Dear WisDOT, roundabouts have their benefits, but...

[tvketchum]

Even with "properly timed" signals, the roundabouts will flow far quicker and easier for all directions of travel...

[Jordanah1]

*ALSO A LOCAL*

once people get used to the roundabouts, they are great...there is certainly a learning curve (pun intended) with them, but they cut travel time significantly, improve safety, and move traffic more efficiently in almost all ways.(there are some problems with people turning right , and having to switch lanes to make a quick left turn after the roundabout, like entering pick 'n save in oshkosh turning right from jackson to murdock)other than that, roundabouts, including the consecutive ones have really had a positive impact onh the city, and i hope that the city decides to replace many more signalized intersections with them as part of general road reconstruction.

[hobsini2]

*ALSO A LOCAL*

once people get used to the roundabouts, they are great...there is certainly a learning curve (pun intended) with them, but they cut travel time significantly, improve safety, and move traffic more efficiently in almost all ways.(there are some problems with people turning right , and having to switch lanes to make a quick left turn after the roundabout, like entering pick 'n save in oshkosh turning right from jackson to murdock)other than that, roundabouts, including the consecutive ones have really had a positive impact onh the city, and i hope that the city decides to replace many more signalized intersections with them as part of general road reconstruction.

Replacing signals for roundabouts really only makes sense if it is a major intersection. For instance, I would not put one at Oshkosh Ave and Westfield St (nearest signal to my grandmother's) but putting one at Sawyer and Witzel would make sense.  BTW, my grandmother, who is originally from Vienna Austria and lived in England and France, absolutely despises the roundabouts in Oshkosh.

[Alps]

Roundabouts don't belong on major routes. (US 9 at NY 43 jumps immediately to mind, but also the NY 85 Slingerlands bypass.) Once you're about 45 mph I would rather see a signalized intersection - you start to run into problems caused by failing to slow in time, unexpected nature of encountering a roundabout in an otherwise open road.

[PurdueBill]

Roundabouts don't belong on major routes. (US 9 at NY 43 jumps immediately to mind, but also the NY 85 Slingerlands bypass.) Once you're about 45 mph I would rather see a signalized intersection - you start to run into problems caused by failing to slow in time, unexpected nature of encountering a roundabout in an otherwise open road.

That's what makes me say Hmm about the new IN 25 tying into the old road at a roundabout just short of the I-65 interchange.  I could swear that's what I read they were doing....is that right?  Why would a 60 mph four-lane divided highway end at a roundabout when just past that is a pair of signals at a diamond interchange with an Interstate, which I recall was staying as is?

[tdindy88]

That's what makes me say Hmm about the new IN 25 tying into the old road at a roundabout just short of the I-65 interchange.  I could swear that's what I read they were doing....is that right?  Why would a 60 mph four-lane divided highway end at a roundabout when just past that is a pair of signals at a diamond interchange with an Interstate, which I recall was staying as is?

That's still the plan. I've been scratching my head at that move too. I suppose with traffic heading toward Lafayette through the roundabout, they just want to make sure that they are going slow approaching the diamond interchange. They just want to slow the traffic down with style I suppose.

[mukade]

Construction has finally started on the SR 25/SR 225 (?) roundabout. Hopefully by this fall we'll see how it works.

[mgk920]

Construction is now under way on the two additional planned parking lot entrance roundabouts on Green Bay Rd, located on either side of the fairly new one on Green Bay Rd at Winneconne Ave (WI 114), just east of US 41.

Mike

[kphoger]

Roundabouts don't belong on major routes. (US 9 at NY 43 jumps immediately to mind, but also the NY 85 Slingerlands bypass.) Once you're about 45 mph I would rather see a signalized intersection - you start to run into problems caused by failing to slow in time, unexpected nature of encountering a roundabout in an otherwise open road.

I'd much rather know ahead of time that I need to slow down to 20 mph every time I make a drive, even in a rural area, than either of these situations:

(a) Find myself looking at a green light for a mile while doing 60 mph, then have to slam on my brakes because one car on the crossroad made my light turn red right at the last minute (a few examples in rural Minnesota come to mind);

(b) Have a turning car from a side road dart out in front of me such that I nearly rear-end him (Fredonia, KS, is a perfect example of this one, and the junction now has a roundabout).

[PurdueBill]

Construction has finally started on the SR 25/SR 225 (?) roundabout. Hopefully by this fall we'll see how it works.

Interesting--I hadn't noticed that before.  Old 25 from the new roundabout to existing 225 is going to become part of 225?

(a) Find myself looking at a green light for a mile while doing 60 mph, then have to slam on my brakes because one car on the crossroad made my light turn red right at the last minute (a few examples in rural Minnesota come to mind);

Indiana has plenty of those--the "end" of I-469 at the GM plant (where an END 469 assembly is posted, despite it officially ending at the centerline of I-69) where traffic coming from 469 sees a green light, is rolling along coming down from 70 mph on 469 to theoretically the 50 mph limit on Lafayette Center Road, and if one vehicle pulls up to their red light from the plant or the road across from it, boom!  Light changes instantly.  All it does is make you step on it on 469 to make sure you don't get hit by that.  Yikes, INDOT better not see this and get an idea for a roundabout at the end of 469!

