Improving the Parclo

[tradephoric]

Why no right turn for the "southbound" off-ramp (top-left)?

Can you see if you can compact the interchange size down a bit? Preferably, narrow the arterial a bit. The "eastbound" carriageway could be brought much closer to the "westbound" carriageway without losing functionality.

Hey Jake, I just forgot to add that SB RT movement in that original model .  Here's a "compact" version of the interchange with that movement added.

https://www.youtube.com/watch?v=FMm8c_EIr98

Here's a slight variation of the interchange.  The contraflow lefts are removed and instead traffic utilizes the through lanes along the arterial.  The way traffic is handled on the arterial reminds me of a spread out version of a Florida T intersection.  I realize that in the model some SB off-ramp traffic immediately reenters the NB on-ramp.   In this particular scenario i don't know how to prevent this from occurring in SYNCHRO but just assume they are continuing EB on the arterial!

https://www.youtube.com/watch?v=mYbldq17MSc

The link below is a Florida T intersection similar to the model where the left lane along the arterial is signal controlled while the middle/right lane is free flowing.  This intersection is unique in that there is no separation between the signal controlled lane and the free-flowing lanes along the arterial.  I remember driving through this intersection and always found it odd!  Do other Florida T intersections like this exist?

https://www.google.com/maps/@26.1777026,-81.7999424,3a,61.3y,147.42h,85.65t/data=!3m6!1e1!3m4!1spK2MxCz631G8QzrkQAwpyA!2e0!7i13312!8i6656

[jakeroot]

I've never liked how western states don't stripe stop bars in advance of standard/ladder crosswalks. It's such a clear operational safety deficiency for very little cost benefit.

That's always bothered me as well. In fairness to other Western States, only Oregon and California use one of the crosswalk lines as a stop line. Others use a stop line or zebra markings.

[mrsman]

The link below is a Florida T intersection similar to the model where the left lane along the arterial is signal controlled while the middle/right lane is free flowing.  This intersection is unique in that there is no separation between the signal controlled lane and the free-flowing lanes along the arterial.  I remember driving through this intersection and always found it odd!  Do other Florida T intersections like this exist?

https://www.google.com/maps/@26.1777026,-81.7999424,3a,61.3y,147.42h,85.65t/data=!3m6!1e1!3m4!1spK2MxCz631G8QzrkQAwpyA!2e0!7i13312!8i6656

Here is a better one in Cape Canaveral.  Note that there are cones separating the non-stop right lane and the signal controlled left lane.

I like this arrangement as it allows for some traffic to continue without stopping, even if turning traffic needs to stop one of the lanes so that it can merge in.  Those in the know would drive in the right lane and merge back left to skip the signal.



https://www.google.com/maps/@28.5263445,-80.6925575,3a,75y,270.19h,86.87t/data=!3m6!1e1!3m4!1sKBNlNbpyH2iY11rD71ROHA!2e0!7i13312!8i6656

It even comes with a unique warning sign:

https://www.google.com/maps/@28.5262879,-80.6885463,3a,75y,319.61h,83.62t/data=!3m6!1e1!3m4!1slvumGKSvzuiu3EdrEw88aw!2e0!7i13312!8i6656

[tradephoric]

From a safety perspective, you definitely wouldn't want a driver to accidentally enter the freeway from an off-ramp.  You could make the case that this dangerous scenario would be more likely to occur at a Single-Point Parclo B4 interchange (but I'm sure there is a design that could mitigate the risk). 

A slight variation of the Single Point Parclo B4 that would mitigate the risk of a wrong way driver onto the freeway:

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

[roadfro]

From a safety perspective, you definitely wouldn't want a driver to accidentally enter the freeway from an off-ramp.  You could make the case that this dangerous scenario would be more likely to occur at a Single-Point Parclo B4 interchange (but I'm sure there is a design that could mitigate the risk). 

A slight variation of the Single Point Parclo B4 that would mitigate the risk of a wrong way driver onto the freeway:

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

At that point, you're beginning to take up way more space than a SPUI... Also, not sure why the loop ramp needs to stop with the opposite direction ramps–it could just merge into the arterial.

[jakeroot]

Also, not sure why the loop ramp needs to stop with the opposite direction ramps–it could just merge into the arterial.

Some of the more pedantic agencies prefer signalized ped crossings at right angles instead of merges that require yielding to peds, though I agree a simple add-lane would be sufficient.

[jakeroot]

Ancient thread. But I found a cool Parclo (A4 configuration) in East St Louis, Illinois, that has left-side merges for both off-ramps. Only the northern off-ramp is signalized.

https://www.google.com/maps/@38.6210941,-90.0927823,450m/data=!3m1!1e3

[kphoger]

Ancient thread. But I found a cool Parclo (A4 configuration) in East St Louis, Illinois, that has left-side merges for both off-ramps. Only the northern off-ramp is signalized.

https://www.google.com/maps/@38.6210941,-90.0927823,450m/data=!3m1!1e3

As soon as you said "East St Louis", I knew immediately where that was.  It's the first such left-side merge I remember encountering.  That was back when I ran a delivery route in and around southern Illinois.  I once delivered to the prison at that interchange in 2007 or so, and I remember the interchange from back then.