Navigation & TACC

[Jack6591]

I wasn't quite sure where to post this, but here goes.

Using my TACC on the way to work, just as I come upon the Buena Vista exit on Interstate 5 in Burbank, the speed limit indicator drops from 65 mph to 25 mph and my car slows dramatically. Always at this particular spot, right next to the Ramada Inn. Anyone else seeing this problem?

 

[eSpiritIV]

Paid advertising???

 

[gambit48]

I can see following the speed limit signs super closely in certain parts of the country where little towns create speed traps. In the high population zones of California such as LA/Orange/SD counties or the Bay Area, that could get dangerous. Like the 101 freeway up in Hollywood. It's 55 mph for a big stretch from downtown up towards Universal Studios. If traffic allows for it, NO ONE goes 55. It's like 80+. You may as well just stop your car in the middle of the freeway and cause the same amount of traffic issues.

 

[TT97]

I can see following the speed limit signs super closely in certain parts of the country where little towns create speed traps. In the high population zones of California such as LA/Orange/SD counties or the Bay Area, that could get dangerous. Like the 101 freeway up in Hollywood. It's 55 mph for a big stretch from downtown up towards Universal Studios. If traffic allows for it, NO ONE goes 55. It's like 80+. You may as well just stop your car in the middle of the freeway and cause the same amount of traffic issues.

There are a ton of places in the L.A. area on the freeways that are listed as 55. The 405 at the Sepulveda Pass was 55 for years but they recently raised it to 65. It's good to know in case I'll ever be able to go over 20 mph on that stretch.

 

[Jack6591]

The point I was attempting to make—was that my Model 3 senses a 25 mph zone on the Interstate—where it should sense 65 mph.

 

[buddhra]

I've seen a stretch of 2-lane road where my speed set point will drop to 45 mph max, but the road is posted as 50 mph. I'm pretty sure it has to do with the road type information coded in the navigation maps.

For your situation, could it be that while you're on this section of interstate the map is showing you on some side street that is posted at 25 mph?

Or maybe there is a segment of the I-5 that has an error in Google Maps. Here are some instructions to investigate in Google Maps: https://www.localguidesconnect.com/...dit-a-road-segment-in-Google-Maps/ba-p/149865 or give me the coordinates for the location and I'll see what I can tell.

 

[chronopc]

The point I was attempting to make—was that my Model 3 senses a 25 mph zone on the Interstate—where it should sense 65 mph.

The Model 3 doesn't read speed limit signs yet. It uses map information and based on my experience there are many times it shows the wrong speed limit. Just notify them and they should be able to update it.

 

[T-Will]

Maybe it thinks you're on the exit and the new "slow down when taking offramps" is kicking in? But from videos I've seen, it should gradually decrease the max speed while taking the offramp (65 -> 55 -> 45 -> 35), rather than just jump from 65 to 25.

 

[insaneoctane]

This ^^^^
The latest software adds stepped slow downs for exit ramps. Were you driving in the slow lane?

 

[animorph]

I agree it sounds like the exit speed AP feature. You could zoom in the map and see if it thinks you're on the exit.

I see the speed limit jump on my display at various crossings while I'm on the freeway, but that never affects my set speed.

 

[d21mike]

My wish is that they would have a "reasonable test". I think it is very unusual that the speed limit would change from 65 to 25. I.E. Instead of stopping rapidly I would prefer it gives a good size WARNING and maybe start to slow down more gently.

 

[chillaban]

My wish is that they would have a "reasonable test". I think it is very unusual that the speed limit would change from 65 to 25. I.E. Instead of stopping rapidly I would prefer it gives a good size WARNING and maybe start to slow down more gently.

The TACC speed limit adjustment is pretty slow, like -3mph per second or so. Not sure I'd consider that non-gentle -- it takes a long time to make an appreciable speed adjustment and that gives plenty of time for feathering the throttle to control or override.

 

[d21mike]

The TACC speed limit adjustment is pretty slow, like -3mph per second or so. Not sure I'd consider that non-gentle -- it takes a long time to make an appreciable speed adjustment and that gives plenty of time for feathering the throttle to control or override.

I was responding to the OP:

the speed limit indicator drops from 65 mph to 25 mph and my car slows dramatically.

 

[chillaban]

I was responding to the OP:

the speed limit indicator drops from 65 mph to 25 mph and my car slows dramatically.

I guess dramatically and rapidly meant different things to me. I'm not sure if I'm disagreeing with you or not, but all I'm saying is that even when TACC suddenly drops your set speed from 75 to 25, it's not like it emergency-brakes for that (as opposed to sudden overpass braking or false AEB where it's literally strong enough to trip ABS and knock the wind out of you).

Humans have a pretty exaggerated sense of relative speed changes and it sure feels dramatic, but any decently attentive driver can correct that before even 10mph gets shaved off your travel speed.

 

[T34ME]

Like the 101 freeway up in Hollywood. It's 55 mph for a big stretch from downtown up towards Universal Studios. If traffic allows for it, NO ONE goes 55. It's like 80+. You may as well just stop your car in the middle of the freeway and cause the same amount of traffic issues.

The ones going 80+ are causing the traffic issues, not the ones following the posted speed limit (I am one of those and stay in the far right lane when practical).

 

[chronopc]

The ones going 80+ are causing the traffic issues, not the ones following the posted speed limit (I am one of those and stay in the far right lane when practical).

Actually people not traveling at the flow of traffic is what causes traffic issues. It's safer to go slightly faster than the speed limit than going slower than the speed limit. People who drive slow causes traffic issues because it leads to more people changing lanes to go around them.

 

[Moderatefan]

This ^^^^
The latest software adds stepped slow downs for exit ramps. Were you driving in the slow lane?

I know that when I use maps on my phone it happens quite often that GPS gets confused whether I am on the highway or have taken an exit and on a parallel road. I guess there's some error to this estimate. Or maybe there was a minor road construction that moved one of the roads a few feet, but the map was never updated.

 

[Jack6591]

Southbound side of I5 at the Buena Vista exit. All lanes.

 

[T34ME]

Actually people not traveling at the flow of traffic is what causes traffic issues. It's safer to go slightly faster than the speed limit than going slower than the speed limit. People who drive slow causes traffic issues because it leads to more people changing lanes to go around them.

You are changing the discussion. The flow of traffic should be going at the posted speed limit, not faster not slower. Some impatient people are changing lanes when I am going the posted speed limit, even in the far right lane. They are equally unsafe compared to people going slower than the posted speed limit.

 

[chronopc]

You are changing the discussion. The flow of traffic should be going at the posted speed limit, not faster not slower. Some impatient people are changing lanes when I am going the posted speed limit, even in the far right lane. They are equally unsafe compared to people going slower than the posted speed limit.

You are correct in theory. But in reality people don't follow the speed limit. So going the flow of traffic is the safest thing to do. If you compare accident rates on US Highways vs. the Autobahn you will see that the rate of accidents is much higher on US Highways.