Autopilot question

[MrBadger]

On reflection, it would not surprise me if there was another source of speed information going on.
So maybe

• visual for corner speeds
• database gpx linked to show speed limit
• something else for TACC speeds?
• one day, visual speed limit recognition

 

[ElectricJoules]

I too went for a drive today to test things, no dual carriageway.

I always had a navigation destination set (don't know if that make any difference).

If I set autopilot on in a 30 limit the TACC speed stays at 30 when I enter a 40 limit (but speed limit sign on the right does increase to 40).

If I set autopilot on a 60 limit then enter a 40 and then a 30, then the TACC blue speed limit reduces to match the limit. Then, without having done anything other than watch, the TACC limit increased going into a 40, and increased again going into a 60. So the car slowed down when the speed limit was reduced, and sped up when the speed limit increased.

All changes to TACC speed limit were within 50 yds of passing a speed limit sign.

 

[MacJester]

Dual or Single carriageway? My new theory is that TACC speed change only occurs on single carriageway (when speed limit change is also displayed ... which itself depends on GPS location from database)

It’s definitely GPS driven, not reading the speed signs. We’ve had a lot of changes in my area in the last year or two and the displayed speed is at least one set of changes behind.

 

[WannabeOwner]

If I set autopilot on in a 30 limit the TACC speed stays at 30 when I enter a 40 limit (but speed limit sign on the right does increase to 40).

That was my experience with AP1 too.

So the car slowed down when the speed limit was reduced, and sped up when the speed limit increased.

Again, same on AP1.

Had to set TACC before getting into the (30) for it to then change TACC (i.e. and accelerate) when leaving the Limit (or the Limit increased to e.g. (40) )

I have tried setting TACC on in a (40), driving into a (30) [it should reduce speed] then back into a (40) [it should increase] but then what about on leaving the (40) - I wonder if it would it increase to (60)? I expect that it will be limited at whatever was the speed when TACC original engaged.

I find it pretty unnerving accelerating to 60, coming out of a (30) or (40). The fact that I might have had TACC set to 60 on the way in is not a reliable indication that 60 is correct for the road after leaving the limit!

It’s definitely GPS driven, not reading the speed signs.

To clarify what I wrote / meant:

"speed limit change is also displayed" as in "on the dashboard", and that comes from a GPS database [of speed limits] on AP2 (not relevant, but in AP1 the speed sign was read instead). That GPS database may be "off" by some distance, or indeed, as you say, out of date or just plain wrong

Separately from that the TACC speed may automatically change to match ... or not. My theory being that it does on single carriageway, but does not on dual carriageway.

 

[ElectricJoules]

I expect that it will be limited at whatever was the speed when TACC original engaged.

Yes, that's my current theory too. Need to engage and drive through a 40 - 30 - 40 - 60 and see if it limits to 40.

 

[MrBadger]

Dual or Single carriageway? My new theory is that TACC speed change only occurs on single carriageway (when speed limit change is also displayed ... which itself depends on GPS location from database)

single carriage way

Google Maps blimey - never seen a queue like that there before - must have been another sink hole near McLaren - 50 down to 30. I gave it plenty enough time to show that it was going to react before manually braking. Nothing in front of me, empty dead straight road.

I remember reading somewhere that the Tesla fleet contributed to road speeds, which may form part of the TACC/AP speed limit.

 

[Mr Miserable]

I may have to eat some humble pie here...

Left the M25 with TACC set to 70 and where it joins the M3 is a 50 speed limit. Without changing anything the car slowed and set 50 in the TACC.
Never seen it happen before and I'm sure it wasn't meant to do that.

v2019.36.2.1

 

[MrBadger]

I may have to eat some humble pie here...

Left the M25 with TACC set to 70 and where it joins the M3 is a 50 speed limit. Without changing anything the car slowed and set 50 in the TACC.
Never seen it happen before and I'm sure it wasn't meant to do that.

v2019.36.2.1

Was that clockwise? Thats what I found yesterday, except speed limit showed 70 (its really a 50), and TACC said 55 and something else said 50 - probably current speed - may have got speeds reversed though as I was paying more attention to the lane following as its a bit of a tight curve.

Also, did you notice TACC limit speed up heading back south/west up M3? It was past the national sign and closer to the gantry that had its own set of national signs.

 

[Mr Miserable]

Coming from Heathrow.
I know the speed limit was slow to register the resumption of the 70 limit on the M3 but I wasn't going to wait for anything to happen.
It definitely showed the 50 limit when we entered it and somehow sent it to the TACC.
Not seen that happen anywhere else.

 

[xdcthedoc]

I was using a lot of AP over the past few days on a lot of different roads.... never once saw the car slow down automatically for a reduced speed limit.

I don't doubt it happens sometimes in some circumstances... just not for me so far.

Only had one episode of phantom braking in about 400 miles if that is good?

 

[WannabeOwner]

Not seen that happen anywhere else.

Long shot: The intersection / slip is seen to be single-carriageway rather that dual-carriageway (coudl explain a single annomoly if, accidentally, wrongly recorded in the database.

never once saw the car slow down automatically for a reduced speed limit.

Seems bizarre to me that this feature is some-and-some across the fleet. Maybe there is some common attribute, but I'm struggling to think what it might be.

 

[Mr Miserable]

I
Only had one episode of phantom braking in about 400 miles if that is good?

Agree the phantom braking problem appears to have been successfuly adddressed - thank God. Although I still remain mentally scarred by the experience as I still anticipate it occuring every time a bridge or gantry appears.

 

[MrBadger]

Hopefully it is sorted and not a sun angle thing not applicable at this time of year.

 

[Mr Miserable]

OK So the behaviour of the car slowing in response to speed limit changes was confirmed again this evening. Definitely based on GPS though this time on an A road from Newbury.
I have yet to see a corresponding speed increase though.

 

[MacJester]

I also find speed doesn’t increase with speed limit. Tapping the speed limit on the screen will do that tho.

 

[WannabeOwner]

I also find speed doesn’t increase with speed limit. Tapping the speed limit on the screen will do that tho.

Was it Single or Dual Carriageway?

 

[MacJester]

Was it Single or Dual Carriageway?

Normal single carriageway country road