Roundabout near signalized intersection

[kphoger]

Technically, I suppose, this is a traffic circle and not a proper roundabout.  But the first location I thought of was Belleville, IL.

https://maps.google.com/?ll=38.513377,-89.984019&spn=0.004761,0.004801&t=k&z=18

[silverback1065]

How about a signalized intersection 0 feet from a rotary? 

http://goo.gl/maps/clslM

This looks a lot like the former intersection between NJ-70 and NJ-73. It was basically a circle where cut 73 through the middle with traffic lights added at the circumference intersecting points. There's other examples of that in NJ (just can't think of them off the top of my head).

Edit: Here we go... NJ-38 @ Church Rd... drove through this one on the way to the mall a few months ago: http://goo.gl/Dc0fk1

thats actually a hamburger intersection not a roundabout

[jeffandnicole]

Hamburger intersection?  Hmmm...never heard that one before. 

[english si]

Either way, good thing it's where it is, then–you wouldn't have to! From the car hire at Heathrow to the Magic Roundabout via the M4 is around 67 miles, so I'd had plenty of time to re-adjust to the car being the other way round. (The Magic Roundabout was my first stop on that particular trip, followed by Stonehenge, en route from Heathrow to Bristol. I ultimately found Stonehenge underwhelming and the Magic Roundabout more interesting, although I'm glad I went to Stonehenge just to have seen it.)

You do know there are other magic roundabouts in England? Swindon is one of the furthest away from Heathrow (Cannock has a triangle one, but that's it). Hemel Hempstead's is much closer (about 20 miles), but like Swindon, is off the tourist's beaten path.

Wycombe's is about 13 miles from Heathrow and Denham's (which has signals where the M/A40 slip roads meet the roundabout) is about 5 miles away - however there's a closer one...

I don't think I'd have much trouble with it if it were right-hand-drive, but the fact that it's left-hand means I wouldn't want to encounter it straight out of the rental car lot after landing.

good job there aren't rental car places on this side of the A30.

Yes, that is a magic roundabout in Heathrow.

What I hate when you encounter these things is when you have to stop and give way as you go from one mini-roundabout to the other.

You don't have to stop - just yield at each junction if there's right turning traffic.

Even all my British friends say these things are a nuisance (whereas they don't much mind the Magic Roundabout either because there's space between them if you have to give way).

I guess I don't count - I quite like them. Though I understand the point - only about a car length between the two junctions, pedestrians crossing between the two - if there's reduced visibility or too much traffic, then they are awful.

I find the two paired mini roundabouts in my town work rather well.

[1995hoo]

What I hate when you encounter these things is when you have to stop and give way as you go from one mini-roundabout to the other.

You don't have to stop - just yield at each junction if there's right turning traffic.

That's what I said–I hate it when you have to stop and give way. I didn't say you always have to stop.

[tradephoric]

Here's a traffic signal 190 feet away from a major roundabout. 


https://www.google.com/maps/@42.5288999,-83.3596994,323m/data=!3m1!1e3

[lordsutch]

Looks like the south and west entrances to the roundabout are signalized too, presumably to stop traffic from entering if it backs up into the roundabout (in addition to providing a signalized pedestrian crossing).

[tradephoric]

Looks like the south and west entrances to the roundabout are signalized too, presumably to stop traffic from entering if it backs up into the roundabout (in addition to providing a signalized pedestrian crossing).

The signals at the south and west entrances are HAWK signals.  They are only on when a pedestrian activates the pushbutton.

It appears the roadway could have been redesigned to give an additional 50-75 feet of storage space.  Every bit of storage helps when a traffic signal is so close to the roundabout:

[TEG24601]

MDOT, always experimenting with M-10 and other people's money.

[coatimundi]

Is it just me, or are the more suburban and often wealthier municipalities more prone to the roundabout fad?

The new US 31 features this:


http://us31hamiltoncounty.in.gov/individual-interchanges/106th-street/
That's four within a half mile. East of it, 106th becomes a 2-lane road with no shoulders.

Or how about Main Street, two exits up?
https://www.google.com/maps/@39.9785858,-86.1552893,16z

Carmel, IN is posed to possibly be the nation's roundabout king/queen. I wonder how this will go over in 20 years.
http://www.indystar.com/story/news/local/hamilton-county/2016/05/30/carmel-releases-timeline-229m-roadwork/84968662/

[lordsutch]

Well, it's the suburbs and wealthier municipalities that are building new intersections, or upgrading old ones to handle more traffic, in general. If your traffic is declining, you're ripping out traffic signals to save on electricity and maintenance, not replacing them with new traffic controls at 500k a pop.

