Self-driving Uber kills Arizona woman in first fatal crash involving pedestrian

"Gene Malvern" wrote

| There was a second or two that
| an actual driver would have at least slammed on
| the brakes. They might not have ben able to avoid
| hitting the woman, but they wouldn't have hit her
| at 38 mph.
|
| Self-driving cars are a tort lawyer's dream.
| Every time one of these cars kills someone, the
| manufacturer of the car is going to be sued.
| And that car manufacturer is going to lose.
|
That's a nice thought. I hope they get sued
"up the yazoo" for this half-witted arrogance.
I'm still dumbfounded at how these companies
have managed to get away with running robot
road tests on public streets, with apparently no
oversight. The only reason I can think of is a
fever of technophilia in officialdom, combined
with loads of money/lobbying coming from
corporate sponsors and investors.

I wondered whether that may have had an
effect on the Tempe police chief. His public
comment after viewing the video was that it
seemed no was was at fault. A driver kills a
woman crossing the road while paying no
attention at all to the road ahead, yet no
one is at fault! It was a ludicrous statement.

I'm guessing that the chief was probably
swamped by very rich and very important people,
warning him that this was an important test
case and that if the chief says the wrong thing
he might cause a lot of people to lose a lot of
money. Or worse, he might "hold up the future".

Fortunately, last I heard, experts were starting
to weigh in on the side of common sense.

On Thu, 22 Mar 2018 19:30:43 -0400, Paul wrote:

Char Jackson wrote:


If you have time to use the horn, you have time to avoid the accident.
It's not about being timid or aggressive or any of that hogwash.

What if there's a driver right on your rear bumper, there's no place to
back up to get away from a wild driver in front of you.

Slow down. Change lanes, if possible. Problem solved.

Yes, you can drive defensively, read situations before they happen,
and take measures. But once in a while, it's just "the enemy in
front of you" and a brick wall behind. And at that point,
it's horn time.

If I understand correctly, you sometimes use your horn to make yourself
feel better, not to actually accomplish anything useful with regards to
traffic conditions. It seems like you could find something more
productive.

Mayayana wrote:
"Gene Malvern" wrote

| There was a second or two that
| an actual driver would have at least slammed on
| the brakes. They might not have ben able to avoid
| hitting the woman, but they wouldn't have hit her
| at 38 mph.
|
| Self-driving cars are a tort lawyer's dream.
| Every time one of these cars kills someone, the
| manufacturer of the car is going to be sued.
| And that car manufacturer is going to lose.
|
That's a nice thought. I hope they get sued
"up the yazoo" for this half-witted arrogance.
I'm still dumbfounded at how these companies
have managed to get away with running robot
road tests on public streets

There are at least a couple artificially constructed
towns, built up for the purpose of that sort of testing.
For the car companies (for reasons unknown), they seem
to think they're past that point. But, what does this
Uber experience tell us (no reaction at all to stimuli).

The Uber track record on "disengagement events", suggests
the technology isn't as ready as it sounds. There's at least
one web site that examined the log for trends. Disengagement
is where the driver takes the wheel for some reason, and
it seems to happen about once a mile. This is hardly
autonomy in the "ready-to-ship" state for finished goods.
Why doesn't the car drive smoothly ? Why does it see
false positives and stop for no reason ? An academic in
a university, would be interested in these phenomenon,
and conduct research to drop the incidence to a low
percentage value.

Just about everyone involved in this, is complicit in a
"gold rush" sense. I saw an idiotic product promotion page,
where the author (a technology company) kept tossing around
"trillion dollar numbers" for economic benefit. All involved
have $$$ in their eyes. "Build your factory here sir,
we don't care if you run over our cats." That seems
to be the thinking.

The traditional car industry was risk averse enough from
previous lawsuits, to not make these kinds of mistakes.
The gold rush people are only too willing to go bankrupt
running over stuff, if only "they can get some gold
and become Google while doing so". There is a drive to
being "top bitch" in this, which is why so many "alliances"
are being formed.

What was particularly scary about the promotion I was reading,
is the industry feels part of the benefit comes from "big data".
Yes, Petunia, they'll be keeping a log of where you drove,
what you were doing, and so on. It's "for your own good"
and "you'll want to watch these Disney cartoons for $11.39
until we get to your destination". These classifier issues
are merely a speed bump to getting some gold.

