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Comment by hexator | Hacker News Reader

The article doesn't mention the numerous downsides to pedestrians for diverging diamond interchanges. Four crossing points means a lot more conflict points and a lot more chances for death.

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Four crossing points (two with traffic lights, in this case), whereas for a "normal" interchange, you'd get...also four crossing points.

diverging diamond: https://www.openstreetmap.org/directions?engine=fossgis_osrm...

cloverleaf: https://www.openstreetmap.org/directions?engine=fossgis_osrm...

I dunno, they seem better to me (from experience actually walking across [1], not just looking at pictures on the internet)

The crossing are controlled, distances are relatively short and the cars are only coming from one direction. It's a couple of crossings to get all the way through, but they're easy crossings.

[1] https://maps.app.goo.gl/6SwfTPrnXkUtTyym8?g_st=ic

But each conflict point is crossing only one direction of traffic, and there are no cars turning left or right into the crosswalks (which is huge cause of pedestrian impacts). So even though there are 4 crosswalks, maybe the aggregate danger is less?

It’s just extremely unpleasant as a pedestrian to be in the middle of 55MPH (88km/h) traffic, even if you are separated by concrete barriers, due to all the noise and particulates.

Each individual crossing is also wider if you are staying on the same side of the road. In a traditional diamond you’d be crossing one-lane on and off ramps, not half of one of the major roads each time.

Wouldn't the crossings themselves be safer because the cars are coming from fewer directions? I'd rather have four crossings, each with only one direction to look in, than two where I have to scan a whole intersection.

Roadguyrob has a video detailing this issue. https://youtube.com/watch?v=xlnz04EZpMQ

I don't see why this is unique to a divergent diamond as it only applies to non-light controlled points of conflict of which there are at most two in both designs...

This specific interchange looks superior to both a traditional diamond and a cloverleaf for pedestrians. All crossing points are controlled by a light (unlike a cloverleaf), and you don't have to worry about cars taking an unprotected left-turn into you:

https://www.google.com/maps/@38.8171139,-77.6412514,3a,75y,3...

[edit]

The westbound on-ramp crossing appears to not be protected by a light[1], so would be similar to a cloverleaf onramp; still it's "not bad" as far as non-human-scale interchanges go.

1: https://www.google.com/maps/@38.8191922,-77.6383384,3a,75y,2...

There is one ten mins from me. It is definitely safer for pedestrians and bike riders. It wasn’t built for golf carts (this is Florida) which really chaps people here. But once they got the lights synchronized, the design works really well. There are little to no accidents. We also have two traffic circles that people call murder circles. The main one has high incident of traffic accidents albeit very very minor in terms of damage and almost no injury.

There’s actually fewer crossings involved, so safety for pedestrians should improve as well. But notably these interchanges are often in extremely pedestrian-hostile areas anyway, but it seems more likely that a newly constructed interchange will make at least some attempt to accommodate pedestrians, whereas interchanges built 30+ years ago often ignore pedestrian concerns entirely.

It seems OK as pictured in the article with a dedicated MUP on one side of the formation. There's probably no interchange design for this volume of traffic that will work all that well for pedestrians and cyclists, though.

Anywhere with an intersection this large seems like it is inherently hostile to pedestrians to begin with.

Yeah, that's why it's illegal to walk on the side of highways.

We have an intersection like this just south of Santa Fe, where NM14 intersects I25.

NM14 is not a highway.

But you may want to walk across the highway which is almost always allowed.

Making walking illegal is how you create the car-first culture that we now know the downsides of.

Not everyone agrees that car-first design is a problem.

Not everyone who smokes cigarettes agrees that they are a problem

Amen!

Even without car first culture, you're going to have big roadways meeting at some points, and it doesn't seem particularly smart to have pedestrians mixed in with that.

It's completely legal to walk on the side of one of these two highways (US-15, a.k.a James Madison Highway) there's even an asphalt MUP for just such a purpose.

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