7 ms·

Roundabouts reduced accidents and are environmentally friendly

61 points by cyrksoft 5y ago

musicale 5y ago
I don't really enjoy roundabouts, but I like the idea of a non-blocking (or less-blocking) traffic network. Head-of-line blocking, where left turns can block through traffic or through traffic can block a left turn lane, is a particularly irritating feature of traditional intersections.
- throwaway0a5e 5y ago
  Yeah, they're great when they work but they give timid morons an opportunity to get stuck that a light doesn't. Two lanes helps but nothing really beats a light for getting people who don't know what they're doing through an intersection.
nameisname 5y ago
I've driven through an intersection almost daily my entire life. It was switched to a roundabout a few years ago. I have had more near misses in that roundabout from people not yielding or people continuing around in the outside lane than my entire life driving and never had a single issue with the intersection prior to it being a roundabout. I like roundabouts. I would like to see a study on how many near misses happen in roundabout vs. regular intersections. Too much stress.
- julianlam 5y ago
  That's an educational problem. It's much the same here in Canada (southern Ontario to be exact), but the more roundabouts are installed, the better drivers are at navigating them. One funny story my wife told me was, she was once a passenger in a car driven by someone unfamiliar with roundabouts. Upon encountering their first one, they proceeded to drive round and round, afraid to exit. The unfortunate truth, is that because there are so few roundabouts here, driving schools do not make it part of their curriculum. Chicken, meet egg. However, I am a firm believer in roundabouts. Ignorance is a poor justification for continuing to build four-way intersections in places that do not require them.
  - alephxyz 5y ago
    My driving school had us drive 25 minutes just to use a roundabout situated in a small suburban town. Gave us the occasion to practice both roundabouts and highway driving in the same session.
- makeitdouble 5y ago
  It requires more attention, brings more stress, in exchange for less critical accidents. I think this is pretty much a constant in road security, where putting more stress and forcing the driver to pay attention leads to overall better outputs (enforced road bumps, sound inducing road sides, fake people display on crossing paths etc.) PS: on people not yielding, speed are lower than on straight lines so it's still less problematic than usual non yielding. But I hope your neighbors will get used to roundabouts and navigate them better.
  - hinkley 5y ago
    I have long suspected that what makes roundabouts safe is that they feel like they aren’t. People speed when the lanes are wide as well. There have been some people experimenting with optical illusions that make highways feel less safe than they actually are, such as forced perspective to make obstacles off the highway look closer, which encourages the drivers to slow down and pay attention.
- speedbird 5y ago
  Brit here. Roundabouts are pretty easy once you get used to them, extensive discussion of associated signage etc from another respondent here as to the need for ancillary features. This, however https://en.m.wikipedia.org/wiki/Magic_Roundabout_(Swindon) https://en.m.wikipedia.org/wiki/Magic_Roundabout_(Swindon)
UncleEntity 5y ago
Phoenix area added a bunch of roundabouts a while ago and last I heard they were in the process of taking them out. Problem is if people are used to them they work well but if you rarely see them people don’t really understand the concept and just kind of blast through them without yielding. Almost got taken out a few times when I was a cabbie, people just go full speed into them without looking. The new hotness seems to be intersections where the traffic crosses over to the other side and left turns are uncontested(?).
- throwaway0a5e 5y ago
  >Problem is if people are used to them they work well but (un)friendly reminder that this goes for the people in the city plannign department first and foremost. You can't just dump one in at every intersection and expect them to work out. It only works out when there's similiar traffic volumes on the intersecting streets. Of course people just drive on through when the volumes are such that that's the prevailing flow. Not that I have anything against 2-way stops but that's basically what you create a lot of when you start carpet bombing your town with roundabouts because they're trendy.
  - sagarm 5y ago
