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Do diverging diamonds get built anyplace a person would want to walk? Around here (suburban DC,USA) they’re exclusively used where two massive highways interse

Do diverging diamonds get built anyplace a person would want to walk? Around here (suburban DC,USA) they’re exclusively used where two massive highways intersect. Usually one 6+ lane interstate with a 4+ lane state highway. And the interchange itself is enormous - long, wide, noisy, stinky with fumes. Any pedestrian traffic is carried by a physically separate walking path. Not “local” sidewalks. It’s a very car-centric design. But where the highways already existed, it’s at least a traffic improvement with no reduction in pedestrian access (which was usually nil before the interchange, and improved by addition of separate walkway during construction).

themodelplumber 4y ago
I usually see some not-terrible walking infrastructure around these. Though, having lived in Utah and having dined on I-5 up and down the west coast, the idea of finding oneself walking right over one, as if a car, isn't as far out there as some may believe.
epage 4y ago
In Austin they are putting in diverging diamonds where regular roads intersect the interstate going through town. One of those roads in particular (Parmer Lane), they've been building out its sidewalk on the east side. So it is meant to for local pedestrian traffic except at the diverging diamond.
- Bluestrike2 4y ago
  I was curious and looked it up on Google Maps[0] and that's definitely not a road; it's a six-lane stroad[1] optimized solely for traffic flow. Those are really good at killing pedestrians because people perceive them as being wide open, all but inviting drivers to speed up. I'm guessing the diverging diamond replaced a bridge with two intersections? In which case, the oddity of the diverging diamond might at least serve as a traffic calming measure. Even when you get used to it, switching travel directions is uncomfortable for drivers which can force them to be a bit more cautious. That said, the new sidewalks in the satellite photos are probably a big improvement over the old ones (if there were any). They at least have some small curbs and ~2-4 feet of separation from the cars traveling at high speeds along the stroad. If you look at the sidewalks to the west, where there's no separation from the stroad, they're...well, at least not that? But for the most part, sidewalks alongside stroads are just an afterthought. 0. https://goo.gl/maps/ZytZNN7TumnHqozU9 https://goo.gl/maps/ZytZNN7TumnHqozU9 1. https://en.wikipedia.org/wiki/Stroad https://en.wikipedia.org/wiki/Stroad
- alistairSH 4y ago
  Oh wow, what a mess. That whole area is a pedestrian (and car and bike and ...) nightmare. Yeah, there's a sidewalk, but it's like a square mile of car-centric asphalt wasteland. Even if you don't get Froggered on the frontage road sidewalk or Palmer at-grade crossings, you still have 1000 yards of distracted drivers to dodge in all those parking lots. Oof.
hkwerf 4y ago
I'm not an expert on this topic and while I have spent some time in the US, my experience is limited. The particular case of two highways intersecting is one thing. Go ahead and have your diverging diamond interchange there. However, I don't believe Interstate-Interstate-Crossings are the most common use in the US? See for example https://wsdot.wa.gov/travel/traffic-safety-methods/diverging-diamond-interchange https://wsdot.wa.gov/travel/traffic-safety-methods/diverging.... Three crossings, none are between two interstates? Or am I misreading this? I actually believe it comes down to this: You only need the diverging diamond interchange if you build a highway in tight spaces, such as inside cities. In particular you want them on heavily frequented entries/exits that would otherwise let traffic back up into the cities. Thus, the interchange is at or close to a location with a lot of important destinations, otherwise you wouldn't build it there. Not having that interchange then open to traffic other than cars then clearly makes it harder to cross the highway at these places. You'll have to go up or down each of the roads until you hit an over- or underpass or crossing. In my experience, in the US, this is generally very far - as of course everything is already bigger than in other places because of parking lots.
- alistairSH 4y ago
  You're correct - they aren't typically used for interstate-interstate interchanges (those tend to be far more complicated). Here's a new example that opened a few years ago... https://www.google.com/maps/place/Haymarket,+VA+20169/@38.8176254,-77.6450501,1333m/data=!3m1!1e3!4m6!3m5!1s0x89b66613e8cbf987:0xf898225f4997dc7c!8m2!3d38.8120591!4d-77.6363806!16zL20vMDEwbm1f https://www.google.com/maps/place/Haymarket,+VA+20169/@38.81... It handles the intersection of a busy interstate and a busy local highway/stroad. Here's a new interchange just down the road from the first, same interstate, but even busier highway. Instead of a diverging diamond, it's a bowl of spaghetti. https://www.google.com/maps/@38.848214,-77.4319326,1404m/data=!3m1!1e3 https://www.google.com/maps/@38.848214,-77.4319326,1404m/dat... And the infamous "Springfield Mixing Bowl" that's the bane of suburban DC/VA commuter's existence... https://www.google.com/maps/@38.7874973,-77.1801693,4741m/data=!3m1!1e3 https://www.google.com/maps/@38.7874973,-77.1801693,4741m/da... Two massive interstates, plus interchanges with busy local stroads in close proximity.
hansvm 4y ago
It could be a means to an end. Finding safe bike routes to get from one side of a freeway/river/mountain to the other can be challenging. A few miles on a state highway shoulder aren't an uncommon requirement to make a longer trip feasible. If the diverging diamond isn't paired with a dedicated pedestrian crossing over the freeway then it significantly hampers bike traffic.
- alistairSH 4y ago
  Understood. At least near me, when I cycle, I'll pick a local overpass/underpass instead of using the diverging diamond (when possible). There are usually enough of them to make that work, but there are definitely places where that means riding 5 miles out the way. On the plus side, VA and Fairfax County are doing a better job building bike/ped infrastructure on most new projects. Sometimes what the build makes me scratch my head, but usually it's a welcome addition.

