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Safety benefits of roundabouts

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Re: Safety benefits of roundabouts

#141

Post by michaelteter »

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 (go away from the roundabout) or continue (cross the adjacent road circularly around the roundabout.

In good visibility conditions, it's ok. And by OK, I mean it can still really f* up car traffic, especially when it is a high traffic area not far from a school. In lower vis conditions, and/or when electric higher speed bikes are concerned, it becomes a whole new kind of danger.

I would argue that the benefits of roundabouts diminish or fully disappear when the number of lanes exceeds 2, or when traffic lights are added to roundabouts, or (and!) especially when bike paths intersect with and circulate around the roundabouts.

Re: Safety benefits of roundabouts

#142

Post by lotsofpulp »

RandallBrown wrote: post #124
kmeisthax wrote: post #112

Earlier quoted context omitted.

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

They are in most contexts. There are "traffic circles" that aren't roundabouts but just a round block in the middle of an intersection that requires the traffic to move around in a circle so cross traffic is slowed. Also called a "traffic calming circle." https://www.seattle.gov/transportation/projects-and-programs... That could also be a location specific term too. These circles are very common in Seattle.

I thought that was a roundabout. At least my UK family would call that a roundabout.

Re: Safety benefits of roundabouts

#143

Post by adrianmonk »

marginalia_nu wrote: post #28
rwmj wrote: post #11

If you like roundabouts, try a roundabout of roundabouts: https://en.wikipedia.org/wiki/Magic_Roundabout_(Hemel_Hempst... This is near where I live and it is indeed safe, mainly because everyone drives incredibly slowly and cautiously since the experience is scary as hell.

Using roundabouts of roundabouts it's actually possible to build a 3 dimensional roundabout where traffic along the x, y and z axis can safely meet on the surface of a sphere.

Can you build a 4 dimensional one on a hypersphere, so that traffic can go around in circles in time?

Bonus question: if you can, what happens if you drive a DeLorean at 88 miles/hour on it?

Re: Safety benefits of roundabouts

#144

Post by JohnFen »

giantg2 wrote: post #59
dfxm12 wrote: post #30

Earlier quoted context omitted.

You're never going to "solve" traffic problems when people are driving cars, but when you look at the data, crashes that lead to injuries and, importantly, fatalities, go down with roundabouts. and two or three lane roundabouts with complex exit decisions you need to make on a split second - it's actually very confusing to navigate. I think you're confusing what today might be called a "rotary" (?) with a modern roun…

I've seen 2 lane roundabouts brand new in the US.

Same in my part of the US. They're the most common kind, and new ones are constantly being constructed.

Re: Safety benefits of roundabouts

#145

Post by JohnFen »

peterpost2 wrote: post #40
Minor49er wrote: post #4

Earlier quoted context omitted.

As an American, I can assure you that we have loads of these

France has about 30k of them, the UK has about 25k of them and those countries have a fraction of the population of the US. The us does not have loads of them they are few and far between

It must depend on where in the US you are. Where I am, they are pretty common.

Re: Safety benefits of roundabouts

#146

Post by patja »

lotsofpulp wrote: post #142
RandallBrown wrote: post #124

Earlier quoted context omitted.

They are in most contexts. There are "traffic circles" that aren't roundabouts but just a round block in the middle of an intersection that requires the traffic to move around in a circle so cross traffic is slowed. Also called a "traffic calming circle." https://www.seattle.gov/transportation/projects-and-programs... That could also be a location specific term too. These circles are very common in Seattle.

I thought that was a roundabout. At least my UK family would call that a roundabout.

Roundabouts have to have splitters and other features that traffic calming circles lack. Also, technically you can go whichever way you want around a traffic calming circle: counterclockwise is recommended, but many trucks physically cannot navigate them that way. And there are zero traffic laws distinguishing a traffic calming circle from an uncontrolled intersection.

Re: Safety benefits of roundabouts

#147

Post by fnordpiglet »

Seattle roundabouts are absurd - they’re actually not roundabouts despite being shaped like them, but are traffic slow down artifacts. But people insist on treating them like roundabouts despite being too tight a radius for some cars and the city advising to not treat them as such.

Re: Safety benefits of roundabouts

#148

Post by Clent »

olyjohn wrote: post #125
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.

Correct me if I'm wrong... but compared to a traffic light, you have to go significantly slower, so most accidents are not as severe as at a traffic light. You also aren't crashing into someone in a t-bone situation, usually they are sideswiped at more of an angle for less impact force. Of course someone could still fly into a roundabout at full speed. Anything is possible, but feel like think overall there still hav…

Correct. Anyone that says roundabouts are less safe doesn't have science backing their claim. While, they do not reduce the number of accidents and in some cases can increase accidents, but they consistently reduce the severity of the accidents.

A three lane roundabout may be annoying when encounter as a tourist but the majority of locals going about their daily commutes quickly master them. For a three lane roundabout the inner lane is left turn only. The inner lane is left turn or straight and the right lane is right turns only.

The ones in my area have ample signage indicating which lane allows for each type of turn.

Re: Safety benefits of roundabouts

#150

Post by Clamchop »

fnordpiglet wrote: post #147

Seattle roundabouts are absurd - they’re actually not roundabouts despite being shaped like them, but are traffic slow down artifacts. But people insist on treating them like roundabouts despite being too tight a radius for some cars and the city advising to not treat them as such.

Traffic calming features: https://en.m.wikipedia.org/wiki/Traffic_calming
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