5 ms·

Mythbusters does the 4 Way Stop Vs Roundabout

16 points by kposehn 13y ago

dmak 13y ago
For people who just want to know the results: 385 cars in 15 minutes for the 4-way intersection 460 cars in 15 minutes for the roundabout
bane 13y ago
I finally got a chance to visit a couple roundabout heavy countries this past year and absolutely love them. Growing up in the U.S. 4-way stops are terrible congestion sources, nobody follows the rules (right of way), and it's generally an irritating experience with all the stopping and going. In my local area there are two interesting stretches of road, on the first there are three close proximity 4-way stops. Traffic is always messed up on them. In the other stretch, there used to be an intersection with only a stop on the access road and then a 4-way lighted stop. In the evenings, traffic heading towards the intersection would back up for 10 miles or more and take an hour to cross the intersection. They decided to replace both intersections with three roundabouts and poof, they haven't had a traffic issue in years despite more than tripling the number of cars on the same road. American's still don't do them quite right, they're usually too tight or we put lights all over them defeating the purpose. In a proper roundabout country, they're amazing, traffic moves pretty steady, everybody knows what's going on, they don't really ever feel threatening and if you miss your exit it's a pretty easy trip round back to it. I think at some scale level, they start not to work as well as the American solution though (big highway exits and interchanges). Some of the really large ones I drove through were more problematic in terms of getting traffic through, even if navigating was still better. The American method moves more traffic, but at a loss of driver clarity in many cases.
kt9 13y ago
Roundabouts also become more efficient when you add additional lanes like they do in Australia. Stop signs work best only on single lanes of traffic and things break down if there is more one lane per side.
chris_wot 13y ago
Don't Americans have roundabouts?!? Anyway, curious about which has more accidents.
- Randgalt 13y ago
  Yes, they are called "traffic circles" here. http://en.wikipedia.org/wiki/Traffic_circle http://en.wikipedia.org/wiki/Traffic_circle
jacques_chester 13y ago
So, a few days ago, I drove in the USA for the first time. Until then I'd never seen a 4-way stop. I never knew such a thing existed. It took me a while to work out what the heck to do. As an Australian I am used to one direction having stop signs, meaning that the other direction has right of way. But then I come across stop signs in both directions and I've suddenly got people in other cars looking at me expectantly while I try to work out what the hell I am meant to do. We have roundabouts in Australia and yes, they are definitely smoother.
shirro 13y ago
Roundabouts can be too big or too small. The worst types are the retrofitted ones in tiny inner suburban streets installed as hazards to slow through traffic and the huge ones on massive lopsided intersections with more than 4 exits where you can't see the other side. Inbetween on light to moderate traffic intersections they are absolutely brilliant. They are a floral centerpiece at the heart of some Aussie country towns. One problem with them is that the large well functioning ones maximise the traffic through the intersection and drivers maintain a lot of their speed. It can be very difficult for a pedestrian to cross at them, particularly with children, compared with a traffic light.
jakozaur 13y ago
Nice show! Also the research shows that roundabout are much safer: http://www.ite.org/traffic/documents/CCA99A33.pdf http://www.ite.org/traffic/documents/CCA99A33.pdf http://www.ce.udel.edu/dct/publications_files/Rpt.%20199%20Roundabouts.pdf http://www.ce.udel.edu/dct/publications_files/Rpt.%20199%20R... Quote: "In instances where roundabouts have replaced other types of intersection control, the benefits in terms of safety have been remarkable and many examples can be found in the literature."

16 points by kposehn 13y ago

dmak 13y ago

For people who just want to know the results: 385 cars in 15 minutes for the 4-way intersection 460 cars in 15 minutes for the roundabout

bane 13y ago

I finally got a chance to visit a couple roundabout heavy countries this past year and absolutely love them. Growing up in the U.S. 4-way stops are terrible congestion sources, nobody follows the rules (right of way), and it's generally an irritating experience with all the stopping and going. In my local area there are two interesting stretches of road, on the first there are three close proximity 4-way stops. Traffic is always messed up on them. In the other stretch, there used to be an intersection with only a stop on the access road and then a 4-way lighted stop. In the evenings, traffic heading towards the intersection would back up for 10 miles or more and take an hour to cross the intersection. They decided to replace both intersections with three roundabouts and poof, they haven't had a traffic issue in years despite more than tripling the number of cars on the same road. American's still don't do them quite right, they're usually too tight or we put lights all over them defeating the purpose. In a proper roundabout country, they're amazing, traffic moves pretty steady, everybody knows what's going on, they don't really ever feel threatening and if you miss your exit it's a pretty easy trip round back to it. I think at some scale level, they start not to work as well as the American solution though (big highway exits and interchanges). Some of the really large ones I drove through were more problematic in terms of getting traffic through, even if navigating was still better. The American method moves more traffic, but at a loss of driver clarity in many cases.

kt9 13y ago

Roundabouts also become more efficient when you add additional lanes like they do in Australia. Stop signs work best only on single lanes of traffic and things break down if there is more one lane per side.

chris_wot 13y ago

Don't Americans have roundabouts?!? Anyway, curious about which has more accidents.

Randgalt 13y ago
Yes, they are called "traffic circles" here. http://en.wikipedia.org/wiki/Traffic_circle http://en.wikipedia.org/wiki/Traffic_circle

jacques_chester 13y ago

So, a few days ago, I drove in the USA for the first time. Until then I'd never seen a 4-way stop. I never knew such a thing existed. It took me a while to work out what the heck to do. As an Australian I am used to one direction having stop signs, meaning that the other direction has right of way. But then I come across stop signs in both directions and I've suddenly got people in other cars looking at me expectantly while I try to work out what the hell I am meant to do. We have roundabouts in Australia and yes, they are definitely smoother.

shirro 13y ago

Roundabouts can be too big or too small. The worst types are the retrofitted ones in tiny inner suburban streets installed as hazards to slow through traffic and the huge ones on massive lopsided intersections with more than 4 exits where you can't see the other side. Inbetween on light to moderate traffic intersections they are absolutely brilliant. They are a floral centerpiece at the heart of some Aussie country towns. One problem with them is that the large well functioning ones maximise the traffic through the intersection and drivers maintain a lot of their speed. It can be very difficult for a pedestrian to cross at them, particularly with children, compared with a traffic light.

jakozaur 13y ago

Nice show! Also the research shows that roundabout are much safer: http://www.ite.org/traffic/documents/CCA99A33.pdf http://www.ite.org/traffic/documents/CCA99A33.pdf http://www.ce.udel.edu/dct/publications_files/Rpt.%20199%20Roundabouts.pdf http://www.ce.udel.edu/dct/publications_files/Rpt.%20199%20R... Quote: "In instances where roundabouts have replaced other types of intersection control, the benefits in terms of safety have been remarkable and many examples can be found in the literature."