Strange speed limit phenomenon

[Tom,]

On a half mile section of country road my RX450h+ always bleeps and shows 20mph limit. This always happens in exactly the same place and reverts back to 60mph after about half a mile in exactly the same place. This is a country road with no speed limit signs or road signs of any description, just lots of trees. The only explanation I can think of is that the sat nav is telling the car to show 20mph at that location. Does anyone have any ideas?

Tom

[NemesisUK]

I posted a similar experience with speed limit displayed..

 

[YvesD]

On 2/21/2024 at 3:39 PM, NemesisUK said:

I posted a similar experience with speed limit displayed..

 

Mines the same, sometimes I get a 120mph limit in a 30!

 

[Xez]

Hi Tom, yes I get a very similar experience going along a country lane that is signed at national speed limit (60mph) but the car shows a 40mph limit. It always changes to 60 mph at exactly the same place along the road despite there not being any signage present. The RSA is reputedly using the front camera to indicate the applicable speed limit, however when coming back along this road the speed limit displayed changes from 60mph to 40mph with no signage present.

[Tom,]

I'm going into my dealer next week to pick up my spare key (at last!). I will ask about this weird speed limit behaviour.

Tom

[Spock66]

I think it must be the sat nav.

Older models like the Gen 4 only use the camera I believe, hence you get 120 etc as that's often a sticker on the back of a truck.

[NemesisUK]

2 minutes ago, Spock66 said:

I think it must be the sat nav.

Older models like the Gen 4 only use the camera I believe, hence you get 120 etc as that's often a sticker on the back of a truck.

Mine is showing the 'old' speed limits and ignoring the new speed limit signs, the changes happen in exactly the correct places but with the old limits. It briefly shows the new limit (from the camera info) then reverts to the old limit (presumably from the out-of-date sat nav info) 

[PDM]

53 minutes ago, Spock66 said:

I think it must be the sat nav.

Older models like the Gen 4 only use the camera I believe, hence you get 120 etc as that's often a sticker on the back of a truck.

The facelift MK4 certainly uses a combination of sat nav data and speed limit signs.  When I pull off the drive onto the street it has not seen a speed limit sign but it does know the limit is 30mph. Not sure about the pre facelift MK4.

However, I believe there is a TSB for a software update to prevent the camera recognising signs on trucks as speed limit signs.  (I saw that on Lexus Tech at some point... Perhaps check with the dealer).

Paul

[Spock66]

Just now, PDM said:

The facelift MK4 certainly uses a combination of sat nav data and speed limit signs.  When I pull off the drive onto the street it has not seen a speed limit sign but it does know the limit is 30mph. Not sure about the pre facelift MK4.

Yes I think you're right, I have a pre face-lift Gen 4.  Speed limit is only displayed when there is a sign and that times out after a few minutes, often sign is missed or wrongly interpreted.