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JKRhodes:
I'm trying to understand the rationale behind this "hybrid SPUI" at PDN and 2nd Street. There certainly doesn't seem to be any savings in ROW vs a standard SPUI. If anything it appears to take up more:

https://goo.gl/maps/NAQ6UUpRP5dErPkX7

Plutonic Panda:
And it has left exits yuck

JKRhodes:

--- Quote from: Plutonic Panda on July 05, 2021, 10:52:16 PM ---And it has left exits yuck

--- End quote ---
My main gripe. Upon further study it seems  they may have designed it that way in order to buy a few extra car lengths of queue space for SB 2nd street approaching El Pueblo. Still, very odd. Based on each iteration of street view it doesn't look heavily traveled enough to routinely back up into the SPUI, and there are pylons to eliminate weaving. So a standard SPUI would have probably served its purpose just fine.

abqtraveler:

--- Quote from: JKRhodes on July 05, 2021, 11:12:13 PM ---
--- Quote from: Plutonic Panda on July 05, 2021, 10:52:16 PM ---And it has left exits yuck

--- End quote ---
My main gripe. Upon further study it seems  they may have designed it that way in order to buy a few extra car lengths of queue space for SB 2nd street approaching El Pueblo. Still, very odd. Based on each iteration of street view it doesn't look heavily traveled enough to routinely back up into the SPUI, and there are pylons to eliminate weaving. So a standard SPUI would have probably served its purpose just fine.

--- End quote ---

Using historicaerials.com to view the PDN/2nd Street interchange, it was previously an at-grade intersection that was converted to the current interchange some time between 1991 and 1996. My theory into why they built it the way they did is they had to keep the existing intersection open and unobstructed while construction of the interchange proceeded. You'll notice that the EB and WB left-hand offramps both intersect 2nd Street at the same point where the previous at-grade intersection used to lie. From that, it looks like they built the overpasses outside of the existing intersection to keep the intersection and its approaches unimpeded during construction. When the overpasses were completed, it would be relatively easy to shift PDN traffic onto the new overpasses, and then convert the old PDN roadway to the offramps you see today. 

It's not necessarily how I would have built the interchange, but I can see the logic in the design...it was all about maintaining traffic flow through the intersection while the interchange was being built. 

triplemultiplex:

--- Quote from: abqtraveler on July 05, 2021, 11:41:38 PM ---Using historicaerials.com to view the PDN/2nd Street interchange, it was previously an at-grade intersection that was converted to the current interchange some time between 1991 and 1996. My theory into why they built it the way they did is they had to keep the existing intersection open and unobstructed while construction of the interchange proceeded. You'll notice that the EB and WB left-hand offramps both intersect 2nd Street at the same point where the previous at-grade intersection used to lie. From that, it looks like they built the overpasses outside of the existing intersection to keep the intersection and its approaches unimpeded during construction. When the overpasses were completed, it would be relatively easy to shift PDN traffic onto the new overpasses, and then convert the old PDN roadway to the offramps you see today.
--- End quote ---

This has always been my assumption as well.  It was the result of someone's poor planning in terms of construction staging.
Everyone knows that to build a single point interchange under traffic, you rough in the ramps first, shift the traffic over to the ramps, and then build your bridges in the 'median'.  Once the bridges are done, traffic is shifted there, then you clean up the ramps and voila: completed SPUI.

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