Do Roundabouts Relieve/Alleviate Traffic? Why/Why Not? (suburban, highway, area)

[hickoryfan]

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?

[turf3]

The theory is that traffic flow is maintained better because you don't have a big wad of cars at a dead stop while the light's red.

In practice, there's a big wad of cars at a dead stop waiting to get into the rotary.

I'm not convinced. See West Concord, MA for an example. That rotary stops all traffic for miles in every direction at rush hour.

[Hemlock140]

Here in our area roundabouts are going in like crazy. Our experience is that many people are not used to them and have problems, delaying everyone by being afraid to jump in. The other thing is that at commute times (pre-Covid)
they worked great for the people going straight thru on a thoroughfare, but for those turning out or going in it may take longer than at a signal light. While in most cases they cost more to build than signal lights, there is no ongoing cost for electricity and light replacements, so I would consider that the main reason for their use, not traffic relief.

[hickoryfan]

Originally Posted by Hemlock140

Here in our area roundabouts are going in like crazy. Our experience is that many people are not used to them and have problems, delaying everyone by being afraid to jump in. The other thing is that at commute times (pre-Covid)
they worked great for the people going straight thru on a thoroughfare, but for those turning out or going in it may take longer than at a signal light. While in most cases they cost more to build than signal lights, there is no ongoing cost for electricity and light replacements, so I would consider that the main reason for their use, not traffic relief.

Good information here. I still low down immensely when I approach one. I look for the traffic sign that has the arrows to show you how the traffic should flow around them. I would think they would be centers for traffic accidents.

[jcp123]

Roundabouts work - provided people actually know what to do with them.

Most folks here don’t, so I find they tend to hinder traffic.

It’s a chicken-or-egg problem.

[46H]

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.

[tnff]

The seem to work pretty well in low to medium traffic situations. But jam up quickly when the traffic load gets high, like during rush hour. And especially when a lot of that traffic is making a direction change and not going through.

[MidValleyDad]

They also reduce the severity of crashes at intersections because there are no head on or right angle crashes. That is a reason Maryland is putting them at many suburban and rural intersections.

[RamenAddict]

I think it depends on the location. In the last place I lived (on a barrier island), we had a roundabout where the main roads met. It worked well as there was a grocery store there and it would have otherwise gotten really backed up at a light. I think it still backed up, but not as badly.

The town I was in before that had a variety of roundabouts. Some were just for traffic calming and were basically just a lone tree planted in the middle of an intersection that everyone had to go around. It was not needed and seemed dangerous to me. Who expects a tree in the middle of the road? The larger ones worked better.

When I lived in the UK they had roundabouts WITH streetlights, which I thought was totally idiotic.

[tnff]

Originally Posted by RamenAddict

I think it depends on the location. In the last place I lived (on a barrier island), we had a roundabout where the main roads met. It worked well as there was a grocery store there and it would have otherwise gotten really backed up at a light. I think it still backed up, but not as badly.

The town I was in before that had a variety of roundabouts. Some were just for traffic calming and were basically just a lone tree planted in the middle of an intersection that everyone had to go around. It was not needed and seemed dangerous to me. Who expects a tree in the middle of the road? The larger ones worked better.

When I lived in the UK they had roundabouts WITH streetlights, which I thought was totally idiotic.

I assume you mean stoplights. I can see the need for that. If the traffic gets dense enough, you still need some method to create a break in traffic from one point to allow traffic from another to enter or to move between lanes.

There's one were my son attends school that is just horrible during morning and afternoon rush. Total gridlock. So many cars that you can't move from lane to lane unless someone stops and lets you in.