[Alps]

(a) Find myself looking at a green light for a mile while doing 60 mph, then have to slam on my brakes because one car on the crossroad made my light turn red right at the last minute (a few examples in rural Minnesota come to mind);

That's why you have 1 second of yellow per 10 mph of side road speed, and why you use 85th percentile instead of speed limit for that calculation. There's no slamming of brakes - either you slow down acceptably or have enough time to run through on yellow.

(b) Have a turning car from a side road dart out in front of me such that I nearly rear-end him (Fredonia, KS, is a perfect example of this one, and the junction now has a roundabout).

That would happen at every single intersection regardless of signalization. Do you want every intersection to be a roundabout?

[kphoger]

That would happen at every single intersection regardless of signalization. Do you want every intersection to be a roundabout?

No, at most intersections, traffic is light enough that it's not a major issue.  US-400 outside of Fredonia is an example where side traffic was constant enough that collisions were becoming a problem.  KsDOT chose to go with a roundabout rather than a stoplight, even in this rural setting.  I find it less annoying to slow down to 15 or 20 mph every time than to wonder who's going to cut out in front of me (as I used to every time I'd drive through there) or whether the light's going to be green or red (as I would every time if they had gone with a light).

[Alps]

Well I don't care about US 400 (or 412, 425, 437) so fine.

[agentsteel53]

That's why you have 1 second of yellow per 10 mph of side road speed, and why you use 85th percentile instead of speed limit for that calculation. There's no slamming of brakes - either you slow down acceptably or have enough time to run through on yellow.

except you don't know if a yellow light is a correctly engineered 7-seconds-at-70mph or a badly fucked up (hello Texas state route 71!) 3-seconds-at-80-mph.

because the MUTCD refuses to permit countdown timers, but apparently allows TXDOT to do as they wish.

[agentsteel53]

Well I don't care about US 400 (or 412, 425, 437) so fine.

what is the proposed routing of US 437 anyway? 

[kphoger]

Well I don't care about US 400 (or 412, 425, 437) so fine.

Yes, thank you for that.  So, what I hear you saying is:
A roundabout may be a great feature on a 4xx US Highway that I don't drive on, but it will perform poorly on any other highway, especially one I drive on.

...because, apparently, a green light changing to red is less unexpected than a permanent, lit, landscaped, roundabout with warning signs.
(If said roundabout is not lit, landscaped, and posted with warning signs, then we have other problems to address.)

[hbelkins]

Kentucky has successfully implemented "Prepare to Stop when Flashing" assemblies with yellow beacons in a lot of places in advance of traffic signals on rural routes. The beacons flash when the signal is in a yellow or red phase. Ofttimes they activate while the light is still green, but a vehicle on the intersecting road has triggered the change. Very handy and they certainly tell you when you need to start slowing down, eliminating the need for slamming on the brakes.

[kphoger]

Kentucky has successfully implemented "Prepare to Stop when Flashing" assemblies with yellow beacons in a lot of places in advance of traffic signals on rural routes. The beacons flash when the signal is in a yellow or red phase. Ofttimes they activate while the light is still green, but a vehicle on the intersecting road has triggered the change. Very handy and they certainly tell you when you need to start slowing down, eliminating the need for slamming on the brakes.

I love those.  Around here (and there aren't many anyway) they prefer the ones that just flash all the time.  Fat lot of good that does me.  A flashing yellow light on the side of the road isn't going to catch my eye any more than an actual stoplight above my lane.....

But that's all about rural situations.  Let's get the thread back to urban roundabouts in series.

[Scott5114]

Well I don't care about US 400 (or 412, 425, 437) so fine.

Yes, thank you for that.  So, what I hear you saying is:
A roundabout may be a great feature on a 4xx US Highway that I don't drive on, but it will perform poorly on any other highway, especially one I drive on.

I think Steve was making a tongue-in-cheek crack at US 400's nonstandard designation, which 412 and 425 share.

[1995hoo]

Roundabouts don't belong on major routes. (US 9 at NY 43 jumps immediately to mind, but also the NY 85 Slingerlands bypass.) Once you're about 45 mph I would rather see a signalized intersection - you start to run into problems caused by failing to slow in time, unexpected nature of encountering a roundabout in an otherwise open road.

I don't see the problem. I've encountered roundabouts in the UK on dual-carriageways with 70-mph speed limits and there was never any problem. Here's one I encountered in Scotland on the way to St Andrews. Here's the approach to another going the other way (I used a different road going back to Edinburgh). They have these big signs in advance that warn you of the roundabout and tell you which exit to use for which destination. Seems simple enough to me. True, in the USA you'd have the situation of people not necessarily being used to encountering a roundabout on a rural road of that sort, but that's what the signage is for. If the "people aren't used to it" argument were so convincing, we wouldn't have diverging diamonds or SPUIs or HOV lanes or electronic toll lanes or any number of other things that have come to be considered routine.