[silverback1065]

that and the fact that suburbs usually have more money to spend on infrastructure.  Having all of these roundabouts in Carmel makes traffic so much better, there are only a handful of signals left, and the ultimate goal is to have only 1 signal left in the entire city.  The only reason why the one signal won't be removed is because it is the first signal in the state of Indiana, and one of the first modern ones in the US. this is the location of the signal: https://www.google.com/maps/@39.9783909,-86.127055,3a,75y,15h,90t/data=!3m7!1e1!3m5!1sd7J_FDFsaI1Fw4JiQFn7-g!2e0!6s%2F%2Fgeo3.ggpht.com%2Fcbk%3Fpanoid%3Dd7J_FDFsaI1Fw4JiQFn7-g%26output%3Dthumbnail%26cb_client%3Dsearch.TACTILE.gps%26thumb%3D2%26w%3D392%26h%3D106%26yaw%3D15.4735%26pitch%3D0!7i13312!8i6656

[tradephoric]

Silverback, are there any roundabouts in Carmel that you believe shouldn't have been built?  One of the commenters in the article coatimundi cited stated that the roundabout at 96th and Ditch sees mile long backups during rush hour.  I happened to stumble upon a short video of the roundabout.  It appears one leg of the roundabout is dominate making it difficult for traffic in the other leg from entering.

https://www.youtube.com/watch?v=Ehyg4X40ehM

[silverback1065]

Silverback, are there any roundabouts in Carmel that you believe shouldn't have been built?  One of the commenters in the article coatimundi cited stated that the roundabout at 96th and Ditch sees mile long backups during rush hour.  I happened to stumble upon a short video of the roundabout.  It appears one leg of the roundabout is dominate making it difficult for traffic in the other leg from entering.

https://www.youtube.com/watch?v=Ehyg4X40ehM

Most certainly, the only reason why there are so many is because the mayor is obsessed with them, and that particular roundabout is TERRIBLE, it's no better than the 4 way stop it replaced.  It suffers from what I call "bullying" where one (or more) approach gets more cars through, causing the less busy legs to back up, or be bullied into congestion.  All 4 approaches should be 2 lanes. Honestly, there are a lot of roundabouts that either should never have been built, could have waited, or were built and are inadequate.  I think a lot of these intersections prove that roundabouts aren't the end all be all.  If you take a look at some of the future roundabouts to be built in the next 5 yrs, a lot of them make no sense, but some do.  There are a few roundabouts that are replacing shopping center signals, something I think is something that either can wait for a while or not be changed at all. 

[silverback1065]

a few quick examples of ones that shouldn't have been built, look at oak ridge road, the 2 located between 136th and 146th don't need to be there.  Look just to the east, there are way too many roundabouts at us 31 and 136th (these were built by the state when they redid 31).  I don't think there should have been an exit there either, but that's a different matter.  https://www.google.com/maps/@39.9906764,-86.1406584,15.94z
another one i can think of really quick is spring mill and dorset: https://www.google.com/maps/@39.9745058,-86.1617953,16.96z

Again I can think of many other infrastructure needs that could have been met before building any of these (the city has areas that suffer from terrible drainage problems).  US 31 was never supposed to have roundabout interchanges but the city won and they changed it to what it is now, I like the idea, I just don't like the clusterfuck at 136th, terribly confusing to new drivers driving in that area for the 1st time.

[jeffandnicole]

Looks like the south and west entrances to the roundabout are signalized too, presumably to stop traffic from entering if it backs up into the roundabout (in addition to providing a signalized pedestrian crossing).

The signals at the south and west entrances are HAWK signals.  They are only on when a pedestrian activates the pushbutton.

It appears the roadway could have been redesigned to give an additional 50-75 feet of storage space.  Every bit of storage helps when a traffic signal is so close to the roundabout:

Except you haven't demonstrated that the extra room is needed.  You're just redrawing roads for the sake of it, regardless if there's a reason for it.

[wanderer2575]

Looks like the south and west entrances to the roundabout are signalized too, presumably to stop traffic from entering if it backs up into the roundabout (in addition to providing a signalized pedestrian crossing).