    2-way stops often feel stressful or unsafe if there is any significant traffic. Roundabouts seem like an improvement with the much lower chance of being t-boned.
  - Symbiote 5y ago
    Britain has mini-roundabouts, which are a good alternative to many smaller junctions. It's just a painted white dot, about the size of a small car, in the middle of the junction. Since the "circle" is so small, you yield to approaching vehicles on the junction, but also to a vehicle waiting at the entrance to your right¹, i.e. the vehicle that is waiting in the direction you're looking in anyway for traffic on the "circle". If there are no other cars, you barely need to slow down. In most cases, even if the junction is busy, a car trying to enter from an uncommon direction will quickly be able to go as someone in the main direction will need to yield. ¹ Driving on the left in Britain, of course.
prirun 5y ago
They put two roundabouts in here on a state highway. I've never talked to anyone who had good things to say about them. The main problems IMO are: - you can just go around again if you aren't sure which exit you need; you are forced into taking an exit, right or wrong - the radius is too small so there is not much time to make a complex decision, especially if you aren't already familiar with the exits - it's hard to monitor traffic entering the roundabout to make sure I don't get hit by someone having a harder time navigating this than me, while at the same time trying to figure out what the crazy sign diagrams mean. - there's no confirmation when you do take an exit that you've taken the right one. Might not be a road sign for 10-15 seconds, which is a long time when you're not sure where you're going. - they're even worse at night because there's not enough lighting. Not too bad for the exits toward civilization, but pretty confusing for the more rustic ones. I think the idea is okay, but at least for the ones they put in here, the execution is not so hot.
- mc32 5y ago
  I think the problems above are mostly for new users. Those unfamiliar with their way. But... lots of this is solved via navigation apps and even proper signage. On there other hand they have a maximum throughput and that can only be alleviated by an interchange --even modest ones.
  - derbOac 5y ago
    My experience with roundabouts is they work wonderfully in some places, and horribly in others. I feel like at least where I am, because they work so perfectly and elegantly in certain situations, better than other solutions, they then get overapplied, in situations where they are horrible. It's a variant of the "when you only have a hammer" analogy: when you first learn how great a hammer can be, everything looks like a nail.
- ramblerman 5y ago
  how is 1 negative? And how is 2 not solved by 1.
  - 5y ago
fy20 5y ago
My city has a lot of roundabouts, some are quite big (~150m diameter) as they are used where two or more main roads meet. When I first came here they usually had three lanes, with the idea that you change lanes as you move through the roundabout - this meant almost daily you would see a minor RTI on a roundabout, which would cause large queues of traffic. Some roundabouts also had three lanes where you enter and exit, but they were usually signalled. A few years ago they reduced the roundabouts to two lanes, and all exits to one lane. The idea being that for the first and second exit you need to use the outer lane, and for the third or fourth exit you use the inner lane. That inner lane becomes the outer lane after the second exit, so you just stick to the same lane once on the roundabout. The only time you need to change lanes is if you miss your exit and need to go around again. There are clear signs before you reach the roundabout saying which lane you need for which exit. Since this change was made, I think I've seen maybe one RTI on a roundabout - when somebody was being stupid and tried to overtake a bus. It's such a simple change, but it's crazy how effective it has been. They've also started adding speed bumps to some roundabouts to slow traffic, which actually increases capacity as it's easier to join with slow moving traffic.
- nkurz 5y ago
  RTI: Road Traffic Incident, an updated term for a "car accident" or "motor vehicle collision". From a quick search, I think it's British. As an American, I'd never encountered either the acronym or the expanded form.
  - ZeroGravitas 5y ago
    There was some discussion about how accident carried some implication of 'no ones fault' that that didnt quite cover all the incidents. If someone tried to run your child over intentionally, it would be somewhat annoying if the police and legal system kept referring to it as an 'accident'
