California

[bing101]

Here is a tour of the I-5 Widening project.

[TheStranger]

There is an update on the I-5 widening from Streetsblog. You may not like the commentary, but the timeline and the documents are informative: https://la.streetsblog.org/2020/10/29/documents-show-metro-drastically-increased-605-5-freeway-widening/

Since the overpass will get rebuilt anyway, why not use a SPUI instead?

It looks like Caltrans only has partial cloverleaf and diamond interchanges in their design books.

Could this be a district preference sort of thing?  In San Jose, there are two or so SPUIs along the Guadalupe Parkway (Route 87) north of downtown.

SAMSUNG-SM-G930A

[jrouse]

Since the overpass will get rebuilt anyway, why not use a SPUI instead?

It looks like Caltrans only has partial cloverleaf and diamond interchanges in their design books.

The SPUI is not a preferred alternative for interchange design in California because it is a bit more costly and it also does not accommodate bicyclists and pedestrians very well.  It is more "car-centric"  and Caltrans is trying to be more ped and bike friendly in its designs.  A better alternative might be the diverging diamond interchange.  I know there were proposals for several DDIs on I-710 as part of the plans for that corridor.  I can't speak as to why DDIs are not an option for I-605. 

[roadfro]

Since the overpass will get rebuilt anyway, why not use a SPUI instead?

It looks like Caltrans only has partial cloverleaf and diamond interchanges in their design books.

The SPUI is not a preferred alternative for interchange design in California because it is a bit more costly and it also does not accommodate bicyclists and pedestrians very well.  It is more "car-centric"  and Caltrans is trying to be more ped and bike friendly in its designs.  A better alternative might be the diverging diamond interchange.  I know there were proposals for several DDIs on I-710 as part of the plans for that corridor.  I can't speak as to why DDIs are not an option for I-605.

I acknowledge that SPUIs typically necessitate a wider/longer structure, so understand the cost factor. But could you elaborate on how a SPUI is not accommodating to bicyclists and pedestrians? Seems like it would have the same number of conflict points for bikes and same number of pedestrian crossings (signalized or not) when compared to a standard diamond with right turn slip lanes onto the freeway. Only thing I can think of is it's a large intersection to cross, which may initiate conflict if a bicyclist enters later in the arterial green.

DDIs do save on that cost factor. I've seen commentary that the center-running sidewalks are not as pedestrian friendly (and can be less intuitive for people with low vision ability).

[SeriesE]

Since the overpass will get rebuilt anyway, why not use a SPUI instead?

It looks like Caltrans only has partial cloverleaf and diamond interchanges in their design books.

The SPUI is not a preferred alternative for interchange design in California because it is a bit more costly and it also does not accommodate bicyclists and pedestrians very well.  It is more "car-centric"  and Caltrans is trying to be more ped and bike friendly in its designs.  A better alternative might be the diverging diamond interchange.  I know there were proposals for several DDIs on I-710 as part of the plans for that corridor.  I can't speak as to why DDIs are not an option for I-605.

I wonder if the more costly structure is offset by the reduced cost in property acquisitions for urban situations, like this Lakewood Blvd interchange?

[jakeroot]

There is an update on the I-5 widening from Streetsblog. You may not like the commentary, but the timeline and the documents are informative: https://la.streetsblog.org/2020/10/29/documents-show-metro-drastically-increased-605-5-freeway-widening/

Since the overpass will get rebuilt anyway, why not use a SPUI instead?

It looks like Caltrans only has partial cloverleaf and diamond interchanges in their design books.

SPUIs have capacity limitations because of their three-phase designs. The partial cloverleafs proposed by Caltrans have much higher capacity.

I don't fully understand some of their decisions. For example, on the southside of the 5, they've designed the ramps to all start at one intersection. This isn't necessary for A4 parclos. Here, it makes the ramp through Dennis the Menace Park much straighter and more destructive than it needs to be.

For the other proposal, why does the on-ramp loop on the north side become so elongated, but remains more circular in the other proposal? More needless ROW acquisition, it seems.

If it were up to me, I'd design the northbound to southbound ramp to become less destructive to the park, and keep the northbound to northbound loop more circular.