The signals at the south and west entrances are HAWK signals.  They are only on when a pedestrian activates the pushbutton.

It appears the roadway could have been redesigned to give an additional 50-75 feet of storage space.  Every bit of storage helps when a traffic signal is so close to the roundabout:

Except you haven't demonstrated that the extra room is needed.  You're just redrawing roads for the sake of it, regardless if there's a reason for it.

The need is there.  I drive through this roundabout often and have seen northbound traffic back up into the roundabout, which also blocks westbound traffic.  When this was under construction, I thought for sure they were going to turn Northwestern Highway to be the eastern leg of the roundabout and eliminate the intersection with Orchard Lake Road altogether.  I can't believe MDOT and Oakland County built it as they did instead. 

[english si]

It appears the roadway could have been redesigned to give an additional 50-75 feet of storage space.  Every bit of storage helps when a traffic signal is so close to the roundabout:

It would surely be far cheaper to just redraw the path to cross right by the junction so that stop line can move forward a car length or two to be as close to the road as possible? Gives you about half of the stacking space benefit of realigning, but for a much smaller fraction of the cost.

When this was under construction, I thought for sure they were going to turn Northwestern Highway to be the eastern leg of the roundabout and eliminate the intersection with Orchard Lake Road altogether.  I can't believe MDOT and Oakland County built it as they did instead.

Yes, it is a silly design and should have been more radical in the building.

[tradephoric]

It would surely be far cheaper to just redraw the path to cross right by the junction so that stop line can move forward a car length or two to be as close to the road as possible? Gives you about half of the stacking space benefit of realigning, but for a much smaller fraction of the cost.

The funny thing is the redline design matches the geometry of Northwestern before the roundabout was constructed.  When they rebuilt this last year, they realigned Northwestern to the south (there may have been a logical reason for doing this; but the downside is it reduced the amount of storage space between the roundabout and traffic signal).

[silverback1065]

the diagonal should have been removed

[english si]

The funny thing is the redline design matches the geometry of Northwestern before the roundabout was constructed.

Ah, got you now.

When they rebuilt this last year, they realigned Northwestern to the south (there may have been a logical reason for doing this; but the downside is it reduced the amount of storage space between the roundabout and traffic signal).

Presumably to create more space out the driveways? They could have made the median smaller and the u-turns tighter, so the southbound could remain in situ.

[dvferyance]

I would have to say the roundabout on Moorland Rd in New Berlin at the I-43 ramps on the northside is pretty close to the signalized intersection at Beloit Rd. Can be a problem during peak times as SB traffic trying to enter the roundabout often backs up to Beloit Rd.

[roadfro]

The signals at the south and west entrances are HAWK signals.  They are only on when a pedestrian activates the pushbutton.

It appears the roadway could have been redesigned to give an additional 50-75 feet of storage space.  Every bit of storage helps when a traffic signal is so close to the roundabout:

Except you haven't demonstrated that the extra room is needed.  You're just redrawing roads for the sake of it, regardless if there's a reason for it.

The need is there.  I drive through this roundabout often and have seen northbound traffic back up into the roundabout, which also blocks westbound traffic.  When this was under construction, I thought for sure they were going to turn Northwestern Highway to be the eastern leg of the roundabout and eliminate the intersection with Orchard Lake Road altogether.  I can't believe MDOT and Oakland County built it as they did instead.

I would think the project was built this way to avoid funneling all the traffic going between Northwestern Hwy and Orchard Lake Road north through the roundabout. That would probably have increased strain on the roundabout.

What are the cycle lengths on those signalized intersections on the north and east legs? It would stand to reason that you could run phases that are pretty short (i.e. minimum pedestrian clearances, or shorter when no peds are present) to help prevent backups into the roundabout.

[tradephoric]

What are the cycle lengths on those signalized intersections on the north and east legs? It would stand to reason that you could run phases that are pretty short (i.e. minimum pedestrian clearances, or shorter when no peds are present) to help prevent backups into the roundabout.

The cycle lengths range from 60 to 80 seconds.  The signals could run shorter than 60 seconds but the north leg signal has some lengthy vehicle clearance times (leading to a lot of loss time at short cycles).  Ultimately, the signal is too close to the roundabout and traffic will periodically queue up through the roundabout.  It's most evident during the PM rush but it can occur during off-peak times as well. 

[JMAN_WiS&S]

This is how i would fix it