Automatic speed changes

Automatic speed changes

QQ: Is there any way to prevent TACC/AP from changing the set speed?

I do understand the need to lower a set speed when the car runs into a restricted zone and would not allow Autosteer to continue otherwise, but there is two scenarios that I don't want:
1) When the speed limit drops, but the set speed is still within the parameters for AutoSteer.
2) When the speed limit increases.

Both are majorly annoying. The first one sometimes leads to pretty harsh breaking and is especially problematic when the speed limit in the maps is wrong. The second one even more annoying for me personally though. I tend to stay way below speed limits on most highways (we have by far higher limits than you have in the US...) to both reduce power consumption as well as keep the wind noise level down. And I more than once had the car bump up the speed by 20-30 MPH without prewarning.

bp | 2020年5月6日


Because Tesla hasn't licensed a patent from Mobileye, Tesla's AP system is not able to read speed limit signs. The system instead appears to rely on a combination of a stored speed limit data base coupled with "fleet speed" data from other Tesla vehicles driving the same section of road.

The speed limit database has numerous errors with missing or incorrect speed limit data, especially in areas with current and recent construction. And because this database isn't updated very often, these errors can be there for a long time.

Fleet speed also has some challenges, because those speeds don't necessarily reflect current road conditions.

Ultimately, this won't work well until Tesla figures out how to read speed limit signs, either by licensing the Mobileye patent or finding a way to work around that patent.

Until then, Tesla should provide a setting that would disable automatic speed adjustment OR do something similar to the new traffic sign/stop light feature - and issue a warning on the dashboard when approaching a speed change, providing an opportunity for the driver to override that change - before it is made (rather than after slowing down).

EVRider | 2020年5月6日

Once engaged, TACC/AP does not change your speed based on speed limits on the highway. There are other factors that change your speed on the highway, but the speed limit isn’t one of them. So, it already works the way you would like it to.

If you engage AP or TACC while traveling below the speed limit on the highway, the set speed will change to the speed limit (plus any offset), but that’s not the same as your second scenario.

FISHEV | 2020年5月6日

The problems with Tesla's adaptive cruise are legend. The hard braking for overpasses or cars on curves or who knows what. The set speed changes are right up there. The sudden braking because it is reading out dates map data. The unexpected acceleration because it uses map data instead of the car's speed for the set speed.

Teslas adaptive cruise, brand name TACC, has been turned into a liability in the car due to brand name "Full Self Driving". No doubt all the problems are Tesla trying to figure out how to automate the car's functions when all drivers with base brand name "Autopilot" want is safe reliable adaptive cruise. Drivers sets the speed, changes the speed when he deems necessary and ignore the overpasses, cars safely in their lane and other "FSD" mishaps.

RickD | 2020年5月6日

@EVRider: Evidence is contrary unfortunately. Here is the exact scenario: (Tested it with 2020.12.10, had no chance yet with the new firmware.) (Please note: Speeds are in KM/H not MPH)
I get onto a highway, engage NoA and set the cruise speed to 95. (While the limit displayed on screen is 130)
20 kilometers later the speed limit changes to 100. NoA does nothing, cruise speed remains at 95
10 kilometers later the speed limit changes back to 130. NoA at that point INCREASES cruise speed to 130. And THAT is what I don't want...

On the down regulation: If the speed limit at the 20 kilometer mark would have been 90 (instead of 100) NoA would decrease my cruise speed to 90, although I can then regulate it back up to 95. This is also something I do not want to happen.
I do understand it in situations where I have 95 set and the new limit is 60. At that speed NoA wouldn't allow me to go back to 95, as it is too far above the limit. So reducing it there is perfectly fine.

EVRider | 2020年5月6日

@RickD: The speeding up sounds like it might be a bug, unless it's a recently-added feature. In the TACC section of the manual (Model S, but it shouldn't matter), it says this:

"Warning: When you adjust the cruising speed based on the speed limit, the set speed does not change when the speed limit changes. You must pull the cruise control lever again to cruise at the new speed limit. You can also manually adjust your cruising speed at any time (see Changing the Set Speed on page 90)."