themodelplumber 4y ago

I usually see some not-terrible walking infrastructure around these. Though, having lived in Utah and having dined on I-5 up and down the west coast, the idea of finding oneself walking right over one, as if a car, isn't as far out there as some may believe.

epage 4y ago

In Austin they are putting in diverging diamonds where regular roads intersect the interstate going through town. One of those roads in particular (Parmer Lane), they've been building out its sidewalk on the east side. So it is meant to for local pedestrian traffic except at the diverging diamond.

Bluestrike2 4y ago
I was curious and looked it up on Google Maps[0] and that's definitely not a road; it's a six-lane stroad[1] optimized solely for traffic flow. Those are really good at killing pedestrians because people perceive them as being wide open, all but inviting drivers to speed up. I'm guessing the diverging diamond replaced a bridge with two intersections? In which case, the oddity of the diverging diamond might at least serve as a traffic calming measure. Even when you get used to it, switching travel directions is uncomfortable for drivers which can force them to be a bit more cautious. That said, the new sidewalks in the satellite photos are probably a big improvement over the old ones (if there were any). They at least have some small curbs and ~2-4 feet of separation from the cars traveling at high speeds along the stroad. If you look at the sidewalks to the west, where there's no separation from the stroad, they're...well, at least not that? But for the most part, sidewalks alongside stroads are just an afterthought. 0. https://goo.gl/maps/ZytZNN7TumnHqozU9 https://goo.gl/maps/ZytZNN7TumnHqozU9 1. https://en.wikipedia.org/wiki/Stroad https://en.wikipedia.org/wiki/Stroad
alistairSH 4y ago
Oh wow, what a mess. That whole area is a pedestrian (and car and bike and ...) nightmare. Yeah, there's a sidewalk, but it's like a square mile of car-centric asphalt wasteland. Even if you don't get Froggered on the frontage road sidewalk or Palmer at-grade crossings, you still have 1000 yards of distracted drivers to dodge in all those parking lots. Oof.

hkwerf 4y ago

I'm not an expert on this topic and while I have spent some time in the US, my experience is limited. The particular case of two highways intersecting is one thing. Go ahead and have your diverging diamond interchange there. However, I don't believe Interstate-Interstate-Crossings are the most common use in the US? See for example https://wsdot.wa.gov/travel/traffic-safety-methods/diverging-diamond-interchange https://wsdot.wa.gov/travel/traffic-safety-methods/diverging.... Three crossings, none are between two interstates? Or am I misreading this? I actually believe it comes down to this: You only need the diverging diamond interchange if you build a highway in tight spaces, such as inside cities. In particular you want them on heavily frequented entries/exits that would otherwise let traffic back up into the cities. Thus, the interchange is at or close to a location with a lot of important destinations, otherwise you wouldn't build it there. Not having that interchange then open to traffic other than cars then clearly makes it harder to cross the highway at these places. You'll have to go up or down each of the roads until you hit an over- or underpass or crossing. In my experience, in the US, this is generally very far - as of course everything is already bigger than in other places because of parking lots.

alistairSH 4y ago
You're correct - they aren't typically used for interstate-interstate interchanges (those tend to be far more complicated). Here's a new example that opened a few years ago... https://www.google.com/maps/place/Haymarket,+VA+20169/@38.8176254,-77.6450501,1333m/data=!3m1!1e3!4m6!3m5!1s0x89b66613e8cbf987:0xf898225f4997dc7c!8m2!3d38.8120591!4d-77.6363806!16zL20vMDEwbm1f https://www.google.com/maps/place/Haymarket,+VA+20169/@38.81... It handles the intersection of a busy interstate and a busy local highway/stroad. Here's a new interchange just down the road from the first, same interstate, but even busier highway. Instead of a diverging diamond, it's a bowl of spaghetti. https://www.google.com/maps/@38.848214,-77.4319326,1404m/data=!3m1!1e3 https://www.google.com/maps/@38.848214,-77.4319326,1404m/dat... And the infamous "Springfield Mixing Bowl" that's the bane of suburban DC/VA commuter's existence... https://www.google.com/maps/@38.7874973,-77.1801693,4741m/data=!3m1!1e3 https://www.google.com/maps/@38.7874973,-77.1801693,4741m/da... Two massive interstates, plus interchanges with busy local stroads in close proximity.

hansvm 4y ago

It could be a means to an end. Finding safe bike routes to get from one side of a freeway/river/mountain to the other can be challenging. A few miles on a state highway shoulder aren't an uncommon requirement to make a longer trip feasible. If the diverging diamond isn't paired with a dedicated pedestrian crossing over the freeway then it significantly hampers bike traffic.

alistairSH 4y ago
Understood. At least near me, when I cycle, I'll pick a local overpass/underpass instead of using the diverging diamond (when possible). There are usually enough of them to make that work, but there are definitely places where that means riding 5 miles out the way. On the plus side, VA and Fairfax County are doing a better job building bike/ped infrastructure on most new projects. Sometimes what the build makes me scratch my head, but usually it's a welcome addition.