Paul

On 3/23/2018 10:47 AM, Wolf K wrote:
On 2018-03-22 22:41, J. P. Gilliver (John) wrote:
In message , Char Jackson
writes:
[]
Here in the US, especially in smaller towns, as you approach the town
you'll be likely to see two signs. The first might say, "Welcome to
Mayberry, birthplace of Andy Griffith. Population 367." The second sign
might say, "Speed Limit 25 MPH unless otherwise posted."

So now you know the name of the town that you're entering, and you know
the default speed limit in that town. The town doesn't need to stick a
speed limit sign on every single street that says "Speed Limit 25 MPH"
because they stuck a sign out at the city limits that applies to the
whole town. They only need to erect and maintain signs where the speed
limit is different from 25 MPH.

If I passed a sign saying limit 25, I would assume the limit was 25
until I saw a sign saying otherwise. I would not _expect_ to see signs
repeating the 25. I do not see the need for the words "unless
otherwise posted".
[...]

What if you do not see a speed limit sign for the next 25 miles as you
drive through rural parts of the mid west and great plains.

--
2018: The year we learn to play the great game of Euchre

"Mayayana" on Wed, 21 Mar 2018 22:38:16
-0400 typed in alt.windows7.general the following:
"Char Jackson" wrote
...

Here's the video:

https://www.youtube.com/watch?v=XtTB8hTgHbM

Driver looking down. There was a second or two that
an actual driver would have at least slammed on
the brakes. They might not have ben able to avoid
hitting the woman, but they wouldn't have hit her
at 38 mph.

So what Uber has is not so much an "autonomous car" (Which can be
told "to the office" and it drives there) as an "enhanced autopilot
system" where the 'driver' still has to man the driver seat, prepared
at all times to resume actual operation of the vehicle.
I'll wait for the full "Johnny Cab" option.


--
pyotr filipivich
Next month's Panel: Graft - Boon or blessing?

On 3/23/2018 11:19 AM, Paul wrote:
Mayayana wrote:
"Gene Malvern" wrote

| There was a second or two that
| an actual driver would have at least slammed on
| the brakes. They might not have ben able to avoid
| hitting the woman, but they wouldn't have hit her
| at 38 mph.
|
| Self-driving cars are a tort lawyer's dream.
| Every time one of these cars kills someone, the
| manufacturer of the car is going to be sued.
| And that car manufacturer is going to lose.
|
Â*Â* That's a nice thought. I hope they get sued
"up the yazoo" for this half-witted arrogance.
I'm still dumbfounded at how these companies
have managed to get away with running robot
road tests on public streets

There are at least a couple artificially constructed
towns, built up for the purpose of that sort of testing.
For the car companies (for reasons unknown), they seem
to think they're past that point. But, what does this
Uber experience tell us (no reaction at all to stimuli).

The Uber track record on "disengagement events", suggests
the technology isn't as ready as it sounds. There's at least
one web site that examined the log for trends. Disengagement
is where the driver takes the wheel for some reason, and
it seems to happen about once a mile. This is hardly
autonomy in the "ready-to-ship" state for finished goods.
Why doesn't the car drive smoothly ? Why does it see
false positives and stop for no reason ? An academic in
a university, would be interested in these phenomenon,
and conduct research to drop the incidence to a low
percentage value.

Just about everyone involved in this, is complicit in a
"gold rush" sense. I saw an idiotic product promotion page,
where the author (a technology company) kept tossing around
"trillion dollar numbers" for economic benefit. All involved
have $$$ in their eyes. "Build your factory here sir,
we don't care if you run over our cats." That seems
to be the thinking.

The traditional car industry was risk averse enough from
previous lawsuits, to not make these kinds of mistakes.
The gold rush people are only too willing to go bankrupt
running over stuff, if only "they can get some gold
and become Google while doing so". There is a drive to
being "top bitch" in this, which is why so many "alliances"
are being formed.

What was particularly scary about the promotion I was reading,
is the industry feels part of the benefit comes from "big data".
Yes, Petunia, they'll be keeping a log of where you drove,
what you were doing, and so on. It's "for your own good"
and "you'll want to watch these Disney cartoons for $11.39
until we get to your destination". These classifier issues
are merely a speed bump to getting some gold.

Â*Â* Paul
If you have ever done any experimentation particularly the kind
involving people, you will realize that they will respond as the
experimenter expected. This is a fact of life.

I went to a management course once where the presenter had this great
new technique to change the enviroment of the work place. When I asked
about this effect he acknowledged it existed, and his only solution was
to take credit for it.