[STLmapboy]

Here's a cool video on Caltrans wrong-way signs and two-way pavement reflectors.

https://www.youtube.com/watch?v=0tcgZlYNUus&ab_channel=CaltransVideo

[SeriesE]

There is an update on the I-5 widening from Streetsblog. You may not like the commentary, but the timeline and the documents are informative: https://la.streetsblog.org/2020/10/29/documents-show-metro-drastically-increased-605-5-freeway-widening/

Since the overpass will get rebuilt anyway, why not use a SPUI instead?

It looks like Caltrans only has partial cloverleaf and diamond interchanges in their design books.

SPUIs have capacity limitations because of their three-phase designs. The partial cloverleafs proposed by Caltrans have much higher capacity.

I don't fully understand some of their decisions. For example, on the southside of the 5, they've designed the ramps to all start at one intersection. This isn't necessary for A4 parclos. Here, it makes the ramp through Dennis the Menace Park much straighter and more destructive than it needs to be.

For the other proposal, why does the on-ramp loop on the north side become so elongated, but remains more circular in the other proposal? More needless ROW acquisition, it seems.

If it were up to me, I'd design the northbound to southbound ramp to become less destructive to the park, and keep the northbound to northbound loop more circular.

Since the concern here is the large number of properties affected, the interchange design with moderate capacity but least right of way required should be the preferred design. SPUI or DDI both fits these requirements.

[jrouse]

Since the overpass will get rebuilt anyway, why not use a SPUI instead?

It looks like Caltrans only has partial cloverleaf and diamond interchanges in their design books.

SPUIs have capacity limitations because of their three-phase designs. The partial cloverleafs proposed by Caltrans have much higher capacity.

I don't fully understand some of their decisions. For example, on the southside of the 5, they've designed the ramps to all start at one intersection. This isn't necessary for A4 parclos. Here, it makes the ramp through Dennis the Menace Park much straighter and more destructive than it needs to be.

For the other proposal, why does the on-ramp loop on the north side become so elongated, but remains more circular in the other proposal? More needless ROW acquisition, it seems.

If it were up to me, I'd design the northbound to southbound ramp to become less destructive to the park, and keep the northbound to northbound loop more circular.

Keep in mind that these ramps are going to be metered and they need adequate storage to keep traffic contained on the ramp.  That is probably why they are designed the way they are.  Ramp metering is another challenge with SPUIs and DDIs because the ramps cannot always be designed to handle the storage needs. 

[skluth]

Since the overpass will get rebuilt anyway, why not use a SPUI instead?

It looks like Caltrans only has partial cloverleaf and diamond interchanges in their design books.

The SPUI is not a preferred alternative for interchange design in California because it is a bit more costly and it also does not accommodate bicyclists and pedestrians very well.  It is more "car-centric"  and Caltrans is trying to be more ped and bike friendly in its designs.  A better alternative might be the diverging diamond interchange.  I know there were proposals for several DDIs on I-710 as part of the plans for that corridor.  I can't speak as to why DDIs are not an option for I-605.

I acknowledge that SPUIs typically necessitate a wider/longer structure, so understand the cost factor. But could you elaborate on how a SPUI is not accommodating to bicyclists and pedestrians? Seems like it would have the same number of conflict points for bikes and same number of pedestrian crossings (signalized or not) when compared to a standard diamond with right turn slip lanes onto the freeway. Only thing I can think of is it's a large intersection to cross, which may initiate conflict if a bicyclist enters later in the arterial green.

DDIs do save on that cost factor. I've seen commentary that the center-running sidewalks are not as pedestrian friendly (and can be less intuitive for people with low vision ability).

Webinar with FHA slides describing pedestrian/highway conflicts. SPUI starts on page 26. Traveling along the road crossing the freeway takes time and involves four crossings, but can be done. The main conflict, which is crossing the road itself anywhere near the interchange, can be seen on page 43. It doesn't discuss DDIs.

[jakeroot]

Since the overpass will get rebuilt anyway, why not use a SPUI instead?

