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4 ways stops should be roundabouts, but the US is allergic to them for some reason.
by XorNot 9mo ago
4 ways stops should be roundabouts, but the US is allergic to them for some reason.
- cucumber3732842 9mo agoRoundabouts excel when traffic volumes on the intersecting are comparable. They are crap when traffic volumes are highly disparate
- XorNot 9mo agoRight but it's not like a 4 way stop is going to perform better. In the same case you'd expect it to be a 2 way stop.
- cucumber3732842 9mo ago>In the same case you'd expect it to be a 2 way stop Which is what it was for the first 70yr... And what most of them in this particular neighborhood still are, with a 0-6mo intermission.
- josephcsible 9mo ago> Right but it's not like a 4 way stop is going to perform better. A 4 way stop does perform better than a roundabout given highly disparate traffic volumes, because roundabouts suffer from resource starvation in that scenario, but 4 way stops are starvation-free.
- lillecarl 9mo agoIf this is the case you can install stop lights and traffic sensing at roundabout ingress points, you can also provide a "turn right" lane that bypasses the roundabout entirely. Intersections are dangerous.
- josephcsible 9mo ago> If this is the case you can install stop lights and traffic sensing at roundabout ingress points But those options are a lot more expensive and need a lot more maintenance than just a regular roundabout or four way stop. > you can also provide a "turn right" lane that bypasses the roundabout entirely. How would that work? Consider a 4-way roundabout, where there's a constant flow of cars from west to east, and one car from the south that wants to go north but can't because of the starvation problem. None of the involved cars would want to use a "turn right" lane.
- 1718627440 9mo agoPutting a stop sign or traffic light in your scenario will just cause traffic jams. If the density is low enough to allow flow with a gap created by a stop sign, without causing traffic jams, then there will also be gaps for the secondary flow.
- orwin 9mo agoThey make people on the main road slow down, which is a feature, not a bug. What you mean is that they're the most efficient at what they do when the traffic is comparable. They only reduce accident at the expense of a slightly lowered throughput if the traffic is highly disparate.
- olyjohn 9mo agoIf the volume is disparate, then the road with less traffic can wait... kind of like a stop sign! Except the road with more traffic won't back up and cause massive problems.
- 1718627440 9mo agoIf the traffic intensity of the main flow is so high, that there are never any gaps, then it is near the saturation and will cause traffic jams anyway. Which first needs to be fixed anyway and second will also cause gaps to be created again, because the main flow comes to a halt.
- paulclinger 9mo agoRoundabouts are great (we just had two complex intersections with traffic lights replaced by roundabouts and the traffic flow is much better), but they take significantly more space than a 4-way stop.
- InfraScaler 9mo agoNot necessarily. They could be just painted and barely take any room.
- kjkjadksj 9mo agoBecause retrofitting them properly requires emminent domain. The ones they shoehorn onto former four way stops are so useless. They are so tight you still have to face a stop sign vs being able to just seamlessly zipper merge in a proper larger circumference roundabout. When they have room to build out a proper roundabout they are usually OK but that is hard to do outside say new suburban construction due to lack of available land on the right of way.
- Mountain_Skies 9mo agoEven rural Georgia has double roundabouts now. Not sure why people on the internet can't contain their glee at stating the US is "allergic" to them when the frequency of roundabouts has grown significantly in recent decades.
- 47282847 9mo agoAllergies only show when there is something to cause the irritation. Without irritant no allergy.
- seanmcdirmid 9mo agoA lot of legacy intersections don’t have space for round abouts even in cites that embrace them.
- masfuerte 9mo agoSo use a mini roundabout. They are common in the UK. It's just a painted circle with a slight hump, in the middle of a four-way junction. Vehicles can drive over it (and larger ones have to) but it indicates to everyone that they have to give way to traffic from the right and don't have to stop otherwise. They typically aren't big enough for multiple vehicles to be turning a corner at the same time. They fit anywhere.
- seanmcdirmid 9mo agoIt won’t work for a four way stop with lots of traffic, it will just make things worse actually.
- smallerfish 9mo agoWhat is the traffic flow rate in an intersection with a 4 way stop? For single lane, since only one vehicle can be in the intersection at once, and probably takes _at least_ 5 seconds to start from stopped and cross the intersection, I'm guessing in the 10-12 region per minute best case, so maybe 600 an hour? Now if you convert it to a mini roundabout, you can have at least two vehicles in the intersection at all times. I fail to see how it wouldn't be an improvement.
- seanmcdirmid 9mo agoI think you are making lots of assumptions here, like when I say space, I guess you assume it is still perfectly flat and the roads are perfectly aligned? The particular four way I'm thinking about, which really should be a traffic circle if they could blow away some houses, is 65th NW and 3rd in Seattle: https://maps.app.goo.gl/7KBhbJ9oAvDwrfGN8 https://maps.app.goo.gl/7KBhbJ9oAvDwrfGN8 So notice we already have problems in a bad alignment of 3rd, and 65th is basically a steep grade, even coming up form the west. I think you could put a circle in if it were flat, even with the bad alignment (or maybe because of the bad alignment), but this hills make a non-starter. It also gets enough traffic that I'm pretty sure they are just going to put a stop light up eventually.
