Why highways move more swiftly when you force cars to crawl along at55 mph.

On Oct 23, 10:51*am, gpsman > wrote:
> On Oct 21, 9:38*am, deanej > wrote:
>
> > On Oct 20, 8:35*am, gpsman > wrote:
>
> > > On Oct 20, 6:26*am, deanej > wrote:
>
> > > > On a congested four lane interstate, someone doing 10 under will force
> > > > the person trying to do the speed limit to also do 10 under, as the
> > > > left lane is usually filled with people doing 15-20 over.
>
> > > Why is the issue not attributable to the motorists in the L lane...?
>
> > Because even if they're all going the speed limit, often times the
> > line is long enough that you still can't move over!
>
> In that case your head is probably not far enough ahead of your
> vehicle. *Slower traffic doesn't fall from the sky.
>
> > Also, because if you force me to turn off my cruise control, you're
> > the one I hate, and it's always the slower people forcing me to turn
> > the cruise control off, not the faster ones.
>
> That premise is false by your original complaint; no speeding
> motorists occupying your ROW to the L lane, no problem.
> *-----
>
> - gpsman

Well, I was taught that you shouldn't move over until you can't
maintain a safe following distance, even when passing. I do admit
that most of my issues are probably caused by driving the way I was
taught in driver's ed, instead of just going with the flow with only
the necessary amount of care for procedure as is needed.

On Oct 24, 3:42*am, Dave Head > wrote:
> On Wed, 19 Oct 2011 15:02:45 -0700 (PDT), ChrisCoaster
>
>
>
>
>
> > wrote:
> >On Oct 16, 11:00*am, Harry K > wrote:
> >> On Oct 16, 6:26*am, gpsman > wrote:
>
> >> > Go Slow To Go Fast
> >> > Why highways move more swiftly when you force cars to crawl along at
> >> > 55 mph.
>
> >> > Slate Magazine
> >> > By Tom Vanderbilt | Posted Wednesday, Oct. 12, 2011, at 3:19 PM ET
>
> >> > There is no more common lament voiced by the American driver than of
> >> > the one about the “idiot” in the “fast lane” who’s slowing down
> >> > traffic. If everyone could just drive faster, the thinking goes—if we
> >> > could only cull the weak gazelles in our furiously charging migration—
> >> > we could stamp out congestion.
>
> >> > We equate speed in traffic with efficiency. In the U.K., the Tory
> >> > government is currently advocating raising the speed limit on certain
> >> > motorway sections to 80 MPH, anticipating a massive windfall in
> >> > economic productivity and time saved. It’s speed as the health of the
> >> > state! (Though not all projections are so rosy.)
>
> >> > But one thing that tends to be lost on the individual driver, who
> >> > through the proscenium of his windshield commands what he believes to
> >> > be an empirically incontrovertible perspective on the ground truth of
> >> > traffic, is that sometimes you have to go slower to go faster.
>
> >> > Full article:http://www.slate.com/articles/life/t...lling_speed_ha...
> >> > *-----
>
> >> > - gpsman
>
> >> lots of print space used to sum up what has been known since way
> >> back.
>
> >> "If everyone would just "go with the flow" traffic would move a lot
> >> better".
>
> >> Harry K- Hide quoted text -
>
> >> - Show quoted text -
> >___________________
> >Only problem is, the "flow" has been going 3-5mph faster on average
> >every decade since "horseless carriages" were invented. *The posted
> >speed limits may be either 55 or 65 in a lot of states, but I'd
> >guarantee the actual "flow" is at least 10-20mph faster than it was in
> >the '70s. *What will the flow be in 2020? *80 in slow lane, 100 fast
> >lane??
>
> >-CC
>
> As someone who drove in the 70's, I can tell you that the flow was
> about 7 - 10 mph above the speed limit. *And, lots of us increased our
> speed when the 55 mph limit was instituted, figuring that if we're
> gonna get a ticket anway, due to inability to safely go that slow on
> interstate and rural highways (I kept going to sleep... in the middle
> of the daytime... while attempting to actually drive 55 mph - I
> literally could NOT drive 55 safely) we might as well get somewhere
> doing it. *So I went most everywhere at about 85 during the 70's after
> the 55.
>
> Anyway, the flow in the 70's on midwest interstates was about 77 mph,
> thereabouts.- Hide quoted text -
>
> - Show quoted text -

I made a couple cross country trips in the double nickel days.
Staying awake boring along about 60 in the midwest ws all but
impossible. It was always nice tocross the Montana border that used
to be posted "step on it" (okay that isn't what the signs said but it
is what they meant). Even in the 55 days you could pretty much do
whatevr speed turned you on as Montana would only charge you $5 and it
could be paid on the spot...at least until the feds ended that.

