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Here in NJ, in the 1960s, there were circles where 50 mph 2 lane separated highways intersected with secondary roads. It was a complete disaster including deaths. Periodically, drunk drivers would drive straight thru the circle. There were 5 of these crazy things within 5 miles from where I grew up. By the 1980s, most had been replaced with overpasses or the absurd traffic light/jug handle combo.
That's when circles were cool! Heck, driver's ed classes specifically took the kids through the Laurelton Circle as it was "survival" training for their new driving skills.
I remember the fun of coming out of Wall Stadium after the races each Saturday night and hitting the circles on Route 34 like they were turns 3 & 4 at the track.
As much fun as they were, I can see the issues with them too. There are different entry/exit practices at each circle and the roads themselves by local tradition (as far as who has the right of way goes).
Now they're building all of these smaller roundabouts with defined right of way rules that still seem to trigger some people into not being able to navigate them. I their only purpose is to save the cost of operating a traffic light at the intersection.
One thing that hasn't been brought up is that roundabouts are great because they reduce the chances of a crash. At a signalized or stop sign controlled 4 way intersection, there are 32 potential conflict points where a crash could occur. With a roundabout, the number of conflict points is reduced to 8 (and when there are crashes, the speeds are low so the severity is less)
Of course, like most have alluded, there is a volume threshold above which, roundabouts quickly degrade. It really doesn't take much between a smoothly operating roundabout and one where you have mile long queues waiting to get into the roundabout once you've exceeded that threshold. For a single lane roundabout, that's about 20-30,000 vehicles per day (total for all approaches) and for 2 lane roundabouts, that's about 40-50,000 vehicles per day (the more "left turn" movements there are, the lower that threshold is).
Also I'll note there's a difference between the modern day roundabout and the larger "traffic circle/rotaries" of the past. The modern day roundabout is a lot smaller and lower speed.
Last edited by pierretong1991; 02-13-2021 at 09:11 AM..
Roundabouts (or circles) can work in low traffic areas were the meeting streets have the same low speed limit like 25 mph. They are a fail in high density areas with speeds above 35 mph. People cannot accelerate fast enough to enter higher speed traffic flow from a complete stop. They also fail if there is a big difference between the intersecting roads.
Here in NJ, in the 1960s, there were circles where 50 mph 2 lane separated highways intersected with secondary roads. It was a complete disaster including deaths. Periodically, drunk drivers would drive straight thru the circle. There were 5 of these crazy things within 5 miles from where I grew up. By the 1980s, most had been replaced with overpasses or the absurd traffic light/jug handle combo.
I knew you were going to say NJ when I read circle because that's what they're called here.
Where did you grow up? I'm originally from Union county. I mostly saw jug handles in North Jersey. We had jug handles on route 22 up by the Watchung Sears.
I also lived in Browns Mills by route 70, there was one where it met route 72, another at route 202 with another at route 73. They did away with the route 73 one. If you go towards Ocean county on route 70, there are 2 more I believe so I'm wondering if that's where you lived.
I'm not sure. There are so many here who see one and hit the gas like, "Oh yay, watch me fly through this" and others who either don't know how to use them or don't care to follow the rules. That causes me to slow down when I approach one.
I believe they made ours too small and a wider circumference might have helped.
They are popping up all over our cities and towns now. I haven't noticed a difference really, other than getting to drive around in a semi-circle. Why do engineering teams love them so much?
I've noticed I don't sit at a light for 30 seconds to a minute or more. Traffic circles, as they were called when the earth was still cooling, keep it moving. That is the traffic engineers' job.
Recently the engineering geniuses modified a busy intersection near me. They made it extremely complex, there are 22 or 24 stoplights now. Obviously someone got a sweet, fat contract for those. You don't need stoplights at a roundabout.
There is always some corruption is any public works project. When I was a kid my father told me the state highway department was the most corrupt agency in that state's government.
There's engineering and there's scratch your buddy's back. IMO roundabout solve far more problems than they create.
They have been a big improvement at the intersections I'm familiar with in Alaska and Hawaii.
Slowing cars down is always a good thing, IMO.
Not the case in the places I'm familiar with, but in heavy traffic I can imagine there could still be some gridlock. The simple solution would be for individual drivers to be courteous and stop to let others through.
Alleviating traffic congestion should not be the objective.
Reducing the absolute number of cars on the road should be the objective. Alleviating traffic congestion just encourages more cars to be on the road.
Wrong answer.
Traffic engineers' job is to move traffic as efficiently as possible.
Social engineers' job is whatever they think they can do to manage and control other peoples' lives. These cars are on the road for a reason.
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