It looks like Caltrans only has partial cloverleaf and diamond interchanges in their design books.

SPUIs have capacity limitations because of their three-phase designs. The partial cloverleafs proposed by Caltrans have much higher capacity.

I don't fully understand some of their decisions. For example, on the southside of the 5, they've designed the ramps to all start at one intersection. This isn't necessary for A4 parclos. Here, it makes the ramp through Dennis the Menace Park much straighter and more destructive than it needs to be.

For the other proposal, why does the on-ramp loop on the north side become so elongated, but remains more circular in the other proposal? More needless ROW acquisition, it seems.

If it were up to me, I'd design the northbound to southbound ramp to become less destructive to the park, and keep the northbound to northbound loop more circular.

Keep in mind that these ramps are going to be metered and they need adequate storage to keep traffic contained on the ramp.  That is probably why they are designed the way they are.  Ramp metering is another challenge with SPUIs and DDIs because the ramps cannot always be designed to handle the storage needs.

I see. Thank you for the explanation.

My major concern would actually be with the right turn on-ramp from northbound to southbound. I can understand having to redesign loops, especially if that loop has to accommodate more cars if another ramp is not built, but the slip lane ramp as designed has less capacity than if it were curved (which could begin as a single lane for the pedestrian crossing, and then widen to two or three lanes). I can understand the pedestrian argument as well, although a more curved design that begins prior to the off-ramp signal (for "A4 Parclos") isn't an uncommon design in California (westbound Jeffrey Ave to northbound 5 fwy in Irvine as an example), and I don't have any reason to believe the design is even slightly worse than a regular right turn. At least majorly.

Here is a drawing showing a similar on-ramp here in WA compared to how it could be curved to make it longer. The blue lines represent roughly where the extra length is:

[skluth]

Since the overpass will get rebuilt anyway, why not use a SPUI instead?

It looks like Caltrans only has partial cloverleaf and diamond interchanges in their design books.

SPUIs have capacity limitations because of their three-phase designs. The partial cloverleafs proposed by Caltrans have much higher capacity.

I don't fully understand some of their decisions. For example, on the southside of the 5, they've designed the ramps to all start at one intersection. This isn't necessary for A4 parclos. Here, it makes the ramp through Dennis the Menace Park much straighter and more destructive than it needs to be.

For the other proposal, why does the on-ramp loop on the north side become so elongated, but remains more circular in the other proposal? More needless ROW acquisition, it seems.

If it were up to me, I'd design the northbound to southbound ramp to become less destructive to the park, and keep the northbound to northbound loop more circular.

Keep in mind that these ramps are going to be metered and they need adequate storage to keep traffic contained on the ramp.  That is probably why they are designed the way they are.  Ramp metering is another challenge with SPUIs and DDIs because the ramps cannot always be designed to handle the storage needs.

I see. Thank you for the explanation.

My major concern would actually be with the right turn on-ramp from northbound to southbound. I can understand having to redesign loops, especially if that loop has to accommodate more cars if another ramp is not built, but the slip lane ramp as designed has less capacity than if it were curved (which could begin as a single lane for the pedestrian crossing, and then widen to two or three lanes). I can understand the pedestrian argument as well, although a more curved design that begins prior to the off-ramp signal (for "A4 Parclos") isn't an uncommon design in California (westbound Jeffrey Ave to northbound 5 fwy in Irvine as an example), and I don't have any reason to believe the design is even slightly worse than a regular right turn. At least majorly.

Here is a drawing showing a similar on-ramp here in WA compared to how it could be curved to make it longer. The blue lines represent roughly where the extra length is:

You don't understand the pedestrian argument. Your desire for a smoother curve is incredibly dangerous for pedestrians. Just because you've seen it elsewhere doesn't make it less dangerous. This isn't a freeway-to-freeway connection where you are trying to maintain high speeds. I see no advantage to a smoother curve there other than it's more fun to drive because drivers can test how fast they can take the curve.

[jakeroot]

You don't understand the pedestrian argument. Your desire for a smoother curve is incredibly dangerous for pedestrians. Just because you've seen it elsewhere doesn't make it less dangerous. This isn't a freeway-to-freeway connection where you are trying to maintain high speeds. I see no advantage to a smoother curve there other than it's more fun to drive because drivers can test how fast they can take the curve.

