[Fox530]

Hi all,

The speed limit information on my M340i seems to be really unreliable.

It frequently misses speed limit signs and also does things like doesn't seem to notice I've left a carpark, with a speed limit of 5mph, and have now driven 500 metres down a 30mph road. From time to time it also displays speed limits which are clearly never going to be correct - the navigation knows we are on a dual carriageway, but it continues to display 60mph for several miles before it realises and updates to 70mph.

This not a new feature to me - I had it on my 530d and it was really good - is there something wrong or is it just not very good on these cars?

[ZedsRedBaby]

It's just not very good. Reads signs on side roads, misreads signs altogether (eg told me the speed limit on the Fosse Way was 80mph the other day), uses out of date sat nav info, misses overhead signs, ignores the fact that limits only apply to certain classes of vehicle, ignores the fact that the sign says the limit applies in 300 yds etc etc etc.

What the sales blurb says: "With Speed Limit Display, cameras installed in the rear view mirror are constantly detecting speed limit signs on the road side, whether they are permanent or temporary speed limits. Combining this with information from the navigation system ensures that you always see an accurate speed limit in your instrument panel or Head-Up Display."

What they'll say when you complain that it's a pile of shite: "Onboard systems are intended as an aid. The driver remains responsible at all times for knowing the correct speed limit."

[Charlie (Wessex)]

I'd advise never to set the auto limit feature. For example. on the M3, through the roadworks, it often picks up the work site speed limit of 10mph rather than 50mph.

[Mason Hatcher]

Mine seems to work just fine.

[thescouselander]

Yes, it's wrong quite a lot on my car including on a 30 mph stretch in a local village which is displayed as 80 mph on the dash.

[a.summers86]

I’ve always thought mine has worked well. I’d say it gets it right 99% of the time.

I can count on one hand the amount of times it’s mis read a sign in circa 30k miles.

Most recently it read a roadwork sign of 5mph on a motorway but corrected itself within a few hundred yards.

[AP]

What market are you in?
Speed limits come fro 2 sources , the data in the sat nav map and the quality of that may vary country to country.
Always found pretty good although quite 100% in the U.K.
The other source whichbiverides that is the camera which detect speed limit signs

This can be a bit hit and miss
My g30 pre LCI would read signs on parallel roads , the LCI is much better

[paulockenden]

The underlying map data is pretty good round here, but the camera based over-rides are ridiculous. Picking up from side roads, reading the speed limit signs on the back of vans, and in one case seeing the SO of a SOLD board as 80!

I wish you could turn off the camera recognition.

[gavinwong]

Works well most of the time here in the Netherlands. Even picks up the time limit maximum speed limits. Eg some motorway roads are 120km per hour between 7pm and 6am, other times it’s 100km per hour. Seems to know when these are in effect and also reads a change in speed limit due to traffic or an accident when the signs above the motorways are indicating a slower speed limit. Same in Germany too, noticed a little less reliable in Italy, especially on some of the small town back roads where it claims to be 80km per hour but anything over 40km per hour you’d need to be a rally driver 😂
Like others have said, that auto speed limit correction on the drivers assistant pro is a switch off for me too after a few too many incidents of hard braking.

[Seaford]

There have been slight anomalies on all my BMWs….the most memorable being my 840 taking off like a rocket when the reactive cruise control engaged in a 50 while leaving the M23 to join the M25 in a ‘smart motorway’ section…..after a moment of ‘WTF’ I noticed the speed limit display was showing 120mph!

[B6WAF]

Originally Posted by Seaford

There have been slight anomalies on all my BMWs….the most memorable being my 840 taking off like a rocket when the reactive cruise control engaged in a 50 while leaving the M23 to join the M25 in a ‘smart motorway’ section…..after a moment of ‘WTF’ I noticed the speed limit display was showing 120mph!

My M340i (2020 model, to be replaced next week) very occasionally has done the same (120mph in a 30mph had the potential to be very exciting if I hadn't intervened) but generally it is very reliable indeed (I would say 95%, which isn't bad for an optical system). I never regard it as 100% gospel but if ever my concentration has lapsed and I'm not sure what the limit is, I still find it to be a very helpful guide.

[UnluckySaxon]

Its mostly right for me but was showing 90 mph a lot of the time in the Blackwall tunnel

[Kleev]

I found it generally really good. A few times on a certain A road I travel down it incorrectly displays the speed limit of a side road running parallel to the dual carriageway as 30mph when clearly the A road I am actually driving on is 50mph. But 99% it's spot on.

Generally a few mistakes but nothing to really complain about.

[Seaford]

Originally Posted by UnluckySaxon

Its mostly right for me but was showing 90 mph a lot of the time in the Blackwall tunnel

From my years of experience going through that in rush hour you’ll be lucky to do 9mph!

[225]

Works most of the time but I ignore it as no point really, I would never use it to automatically control the car. What does work well is recognising people it thinks are about to leap in front of me. I saw the person icon flash up and the warning sound as someone started to cross and thought better of it the other week.

[AP]

I’ve found it to be pretty good (U.K.) for the most part
The speed limits are obviously primarily what’s in the satnav data overridden by any speed limit signs the camera sees
There have been the odd road where the speed limit is obviously wrong but I’ve found the cameras in the LCI g30 to be an improvement over the pre LCI 30. The pre LCI would read signs on parallel towards whereas the LCI is way better on that now

[srbs73]

I find it's good for the vast majority of journeys and I use it a lot to control the speed of the car even in towns. I've had dodgy map updates where i've experienced the 120mph limit in a 30 but I quickly cancel on the steering wheel before it's really accelerated. I wouldn't want to use it without the HUD as it would be so easy to spot the issues quickly.

[marksandygill]

It's all very well and good saying it doesn't happen very often (I've had 30mph pop up on the A3 before), when automatic speed limiters come into effect it could be carnage with cars slamming their brakes on at 70mph braking down to 30mph!!

[srbs73]

You can make the same argument about EV's when they lift off and the brake lights come on because of regen.

[AP]

Yeh speed limiters
That’s all gone a bit quiet, I thought it was supposed to have implemented in the EU but not heard anything about it
The U.K. obviously not in the EU now , I think the plan was that we would copy that
The technology needs to improve before that’s workable in my opinion , not that I want it though