Fun trip was from Syracuse, NY to Spokane Wa in the late 60s (after
55). 1954 chev 6, two GIs with all their goods and a motorcycle
stuffed in the back seat. Headlights illuminating the tops of the
trees at night.

Harry K

In article <69d344d9-818f-4bd7-b5e1-29d6f2ed2b14
@t38g2000prg.googlegroups.com>, Harry K says...


> Fun trip was from Syracuse, NY to Spokane Wa in the late 60s (after
> 55). 1954 chev 6, two GIs with all their goods and a motorcycle
> stuffed in the back seat. Headlights illuminating the tops of the
> trees at night.

I-90 all the way?

There are certain cities along that route (Buffalo and Chicago come to
mind) where the speed limit is irrelevant during much of the day because
traffic would be at a standstill anyhow...



--
Steve Sobol - Programming/WebDev/IT Support

On 10/24/2011 1:59 pm, Steve Sobol wrote:
> In article<69d344d9-818f-4bd7-b5e1-29d6f2ed2b14
> @t38g2000prg.googlegroups.com>, Harry K says...
>
>
>> Fun trip was from Syracuse, NY to Spokane Wa in the late 60s (after
>> 55). 1954 chev 6, two GIs with all their goods and a motorcycle
>> stuffed in the back seat. Headlights illuminating the tops of the
>> trees at night.
>
> I-90 all the way?
>
> There are certain cities along that route (Buffalo and Chicago come to
> mind) where the speed limit is irrelevant during much of the day because
> traffic would be at a standstill anyhow...


The speed limit is irrelevant in Chicago even when traffic isn't at a
standstill. :-P

--
Larry Harvilla
e-mail: larry AT phatpage DOT org
http://www.phatpage.org/
http://www.flickr.com/photos/larrysphatpage

On 10/21/2011 10:13 PM, James Robinson wrote:
> Arif > wrote:
>
>> James Robinson wrote:
>>
>>> Arif > wrote:
>>>
>>>> If you have 2 lanes of traffic moving at exactly 55 mph, only
>>>> a certain amount of vehicles can pass through a given point for a
>>>> given time period. If one lane is moving 55 mph and faster traffic
>>>> is able to use the other lane to travel at higher speeds, then more
>>>> cars will be able to pass through the same area for a given time
>>>> period (assuming the same amount of traffic and the same timed
>>>> following distance). QED.
>>>
>>> And all the emperical data says that to get the maximum throughput,
>>> the flow of traffic will drop to about 50 or 55 mph all by itself.
>>
>> What causes throughput to drop below 50 to 55 mph?
>
> That's the point where the flow goes unstable. Once the density of
> vehicles gets to the point where people start applying brakes, the
> ripple effect causes traffic to start stop-and-go flow instead of
> constant flow.

Okay, now go back to the article linked in the OP. It claimed that
artificially slowing down traffic to 55 mph would increase the
throughput. The cites you provided indicate that given the increased
traffic volume, the free flow status is maintained until speeds drop
below 80 to 90 km/h.

Now, if you slow down traffic before it naturally reaches that state
where free flow degrades to stop and go, wouldn't it stand to reason
that traffic could prematurely end up in a non free flow state. I
certainly could see the situation where a pack of faster traveling
vehicles catches up with the platoon, and some of them slow down more
than necessary. Then vehicles behind them have to slow down even more,
and eventually, you have stop and go traffic.

If that's the case, then there's really no benefit in slowing down
traffic before it happens on its own.