eek2121 5y ago
* Except in the rest of the United States.
a9h74j 5y ago
Had to remind myself of the difference between a roundabout and a traffic circle, suspecting some local mislabeling. From https://www.ofallon.org/street-division/faq/what-is-the-difference-between-a-traffic-circle-and-a-roundabout https://www.ofallon.org/street-division/faq/what-is-the-diff... : > Roundabouts are not traffic circles. Roundabouts follow a yield at entry rule, which requires approaching vehicles to wait for a gap in the circulating traffic before entering the roundabout. Roundabouts involve low speeds for traffic entering and driving through the roundabout; they use deflection to slow entering traffic and enhance safety. Vehicles in the roundabout have the right of way. > Another distinguishing difference between traffic circles and roundabouts is that roundabouts have a smaller diameter than most traffic circles, resulting in safer conditions and lower speeds. Vehicles can enter modern roundabouts much easier than traffic circles due to flared approaches, entry angles, slower speeds on the circulating roadway and the fact that vehicles entering roundabouts always yield to circulating traffic. > Entering a roundabout is as easy as making a right hand turn onto a one-way street.
binarynate 5y ago
I drive through Carmel frequently and love the efficiency of their roundabouts. Anecdotally, I haven't had significant issues with other drivers not using them effectively. Meanwhile in Indianapolis, I often find myself stopped at a stoplight with no cross traffic, wishing that we would invest more in roundabouts like Carmel has. Granted, Indy is much larger, older, and more dense than Carmel, but there are still plenty of locations where roundabouts would be a good fit.
- binarynate 5y ago
  Also, in case anyone's interested, Freakonomics did an episode on Carmel's roundabouts last year. The discussion with the mayor of Carmel starts at 7:33: https://podcasts.apple.com/us/podcast/should-traffic-lights-be-abolished/id354668519?i=1000512490182 https://podcasts.apple.com/us/podcast/should-traffic-lights-...
steelframe 5y ago
Not sure if this is also the case with roundabouts, but traffic circles are significantly more hazardous for cyclists than intersections. https://cyclingincities-spph.sites.olt.ubc.ca/files/2018/06/Traffic-Circles-CARSP-2018.pdf https://cyclingincities-spph.sites.olt.ubc.ca/files/2018/06/...
- bramblerose 5y ago
  Depends on the design. Roundabouts decrease speed (good) but if the cyclists follow the same path as cars they are more difficult to see in mirrors (bad). The Dutch solution is having cyclists follow a route about 1-2m from the main roundabout, which means cars and cyclists intersect at a near-90° angle again.
fatnoah 5y ago
I live in Massachusetts, the land of the rotary. Rotaries here are amazing with multiple lanes of crossing traffic, traffic lights, and occasionally making traffic IN the rotary yield to entering traffic. My favorite is Newton Corner, 3-4 lanes of chaos in a 1/2 mile circumference featuring 200+ street signs, 23 crosswalks, 12 traffic lights, intersecting 6 local roads, and a highway interchange. Oh, there's also a couple bus stops for the 10 or so bus routes. One is generally required to cross several lanes of traffic to exit the rotary at the desired location. The roundabouts that have popped up are downright relaxing in comparison.
nine_zeros 5y ago
Roundabouts are an amazing alternative to stop signs and red lights, especially in busy streets of medium/small cities. Rotaries on the other hand are super-confusing and an aberration in the history of traffic management.
PeterStuer 5y ago
They reduce car on car accidents, but sadly increase car on bicycle accidents as many car drivers fail to yield to the cyclists that are circling, especially when exiting the roundabout.
nuvious 5y ago
For sure, though "it depends" comes into play. Roundabouts down scale well beyond 3 lanes and if one gets clogged up it can have a butterfly effect that causes clog ups at other intersections At least with a standard crossing intersection of say the E->W road is hosed up because of a traffic accident the other flows of traffic are unaffected as long as the intersection remains clear. Even if some jerk gets stuck in the middle they have the ability to U turn out to unblock the intersection. With a roundabout when it's not clogged its very nice and I do enjoy them. But I've also been stuck at an intersection for more than an hour because of a fender bender in a roundabout causing a full traffic stoppage with no way out.

