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Safety benefits of roundabouts

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Re: Safety benefits of roundabouts

#121

Post by kgermino »

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.

> Also, on the small side where you have traffic circles rather than roundabouts, those also suck.

Interesting. Can you elaborate? We have a few of them (and growing) by me and they’re fantastic as far as I can tell. No stopping every block for stop signs, I’ve seen landscaping truck with trailers sneak through them fine, and it’s so much easier on a bike or while walking. What’s the downside?

Re: Safety benefits of roundabouts

#122

Post by AmericanChopper »

squarefoot wrote: post #8

Safety aside, roundabouts lower traffic significantly by never forcing cars to stop. Congestion increases as cars need to stop because of the inevitable latency propagating along the tails, and having more than one traditional intersections along the way can only make things even worse, so any solution to prevent cars from slowing down to a stop would mitigate those effects.

They’re often worse in heavy traffic situations. Especially if you have two entrances that feed heavy traffic into the roundabout at peak times, the one that has to yield can end up basically locked out of the flow.

Re: Safety benefits of roundabouts

#123

Post by hasbot »

What confuses me on roundabouts is the intended speed. Some are very tight and requires slowing down to 15mph and others can handle faster speeds. Rarely is the intended speed marked.

A new roundabout in Brevard, NC has a very tight turning radius. There is a sign warning drivers in the outer lane to watch out for tractor trailers who will have to take both lanes to navigate the circle.

Re: Safety benefits of roundabouts

#124

Post by RandallBrown »

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

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.

Re: Safety benefits of roundabouts

#125

Post by olyjohn »

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.

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 have to be benefits.

People generally don't slow down for lights, and lots of times accelerate to make it through before it turns red.

Re: Safety benefits of roundabouts

#126

Post by js2 »

dfee wrote: post #118

Just adding to the already rich discussion an anecdote about stop signs preceeding a round-about: worst of both worlds. Example: https://www.reddit.com/r/bayarea/comments/10pihgk/roundabout...

Richmond has a circle with a traffic light for exiting! If you stop for the light when it's red everyone honks at you.

https://maps.app.goo.gl/BVrKXUqV6Ck7QTdQ6?g_st=ic

The problem is that it's not really a circle. It's like half-circle/half four-way stop.

Re: Safety benefits of roundabouts

#127

Post by oldbbsnickname »

Roundabouts for high traffic areas are good. The problem is when they are overused in low traffic areas where they create obstacles to efficient continuous motion, increase pollution, and waste time.

PS: One place that doesn't do proper traffic design (or architecture): Texas. They insist on placing massive concrete dividers everywhere and have camouflaged by wear obstacles in the middle of paths that are injurious to bicyclists. It's nothing like the Netherlands where there aren't many random, dangerous surprises.

Re: Safety benefits of roundabouts

#128

Post by pandaman »

Symbiote wrote: post #120
pandaman wrote: post #103

Earlier quoted context omitted.

The protection is just by hiding half of the traffic beyond an obstacle, you can still get t-boned on the roundabout, but only by the cars from your right and not from both directions like on an intersection. I guess it's a plus but with the added danger of a head-on collision from people traversing the roundabout in the wrong way I won't say if it's net-positive safety-wise with any degree of confidence.

I have never seen anyone go the wrong way around a roundabout, and I've never heard anyone tell me they've seen it. It's so rare you can ignore it.

I, on the other hand, have seen much fewer people running red (and that only when the red just switched on, without any cross traffic yet) than people taking left on a roundabout. So by your own method you can ignore people running red light on an intersection?

Re: Safety benefits of roundabouts

#129

Post by olyjohn »

Jtsummers wrote: post #29
hristov wrote: post #20

The greatest thing about roundabouts is that they protect against the idiot that goes through an intersection at full speed. He does that either because he is passed out behind the wheel or because he did not notice a stop sign and thought he had the right of way, or maybe because he just does not care. Well with a roundabout if you just go straight ahead you hit the center circle. Good roundabouts always have a slig…

As long as that center circle is high enough. I had a woman in a Toyota (Camry?) fly over one at about 45+mph and slam into me as I looped around it. Totaled her car, broke parts off my Explorer (repairable). Her son then tried to attack me with my bumper. She kept insisting I turned in front of her (technically true, I was in a roundabout). She was arrested for drunk driving, and, later on, fined for all the flowers…

Most accidents in a roundabout don't happen this way. The severity of most accidents in roundabouts are reduced significantly vs a traffic light.

Drunk drivers have launched cars into all kinds of random shit and places where you would not expect an accident.

Re: Safety benefits of roundabouts

#130

Post by oldbbsnickname »

hasbot wrote: post #123

What confuses me on roundabouts is the intended speed. Some are very tight and requires slowing down to 15mph and others can handle faster speeds. Rarely is the intended speed marked. A new roundabout in Brevard, NC has a very tight turning radius. There is a sign warning drivers in the outer lane to watch out for tractor trailers who will have to take both lanes to navigate the circle.

Yes, some residential ones are absurd. This one would've been better as a 4-way stop because there's no way to see traffic from all other sides due to the angles and obstructions. https://maps.app.goo.gl/GWoqaxNfVanXLymp6

One went in here where people normally drive 60 mph:

https://maps.app.goo.gl/Ugnm36mkeHs2zpu7A

On Clark straight through, I would look for approaching traffic from either side or ahead and would cut across the hatched area, mostly maintaining speed. It's honestly better than stop signs or stop lights.

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