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Safety benefits of roundabouts

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Re: Safety benefits of roundabouts

#171

Post by kazinator »

gumby wrote: post #170

Inexplicably, the ones in the Bay Area are often installed with stop signs, which makes the point of a roundabout rather mysterious.

Removing the middle area of the intersection has a safety benefit over the stop signs.

Some drivers habitually ignore stop signs. Since it is a physical barrier, those drivers won't ignore the removed middle of the intersection, unless they are drunk, and in that situation it's unlikely two will do that at the same time, where we would have a fatality.

Re: Safety benefits of roundabouts

#172

Post by kazinator »

Enginerrrd wrote: post #107
devnull3 wrote: post #68

Simple roundabouts are definitely good but in UK I have found spiral roundabouts error prone if you have not driven on it before Example: [1] When visiting for the first time on a specific spiral roundabout: 1. Lane markings are faded 2. You do not know the specific lane unless you come very close to it and have to make a quick decision 3. Often due to queued traffic you cannot even see the lane marking until its too…

Transportation engineer here: Multi-lane roundabouts don't typically have any safety benefits. Single lane roundabouts do. Also, on the small side where you have traffic circles rather than roundabouts, those also suck.

All roundabouts prevent vehicles from just blowing straight through the intersection in the desired direction without so much as slowing down. They remove the middle part of the intersection where conflicting paths intersect.

Two-lane roundabouts are larger; cars go around them faster. There is ambiguity. Some cars short-cut using the middle lane, and veer right out of it to their desired exit. Cars in the outer lane might be wrongly assumed to be turning off at the next exit. North American drivers get really confused by two-lane roundabouts.

I don't think these situations will typically lead to anything worse than fender benders.

The same intersection without a roundabout could be host to fatal collisions, when two vehicles enter at speed and hit each other in the middle.

Re: Safety benefits of roundabouts

#173

Post by peeters »

dublinben wrote: post #164
yreg wrote: post #140

Earlier quoted context omitted.

> people will NOT understand a roundabout with more than one lane We have tons of 2-lane ones and everyone understands them…

The number of drivers who think you can freely exit from the inner lane suggests otherwise.

Not sure exactly what you mean by freely, but in most popular roundabout designs you can exit from the inner lane. A "standard" two lane roundabout will have two lanes entering AND exiting. You never change lanes in roundabouts, at least where I'm from. Only in a massive multi-lane roundabout (that's at that point more like a ring road) would you ever change lanes to exit.

e.g. for a standard two lane roundabout with four exits, if you enter in the left lane, you can exit directly out of the 2nd, 3rd, and 4th (i.e u-turn) exits, but always in the left lane of the exit. If you enter in the right lane, you can exit out of the 1st or 2nd exits, but always in the right lane of the exits. With this design cars travelling alongside you can never cross your path, only cars entering the roundabout ahead of you can cross your path and it's their responsibility to yield.

The thing that most often causes problems is people in the outer lane NOT exiting (e.g. thinking they can take the third exit from the right lane) and swiping the car in the inner lane correctly taking the second exit.

Re: Safety benefits of roundabouts

#174

Post by pests »

kmeisthax wrote: post #112
Enginerrrd wrote: post #107

Earlier quoted context omitted.

Transportation engineer here: Multi-lane roundabouts don't typically have any safety benefits. Single lane roundabouts do. Also, on the small side where you have traffic circles rather than roundabouts, those also suck.

wait I thought "traffic circle" and "roundabout" were synonyms

This is the first time I've even heard the term "traffic circle"

Re: Safety benefits of roundabouts

#175

Post by nonethewiser »

InSteady wrote: post #157
citizenkeen wrote: post #149

Portland, Oregon has a roundabout with four stop signs and I've been mad about it for thirty years. Why?!

Because its on a busy intersection and people are idiots. I've used it hundreds if not thousands of times on my bike, not to mention as a pedestrian. I would not do either one if not for the stop signs. I've seen so many idiotic interactions over the years that were only mitigated by the slow speeds starting from a full stop. People like to zoom down Cesar Chavez especially at night when traffic is light. It would be…

But why not just put a yield sign? I can honestly see why absolutely no sign suggest you have the right of way.

