Diamond-interchange, roundabout all in one

Hi Viatologists,

Its one of the most unique interchanges in the Americas. Less than 15
kilometres from downtown Buenos Aires, it's a diamond-interchange and
roundabout all rolled into one:

http://tinyurl.com/5gkcvr (Google Maps)

Regardless of how you enter this interchange, be prepared to take a
90-degree loop if you want to go left. If you wish to go right, then you
have no loop whatsoever. Due to the unique layout of this interchange, all
left-turn motorists essentially calm traffic and reduce speeding. This
interchange serves as the northern terminus of Ruta Nacional 3, an American
highway that connects the Argentine capital w/ Tierra del Fuego.

Cheers,

Carl Rogers
"Environment first, transportology second"
********
Worldwide Transportation Library (WWTL):
http://wwtl.info
~~~~~~~~~~~~~~~~
Complete coverage of international roads and railways.
Since 2000, we offer several photographs, videos and
Virtual 360 demonstrations -- free of charge.
~~~~~~~~~~~~~~~~
********

On Dec 14, 1:43*pm, "Carl Rogers" > wrote:
> Hi Viatologists,
>
> Its one of the most unique interchanges in the Americas. *Less than 15
> kilometres from downtown Buenos Aires, it's a diamond-interchange and
> roundabout all rolled into one:

But it's not the only one of its type to exist in the Americas:

http://maps.google.com/?ie=UTF8&ll=4...01369&t=h&z=17

Froggie

On Dec 14, 12:03*pm, Froggie > wrote:
> On Dec 14, 1:43*pm, "Carl Rogers" > wrote:
>
> > Hi Viatologists,
>
> > Its one of the most unique interchanges in the Americas. *Less than 15
> > kilometres from downtown Buenos Aires, it's a diamond-interchange and
> > roundabout all rolled into one:
>
> But it's not the only one of its type to exist in the Americas:
>
> http://maps.google.com/?ie=UTF8&ll=4...4&spn=0.003994,...
>
> Froggie

Close, but not exactly. If traffic were to scale to levels found in a
world-class city, that freeway would be put in a particularly
dangerous position. Here's why:

From the street, left-turn motorists would merge onto the freeway,
sharing the same lane as those exiting the freeway a few metres
afterwards. A mixture of low-speed and high-speed traffic is not
ideal, which ultimately would cause more traffic jams.

The Buenos Aires design, though more expensive in design, has one
offramp from the carriageway, and one onramp onto it. All motorists
taking the interchange, coming from the freeway or street, would
negotiate travel in an independent set of loops and ramps that avoid
the short merge found on the freeway.

To make a long story short, your freeway does not have the
characteristics of a diamond-interchange. Simply put, there are more
than two offramps and two onramps from the freeway.

Cheers,

Carl Rogers
"Environment first, transportology second"
********
Worldwide Transportation Library (WWTL):
http://wwtl.info
~~~~~~~~~~~~~~~~
Complete coverage of international roads and railways.
Since 2000, we offer several photographs, videos and
Virtual 360 demonstrations -- free of charge.
~~~~~~~~~~~~~~~~
********

On 12/14/2008 3:47 PM, Carl Rogers wrote:
> On Dec 14, 12:03 pm, Froggie > wrote:
>> On Dec 14, 1:43 pm, "Carl Rogers" > wrote:
>>
>>> Its one of the most unique interchanges in the Americas. Less than 15
>>> kilometres from downtown Buenos Aires, it's a diamond-interchange and
>>> roundabout all rolled into one:
>> But it's not the only one of its type to exist in the Americas:
>>
>> http://maps.google.com/?ie=UTF8&ll=4...4&spn=0.003994,...
>>
>> Froggie
>
> Close, but not exactly. If traffic were to scale to levels found in a
> world-class city, that freeway would be put in a particularly
> dangerous position. Here's why:
>
> From the street, left-turn motorists would merge onto the freeway,
> sharing the same lane as those exiting the freeway a few metres
> afterwards. A mixture of low-speed and high-speed traffic is not
> ideal, which ultimately would cause more traffic jams.
>
> The Buenos Aires design, though more expensive in design, has one
> offramp from the carriageway, and one onramp onto it. All motorists
> taking the interchange, coming from the freeway or street, would
> negotiate travel in an independent set of loops and ramps that avoid
> the short merge found on the freeway.
>
> To make a long story short, your freeway does not have the
> characteristics of a diamond-interchange. Simply put, there are more
> than two offramps and two onramps from the freeway.
>
> Cheers,
>
> Carl Rogers

As much as I hate to admit it, Carl is right, for once. The very short
(350' +/-) weaving sections make the one in West Springfield operate
more like a cloverleaf than a diamond. They just made the "left turns"
into right turns followed by 180 degree turns to the left instead of
single 270 degree right turns. but the entry and exit points for all the
"lefts" are in the same locations as they would be in a cloverleaf. It
uses less land area than a cloverleaf, but it has similar operating
characteristics.