61 points by cyrksoft 5y ago

I don't really enjoy roundabouts, but I like the idea of a non-blocking (or less-blocking) traffic network. Head-of-line blocking, where left turns can block through traffic or through traffic can block a left turn lane, is a particularly irritating feature of traditional intersections.

throwaway0a5e 5y ago
Yeah, they're great when they work but they give timid morons an opportunity to get stuck that a light doesn't. Two lanes helps but nothing really beats a light for getting people who don't know what they're doing through an intersection.

nameisname 5y ago

I've driven through an intersection almost daily my entire life. It was switched to a roundabout a few years ago. I have had more near misses in that roundabout from people not yielding or people continuing around in the outside lane than my entire life driving and never had a single issue with the intersection prior to it being a roundabout. I like roundabouts. I would like to see a study on how many near misses happen in roundabout vs. regular intersections. Too much stress.

julianlam 5y ago
That's an educational problem. It's much the same here in Canada (southern Ontario to be exact), but the more roundabouts are installed, the better drivers are at navigating them. One funny story my wife told me was, she was once a passenger in a car driven by someone unfamiliar with roundabouts. Upon encountering their first one, they proceeded to drive round and round, afraid to exit. The unfortunate truth, is that because there are so few roundabouts here, driving schools do not make it part of their curriculum. Chicken, meet egg. However, I am a firm believer in roundabouts. Ignorance is a poor justification for continuing to build four-way intersections in places that do not require them.
- alephxyz 5y ago
  My driving school had us drive 25 minutes just to use a roundabout situated in a small suburban town. Gave us the occasion to practice both roundabouts and highway driving in the same session.
makeitdouble 5y ago
It requires more attention, brings more stress, in exchange for less critical accidents. I think this is pretty much a constant in road security, where putting more stress and forcing the driver to pay attention leads to overall better outputs (enforced road bumps, sound inducing road sides, fake people display on crossing paths etc.) PS: on people not yielding, speed are lower than on straight lines so it's still less problematic than usual non yielding. But I hope your neighbors will get used to roundabouts and navigate them better.
- hinkley 5y ago
  I have long suspected that what makes roundabouts safe is that they feel like they aren’t. People speed when the lanes are wide as well. There have been some people experimenting with optical illusions that make highways feel less safe than they actually are, such as forced perspective to make obstacles off the highway look closer, which encourages the drivers to slow down and pay attention.
speedbird 5y ago
Brit here. Roundabouts are pretty easy once you get used to them, extensive discussion of associated signage etc from another respondent here as to the need for ancillary features. This, however https://en.m.wikipedia.org/wiki/Magic_Roundabout_(Swindon) https://en.m.wikipedia.org/wiki/Magic_Roundabout_(Swindon)

UncleEntity 5y ago

Phoenix area added a bunch of roundabouts a while ago and last I heard they were in the process of taking them out. Problem is if people are used to them they work well but if you rarely see them people don’t really understand the concept and just kind of blast through them without yielding. Almost got taken out a few times when I was a cabbie, people just go full speed into them without looking. The new hotness seems to be intersections where the traffic crosses over to the other side and left turns are uncontested(?).

throwaway0a5e 5y ago
>Problem is if people are used to them they work well but (un)friendly reminder that this goes for the people in the city plannign department first and foremost. You can't just dump one in at every intersection and expect them to work out. It only works out when there's similiar traffic volumes on the intersecting streets. Of course people just drive on through when the volumes are such that that's the prevailing flow. Not that I have anything against 2-way stops but that's basically what you create a lot of when you start carpet bombing your town with roundabouts because they're trendy.
- sagarm 5y ago
  2-way stops often feel stressful or unsafe if there is any significant traffic. Roundabouts seem like an improvement with the much lower chance of being t-boned.
- Symbiote 5y ago
  Britain has mini-roundabouts, which are a good alternative to many smaller junctions. It's just a painted white dot, about the size of a small car, in the middle of the junction. Since the "circle" is so small, you yield to approaching vehicles on the junction, but also to a vehicle waiting at the entrance to your right¹, i.e. the vehicle that is waiting in the direction you're looking in anyway for traffic on the "circle". If there are no other cars, you barely need to slow down. In most cases, even if the junction is busy, a car trying to enter from an uncommon direction will quickly be able to go as someone in the main direction will need to yield. ¹ Driving on the left in Britain, of course.