The smoother curve would allow for more ramp meter storage capacity, an issue raised by jrouse as being one of the reasons on-ramps are sometimes designed to be longer than necessary or positioned more strangely than a traditional non-metered ramp.

Here's my preferred design (1): https://goo.gl/maps/KsNkXK165Y1VBt2VA (in nearby Irvine)
Here's the Caltrans design (2): https://goo.gl/maps/qF1RrPcdHYixbhj58 (example from WA)

Design (1) is the type preferred by Caltrans by a large margin, whereas design (2) is less common and largely used when there are bus stations on the ramps or to allow oversize/overweight vehicles to safely proceed through the interchange without using the mainline carriageway.

The pedestrian argument is there. However, I feel it is primarily a case of "perception of danger" over actual danger. The general perception is that free-flow (either yield or add-lane) movements are considered dangerous, irrespective of their design, and that right turns via signals are far safer. I feel this is a gross generalization, and that free-flow movements can actually be far superior:

(1) free flow movements are typically single-lane yield situations, much like right turns via a signal;
(2) it is easier to incorporate signage for a free-flow crossing where drivers and pedestrians meet at right or shallower angles;
(3) signalized crossings are much longer, as the intersection must have a large enough corner radius to allow right turns for larger vehicles (note length of crossing in #1 vs #2);
(4) right turns, especially those onto an on-ramp that is busy, can sometimes turn into double turns as drivers attempt to fill both lanes of a meter or access an HOV lane;
(5) turns onto a ramp with no other interfering movements (left turns, primarily) often turn into "California stop" situations where drivers barely observe the red light (it's not "protecting" them from anything);
(5.5) related to above, these signalized right turns cannot use green arrows because the on-ramp typically has a straight-ahead option. This reduces driver obedience of red lights.

The best setup, in my mind, is free-flow ramps with part-time signalized crossings (RRFBs, HAWKs, the standard LADOT flashing red crossing, etc). They have the highest traffic capacity as is often desired by DOTs thanks to their more gradual curves, but pedestrians can still have full protection if they so desire. It would be superior to a standard right turn because the crossing would be shorter, with the shorter minimum walk time allowing easier adaption into a coordinated corridor. As well, an RYG signal (as opposed to an RRFB setup) would not allow movements on red like at signalized right turns, as the crossing is more straight-on than a right turn. This is better for pedestrians, as they can cross without fear of traffic turning into them as they might at a traditional intersection with a "right turn yield to pedestrians on green" setup (the setup at the proposed Lakewood Blvd interchange).

From an urban design perspective, free-flow crossings also break up the intersection a bit, into more manageable "chunks", versus the more typical huge intersection with extraordinarily-long crossings that you see across LA (which aren't exactly bastions of safety anyways); these large intersections also have very long pedestrian walk cycles, resulting in the pedestrian phase being activated only when called for. Shorter crossings (this off-ramp for instance) can institute automatic walk phasing without destroying traffic flow. They would compliment the other crossings to the point where the "average" pedestrian could proceed through the entire intersection without hitting any beg buttons (a feature that Caltrans would certainly implement at an upgraded Lakewood Blvd interchange). Pedestrians with disabilities could activate the part-time crossings and would be afforded full protection without worrying about traffic turning or moving on red.

I'm not trying to craft together some Goldilocks scenario here, but it is incorrect to assume that "free flow" movements are always inferior to right turns.

[roadfro]

Since the overpass will get rebuilt anyway, why not use a SPUI instead?

It looks like Caltrans only has partial cloverleaf and diamond interchanges in their design books.

The SPUI is not a preferred alternative for interchange design in California because it is a bit more costly and it also does not accommodate bicyclists and pedestrians very well.  It is more "car-centric"  and Caltrans is trying to be more ped and bike friendly in its designs.  A better alternative might be the diverging diamond interchange.  I know there were proposals for several DDIs on I-710 as part of the plans for that corridor.  I can't speak as to why DDIs are not an option for I-605.

