SOT - car computer functions

[Jeff Layman]

I have a Jazz just over 4 years old. Like many modern cars, it can
"sense" speed signs and show the limit on a dash display (this is /not/
the satnav display). If required, I can set the speed limiter to what
the display says, and so keep to the speed limit. That's fine, but now
and again I noticed the displayed speed would revert to the "pause"
condition, where the speed sensor is awaiting a sign it can identify.
That's not much use if the speed limiter is set, as in the pause
condition it has no limit to conform to (it can revert to the previous
speed limit after some time, even if still in the pause condition, but I
have yet to find what that time is).

What was puzzling me was the apparently random nature of this pause
condition appearing. I noticed it appeared at some roundabouts, but not
others, where the speed limit displayed would just disappear. I wondered
if it was chevrons at the roundabout or something else confusing the
sensor. It was then I decided to RTFM, and it became clear (sort of...)
what was going on. :

================================================================

The speed limitation function and warning function may switch to pause
if there is no speed limit sign in the screen of the traffic sign
recognition system when:

* the end of speed limit or other designated limit is detected
* your vehicle enters/exits motorway or highway
* you make a turn with a turn signal to change direction at an intersection

===============================================================

The first one makes some sense, the second less so, and the third no
sense at all. Can anyone explain the reasoning behind this? Why should
using an indicator at an intersection (and roundabout!) make the system
assume the speed limit has changed or is no longer in force?

[Roger Mills]

Post by Jeff Layman
I have a Jazz just over 4 years old. Like many modern cars, it can
"sense" speed signs and show the limit on a dash display (this is /not/
the satnav display). If required, I can set the speed limiter to what
the display says, and so keep to the speed limit. That's fine, but now
and again I noticed the displayed speed would revert to the "pause"
condition, where the speed sensor is awaiting a sign it can identify.
That's not much use if the speed limiter is set, as in the pause
condition it has no limit to conform to (it can revert to the previous
speed limit after some time, even if still in the pause condition, but I
have yet to find what that time is).
What was puzzling me was the apparently random nature of this pause
condition appearing. I noticed it appeared at some roundabouts, but not
others, where the speed limit displayed would just disappear. I wondered
if it was chevrons at the roundabout or something else confusing the
sensor. It was then I decided to RTFM, and it became clear (sort of...)
================================================================
The speed limitation function and warning function may switch to pause
if there is no speed limit sign in the screen of the traffic sign
* the end of speed limit or other designated limit is detected
* your vehicle enters/exits motorway or highway
* you make a turn with a turn signal to change direction at an intersection
===============================================================
The first one makes some sense, the second less so, and the third no
sense at all. Can anyone explain the reasoning behind this? Why should
using an indicator at an intersection (and roundabout!) make the system
assume the speed limit has changed or is no longer in force?

I guess it assumes that you are turning into a road with a potentially
different speed limit, and it hasn't seen a sign to know what that limit is.

I have a similar system on my Hyundai Tucson (but without the option of
automatically setting the speed limiter) - and that doesn't seem to know
what the limit is, half the time. I also have a Tomtom stand-alone
satnav which I use for speed camera warnings, and that usually has a
better idea of the speed limit than the built-in system - but if the
limit on a given road changes, it doesn't know about it until the next
map update - if then!

One thing I've discovered about the speed limiter is that if you set the
limit to (say) 40mph, it limits you to what the car's exaggerometer -
sorry, speedometer - thinks is 40pmh, which is actually about 37. The
Tomtom - but not the built-in navigation system - enables a suitable
correction to be made.