prirun 5y ago

They put two roundabouts in here on a state highway. I've never talked to anyone who had good things to say about them. The main problems IMO are: - you can just go around again if you aren't sure which exit you need; you are forced into taking an exit, right or wrong - the radius is too small so there is not much time to make a complex decision, especially if you aren't already familiar with the exits - it's hard to monitor traffic entering the roundabout to make sure I don't get hit by someone having a harder time navigating this than me, while at the same time trying to figure out what the crazy sign diagrams mean. - there's no confirmation when you do take an exit that you've taken the right one. Might not be a road sign for 10-15 seconds, which is a long time when you're not sure where you're going. - they're even worse at night because there's not enough lighting. Not too bad for the exits toward civilization, but pretty confusing for the more rustic ones. I think the idea is okay, but at least for the ones they put in here, the execution is not so hot.

mc32 5y ago
I think the problems above are mostly for new users. Those unfamiliar with their way. But... lots of this is solved via navigation apps and even proper signage. On there other hand they have a maximum throughput and that can only be alleviated by an interchange --even modest ones.
- derbOac 5y ago
  My experience with roundabouts is they work wonderfully in some places, and horribly in others. I feel like at least where I am, because they work so perfectly and elegantly in certain situations, better than other solutions, they then get overapplied, in situations where they are horrible. It's a variant of the "when you only have a hammer" analogy: when you first learn how great a hammer can be, everything looks like a nail.
ramblerman 5y ago
how is 1 negative? And how is 2 not solved by 1.
- 5y ago

fy20 5y ago

My city has a lot of roundabouts, some are quite big (~150m diameter) as they are used where two or more main roads meet. When I first came here they usually had three lanes, with the idea that you change lanes as you move through the roundabout - this meant almost daily you would see a minor RTI on a roundabout, which would cause large queues of traffic. Some roundabouts also had three lanes where you enter and exit, but they were usually signalled. A few years ago they reduced the roundabouts to two lanes, and all exits to one lane. The idea being that for the first and second exit you need to use the outer lane, and for the third or fourth exit you use the inner lane. That inner lane becomes the outer lane after the second exit, so you just stick to the same lane once on the roundabout. The only time you need to change lanes is if you miss your exit and need to go around again. There are clear signs before you reach the roundabout saying which lane you need for which exit. Since this change was made, I think I've seen maybe one RTI on a roundabout - when somebody was being stupid and tried to overtake a bus. It's such a simple change, but it's crazy how effective it has been. They've also started adding speed bumps to some roundabouts to slow traffic, which actually increases capacity as it's easier to join with slow moving traffic.

nkurz 5y ago
RTI: Road Traffic Incident, an updated term for a "car accident" or "motor vehicle collision". From a quick search, I think it's British. As an American, I'd never encountered either the acronym or the expanded form.
- ZeroGravitas 5y ago
  There was some discussion about how accident carried some implication of 'no ones fault' that that didnt quite cover all the incidents. If someone tried to run your child over intentionally, it would be somewhat annoying if the police and legal system kept referring to it as an 'accident'

eek2121 5y ago

* Except in the rest of the United States.

