Speed limiters reading the HGV speed limit

[MattA7]

Has anyone had a problem with the speed limiters in their cars picking up the lower HGV speed limit of 40mph in single carriageway, 50mph in dual carriageway roads.

 

[Nym]

Would this be where such differential limits are actually signed, or simply that the car is getting confused?

 

[ninja-lewis]

It's an issue for Teslas (which use their vision systems to read speed limit signs) on the A9 where the single carriageway sections have signs indicating the 50mph HGV trial limits.

 

[Bletchleyite]

It's an issue for Teslas (which use their vision systems to read speed limit signs) on the A9 where the single carriageway sections have signs indicating the 50mph HGV trial limits.

Must be in Scotland, as in England the HGV single carriageway limit is 50. It was increased a while back because it was seen as actually safer because if they can go up to 50 overtaking is less likely, and overtaking is about the most dangerous thing that happens in normal road use.

Before cameras were clever enough to differentiate (some now are) lorries tended to do 50 anyway of course.

Scotland has still not rolled it out past the A9. I forget about Wales.

 

[TPO]

Yeah, my Focus will sometimes pick up badly located signs e.g. for 5mph in a courtyard adjacent to the road, or the 10mph within roadworks ( but doesn't enforce it). It will pick up the variable speed signs on motorways ok but can get confused between 50 and 60 in some lighting conditions and almost never registers the national speed limit applies sign on a smart motorway although it read the fixed sign version OK.

I noticed recently that roadworks on a motorway had (inside the works) an 11mph sign which did not pick up on the system the way a 10mph would, I suspect this is to prevent misread by cars with this facility.

Yes the tech is good but still a long way off what a human can do!

TPO

 

[JohnMcL7]

It's an issue for Teslas (which use their vision systems to read speed limit signs) on the A9 where the single carriageway sections have signs indicating the 50mph HGV trial limits.

Had the same issue with a car with speed limit recognition on the A9 as well for that reason although it's usually only brief, it also occasionally picks up old 30mph roadworks signs that have been left by the side of the road.

 

[DelW]

I imagine this must be a problem on roads like the Kingston Bypass, which has slip roads with lower limits very close alongside the main carriageway.

One of several such examples is at the Worcester Park / New Malden junction :
Malden Way

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A human driver would realise that the "30"s apply only to the slip road, but how would software be able to judge? I wouldn't want the system to be any more than advisory in that sort of situation.

Incidentally, I wonder how hypothetical autonomous cars would cope? I'd expect some rear end collisions if they were suddenly to slow to 30 when passing the exit slip on a road like that.

 

[Egg Centric]

Also common (especially in other countries) for both advance speed limits and differential lane speed limits (rare in UK but not unknown) to be picked up.

My challenge would be... so what? It's your job as the driver to know what the limit is. Who cares what the car thinks? Even if you wish to disregard it, you should really know what it is!