On Mon, 24 Oct 2011 12:05:52 +0000 (UTC), James Robinson
> wrote:

>Dave Head > wrote:
>
>> As someone who drove in the 70's, I can tell you that the flow was
>> about 7 - 10 mph above the speed limit. And, lots of us increased our
>> speed when the 55 mph limit was instituted, figuring that if we're
>> gonna get a ticket anway, due to inability to safely go that slow on
>> interstate and rural highways (I kept going to sleep... in the middle
>> of the daytime... while attempting to actually drive 55 mph - I
>> literally could NOT drive 55 safely) we might as well get somewhere
>> doing it. So I went most everywhere at about 85 during the 70's after
>> the 55.
>>
>> Anyway, the flow in the 70's on midwest interstates was about 77 mph,
>> thereabouts.
>
>That certainly wasn't my experience. I can recall on a transcontinental
>trip driving that fast in Utah and Wyoming, but as soon as you hit
>Nebraska, the speed noticeably dropped, with the flow only about 60 mph.
>This continued through Iowa and Illinois. There were speed traps
>everywhere, with aircraft monitoring common, so you would be pretty well
>guaranteed to get a ticket on any trip where you tried to drive much over
>the limit. (I got a ticket in Nebraska going only 62 mph in a 55 zone,
>and in those days as an out-of-state driver you either paid on the spot,
>or went to jail.)
>
>In Iowa, I remember they had a trick of parking radar units over two
>consecutive hills. Cars would slow down for the first one, which often
>had a car pulled over, then thinking the coast was clear, pick up speed
>only to be nabbed by the second radar unit over the next hill. I saw
>that three or four times.

We're talking the 70's here. There WASN'T that much radar, and it
wasn't all that good. Even in Ohio. Ohio interstates run up about 77
mph before the 55 limit, 65 after, except for those of us that really
didn't give a F about tickets, since it took 'em a full year to nail
you. 1 ticket for 85 mph every year was not a big deal - pay it and
continue.

On Oct 24, 10:59*am, Steve Sobol > wrote:
> In article <69d344d9-818f-4bd7-b5e1-29d6f2ed2b14
> @t38g2000prg.googlegroups.com>, Harry K says...
>
> > Fun trip was from Syracuse, NY to Spokane Wa in the late 60s (after
> > 55). *1954 chev 6, two GIs with all their goods and a motorcycle
> > stuffed in the back seat. *Headlights illuminating the tops of the
> > trees at night.
>
> I-90 all the way?
>
> There are certain cities along that route (Buffalo and Chicago come to
> mind) where the speed limit is irrelevant during much of the day because
> traffic would be at a standstill anyhow...
>
> --
> Steve Sobol - Programming/WebDev/IT Support
>

Yep, I90 where it existed. Thee were still many gaps in it back
then. East coast to Chicago was (I think) complete. May have still
been that missing link around Cleveland.

Harry K

Arif Khokar > wrote:

> James Robinson wrote:
>
>> Arif > wrote:
>>
>>> James Robinson wrote:
>>>
>>>> Arif > wrote:
>>>>
>>>>> If you have 2 lanes of traffic moving at exactly 55 mph, only
>>>>> a certain amount of vehicles can pass through a given point for a
>>>>> given time period. If one lane is moving 55 mph and faster traffic
>>>>> is able to use the other lane to travel at higher speeds, then more
>>>>> cars will be able to pass through the same area for a given time
>>>>> period (assuming the same amount of traffic and the same timed
>>>>> following distance). QED.
>>>>
>>>> And all the emperical data says that to get the maximum throughput,
>>>> the flow of traffic will drop to about 50 or 55 mph all by itself.
>>>
>>> What causes throughput to drop below 50 to 55 mph?
>>
>> That's the point where the flow goes unstable. Once the density of
>> vehicles gets to the point where people start applying brakes, the
>> ripple effect causes traffic to start stop-and-go flow instead of
>> constant flow.
>
> Okay, now go back to the article linked in the OP. It claimed that
> artificially slowing down traffic to 55 mph would increase the
> throughput. The cites you provided indicate that given the increased
> traffic volume, the free flow status is maintained until speeds drop
> below 80 to 90 km/h.
>
> Now, if you slow down traffic before it naturally reaches that state
> where free flow degrades to stop and go, wouldn't it stand to reason
> that traffic could prematurely end up in a non free flow state. I
> certainly could see the situation where a pack of faster traveling
> vehicles catches up with the platoon, and some of them slow down more
> than necessary. Then vehicles behind them have to slow down even more,
> and eventually, you have stop and go traffic.
>
> If that's the case, then there's really no benefit in slowing down
> traffic before it happens on its own.