--
Paul S. Wolf, PE, FITE mailto Fellow, Institute of Transportation Engineers

Paul S Wolf wrote:

> On 12/14/2008 3:47 PM, Carl Rogers wrote:
>> On Dec 14, 12:03 pm, Froggie > wrote:
>>> On Dec 14, 1:43 pm, "Carl Rogers" > wrote:
>>>
>>>> Its one of the most unique interchanges in the Americas. Less than 15
>>>> kilometres from downtown Buenos Aires, it's a diamond-interchange and
>>>> roundabout all rolled into one:
>>> But it's not the only one of its type to exist in the Americas:
>>>
>>> http://maps.google.com/?ie=UTF8&ll=4...4&spn=0.003994,...
>>>
>>> Froggie
>>
>> Close, but not exactly. If traffic were to scale to levels found in a
>> world-class city, that freeway would be put in a particularly
>> dangerous position. Here's why:
>>
>> From the street, left-turn motorists would merge onto the freeway,
>> sharing the same lane as those exiting the freeway a few metres
>> afterwards. A mixture of low-speed and high-speed traffic is not
>> ideal, which ultimately would cause more traffic jams.
>>
>> The Buenos Aires design, though more expensive in design, has one
>> offramp from the carriageway, and one onramp onto it. All motorists
>> taking the interchange, coming from the freeway or street, would
>> negotiate travel in an independent set of loops and ramps that avoid
>> the short merge found on the freeway.
>>
>> To make a long story short, your freeway does not have the
>> characteristics of a diamond-interchange. Simply put, there are more
>> than two offramps and two onramps from the freeway.
>>
>> Cheers,
>>
>> Carl Rogers
>
> As much as I hate to admit it, Carl is right, for once. The very short
> (350' +/-) weaving sections make the one in West Springfield operate
> more like a cloverleaf than a diamond. They just made the "left turns"
> into right turns followed by 180 degree turns to the left instead of
> single 270 degree right turns. but the entry and exit points for all the
> "lefts" are in the same locations as they would be in a cloverleaf. It
> uses less land area than a cloverleaf, but it has similar operating
> characteristics.
>

Here's one that's all lefts. And even uglier than Springfield.
http://tinyurl.com/5vxmrq

--
Otto Yamamoto

> "Paul S Wolf" > wrote
> As much as I hate to admit it, Carl is right, for once. The very short
> (350' +/-) weaving sections make the one in West Springfield operate more
> like a cloverleaf than a diamond. They just made the "left turns" into
> right turns followed by 180 degree turns to the left instead of single 270
> degree right turns. but the entry and exit points for all the "lefts" are
> in the same locations as they would be in a cloverleaf. It uses less land
> area than a cloverleaf, but it has similar operating characteristics.

The problem with the Buenos Aires interchange is that when turning left from
the surface road, you have to go through four decision points before you're
on the freeway. The Springfield one only has three.

--

Ciao, Paul D. DeRocco
Paul mailto

On Dec 14, 10:28*pm, "Paul D. DeRocco" > wrote:
> > "Paul S Wolf" > wrote
> > As much as I hate to admit it, Carl is right, for once. *The very short
> > (350' +/-) weaving sections make the one in West Springfield operate more
> > like a cloverleaf than a diamond. They just made the "left turns" into
> > right turns followed by 180 degree turns to the left instead of single 270
> > degree right turns. but the entry and exit points for all the "lefts" are
> > in the same locations as they would be in a cloverleaf. *It uses less land
> > area than a cloverleaf, but it has similar operating characteristics.
>
> The problem with the Buenos Aires interchange is that when turning left from
> the surface road, you have to go through four decision points before you're
> on the freeway. The Springfield one only has three.
>
> --
>
> Ciao, * * * * * * * Paul D. DeRocco
> Paul * * * * * * * *mailto

There is one to the West of London, IIRC, that is a gigantic round-
about of five small roundbouts.
I'm sorry that I can't supply a photo. I studied one and it seemed so
simple that just about anyone
could use it, provided they read the signs!

On Dec 16, 3:55 pm, Studemania > wrote:
> On Dec 14, 10:28 pm, "Paul D. DeRocco" > wrote:

> There is one to the West of London, IIRC, that is a gigantic round-
> about of five small roundbouts.
> I'm sorry that I can't supply a photo. I studied one and it seemed so
> simple that just about anyone
> could use it, provided they read the signs!

You must be thinking about the Magic Roundabout in Swindon:
http://maps.google.com/?ll=51.562855,-1.771476&t=k&z=18

There's another variant in the area, with 4 mini-roundabouts in a
square formation. There's a railroad overpass cutting across the
middle, and it's less of a unified whole with a large circular
footprint as in the former case.

http://maps.google.com/?t=k&ll=51.568631,-1.801661&z=18