't we all shoplift packs of gum every week?
Speeding is the one law everyone agrees is fun and acceptable to break a bit, despite being more dangerous than many actual crimes.
Because when the road is built for a safe speed target of 65, then the limit is set at 55 instead, yeah you get people who are breaking the legal limit but not the actual safe speed.
Edit: forgot a link: https://www.fhwa.dot.gov/design/standards/151007.cfm
tl;dr: design speeds and speed limits are not necessarily related. "Selection of a posted speed is an operational decision for which the owner and operator of the facility is responsible."
Where I'm at, they're trying to do that plan where they lower speed limits and change the roads to reflect the slower speeds with narrowing, or bikes lanes, or speed bumps etc to reduce car accident deaths, but they ignored the entire part about changing the roads to reflect the new speeds, and just lowered the speeds.
So you got these 4-6 lane roads that were designed for 50km/h and now they're 30-40km/h and absolutely no one, is doing the posted limit, at the new 30 areas, not even cops.
All I can come up with is now if you speed like people may have before, you're really over the limit, so it's easier to ticket someone? Like before people might have gone 55-60 in the 50 zone, but now going 55 is well over 40, and impound level over 30.
Do you think that every or most roads have the wrong speed limit? I sure don't.
If everyone is speeding on a road and not constantly getting into accidents does that not indicate that the posted speed limit is incorrect?
If it didn't, it would be pretty damn annoying as cars always show higher than actual speed. I've had to set our BMW to do +8km/h so that it actually does 120km/h on GPS and not 112.
Although that is true, your car is quite extreme in that regard. In Germany cars are not allowed to deviate by more than 3kph at speeds below 100, and 3% at speeds above 100. I doubt BMW uses different speedometer for cars sold in foreign countries so I'm pretty sure there is something wrong with yours. Maybe you installed smaller diameter tires than from factory?
Hmmh, could be, though both are "from the factory", the winter/summer tires are slightly different sizes. But the allowed error in the EU overall (or at least in Finland) is 10% +4km/h, so it's still well withing "spec".
Are your tires fully inflated?