Lane Departure Warning... the loud one (S75D).

[DJ_S75D]

All,

I'm experiencing an odd situation where I'm getting an audible and visual alert (on the binnacle display) while changing lanes. It happens often enough that I've had a chance to look at the visual bright red pop-up and it says something about a "Lane Departure Warning". This is a very different warning that I normally get when using the similarly named feature located on the "Driver Assistance" tab, which usually amounts to a momentary vibration of the steering wheel. I have the 'rumbly' warning disabled, so this alert may be related to AP or one of the emergency alert systems...?

I can make this alert occur most often under the following conditions:

• AP2.0, uncorked S75D, April 2017 Delivery.
  
• TACC enabled and engaged
• Auto Lane Change disabled
• Lane Departure Warning disabled
• Autopilot enabled, but recently disengaged
• Turn signal on and in direction of intended lane change
  
• Initiate a normal lane change (think Interstate driving when passing a slower car).

I normally have TACC and AP on while just burning up the interstate, but due to the very aggressive AP lane changes, I have that particular feature disabled. When I put on the turn signal (usually the left direction to pass a slower car), AP disengages automatically in most cases, and TACC remains on. As I cross in to the left lane, the aforementioned alert sounds quite loudly, even though I've got my turn signal on and AP has been disengaged for at least a second or two. I've tried waiting up to five seconds after AP disengages before actually changing lanes, but the alert still sounds. The only reason I'm bringing this up, is that the rapid high-pitched beeps usually wake up everyone in the car rather abruptly and continue to sound until I finish the lane change.

Is anyone else experiencing this? I thought my turn signal would be enough to notify the appropriate systems that I'm going to be departing my lane, but perhaps this is not the case.

-DJ

 

[chillaban]

That seems like it could be a false alarm. There is a "you just turned off Autopilot and are departing your lane" warning which happens when you've disengaged AP, not made any significant steering inputs, and your car drifts out of the lane.

You can generally avoid it by either more forcefully disengaging and then making a lane change, or disengage, steer correctly for a few seconds, then make a lane change.


(You can thank that guy in Montana that ran his model X off the road because he thought AP was still engaged)

 

[cantanko]

I've had that quite a few times, but not recently. Typically I've just disengaged autopilot manually because I reckoned it wouldn't have coped with something ahead and perform a manoeuvre. I'm of the opinion that when you manually disengage AP it takes time for all of the layers (the system seems rather loosely linked such that a failure or malfunction of one does not bring down the others) to stand down, one of the last being the lane departure warning.

I think the car has trained me to provide it with a little more notice on the disengagements and, as chillaban mentions above, driving manually as AP was for a second or two before then performing the manoeuvre. That has reduced the LDW activations to zero over the past couple of months for me.

As an aside, as a tech geek I actually think the reason I like autopilot so much is the "so what's it going to do in this situation" game. I don't trust it in the slightest (I've had it try and make friends with the Armco way too often - usually on reasonably sharp dips or crests in the road - to trust it), but having to nanny it like a parent would a nervous teenager somehow engages me in the driving task more than when I'm driving without AP. It is actually surprisingly predictable - you just have to consider all of the inputs it's probably receiving and its decision tree starts to become way less opaque. Figuring out how it ticks is my new favourite passtime and that game was worth every penny I paid for it