Running thousands of test in an artificial environment does not
necessarily prove the system works.

I have read too many papers where in the summary the experimenter
acknowledge his results did not proof what he wanted, BUT since common
knowledge said is should work the way he thought, his results must in
some way support it.

--
2018: The year we learn to play the great game of Euchre

On Fri, 23 Mar 2018 02:41:40 +0000, "J. P. Gilliver (John)"
wrote:

If you passed a sign telling you the limit was 25 but that _didn't_ say
"unless otherwise posted", what _different_ interpretation would you put
on it, to one that did have those words?

A speed limit applies to the road on which it is posted, so as soon as I
make a turn onto another road, a new speed limit applies. It's value
could be the same as the last one, or it could be different. One thing
is for sure, the speed limit on road A does not apply to road B, or vice
versa.

A speed limit that includes "Unless otherwise posted" applies a speed
limit to an area, for example the area encompassing the city limits. In
this case, as long as I stay in the area, the same speed limit applies,
unless otherwise posted. If I make a turn onto an unposted road within
that area, I'm back to the default speed limit.

In message , Char Jackson
writes:
On Thu, 22 Mar 2018 19:30:43 -0400, Paul wrote:

Char Jackson wrote:


If you have time to use the horn, you have time to avoid the accident.
It's not about being timid or aggressive or any of that hogwash.

What if there's a driver right on your rear bumper, there's no place to
back up to get away from a wild driver in front of you.

Slow down. Change lanes, if possible. Problem solved.

Two lanes of traffic. I'm in the faster one. There isn't an even-faster
one I can move into, nor any gap in the slower one I consider it would
be safe to move into.

Some idiot in the same lane as me has come up fairly close behind me.

Someone in the slower lane, but ahead of me, starts to pull out in front
of me, with sufficient combinations of relative speeds and positions
that _I_ deduce that, if I do nothing, I will hit him. If I brake, the
idiot behind will run into me. (Never mind that it would be his "fault",
I'd rather that didn't happen.)

Perhaps the person pulling out hasn't seen me - I'm in his blind spot,
or something; or, perhaps, he's just not paying attention.

I honk. He notices me, and stops pulling out. Yes, it's not foolproof by
any means; certainly he has to decide that it's him I'm honking at. But
on the whole, someone undertaking such a manoeuvre is IMO more likely to
think it's him I'm honking at than the drivers of the other vehicles
around me who are maintaining lane and speed.

Longer term, yes, I would diddle my brakelights to tell the person
behind that I feel they are too close. But (ignoring the fact that they
probably wouldn't pull back anyway), that wouldn't help the situation
described - where using the horn has _some_ chance of averting an
accident, and not doing so has IMO less chance.

Yes, you can drive defensively, read situations before they happen,
and take measures. But once in a while, it's just "the enemy in
front of you" and a brick wall behind. And at that point,
it's horn time.

(In my case it was the barrier to the side and the idiot behind rather
than a brick wall, but yes.)

If I understand correctly, you sometimes use your horn to make yourself
feel better, not to actually accomplish anything useful with regards to
traffic conditions. It seems like you could find something more
productive.

You did not understand Paul correctly, and the above paragraph is rather
insulting.
--
J. P. Gilliver. UMRA: 1960/1985 MB++G()AL-IS-Ch++(p)Ar@T+H+Sh0!:`)DNAf

(please reply to group - they also serve who only look and lurk)
(William Allen, 1999 - after Milton, of course)

In message , Char Jackson
writes:
On Fri, 23 Mar 2018 02:41:40 +0000, "J. P. Gilliver (John)"
wrote:

If you passed a sign telling you the limit was 25 but that _didn't_ say
"unless otherwise posted", what _different_ interpretation would you put
on it, to one that did have those words?

A speed limit applies to the road on which it is posted, so as soon as I
make a turn onto another road, a new speed limit applies. It's value
could be the same as the last one, or it could be different. One thing
is for sure, the speed limit on road A does not apply to road B, or vice
versa.

A speed limit that includes "Unless otherwise posted" applies a speed
limit to an area, for example the area encompassing the city limits. In
this case, as long as I stay in the area, the same speed limit applies,
unless otherwise posted. If I make a turn onto an unposted road within
that area, I'm back to the default speed limit.

