Do Tesla need to tweak their cruise control algorithms?

[mccgregor]

I've noticed when using cruise control occasionally the car has quite suddenly slowed.
The first time it happened it was quite unnerving and has caused me to be limit my usage of Autopilot, especially when I'm driving my wife.
It happened twice on Sunday on the M6 going South, both times I noticed it was as we drove above a roundabout beneath the motorway.
Both times it modified the maximum speed from 70mph down to 30mph - fortunately we were travelling in 50 mph queues, so it was only mildly annoying.
The conditions were quite cloudy, and I'm thinking that the inexact gps signal was triggering some automatic response i.e. the car's system thinking we were suddenly actually in a 30mph area - not on a motorway.
If that is what caused the slowdown, then the system should be able to cross-check with the cameras and sensors, realise surrounding vehicles are not slowing, and merely give a warning beep - NOT potentially slow dangerously (or embarrassingly) for no obvious reason.
I've since checked the Autopilot settings looking for something that I can reset to avoid this behaviour.
But, all I can see is "Speed Limit" - which, according to the manual (page 114) relates to Speed Assist, and doesn't suggest any automated intervention - just a warning.
Does anybody know more about this?

 

[OfficialMark_H]

I've noticed when using cruise control occasionally the car has quite suddenly slowed.
The first time it happened it was quite unnerving and has caused me to be limit my usage of Autopilot, especially when I'm driving my wife.
It happened twice on Sunday on the M6 going South, both times I noticed it was as we drove above a roundabout beneath the motorway.
Both times it modified the maximum speed from 70mph down to 30mph - fortunately we were travelling in 50 mph queues, so it was only mildly annoying.
The conditions were quite cloudy, and I'm thinking that the inexact gps signal was triggering some automatic response i.e. the car's system thinking we were suddenly actually in a 30mph area - not on a motorway.
If that is what caused the slowdown, then the system should be able to cross-check with the cameras and sensors, realise surrounding vehicles are not slowing, and merely give a warning beep - NOT potentially slow dangerously (or embarrassingly) for no obvious reason.
I've since checked the Autopilot settings looking for something that I can reset to avoid this behaviour.
But, all I can see is "Speed Limit" - which, according to the manual (page 114) relates to Speed Assist, and doesn't suggest any automated intervention - just a warning.
Does anybody know more about this?

It hasn’t happened to me under those conditions, but when it does it’s usually overhanging trees casting a shadow on the road, I’m not sure if that could be what caused yours?

 

[MrBadger]

It happened twice on Sunday on the M6 going South, both times I noticed it was as we drove above a roundabout beneath the motorway.
Both times it modified the maximum speed from 70mph down to 30mph - fortunately we were travelling in 50 mph queues, so it was only mildly annoying.

If that is what caused the slowdown, then the system should be able to cross-check with the cameras and sensors, realise surrounding vehicles are not slowing, and merely give a warning beep - NOT potentially slow dangerously (or embarrassingly) for no obvious reason.

Does anybody know more about this?

Those problems are likely to be caused by gps/mapping mismatch. So bad map data, poor signal, who knows. But I agree that more could be done to mitigate against these issues. Even things such 'how come the car is suddenly at a lead in to a roundabout, when just before it was doing 70 on NOA mapped route and didn't take the offramp' seem not to convince the car that its assessment of the situation is probably wrong. This also applies to some reports of issues with underpasses, where car has suddenly thought it was crossing on the road beneath even though it would be physically impossible to get from overpass to underpass.

My big hate though is adjacent lane speed adjustments - made worse by how rapidly it makes the speed adjustment. If I thought that I needed to modulate my speed, I would probably just coast down to the necessary speed.

Thankfully rare occurances, but I drive with foot over/on accelerator.

 

[Mr Speirs]

I rented a Model S for a few days and ended up getting so freaked out by the AP I ended up not using it.

Issues were:
A bias to sit to the left of centre of the lane...which resulted in the following when passing vehicles who were close to (but not over) the white line.
Sudden and unexpected emergency braking in the fast lane on a motorway.
Lane change assist was too slow. It wouldn’t accelerate into the next one until the car in the lane was the set distance (which I understand but...) which would mean if you were sat behind a lorry you’d enter the lane at 56mph where everyone else was doing 70mph+. This had the other side effect of:
It didn’t speed up to match traffic and therefore would recognise the car behind closing up on you and violently redirect the car back into the lane. Numerous times this happened each time would’ve been perfectly fine had the car increased speed rather than holding until in the lane.

I realise safety and autonomy etc etc but it isn’t a perfect system. On my M3 I don’t have the lane assist but the whole left of the lane bias is not where I want to be and hope you can adjust it somehow or have the option to centre it in an update or something.