Question about side sensors

[David29]

I had a long drive yesterday, with more than 200 miles on I-95, and used AutoPilot virtually the entire time. So I had a lot of opportunity to observe the "cartoon" vehicle display in the instrument cluster.

One thing I had noticed before, and repeatedly confirmed yesterday, is that when the screen displays the rear side detectors detecting an object nearby, the front sensors almost never react to the same object or vehicle. In other words, as I passed another vehicle or another vehicle passed us, the screen would show the colored bands from the rear sensors, but the display never showed any colored bands for the front sensors for the same vehicle.

Have other people observed this? And does anyone have an explanation?

I know the front sensors work, because they are active when parking the car. But they rarely if ever "light up"for passing vehicles or objects. Maybe once in a while, the display shows they are reacting if a guard rail or other object is especially close to the car. But not most of the while when a vehicle passes.

Obviously, my concern is whether or not the sensors are doing what they should during AutoPilot operation.

 

[trils0n]

I would assume the rear sensors are displaying because that is the blind spot monitoring. The front sensors would be detecting things inside your field of view while driving, so they only display that info when parking.

 

[jmsurpri]

I've seen the same behavior pretty consistently. It all looks random to me. Like you said, when parking all the sensors appear to be in use. I'm guessing maybe it's a display timing thing. Like it misses a GUI refresh and so sometimes it's not visualized.

 

[chillaban]

The front sensors definitely detect cars at the same kind of distance as the rear sensors, but the UI doesn't display it. The purpose of blind spot sensors is to notify you about non-obvious cars around you, and I presume having the screen show sensor lines all the time for cars you can obviously see beside you would get annoying/fatiguing.


You can attempt to signal into a car beside you and notice that Auto Lane Change doesn't begin a movement until the front car gets out of the way. Your car definitely sees them, it's just choosing not to tell you about cars next to you unless they get very close and begin to influence Autopilot lane centering offset or produce side collision alerts.

 

[David29]

Oddly enough, driving around my town today, and paying attention to the display, the front sensors do light up when my car passes fixed objects such as parked cars, at least at the low speeds I was using. I wonder if the behavior is speed-dependent?
I'll have to try to puzzle it out....

 

[Max*]

Oddly enough, driving around my town today, and paying attention to the display, the front sensors do light up when my car passes fixed objects such as parked cars, at least at the low speeds I was using. I wonder if the behavior is speed-dependent?
I'll have to try to puzzle it out....

Yes it is.

The front sensors seem to activate below about 25mph OR when you're using AP and standing (ever turn on AP at a red light, with cars surrounding you? all of a sudden the sensors light up) OR when you get REALLY close to something on the highway.

ETA: I had a post somewhere, where I tested the speed when they activate, I can't find it now (I talk a lot...), but it might be closer to 20mph.

 

[David29]

Made another long-ish highway trip (1-hour each way, mostly on divided highways) today, and the front sensors did seem to light up when we were passing other vehicles! So did I come to an incorrect conclusion? Now I am puzzled.
I admit that today, I was only watching the behavior closely for a few minutes. Mostly I was just driving. No drama today, either, thankfully.

 

[Mknac]

I've had BLIS on three previous Ford cars and it works great. Actually I've become very dependent on the merging onto highways and changing lanes. I'm getting worried the Model S BLIS doesn't work like Ford's and I'm going to have to use mirrors on a car with large blind spots.

Any reall life feedback with Tesla BLIS?

 

[msnow]

Just to muddy the waters and add confusion (I do that sometimes ). Mine do light up front and back.

 

[Mknac]

Just to muddy the waters and add confusion (I do that sometimes ). Mine do light up front and back.

What about the sides i.e. the blind spot that it's is supposed to tell you if there is a car there?

 

[chillaban]

I've had BLIS on three previous Ford cars and it works great. Actually I've become very dependent on the merging onto highways and changing lanes. I'm getting worried the Model S BLIS doesn't work like Ford's and I'm going to have to use mirrors on a car with large blind spots.

Any reall life feedback with Tesla BLIS?

It won't detect cars unless they are within the equivalent of parking sensor range. It's enough to avoid colliding with a car but it's not as far ranged as the Ford (and anyone else that uses a K band radar based BSM system).

Radar based BSM can see 10+ car distances behind and warn for high speed differentials like inadvertently cutting off cars as you try to enter a HOV lane.

 

[msnow]

What about the sides i.e. the blind spot that it's is supposed to tell you if there is a car there?

Yes.

 

[Max*]

Made another long-ish highway trip (1-hour each way, mostly on divided highways) today, and the front sensors did seem to light up when we were passing other vehicles! So did I come to an incorrect conclusion? Now I am puzzled.
I admit that today, I was only watching the behavior closely for a few minutes. Mostly I was just driving. No drama today, either, thankfully.

Did it only do it for large vehicles, like trucks?

Also, was AP on or off for the trip? I have noticed varying behaviors with AP.

 

[David29]

Those are good questions. I made a casual observation, but now that you ask, I cannot be certain of either answer. I did use AP for part of the trip, but not the early part. So whether or not AP was on when I made the observation, I cannot swear to it. Also not sure about trucks.
So, sorry -- not a very useful observation! I will be more thorough next time I try to observe this behavior!