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witty_username , (edited )

I don't get the diverging diamond interchanges one

Lux ,

Diverging diamond interchanges are a type of road intersection that appears very chaotic from the outside, but are actually pretty simple and safe to navigate

Silentiea ,
@Silentiea@lemmy.blahaj.zone avatar

Significantly safer to navigate in practice than traditional intersections, and very straightforward to navigate, if not quite as easy as a normal intersection you've seen all your life.

waz , (edited )

Never heard of or seen that, but it makes me think of the ‘magic roundabout’ concept

https://feddit.uk/pictrs/image/90fa7c4b-9992-4e09-a447-f52006a0a703.jpeg

https://feddit.uk/pictrs/image/2e2f47f3-9220-4b73-aea9-4736e597eabf.jpeg

eksb ,
@eksb@programming.dev avatar

Diverging diamonds are great if your only consideration is car throughput.

If you are considering people walking or riding bicycles, they are shit.

Lux ,

I hadn't considered that. I was still pretty car-brained when i watched the cgp grey video on them, but now that you mention it, i definitely agree

eksb , (edited )
@eksb@programming.dev avatar

This is expensive to address because you have to separate cyclists out to the right before the right car lane splits for right turns before the crossover. And then you have to build a bridge or tunnel for cyclists and pedestrians. On each side.

Really, any road busy enough to justify a diverging diamond probably already needed separated bike lanes. But in America (motto: "If you aren't in a car, you don't matter"), there almost certainly was not any cycling infrastructure there before.

There is one of these near me. Their solution for pedestrians is to make them cross the high speed outer lanes four times (where drivers are encouraged to not slow down). Their solution for cyclists is take the lane and pray or get off and do what the pedestrians have to do.

Edited for clarity: pedestrians cross four times, not drivers are encouraged to not slow down four times.

Lux ,

where drivers are encouraged to not slow down FOUR times

Wtf, thats insane

eksb ,
@eksb@programming.dev avatar

To be clear, it is four times that pedestrians have to cross, not four times that drivers are encouraged to not slow down. Drivers are not explicitly encouraged to not slow down, but the point of the diverging diamond is to make drivers not have to slow down.

Lux ,

Ohhh, thanks for the clarification 😅

Oinks ,
@Oinks@lemmy.blahaj.zone avatar

It doesn't help that US diverging diamonds seem to insist on having pedestrians walk through the median.

But honestly all interchanges are varying degrees of horrible and if you want your city to be bearable to navigate as a pedestrian/cyclist you just really don't want to do urban highways, or roads above a certain size in general.

stebo02 ,
@stebo02@lemmy.dbzer0.com avatar

https://lemmy.dbzer0.com/pictrs/image/c4994008-cf46-4d04-b89b-794ad8271354.jpeg

Having to stop for a stoplight twice just to go straight? No thx.

Badabinski ,

There are many of these where I live. The lights are usually timed so that you just go straight through without having to stop. They're much better than the traditional intersections that came before.

I will absolutely concede that they're shitty for pedestrians or cyclists, however.

BearOfaTime ,

The ones I've used time the pedestrian lights with the traffic, so it's safer for them. Still tricky for peds going across turn lanes.

Silentiea ,
@Silentiea@lemmy.blahaj.zone avatar

They're usually built over a motorway where there was already two stoplights just to go straight, so ...

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