So let me get this right. You have a "zone" sign (one of these "unless
otherwise" ones) at the entrance to some area. Within that area, you
might have a length of road that has a (let's say) faster limit, which
would have a sign at its start giving that limit.

1. Are you saying that anyone who has got onto the faster road is
supposed to know when he's leaving it? I could just about see this
working, _if_ it's an obvious highway or something (though see 2.
below). What if it forks, with both forks appearing to be of the same
quality of road?

2. How does someone turning onto this road _from_ a side road (within
the area), rather than coming at it from its end, know what the faster
limit is? If you have a sign telling them, at each such junction, then
surely you'd have one showing the lower limit on the other side of the
same pole?
--
J. P. Gilliver. UMRA: 1960/1985 MB++G()AL-IS-Ch++(p)Ar@T+H+Sh0!:`)DNAf

War is God's way of teaching Americans geography. -Ambrose Bierce, writer
(1842-1914)

In message , Mayayana
writes:
"J. P. Gilliver (John)" wrote

| If you passed a sign telling you the limit was 25 but that _didn't_ say
| "unless otherwise posted", what _different_ interpretation would you put
| on it, to one that did have those words?

That may be a Brit vs American thing. In the US
we generally have default speed limits. 30 mph

We have the same (officially "national speed limits") - they're 30, 60,
and 70.

for "thickly settled", which is an official term with
a defined meaning. Lately, where I live, that seems

We call it a "built-up area" (for which it is 30), and the same applies:
the definition is actually that the streetlamps are closer together than
a specified distance, but I doubt one in ten Brits actually knows that
(we tend to think of it as being inside village/town/city limits), and
_I_ couldn't tell you what the distance actually is.

to have changed to 25. Apparently it's been decided
that we just have to keep going slower until no more
phone addicts get run over while wandering aimlessly
into the street.

(-:

So "unless otherwise posted" defines a context.
25 is in effect on all streets without signs, unless
other signs say otherwise.

In theory here, its 30 in a built-up area unless it says otherwise, but
in practice I can't remember the last time I passed into a built-up area
without there being a sign specifically saying so, even on a back road
into a village. And these signs usually have a derestriction sign on
their back, for people leaving the area.

In VT the state roads have signs saying 50 mph unless
otherwise posted. It's 50 in wooded areas but goes down
when the road passes through town centers or past
large farms.

If it were to work as you describe then a new sign
would be needed at every point where someone can
enter a specific roadway.

I would say we have that; certainly where a main road goes through a
village or town, where the main road is often 40 limit, there will be a
30 sign at each side turn. (I think with a 40 sign on their backs.)

Which reminds me of a great joke from Carrot Top
some years ago, comparing British and American cops.
He explained that in Britain, when police stop someone
for a speeding violation, they pass the car, guide the
driver to the side of the road, walk over politely, and
say something pleasant like, "Misbehaving a bit now,
are we?" When in the US Carrot Top saw the police
lights and waited for the police to pass him, but here
they stop behind the driver. So CT kept driving... waiting
for the cop to pass... until the cop finally pulled
alongside, rolled down his window, and shouted,
"HEY!! MARIO ANDRETTI!! PULL OVER!!"

Yes, here our police usually get in front of you to make you stop -
although they do _sometimes_ flash their (blue only, here) lights at you
from behind, often accompanied by siren. Though if I saw a police car
behind me doing that, I'd probably pull over, but half expect them to
pass me and keep on going, assuming they'd just wanted to get past me
rather than stop me. I've always vaguely assumed that this US/UK
difference is due to firearms: here, a policeman would assume placing
his vehicle in front of yours was probably sufficient to persuade you to
stop, whereas I can imagine in USA, especially if he is alone, he might
not feel safe doing so. But this might not be the reason - there may be
no reason and it's just developed differently.

(The opening statement often includes "sir" - such as "is this _your_
vehicle, sir?" But despite sir being a term of respect, they have learnt
to use it with a strong impression of superiority!)
--
J. P. Gilliver. UMRA: 1960/1985 MB++G()AL-IS-Ch++(p)Ar@T+H+Sh0!:`)DNAf

War is God's way of teaching Americans geography. -Ambrose Bierce, writer
(1842-1914)

In message , Wolf K
writes:
On 2018-03-22 22:41, J. P. Gilliver (John) wrote:
[]
If I passed a sign saying limit 25, I would assume the limit was 25
until I saw a sign saying otherwise. I would not _expect_ to see signs
repeating the 25. I do not see the need for the words "unless
otherwise posted".
[...]