Using Autosteer or NoA adds some additional speed restrictions, but doesn't change the basic behavior documented above.

RickD | 2020年5月6日

Thanks @EVRider, in this case I will add this as a bug for my next service appointment.

hgmichna | 2020年5月7日

From the manual, apparently of the Model S: "You must pull the cruise control lever again to cruise at the new speed limit."

Note that, unlike the Model S, in the Model 3 you cannot pull the cruise control lever. There it has fewer degrees of freedom. You can only push it down to activate TACC, twice for autosteering, up to disable these functions. You cannot pull it towards you or push it away from you.

This, by the way, leads to the inability to enable TACC while staying at the current speed. A Model 3 will automatically speed up to the speed limit, which is an unnerving and dangerous defect. But it has been there since the inception of the Model 3, has been discussed numerous times in all discussion forums, but has never been repaired.

Workarounds are:

* Enable TACC or autopilot behind another car or at least with no other car anywhere near behind you, then dial down the speed.

* Enable TACC or autopilot while gently accelerating, then immediately and quickly dial down the speed with the right scroll wheel. While accelerating with the pedal, TACC will give you a little time to dial down the speed before accelerating more decisively. The precise details and limits of this procedure are not documented and not well known.

RickD | 2020年5月7日

@hgmichna Unfortunately it seems that Model S now behaves like Model 3...

bp | 2020年5月7日

When operating under NOAP, the AP system will automatically increase and decrease speed based on a combination of the speed limit data base and "fleet speed". And when that doesn't match the actual speed limit, the driver must manually override AFTER the speed limit change has been made.

With the new stop sign/light feature that works while operating under TACC and NOAP, a warning message is displayed as the vehicle approaches the intersection, and with the current software, the vehicle will automatically start slowing down and will come to a complete stop, unless the driver overrides.

Unlike the speed changes, the stop sign/light feature provides a warning so the driver can override the action before it begins. With the speed changes, the driver has no warning before the vehicle starts changing speed.

Clearly this is beta software, and Tesla has much left to do to get this working well. Though Tesla could certainly do more to improve the speed change feature, especially reducing the risks of rapidly slowing for no apparent reason in the middle of high speed traffic...

EVRider | 2020年5月7日

@hgmichna: Both the Model S and Model 3 will accelerate to the set speed when you enable TACC, if you're going slower than the set speed. The issue that RickD is reporting is that with TACC already enabled, the car is speeding when the speed limit increases, which neither the Model S nor Model 3 are supposed to do, according to the manual.

As you noted, in the Model 3 you can't pull the cruise control stalk to adjust to a new speed limit because there's no cruise control stalk. Instead, you have to either disable TACC and re-enable it, or adjust the set speed manually.

bp | 2020年5月8日

TACC will slow below the posted speed and the set speed on the highway and requires manual intervention to get the vehicle to go back to the set speed (this happened to me this morning).

This is still "beta" software - and needs work - and that's OK.

The automatic speed adjustment has rough edges, like lane keeping had in the early EAP releases - which tended to hug one of the lane lines or ping pong in the lane between the two lane lines. And now lane keeping works well.

Unfortunately, Tesla hasn't provided a way to turn off the automatic speed adjustment - so the only way to work around the flaws is to drive manually without cruise control or NOAP.

RickD | 2020年5月8日

I have added the topic to my issue list now for the service appointment next week. Let's see what Tesla has to say.

FISHEV | 2020年5月8日

@bp | May 8, 2020 "This is still "beta" software - and needs work - and that's OK."

It's really not OK. Adaptive cruise should not be "Beta" on any 21st century car. This is never mentioned during the buying process. In fact, quite the reverse as Tesla sells itself as being the most tech advanced vehicle when in fact adaptive cruise and auto steer, common features on many cars at half the price, are poor implementations with issues that go from annoying to near dangerous and are "Beta" unfinished products.