a9h74j 5y ago

Had to remind myself of the difference between a roundabout and a traffic circle, suspecting some local mislabeling. From https://www.ofallon.org/street-division/faq/what-is-the-difference-between-a-traffic-circle-and-a-roundabout https://www.ofallon.org/street-division/faq/what-is-the-diff... : > Roundabouts are not traffic circles. Roundabouts follow a yield at entry rule, which requires approaching vehicles to wait for a gap in the circulating traffic before entering the roundabout. Roundabouts involve low speeds for traffic entering and driving through the roundabout; they use deflection to slow entering traffic and enhance safety. Vehicles in the roundabout have the right of way. > Another distinguishing difference between traffic circles and roundabouts is that roundabouts have a smaller diameter than most traffic circles, resulting in safer conditions and lower speeds. Vehicles can enter modern roundabouts much easier than traffic circles due to flared approaches, entry angles, slower speeds on the circulating roadway and the fact that vehicles entering roundabouts always yield to circulating traffic. > Entering a roundabout is as easy as making a right hand turn onto a one-way street.

binarynate 5y ago

I drive through Carmel frequently and love the efficiency of their roundabouts. Anecdotally, I haven't had significant issues with other drivers not using them effectively. Meanwhile in Indianapolis, I often find myself stopped at a stoplight with no cross traffic, wishing that we would invest more in roundabouts like Carmel has. Granted, Indy is much larger, older, and more dense than Carmel, but there are still plenty of locations where roundabouts would be a good fit.

binarynate 5y ago
Also, in case anyone's interested, Freakonomics did an episode on Carmel's roundabouts last year. The discussion with the mayor of Carmel starts at 7:33: https://podcasts.apple.com/us/podcast/should-traffic-lights-be-abolished/id354668519?i=1000512490182 https://podcasts.apple.com/us/podcast/should-traffic-lights-...

steelframe 5y ago

Not sure if this is also the case with roundabouts, but traffic circles are significantly more hazardous for cyclists than intersections. https://cyclingincities-spph.sites.olt.ubc.ca/files/2018/06/Traffic-Circles-CARSP-2018.pdf https://cyclingincities-spph.sites.olt.ubc.ca/files/2018/06/...

bramblerose 5y ago
Depends on the design. Roundabouts decrease speed (good) but if the cyclists follow the same path as cars they are more difficult to see in mirrors (bad). The Dutch solution is having cyclists follow a route about 1-2m from the main roundabout, which means cars and cyclists intersect at a near-90° angle again.

fatnoah 5y ago

I live in Massachusetts, the land of the rotary. Rotaries here are amazing with multiple lanes of crossing traffic, traffic lights, and occasionally making traffic IN the rotary yield to entering traffic. My favorite is Newton Corner, 3-4 lanes of chaos in a 1/2 mile circumference featuring 200+ street signs, 23 crosswalks, 12 traffic lights, intersecting 6 local roads, and a highway interchange. Oh, there's also a couple bus stops for the 10 or so bus routes. One is generally required to cross several lanes of traffic to exit the rotary at the desired location. The roundabouts that have popped up are downright relaxing in comparison.

nine_zeros 5y ago

Roundabouts are an amazing alternative to stop signs and red lights, especially in busy streets of medium/small cities. Rotaries on the other hand are super-confusing and an aberration in the history of traffic management.

PeterStuer 5y ago

They reduce car on car accidents, but sadly increase car on bicycle accidents as many car drivers fail to yield to the cyclists that are circling, especially when exiting the roundabout.

nuvious 5y ago

For sure, though "it depends" comes into play. Roundabouts down scale well beyond 3 lanes and if one gets clogged up it can have a butterfly effect that causes clog ups at other intersections At least with a standard crossing intersection of say the E->W road is hosed up because of a traffic accident the other flows of traffic are unaffected as long as the intersection remains clear. Even if some jerk gets stuck in the middle they have the ability to U turn out to unblock the intersection. With a roundabout when it's not clogged its very nice and I do enjoy them. But I've also been stuck at an intersection for more than an hour because of a fender bender in a roundabout causing a full traffic stoppage with no way out.