The article first notes that by slowing the traffic, they have reduced
the number of accidents, which of course improves capacity by reducing
disruptions. That seems to be what resulted in the majority of flow
improvement. Nothing new there, since they have been doing that in the
LA area for decades.

The article also claims that the reduced speeds improve flow, but is
vague about why. They talk about having traffic stopped at the tunnel
entrances, and by bringing traffic up to the tunnels at reduced speed,
they don't see the same need for heavy braking, and not as many cars
bunch up at the choke point. It appears they are trying to manage the
congested flow with start-stop movement by turning it back into free-
flow, with fewer stops.

The graphs in my links show that unstable flow can have great variation
in throughput, and they may be successfully stabilizing the flow to some
extent, resulting in somewhat greater throughput, but not as high as it
would have been with free-flow.

Dave Head > wrote:

> James Robinson > wrote:
>
>> Dave Head > wrote:
>>
>>> As someone who drove in the 70's, I can tell you that the flow was
>>> about 7 - 10 mph above the speed limit. And, lots of us increased
>>> our speed when the 55 mph limit was instituted, figuring that if
>>> we're gonna get a ticket anway, due to inability to safely go that
>>> slow on interstate and rural highways (I kept going to sleep... in
>>> the middle of the daytime... while attempting to actually drive 55
>>> mph - I literally could NOT drive 55 safely) we might as well get
>>> somewhere doing it. So I went most everywhere at about 85 during
>>> the 70's after the 55.
>>>
>>> Anyway, the flow in the 70's on midwest interstates was about 77
>>> mph, thereabouts.
>>
>> That certainly wasn't my experience. I can recall on a
>> transcontinental trip driving that fast in Utah and Wyoming, but as
>> soon as you hit Nebraska, the speed noticeably dropped, with the flow
>> only about 60 mph. This continued through Iowa and Illinois. There
>> were speed traps everywhere, with aircraft monitoring common, so you
>> would be pretty well guaranteed to get a ticket on any trip where you
>> tried to drive much over the limit. (I got a ticket in Nebraska going
>> only 62 mph in a 55 zone, and in those days as an out-of-state driver
>> you either paid on the spot, or went to jail.)
>>
>> In Iowa, I remember they had a trick of parking radar units over two
>> consecutive hills. Cars would slow down for the first one, which
>> often had a car pulled over, then thinking the coast was clear, pick
>> up speed only to be nabbed by the second radar unit over the next
>> hill. I saw that three or four times.
>
> We're talking the 70's here. There WASN'T that much radar, and it
> wasn't all that good. Even in Ohio. Ohio interstates run up about 77
> mph before the 55 limit, 65 after, except for those of us that really
> didn't give a F about tickets, since it took 'em a full year to nail
> you. 1 ticket for 85 mph every year was not a big deal - pay it and
> continue.

As I recall, there were three speed traps in Nebraska, one was using an
aircraft. There were two pairs of speed traps in Iowa. I don't recall
any in Illinois, but the general traffic flow wasn't moving over about 60
or 65 mph. Sounds like Ohio simply wasn't enforcing things like the
other states.

My experience was soon after the 55 limit had been implemented, and
perhaps some states were being more zealous then. As time progressed, a
few states dropped fines to nothing, and enforcement started to get lax.
Perhaps it is simply a case of what period people remember.

On 10/25/2011 8:47 AM, James Robinson wrote:

> My experience was soon after the 55 limit had been implemented, and
> perhaps some states were being more zealous then. As time progressed, a
> few states dropped fines to nothing, and enforcement started to get lax.
> Perhaps it is simply a case of what period people remember.

I don't really remember the '70s, but I do remember my dad driving
between 70 to 80 mph on interstates in the early to mid '80s through
states like VA, PA, NJ, MD, etc. He wasn't flying past other vehicles
either, so I would guess that the flow was around 65 to 70 mph at the time.