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Roundabout? layout?


redlines show were old bridge was. the area under it was a ditch reserved for the new East/west road. They decided to add roundabouts instead of stop signs when they added the e/w road and exits but did not want to close bridge to do it. So they built new bridge next to it. I think the offset design really has no affect on the speeds going thru the roundabout compared to the old straight bridge since you have to slow for the roundabout. Even with a kink. Sound right?

Roundabouts (aka traffic circles) work fine for low traffic areas. For high volume traffic they are a nightmare. Rt 2 traffic circle in Concord MA is a prime example of roundabouts that I avoid like the plague.

So, the vertical (on the photo) road (north/south?) had a bridge that passed over the horizontal (on the photo) roads (east/west?). Was that bridge not accessible from the "horizontal roads? And now the new road with the roundabouts allows access to the “vertical” bridge road? Do I have it right?

Please clarify and please clarify what you’re asking. I’m trying to understand. It sounds interesting.
Thanks,
CSA
:palm_tree: :sunglasses: :palm_tree:

The East/west road was only built in the last few years. It was a ditch reserved area for the last 20yrs. So the old bridge went over the “ditch” for 20yrs. They put in the e/w road and the exits in 1 job.

Was Rube Goldberg involved with the design?

Seems to me that the old “fly-over” bridge didn’t allow for entrance or exit to/from the east/west road and so the solution was the bridge with the rotaries (roundabouts). They not only allowed ingress and egress, but motorists could choose multiple directions of travel as well, without stopping.

The trade-off for the added features was the roundabouts. However, they create some “traffic calming” (slowing down traffic) which is probably a good idea considering all the choices people will be making.

Do I have it right? I have very limited roundabout experience and it is in low traffic flow environments.

One would have to be there and road test it to get a good feel for if it works or was a good idea or bad decision, I guess.
CSA
:palm_tree: :sunglasses: :palm_tree:

There is room for stop signs on the south/north sides of bridge for the exit ramps. They said, this is a good spot for roundabouts. The north/south road gets lots of traffic and it is 50mph about a 1/2 mile north. So, they put in a roundabout about 1/2 mile north to slow people down. The whole area is a proving ground for them. I used to take this road daily 10 yrs ago. Rarely now.

We have a few roads near me like that. The bridge over the highway has traffic circles at either end where the road over the highway and the highway entrances and exits all must use the circle. The drivers have to respect other traffic or there will be an accident. The only time I find it unsafe is when I go 3/4 of the way around the circle to enter the highway. Traffic coming from the other direction and I have a very short merge to decide who is going to go first. I may get there first, but if the guy coming the other way also wants to use the exit, he may cut me off. I can’t use my turn signal because the approach is too short. I haven’t had a near accident yet, but it’s still a dangerous intersection, IMO. There are no yield or merge signs, BTW.

There is a reason they are called death circles.

This roundabout

is the only one that I have traveled repeatedly over several days and it is never in grid-lock and more often than not moving relatively trouble free. Right turns were eliminated from the circle which helps and most of the traffic is local so that is a big +.

I like the barrier separating the straight through lanes from the exiting lanes, I think it adds safety to the design. I generally like roundabouts, as long as signage makes right of way clear.

Before NY State vehicle and traffic laws were overhauled around 1980, there was a big conflict between state and local law in Buffalo about traffic circles.

State Law said traffic coming from your right had the right of way, so traffic on the circle had to yield to traffic entering the circle.

Buffalo City law said traffic entering the circle had to yield to traffic on the circle. This law far predated yield signs so there was no guidance to help you.

I grew up before the Octagon stop sign was standard. All the stop sighs in our small NY City looked like small Washington monuments,painted canary yellow with incised vertical letters painted white that said STOP. Also there was no uniformity across the state about what color light should be at the top of a traffic light.

Yow! That roundabout is HUGE! :astonished:
Lots of real estate (and money) involved there.
CSA
:palm_tree: :sunglasses: :palm_tree:

This also slows traffic, looks confusing but works quite well. This interchange is three miles from a death circle.
All in all prefer a total cloverleaf, but they require more land and more money to build.

The Rt 2 Rotary in MA is a royal pain. There is a plan in place to build an overpass. Not sure when/if t hat will start. In my town we have had a plan in place to widen the main road through town. It’s been on the books since 1970.

This is a typical commute through that rotary.

610
610 is the E/W road. hwy 81 is old. been there for 50yrs. 610 is a bypass and they blend together so 610 is inside the east and west lanes of old 81. only took 20yrs to build

One of the main benefits of a DDI is removing conflict points - yes, traffic slows in some cases, but if you study that diagram, you’ll see that it eliminates all instances of traffic needing to turn across opposing traffic…research shows that this is where many of the most severte/fatal crashes tend to happen.

Another one you’ll see increasingly used in coming years is a single-point urban interchange (SPUI). Like the DDI, there are significant safety benefits, in addition to not consuming nearly as much land adjacent to the highway.

Edit: also, not sure what you mean by “death circle”…roundabouts a far and away safer than traditional signalized and two-way stop controlled intersections…in many cases, they can also be safer than four-way stop controlled intersections, because drivers are physically forced to slow down instead of just having to obey a sign. In a very few cases, more crashes may result, but these tend to be low-speed, property damage only crashes, not fatal or serious injury ones. My job (as a transportation engineer and professor) is to help reduce blood on the pavement, not plastic.

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True, not death circles, but it sounds better.
I hope you are not responsible for flashing yellow light ( proceed with caution) also means stop for pedestrians, rather than installing solid red lights. Or designated lanes for U-turns On 6 lane roads.

I’m not sure what specific setup you’re describing, but you should always yield to a pedestrian in your path on the street. It doesn’t matter if you’re right or they’re right…you being “right” in this case means a person’s brains splattered on your windshield…

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A1A in Florida, flaming yellow light for mid block pedestrian crossings, 40MPH zone.

According to Wikipedia, A1A is 329 miles long…if you can point to a specific crossing, I’d be happy to give my thoughts. I will say, however, that a 40mph zone probably has many cars going 45mph+. And considering a pedestrian hit at 30mph has a 90% chance of death, this is almost certainly a situation that warrants a traffic control device, rather than simple signage.