I think that's because you are neither a cop nor a traffic engineer. :-)

Best,

No; I _am_ an engineer, and familiar with the concept of (logical) flags
being set and unset. See other posts: it _might_ be a US/Europe
difference.
--
J. P. Gilliver. UMRA: 1960/1985 MB++G()AL-IS-Ch++(p)Ar@T+H+Sh0!:`)DNAf

War is God's way of teaching Americans geography. -Ambrose Bierce, writer
(1842-1914)

In message , Keith Nuttle
writes:
[]
On 2018-03-22 22:41, J. P. Gilliver (John) wrote:
[]
If I passed a sign saying limit 25, I would assume the limit was 25
until I saw a sign saying otherwise. I would not _expect_ to see
signs repeating the 25. I do not see the need for the words "unless
otherwise posted".
[...]

What if you do not see a speed limit sign for the next 25 miles as you
drive through rural parts of the mid west and great plains.

I might eventually assume I'd missed the "end of 25 limit" sign, and
speed up accordingly. If I _knew_ the policy was as you describe (by
implication no "end" signs), I'd look for the back of such signs more.

If _you_ passed a "25 unless otherwise posted" sign, how would _you_
know when you'd left the area to which it applies? Sure, it'd be obvious
after a while, but how would you know the _instant_ you'd left the
restricted area? You can't assume "oh, this looks like open country - I
can speed up", because there might suddenly be more habitation round the
next bend.

[Oh, I forgot: US roads don't have bends ... (-:]
(There's actually some truth in that, or rather its converse: British
roads _are_ windy. If you come across a long very straight bit, you
think "the Romans were here" [and you are probably right]; it's the
exception rather than the rule. Zoom in on Google maps on Britain a bit,
you'll see what I mean.)
--
J. P. Gilliver. UMRA: 1960/1985 MB++G()AL-IS-Ch++(p)Ar@T+H+Sh0!:`)DNAf

War is God's way of teaching Americans geography. -Ambrose Bierce, writer
(1842-1914)

Keith Nuttle wrote:
On 3/23/2018 10:47 AM, Wolf K wrote:
On 2018-03-22 22:41, J. P. Gilliver (John) wrote:
In message , Char Jackson
writes:
[]
Here in the US, especially in smaller towns, as you approach the town
you'll be likely to see two signs. The first might say, "Welcome to
Mayberry, birthplace of Andy Griffith. Population 367." The second sign
might say, "Speed Limit 25 MPH unless otherwise posted."

So now you know the name of the town that you're entering, and you know
the default speed limit in that town. The town doesn't need to stick a
speed limit sign on every single street that says "Speed Limit 25 MPH"
because they stuck a sign out at the city limits that applies to the
whole town. They only need to erect and maintain signs where the speed
limit is different from 25 MPH.

If I passed a sign saying limit 25, I would assume the limit was 25
until I saw a sign saying otherwise. I would not _expect_ to see
signs repeating the 25. I do not see the need for the words "unless
otherwise posted".
[...]

What if you do not see a speed limit sign for the next 25 miles as you
drive through rural parts of the mid west and great plains.


The defaults are roughly

30mph 50kph City
80kph Secondary roads (two lane, no median, no shoulder)
100kph 100-Class highway (i.e. Route 104)

But with decade by decade adjustments to the highway limit.
Some "improved" roads with certain curves removed, get
signed for 110 or 120kph.

Signs are placed on roads, mainly to make speeding tickets
in court, an open-and-shut case. This is why there are
so many signs, when the default definition would have sufficed.

*******

The default parking restriction is stated on a sign
as you enter a city. In our city, the default is
"3 hours parking" unless otherwise signed, which really
means you cannot park overnight on a residential street.

However, the reality of the situation is, a
"neighbor has to complain", before anyone will come out,
chalk the tires, and write up a ticket three hours later.
Yes, there are neighbors who are friendly enough to call
up and complain, when you have visitors. Some of our
cities do not have sufficient police officers to
offer this service, and police will tell you to "find
a new hobby". You can't even get police help with
a B&E in places like that, and you have to "kill someone"
to see a policeman.

Paul

On Fri, 23 Mar 2018 15:49:56 +0000, "J. P. Gilliver (John)"
wrote:

In message , Char Jackson
writes:
On Thu, 22 Mar 2018 19:30:43 -0400, Paul wrote:

Char Jackson wrote:


If you have time to use the horn, you have time to avoid the accident.
It's not about being timid or aggressive or any of that hogwash.