I acknowledge that SPUIs typically necessitate a wider/longer structure, so understand the cost factor. But could you elaborate on how a SPUI is not accommodating to bicyclists and pedestrians? Seems like it would have the same number of conflict points for bikes and same number of pedestrian crossings (signalized or not) when compared to a standard diamond with right turn slip lanes onto the freeway. Only thing I can think of is it's a large intersection to cross, which may initiate conflict if a bicyclist enters later in the arterial green.

DDIs do save on that cost factor. I've seen commentary that the center-running sidewalks are not as pedestrian friendly (and can be less intuitive for people with low vision ability).

Webinar with FHA slides describing pedestrian/highway conflicts. SPUI starts on page 26. Traveling along the road crossing the freeway takes time and involves four crossings, but can be done. The main conflict, which is crossing the road itself anywhere near the interchange, can be seen on page 43. It doesn't discuss DDIs.

Okay, I guess that's valid. But perhaps another question would be why a pedestrian would need to cross the road at the SPUI? In many cases, SPUIs are situated between closely-adjacent signalized intersections where crossing is more likely to occur (making crossing in between at the SPUI itself irrelevant/unnecessary). The FHWA slides do mention nearby crossings and two-stage crossing as alternatives if that crossing movement is actually needed.

[skluth]

Since the overpass will get rebuilt anyway, why not use a SPUI instead?

It looks like Caltrans only has partial cloverleaf and diamond interchanges in their design books.

The SPUI is not a preferred alternative for interchange design in California because it is a bit more costly and it also does not accommodate bicyclists and pedestrians very well.  It is more "car-centric"  and Caltrans is trying to be more ped and bike friendly in its designs.  A better alternative might be the diverging diamond interchange.  I know there were proposals for several DDIs on I-710 as part of the plans for that corridor.  I can't speak as to why DDIs are not an option for I-605.

I acknowledge that SPUIs typically necessitate a wider/longer structure, so understand the cost factor. But could you elaborate on how a SPUI is not accommodating to bicyclists and pedestrians? Seems like it would have the same number of conflict points for bikes and same number of pedestrian crossings (signalized or not) when compared to a standard diamond with right turn slip lanes onto the freeway. Only thing I can think of is it's a large intersection to cross, which may initiate conflict if a bicyclist enters later in the arterial green.

DDIs do save on that cost factor. I've seen commentary that the center-running sidewalks are not as pedestrian friendly (and can be less intuitive for people with low vision ability).

Webinar with FHA slides describing pedestrian/highway conflicts. SPUI starts on page 26. Traveling along the road crossing the freeway takes time and involves four crossings, but can be done. The main conflict, which is crossing the road itself anywhere near the interchange, can be seen on page 43. It doesn't discuss DDIs.

Okay, I guess that's valid. But perhaps another question would be why a pedestrian would need to cross the road at the SPUI? In many cases, SPUIs are situated between closely-adjacent signalized intersections where crossing is more likely to occur (making crossing in between at the SPUI itself irrelevant/unnecessary). The FHWA slides do mention nearby crossings and two-stage crossing as alternatives if that crossing movement is actually needed.

I used this interchange daily for several years when I lived in St Louis. I don't recall any pedestrians crossing between Rusty Road and I-55 west of the interchange; I frequently saw foot traffic between the former Toys R Us/ JoAnn Fabrics and Marshall's, etc. It a dangerous area generally; I can't tell you how many near-miss accidents (along with a few actual accidents) I saw at the Lindbergh/ Crescent Drive intersection from the cross-traffic. This SPUI on I-70 at Florissant Road also has pedestrian issues north of the interchange. The other STL SPUIs are better and like you describe or have other strategies to mitigate pedestrian conflicts.

[roadfro]

MOD NOTE: I split off the few posts about wrong-way driver warning systems and moved that over to the Traffic Control board at Wrong-way driver warning systems, as I thought it might generate some broader discussion there. –Roadfro

[TJS23]

With the first Winter Storm Warning in the Sierra's this weekend, is that all she wrote for the 4,108, and 120 passes?