- Ekaros 9mo agoIt just sounds insane concept. Why stop signs, when you could have equal intersection. Slow enough to observe traffic from right. If none passthrough. Stop signs should be special. Reserved only to those places where there simply is not enough visibility or time to observe.
- onionisafruit 9mo agoThe good ol four-way yield
- estimator7292 9mo agoThat requires a level of consideration for others that your average American simply cannot comprehend. No stop sign means you have unlimited right of way bestowed by god himself and fuck anyone and everyone else. The other option is the person who sits at a 4-way stop until all traffic in a one block radius stops before they move, totally ignoring right of way and all sense of safety and propriety.
- 1718627440 9mo ago> No stop sign means you have unlimited right of way bestowed by god himself and fuck anyone and everyone else. Such a person, should simply not drive on a public road. That is e.g. what the first paragraph of street regulation in Germany is about.
- geekifier 9mo agoThere are 10,000+ roundabouts in the US and the number is growing rapidly. One could argue they may even be overused in certain areas (exhibit: Carmel, Indiana).
- InfraScaler 9mo agoThere are more than 15k only in Spain. 10k in the US is nothing.
- ImPostingOnHN 9mo ago>There are 10,000+ roundabouts in the US So about 0.003 roundabouts per square mile, or 1 roundabouts in 380 square miles
- olyjohn 9mo agoWhat's the significance of roundabouts per square mile? It seems pretty meaningless if I'm honest. There's huge swaths of rural land where roundabouts are totally unnecessary.
- ImPostingOnHN 9mo agoThere are also huge swathes of city, much like other countries. At the same time, the US is much larger than most, so "There are 10,000+ roundabouts in the US" isn't very significant. A proportion would thus be a better metric here than an absolute number. If you have numbers on intersections per country, and what proportion of them are roundabouts, that would be better, but I don't, so I'm using land as a proxy. I would also accept sum total road length as an option for denominator.
- mitchitized 9mo agoThe only places where a 4-way stop has room to make a roundabout are places where there is not enough traffic for it to matter either way. The biggest obstacle is that there are just too many 4-way stops in urban areas where there is no space left to make a roundabout, you would have to tear down buildings. I don't think that is a valid argument in that scenario.
- GJim 9mo ago> The only places where a 4-way stop has room to make a roundabout are places where there is not enough traffic for it to matter either way. You have clearly never heard of a mini-roundabout. They just work. https://thumbsnap.com/sc/u7J6PdTJ.jpg https://thumbsnap.com/sc/u7J6PdTJ.jpg https://assets.publishing.service.gov.uk/media/5a75806ae5274a1622e224ab/mini-roundabouts-report.pdf https://assets.publishing.service.gov.uk/media/5a75806ae5274...
- Cpoll 9mo agoThe more I look at that... Isn't that basically just a four-way yield, and the markings are mostly superfluous? You're basically doing the same motions in a regular intersection. I guess that's the point, and the markings are just to give drivers the intuition of treating it like a regular roundabout (yield to your left [or right in the picture]).
- renewiltord 9mo agoYes. The markings are part of the road language. E.g. the X in the road with Keep Clear doesn’t actually do anything. It won’t keep you clear. You have to keep clear when you read it.
- fc417fc802 9mo ago> the markings are mostly superfluous? You're basically doing the same motions in a regular intersection. The image linked, yes. However I've never seen one quite like that in the US. Instead where I'm at we have a small circular barrier in the center of the intersection (and some very eye catching reflectors) that you actually have to drive around. It's a very good design (imo) because it physically forces vehicles to slow down and swerve so there's no way to inadvertently blow through it at speed the way that sometimes happens with a 4 way stop on a long straightaway in the dead of night. The space requirement is only slightly higher than the one linked above, still much less than a proper full size roundabout. It's basically a cement barrier sticking 1/4 of the way into your lane.
- tootie 9mo agoAt this point in time, why can't we do smart crossings? Like have some sensors and software to change lights based on real-time traffic conditions.
- lillecarl 9mo agoYou don't have this? In Sweden we have sensors to detect cars, pedestrians and bicycles to shift the lights as appropriate. During rush-hour those features are turned off/discarded in favor of "grid optimized" timings. In Netherlands they prioritize pedestrians and cyclists when it's raining. We also have LED lights in our traffic lights which I've come to understand is a saftey hazard in USA because snow falls sometimes.
- estimator7292 9mo agoWe do have them, but it's so expensive that we only use them on the biggest and busiest intersections. We also switched to LED several decades ago.
- Symbiote 9mo agoEven the small bicycle and pedestrian crossing next to my office in Copenhagen has vehicle (bicycle) sensors.
- fc417fc802 9mo agoAssuming you're referring to the US, we do. They're all over the place. But they're a lot more expensive and complicated than roundabouts and depending on the traffic pattern they can still be less efficient.
- estimator7292 9mo agoBecause those systems are exorbitantly expensive and require digging up the road to install sensors. If there's a stop sign instead of lights, you need to dig up more private land to run power and set the utility poles to hang the lights from. A stop sign costs like a hundred bucks, you stick it in the ground, job done. Installing an automated traffic system takes multiple days, a full crew, and heavy equipment. Plus I'm sure that in today's capitalist hellscape it's also a subscription service that your tax money needs to pay monthly, likely for every individual intersection. Stop signs need maintaining every decade or two. The answer is money and who's willing to part with it.