Autopilot switching from 70 to 55mph joining M20 from M26

[ParHunter]

The other day I was driving down to Canterbury. I was on autopilot when the car suddenly decelerated. At first I though this was phantom breaking (which I haven’t really experienced before) but then I’ve noticed that it reduced the speed limit from 70 to 55. This was just before the M26 joins the M20. Then on the way back I had exactly the same behaviour when exiting the M20 to go onto the M26.

Is this due to a bug in the map/speed limit database? Has anyone else have had the same problem on the M26/M20?

 

[MrBadger]

Intersections seem to have their own speed settings irrespective of real speed limits. The fact you have a 55mph car speed coincides with those experiences. Almost certainly not a map change as same behaviour before (with 2019 maps) and after the 2021 maps.

I'm fortunate as the intersection I use most is actually a 50mph merge. So I am manually adjusting the speed anyway.

 

[btc1k]

I experienced this also, on this same bit of road as well as other intersections.

The AutoPilot seems to slow down for those sections of road, as you say it selects a different speed in the blue circle and slows down accordingly. I am in the habit now of adjusting manually beforehand..

 

[Chrisgillett]

I’ve had the same problem for some time, and M49 to M5 interchange it drops you to 65 just before the bend, it’s really annoying, I just switch autopilot off before I get there as mentioned above.

Conversely, the M4 through Newport is now 50 zone and the autopilot doesn’t change at all – and would happily steam through at 70+.
It would be nice if you could submit bug reports!

 

[interbear]

This happens regularly when switching between motorway intersections - for example I’ve experienced it on the intersections between the M48 to M4 in South Wales or M4 to M5. I rarely use Autopilot anyway but when I do use it I switch it off when approaching intersections so that I stay in control at these times.

 

[interbear]

I’ve had the same problem for some time, and M49 to M5 interchange it drops you to 65 just before the bend, it’s really annoying, I just switch autopilot off before I get there as mentioned above.

Conversely, the M4 through Newport is now 50 zone and the autopilot doesn’t change at all – and would happily steam through at 70+.
It would be nice if you could submit bug reports!

I’m also pretty local to this long 50mph stretch of M4 at Newport and had read that it was implemented for air pollution reasons ie. slow traffic down to reduce CO2 emissions. So in my head we should be able to speed through at 70mph + in our zero emission Teslas. Unfortunately the speed cameras do not agree with my perspective, which is a shame

 

[davidmc]

Its a rare occurrence, but does happen. Its happened to me on the M6 junction (M6, M42 & M6 toll) going East from Birmingham. It happens where the M6 goes over the M6/M42 Toll road before merging and the car slams on the breaks going from 70 to 50 even though the road is no where near merging.

This also happens if the car sees a 20mph sign on a parallel road to you and you are on a 40 road.

 

[JupiterMan]

This happens regularly when switching between motorway intersections - for example I’ve experienced it on the intersections between the M48 to M4 in South Wales or M4 to M5.

happens for me also M25 -> M23 and M23 -> M25

on the latter it is totally against the flow of traffic and pretty annoying as no slow down is required, whilst on the former it stops autopilot disengaging on the corner, so could be seen as a positive, but still slows down far to early.

It is not reacting to any signs or corners, so seems to be something on the map as don't recall this behaviour before?

 

[Chrisgillett]

happens for me also M25 -> M23 and M23 -> M25

on the latter it is totally against the flow of traffic and pretty annoying as no slow down is required, whilst on the former it stops autopilot disengaging on the corner, so could be seen as a positive, but still slows down far to early.

It is not reacting to any signs or corners, so seems to be something on the map as don't recall this behaviour before?

I think I actually read the manual about this believe it or not. Tesla claim it is to match the speed of “other road users”. Perhaps the data is taken from Waze or something similar?

 

[bhanorthy]

On the M4 near slough an exit has a 30mph sign.
I don’t take the exit I’m in lane one but the cars cameras spot the sign and immediately reduce the cruise limit. I’m still on the M4 at 50mph average speed and it’s incredibly annoying and dangerous.