Re: Safety benefits of roundabouts

#176

Post by eszed »

mitthrowaway2 wrote: post #132
Enginerrrd wrote: post #107

Earlier quoted context omitted.

Transportation engineer here: Multi-lane roundabouts don't typically have any safety benefits. Single lane roundabouts do. Also, on the small side where you have traffic circles rather than roundabouts, those also suck.

While you're here, can I ask you a question I've always wanted to ask about traffic circles? Perhaps this is also related to why they suck for safety. At least where I live, there are two rules for traffic circles: (1) yield to traffic that is already in the traffic circle, and (2) when two cars arrive at the same time, yield to traffic on your right . Rule 1 is the same as for a roundabout, but rule (2) is a bit str…

Just clarifying: you drive on the right-hand side of the road, so "right" for you means on the outside of the circle?

Yeah, that seems mad.

Re: Safety benefits of roundabouts

#177

Post by peeters »

smeej wrote: post #135
Enginerrrd wrote: post #107

Earlier quoted context omitted.

Transportation engineer here: Multi-lane roundabouts don't typically have any safety benefits. Single lane roundabouts do. Also, on the small side where you have traffic circles rather than roundabouts, those also suck.

I think you're right about single vs. 2+ lanes. It doesn't matter how many diagram signs they put up before the roundabout entry, people will NOT understand a roundabout with more than one lane, and under no circumstance will people going straight through realize they have to yield to someone coming from the opposite side who's going 270° around the circle and exiting from the inner lane. Roundabouts are fine if the…

> expecting anything more than that from most drivers is a lost cause

I can't speak to the area you live, but where I'm from we get along just fine. Yes sometimes you still get the odd unfamiliar driver that doesn't understand them, but for locals there's a critical mass where roundabouts stop being avoidable and you adjust.

See also: https://www.iihs.org/news/detail/safety-at-two-lane-roundabo...

Re: Safety benefits of roundabouts

#178

Post by fshbbdssbbgdd »

mitthrowaway2 wrote: post #132
Enginerrrd wrote: post #107

Earlier quoted context omitted.

Transportation engineer here: Multi-lane roundabouts don't typically have any safety benefits. Single lane roundabouts do. Also, on the small side where you have traffic circles rather than roundabouts, those also suck.

While you're here, can I ask you a question I've always wanted to ask about traffic circles? Perhaps this is also related to why they suck for safety. At least where I live, there are two rules for traffic circles: (1) yield to traffic that is already in the traffic circle, and (2) when two cars arrive at the same time, yield to traffic on your right . Rule 1 is the same as for a roundabout, but rule (2) is a bit str…

They added some circular medians in the middle of 4-way stops where I live, are those traffic circles? Are you suggesting that when I get to a 4 way stop, whether I yield to traffic on the left or right should depend on whether the intersection has one of those medians in the middle?

Personally I find it confusing that yielding works the opposite way on roundabouts and 4-way stops, and nobody else in my neighborhood seems to know what to do either. Whether people yield to me seems to depend mostly on the size of the vehicle I am driving.

Re: Safety benefits of roundabouts

#179

Post by ryukafalz »

LRVNHQ wrote: post #155
michaelteter wrote: post #141

Two lane roundabouts are pretty good. More than two lanes are very questionable. And roundabouts which include... stoplights!?!? are just stupid. I live in the Netherlands, where roundabouts are very common. In many cases, they are an improvement. But NL is also a huge bike country. And at most roundabouts, bikes have right of way. So as a car driver, you have to worry about other cars as well as bikes which may turn…

> But NL is also a huge bike country. And at most roundabouts, bikes have right of way. The fact that it's on a case-by-case basis an not actually a consistent traffic law is really awful. To add insult to injury, the only signage is usually a yield sign painted on the road that is invisible as soon as it's dark and the road is wet. And this is of course further combined with the absolute scandalous amount of cyclist…

> To add insult to injury, the only signage is usually a yield sign painted on the road

Doesn't the red asphalt denoting a cycleway also typically continue across the exits when cyclists have priority?

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