[Max Rockatansky]

With the first Winter Storm Warning in the Sierra's this weekend, is that all she wrote for the 4,108, and 120 passes?

Yes, and 89 over Monitor Pass. 

[sparker]

With the first Winter Storm Warning in the Sierra's this weekend, is that all she wrote for the 4,108, and 120 passes?

Yes, and 89 over Monitor Pass. 

Definitely -- and I remember the days when Carson (88) and Luther (89 up to Tahoe) were included in that group until the late '60's; in those days the only winter road access to Alpine County was through NV!

[Max Rockatansky]

With the first Winter Storm Warning in the Sierra's this weekend, is that all she wrote for the 4,108, and 120 passes?

Yes, and 89 over Monitor Pass. 

Definitely -- and I remember the days when Carson (88) and Luther (89 up to Tahoe) were included in that group until the late '60's; in those days the only winter road access to Alpine County was through NV!

It is kind of interesting to me to see how big of a deal that road over Monitor Pass was in the early 20th Century in terms of getting a direct road between Bridgeport and Markleeville.  The latter had not declined so much over the 20th Century I would venture a guess that there would be a greater push to keep Monitor open all year.

[TheStranger]

With the first Winter Storm Warning in the Sierra's this weekend, is that all she wrote for the 4,108, and 120 passes?

Yes, and 89 over Monitor Pass.

This past week, me and my friend actually got to do 120, 108, 88 and 50.  We were planning on going up 4 but that closed Friday morning.

SAMSUNG-SM-G930A

[Max Rockatansky]

With the first Winter Storm Warning in the Sierra's this weekend, is that all she wrote for the 4,108, and 120 passes?

Yes, and 89 over Monitor Pass.

This past week, me and my friend actually got to do 120, 108, 88 and 50.  We were planning on going up 4 but that closed Friday morning.

SAMSUNG-SM-G930A

I got 4, 89, and 108 in on a single day a back in September.  I did Tioga the week prior and planned for Sherman Pass but the Golden Trout fire started around then.  We bailed from Tahoe this weekend (I wanted to check out the new Bridge on US 50 over Echo Summit) because the snow was going to negate the plans to do some cycling.

[Plutonic Panda]

The CTC allocated a couple billion in funding to some small town/local projects and some bigger freeway projects detailed in the last pages of these links:

https://catc.ca.gov/-/media/ctc-media/documents/programs/senate-bill-1/tcep/recommendation/2020-trade-corridors-enhancement-program-staff-recommendations-111620.pdf

https://catc.ca.gov/-/media/ctc-media/documents/programs/sccp/recommendation/2020-solutions-for-congested-corridors-program-staff-recommendations-111620-a11y.pdf

I'm particularly interested in the 105 HO/T lanes. I really hope they expand the freeways lanes adding one each way making for two HO/T lanes in each direction. Unfortunately they voted out and alternative that would have widened the freeway's footprint allowing for full standards so any improvement would likely be substandard but I would rather have more lanes and no shoulder.

[mapman]

The CTC allocated a couple billion in funding to some small town/local projects and some bigger freeway projects detailed in the last pages of these links:

https://catc.ca.gov/-/media/ctc-media/documents/programs/senate-bill-1/tcep/recommendation/2020-trade-corridors-enhancement-program-staff-recommendations-111620.pdf

https://catc.ca.gov/-/media/ctc-media/documents/programs/sccp/recommendation/2020-solutions-for-congested-corridors-program-staff-recommendations-111620-a11y.pdf

I'm particularly interested in the 105 HO/T lanes. I really hope they expand the freeways lanes adding one each way making for two HO/T lanes in each direction. Unfortunately they voted out and alternative that would have widened the freeway's footprint allowing for full standards so any improvement would likely be substandard but I would rather have more lanes and no shoulder.

I'm happy to see that US 101/SR 25 and SR 156/Castroville Boulevard interchanges are finally getting funding.  Those are much needed interchange improvements in southern Santa Clara and northern Monterey Counties.   

[Plutonic Panda]

Indeed! This was a pretty good round of funding I must say. I am pleased with a lot of the projects.