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Author Topic: California’s first diverging diamond  (Read 258 times)

jander

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California’s first diverging diamond
« on: November 22, 2020, 04:40:05 PM »

The Caltrans video here is great.

https://www.abc10.com/amp/article/news/local/manteca/manteca-diverging-diamond/103-b1ba2174-cbb7-451e-a0d0-06e8e0fe8be5

California's first diverging diamond interchange (DDI) has finally debuted in Manteca.

Other states, like Nevada, have already installed a number of these unique designs over the years, but Manteca just cut the ribbon on on California's first. That being said, drivers will still have to wait until Nov. 25 before they start cruising through it.

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Kniwt

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Re: California’s first diverging diamond
« Reply #1 on: Today at 12:35:09 AM »

The Caltrans video here is great.

Looks pretty, but good grief, that bicycle path is just awful. Serious cyclists will almost certainly stay on the road through the DDI.
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mapman

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Re: California’s first diverging diamond
« Reply #2 on: Today at 01:59:49 AM »

Looks pretty, but good grief, that bicycle path is just awful. Serious cyclists will almost certainly stay on the road through the DDI.

I agree, especially as traffic on the other side of Union Road will need to cross to the other side of the street to use the path.  Yet I guess it's better than providing nothing at all for pedestrians or bicyclists.  That situation would seriously jeopardize pedestrian and bicycle safety.

I assume that this design is unique for how DDIs handle pedestrian and bicycle crossings?
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sparker

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Re: California’s first diverging diamond
« Reply #3 on: Today at 02:13:02 AM »

Looks pretty, but good grief, that bicycle path is just awful. Serious cyclists will almost certainly stay on the road through the DDI.

I agree, especially as traffic on the other side of Union Road will need to cross to the other side of the street to use the path.  Yet I guess it's better than providing nothing at all for pedestrians or bicyclists.  That situation would seriously jeopardize pedestrian and bicycle safety.

I assume that this design is unique for how DDIs handle pedestrian and bicycle crossings?

Got to head up to Galt on business early next month; will get off 120 and check out the interchange on the way.  Be interested to see if & how the actual interchange landscaping varies from the model/depiction shown.  I'm a DDI "virgin", so using it will be a totally new driving experience; looking forward to it!
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heynow415

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Re: California’s first diverging diamond
« Reply #4 on: Today at 12:47:26 PM »

Looks pretty, but good grief, that bicycle path is just awful. Serious cyclists will almost certainly stay on the road through the DDI.

I agree, especially as traffic on the other side of Union Road will need to cross to the other side of the street to use the path.  Yet I guess it's better than providing nothing at all for pedestrians or bicyclists.  That situation would seriously jeopardize pedestrian and bicycle safety.

I assume that this design is unique for how DDIs handle pedestrian and bicycle crossings?

I've seen/been through several of these in Utah and they seem to work well for cars.  In this design for bikes and peds it's a mixed bag:  it does provide completely grade separated passage through the interchange but the sweeping loops add considerable distance and for those going in the other direction they would need to cross the boulevard twice to get to/from the path.  On the plus side for peds, stairways were included so one could use those if they didn't want to walk around the two loops. 

If the multiuse path continues along the boulevard in both directions then that would be better but otherwise you're still confronted with the similar situation of how to transition a two-way bikeway on one side of the street to bike lanes/sidepaths on each side.  I have seen some DD designs where the sidewalks/bike lanes continue up to the point of the first signal, cross over the opposing traffic lanes with the cars, continue across the overpass in the "median" and return to their respective sides after the second signal.  This has the benefit of being more direct and following vehicle flow through the interchange but it still requires crossing the ramps (off ramps are signal controlled but "free right" onramps approaching the interchange are not) which for kids, novice riders, and less agile pedestrians would likely be a bit too intense to be usable for them.  It also introduces the need to factor in ped crossing times for signal phasing which, since the crossings are more diagonal, would increase clearance times.  Will be curious to see how this one works since it would likely be a template for future installations.
« Last Edit: Today at 01:03:29 PM by heynow415 »
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skluth

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Re: California’s first diverging diamond
« Reply #5 on: Today at 06:05:55 PM »

Looks pretty, but good grief, that bicycle path is just awful. Serious cyclists will almost certainly stay on the road through the DDI.

I agree, especially as traffic on the other side of Union Road will need to cross to the other side of the street to use the path.  Yet I guess it's better than providing nothing at all for pedestrians or bicyclists.  That situation would seriously jeopardize pedestrian and bicycle safety.

I assume that this design is unique for how DDIs handle pedestrian and bicycle crossings?

I've seen/been through several of these in Utah and they seem to work well for cars.  In this design for bikes and peds it's a mixed bag:  it does provide completely grade separated passage through the interchange but the sweeping loops add considerable distance and for those going in the other direction they would need to cross the boulevard twice to get to/from the path.  On the plus side for peds, stairways were included so one could use those if they didn't want to walk around the two loops. 

If the multiuse path continues along the boulevard in both directions then that would be better but otherwise you're still confronted with the similar situation of how to transition a two-way bikeway on one side of the street to bike lanes/sidepaths on each side.  I have seen some DD designs where the sidewalks/bike lanes continue up to the point of the first signal, cross over the opposing traffic lanes with the cars, continue across the overpass in the "median" and return to their respective sides after the second signal.  This has the benefit of being more direct and following vehicle flow through the interchange but it still requires crossing the ramps (off ramps are signal controlled but "free right" onramps approaching the interchange are not) which for kids, novice riders, and less agile pedestrians would likely be a bit too intense to be usable for them.  It also introduces the need to factor in ped crossing times for signal phasing which, since the crossings are more diagonal, would increase clearance times.  Will be curious to see how this one works since it would likely be a template for future installations.

I didn't comment originally, because I didn't know what to make of the bike path other than I hated it. I've only seen a few DDIs. I used the one at Dorsett Road and I-270 in the NW St Louis suburbs a lot because my uncle lived just off the highway when I lived there. The sidewalks there follow the typical path and don't go into the median. This interchange in St Peters MO serves a suburban/exurban mall and surrounding commercial businesses. There is only a walk on the west side of the roadway which switches to the median over the bridge, but honestly I'm not sure I've seen a pedestrian outside the parking lots the few times I've been to the Mid Rivers Area. I prefer both Missouri solutions over Union Road.
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