What if there's a driver right on your rear bumper, there's no place to
back up to get away from a wild driver in front of you.

Slow down. Change lanes, if possible. Problem solved.

Two lanes of traffic. I'm in the faster one. There isn't an even-faster
one I can move into, nor any gap in the slower one I consider it would
be safe to move into.

Some idiot in the same lane as me has come up fairly close behind me.

Someone in the slower lane, but ahead of me, starts to pull out in front
of me, with sufficient combinations of relative speeds and positions
that _I_ deduce that, if I do nothing, I will hit him. If I brake, the
idiot behind will run into me. (Never mind that it would be his "fault",
I'd rather that didn't happen.)

Here's where we disagree. The "idiot behind" (now who's being
insulting?) can most likely see the car pulling out in front of you and
will typically proactively slow down in anticipation of you slowing
down. Even if they are oblivious to what's happening ahead of you, they
aren't likely to be oblivious to you slowing down. Unless this is the
very first time the "idiot behind" has decided to tailgate someone, he's
probably very aware that following closely will mean that he has to
brake suddenly from time to time.

Perhaps the person pulling out hasn't seen me - I'm in his blind spot,
or something; or, perhaps, he's just not paying attention.

I honk. He notices me, and stops pulling out. Yes, it's not foolproof by
any means; certainly he has to decide that it's him I'm honking at. But
on the whole, someone undertaking such a manoeuvre is IMO more likely to
think it's him I'm honking at than the drivers of the other vehicles
around me who are maintaining lane and speed.

Longer term, yes, I would diddle my brakelights to tell the person
behind that I feel they are too close. But (ignoring the fact that they
probably wouldn't pull back anyway), that wouldn't help the situation
described - where using the horn has _some_ chance of averting an
accident, and not doing so has IMO less chance.

Yes, you can drive defensively, read situations before they happen,
and take measures. But once in a while, it's just "the enemy in
front of you" and a brick wall behind. And at that point,
it's horn time.

(In my case it was the barrier to the side and the idiot behind rather
than a brick wall, but yes.)

If I understand correctly, you sometimes use your horn to make yourself
feel better, not to actually accomplish anything useful with regards to
traffic conditions. It seems like you could find something more
productive.

You did not understand Paul correctly, and the above paragraph is rather
insulting.

In what way do you think I misunderstood what Paul said? I thought he
was pretty clear. He sometimes uses his horn because it makes him feel
better. I'm sure he's not the only one.

On Fri, 23 Mar 2018 16:03:20 +0000, "J. P. Gilliver (John)"
wrote:

In message , Char Jackson
writes:
On Fri, 23 Mar 2018 02:41:40 +0000, "J. P. Gilliver (John)"
wrote:

If you passed a sign telling you the limit was 25 but that _didn't_ say
"unless otherwise posted", what _different_ interpretation would you put
on it, to one that did have those words?

A speed limit applies to the road on which it is posted, so as soon as I
make a turn onto another road, a new speed limit applies. It's value
could be the same as the last one, or it could be different. One thing
is for sure, the speed limit on road A does not apply to road B, or vice
versa.

A speed limit that includes "Unless otherwise posted" applies a speed
limit to an area, for example the area encompassing the city limits. In
this case, as long as I stay in the area, the same speed limit applies,
unless otherwise posted. If I make a turn onto an unposted road within
that area, I'm back to the default speed limit.

So let me get this right. You have a "zone" sign (one of these "unless
otherwise" ones) at the entrance to some area. Within that area, you
might have a length of road that has a (let's say) faster limit, which
would have a sign at its start giving that limit.

1. Are you saying that anyone who has got onto the faster road is
supposed to know when he's leaving it? I could just about see this
working, _if_ it's an obvious highway or something (though see 2.
below). What if it forks, with both forks appearing to be of the same
quality of road?

2. How does someone turning onto this road _from_ a side road (within
the area), rather than coming at it from its end, know what the faster
limit is? If you have a sign telling them, at each such junction, then
surely you'd have one showing the lower limit on the other side of the
same pole?

We can "what if" this all day. Come over for a visit and drive here.
It's not nearly as hard as you're making it out to be. If I can drive
all over the world, you probably can, as well. It would behoove no one
to make things difficult for the sake of making things difficult.