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AP set speed adjusts itself incorrectly when passing on / off ramps

Battpower

Active Member
Supporting Member
Oct 10, 2019
2,397
2,442
Uk
Raven S fsd.

I have noticed several times now in completely different locations on motorways in UK and autoroutes in France that strange things happen as you pass on & off ramps (junctions).

There might be a clue in the incorrect lane change messages that display, but the messages are just an annoyance.

What is more concerning is that the set speed (TACC / AP) suddenly jumps down while passing either on or off ramps. It doesn't seem to happen every time, but often enough to be a big hassle. Driving on the M1 this evening with ap on (NoA) speed set manually at 65 mph. Suddenly the set speed reduces itself to 50 then 45 then 40 obviously causing the car to slow suddenly.

Is anyone else seeing similar speed changes near junctions? Does it relate to 'merge left' situation on US freeways? The incorrect lane change messages make me think the car is making speed changes because it thinks it is on a different road system.

IMG_20200130_174511.jpg
 

Battpower

Active Member
Supporting Member
Oct 10, 2019
2,397
2,442
Uk
The lane change is to get you out of what it thinks is an exit lane.

When you don’t move over, it then does the usual graduated speed reduction for an exit leading to a roundabout/give way

That's exactly what I'm thinking, and I think that out of date / incorrect map data is the most likely root cause, but the extent I have been seeing this happen is rather disappointing to say the least. Also, to be driving at 70mph on a clear motorway and have the car slow inexplicably and quite agressively to 45 mph is embarrasing if not pretty dangerous. Around on and off ramps are already danger spots where drivers need to behave predicatably and consistently, so to have to worry as you approach each on and off ramp whether your car is going to suddenly decide to slow to half speed is not good!

Also, pretty much every on and off ramp for 1000+ miles on French autoroutes gave the erroneous lane change messages.
 
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Battpower

Active Member
Supporting Member
Oct 10, 2019
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2,442
Uk
Could it be the recent adjacent lane speed functionality? I had sudden braking at a merge and pretty sure it was this. I can see why it may be useful if done gently, but not by slamming on as it does at present. Work is needed on speed change transitions in many areas.

View attachment 506257

I'm sure that's not what I'm seeing. The adjacent lane speed is another hassle though, especially when on ap and the car just asked you to confirm lane change and switched lanes to pass traffic, as the car approaches the cars to pass them, decides to slow to their speed!! I have noticed that ap does not allow 'undertaking' (passing on wrong side) and just slows to maintain position.
 
That's exactly what I'm thinking, and I think that out of date / incorrect map data is the most likely root cause, but the extent I have been seeing this happen is rather disappointing to say the least. Also, to be driving at 70mph on a clear motorway and have the car slow quite agressively to 45 mph is embarrasing if not pretty dangerous. Around on and off ramps are already danger spots where drivers need to behave predicatably and consistently, so to have to worry as you approach each on and off ramp whether your car is going to suddenly decide to slow to half speed is not good!

Also, pretty much every on and off ramp for 1000+ miles on French autoroutes gave the erroneous lane change messages.


since when do we int he uk call a slip road an on off ramp?
 
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Reactions: Battpower

Battpower

Active Member
Supporting Member
Oct 10, 2019
2,397
2,442
Uk
since when do we int he uk call a slip road an on off ramp?
On TMC!

Trying to be audience aware. I end up mixing some UK and some US. Annoying when referring to motorways. I usually refer to them as freeways as that is understood by most. Kinda long winded to type 'Interstate / Freeway / Motorway / Autoroute / dual carriageway' every time!

Actually, Slip Road would have been fine except do slip roads both join and leave the highway? Is it an Exit Ramp to leave a motorway? My particular point needed to emphasise that the speed changes happen while driving alongside both on ramps and off ramps. Slip Road didn't seem specific enough.

Likewise with 'city streets / surface streets / single carriageway / highway'. And having lived in the US for 20 years I appreciate that the terms do not translate perfectly.
 
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VT_EE

Active Member
Apr 22, 2017
2,401
3,311
Maryland
I'm sure that's not what I'm seeing. The adjacent lane speed is another hassle though, especially when on ap and the car just asked you to confirm lane change and switched lanes to pass traffic, as the car approaches the cars to pass them, decides to slow to their speed!! I have noticed that ap does not allow 'undertaking' (passing on wrong side) and just slows to maintain position.
It allows undertaking in the US probably because bad driving is widely accepted here. In fact, I’ve had NoA pass vehicles on the wrong side. I assume limiting this behavior is region specific.
 
For any overseas visitors, here’s a handy guide to British Motoring Terms:

Belisha Beacons - Beacons were fires lit on hills to communicate across long distances. These are very similar.
Bonnet - Worn on the head like a hood.
Boot - Worn on the feet like trunks.
Windscreen - Keeps the wind off your butties on the beach
Bollards - Interchangeable with b*ll*cks
Cat’s Eyes - What else are you going to do with a dead cat?
Kerb Crawler - What you sometimes have to do to find a parking space.
Lay-by - A place for dogging
Verge - Had a hit with ‘Bitter Sweet Symphony’ in the late nineties

You’re welcome
 

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