I think in my mind the real question on a roundabout versus a traffic light is two-fold: (a) Are the traffic volumes balanced enough to allow people on both roads reasonable access to the roundabout without long tailbacks? (If "No," then a roundabout is inappropriate.) (b) Is there a particular feature of that intersection that would create a compelling reason to require drivers to stop every time? (If "Yes," then a roundabout is inappropriate. An example might be if there were obstructed visibility to one side even if you did some reconfiguring.) What frustrates me about stop signs and red lights and the like is that so often you have to sit there waiting even though you can see that the other road is clear and that it would have been perfectly safe to go. I don't see why the authorities in this country are so fascinated with the idea that "you might have to stop sometime, so we'll make you stop every time."

[agentsteel53]

70mph roads don't need roundabouts or traffic signals - they need grade separations!

[1995hoo]

70mph roads don't need roundabouts or traffic signals - they need grade separations!

I'd think that would be a question of traffic volume and whether it's high enough to justify the added expense of a grade separation.

[kphoger]

70mph roads don't need roundabouts or traffic signals - they need grade separations!

Now, I know you wouldn't want those rural Texas FM routes to lower their speed limits, so are you really advocating grade separation at those intersections?  

Wait!  We never got back on track!

Urban roundabouts in series.  Urban stoplights timed in series.  Does anyone have any arguments against the situation that started this whole thread that don't sound something like, 'I don't like roundabouts, therefore it's a bad design' or 'I don't like having to steer very much, therefore it's a bad design' or 'Drunk drivers might hit the center island, therefore it's a bad design'?  Because, you know, I don't like sitting in a line of traffic at a red light, and I don't like accelerating only to have to stop again, and drunk drivers might hit cross traffic, so I might as well call a series of stoplights a bad design based on that.

[agentsteel53]

Now, I know you wouldn't want those rural Texas FM routes to lower their speed limits, so are you really advocating grade separation at those intersections?  

leave it to Texas to get that done.

a roundabout, or even just a pair of yield signs for one direction or the other, sure beats a traffic light.  especially, as I mentioned, the way Texas does their traffic lights: 3 second yellow regardless of approach speed.

[J N Winkler]

The choice between roundabouts and traffic signals can be settled by cost-benefit analysis (whether it is in fact so settled in any given case is another matter entirely).  Cost-benefit analysis is comparison of time streams of consumption gained with time streams of consumption foregone, ignoring transfer payments within society (such as fines and taxes).

For isolated rural intersections of state highways which do not otherwise carry enough traffic to warrant widening and are not close enough to a populated area to justify conversion to an urban section, there is no opportunity to offset the delays associated with signalization by imposing progression on a set of signals in sequence.  In rural locations traffic volumes tend to be steady through the day, with little periodicity of the kind that would allow signals to be operated part-time only.  So in this case the choice of a roundabout versus a signal involves a tradeoff in delay, the details of which vary according to the traffic volumes on the intersecting roads since it is rarely the case that a two-lane rural state highway carries enough traffic for the propensity of a roundabout to "lock up" to be a relevant consideration (normally around 20,000 VPD, IIRC).  Roundabouts tend to impose delay in small lumps on the entire population of vehicles progressing through the intersection while traffic signals impose delay in large lumps on a smaller share of this population.

Experience in Kansas has generally been that a roundabout at a high-speed rural intersection is a safety improvement, defined in economic terms as an improvement whose capital cost is justified principally (if not almost entirely) by the expected reduction in accidents, in contradistinction to other forms of highway investment where the justification comes principally from reductions in delay.

One of the earliest examples of rural roundabout projects of this type in Kansas was the intersection of US 50 and US 77 near Florence, done about ten years ago.  US 77 was formerly subject to stop control at US 50, and neither road carried enough traffic to warrant signals; queues at the US 77 stop signs were short if they existed at all.  However, this intersection had a bad reputation for side-impact collisions (many fatal) which prompted KDOT to install flashing red lights and "US-50 DOES NOT STOP" supplementary plates under the US 77 stop signs.

In this case doing nothing would have had the lowest cost (essentially zero), but also the highest cost in terms of accidents and their collateral consequences.  A traffic signal would have had approximately the same capital cost as a roundabout (say about $500,000), but significantly higher recurrent expenses (say about $10,000 for electricity), and would not have removed the mechanism underlying the fatal side-impact collisions (i.e., failure to obey traffic control devices at a right-angle crossroads).  The outcome in terms of delay might very well have been worse than with a roundabout even after full optimization and sophisticated actuation (such as additional loops designed specifically to register large trucks and allow them to be given added priority).

The roundabout imposes about 20 seconds of delay for traffic using US 50 that was not there before with the stop-sign installation, but for about 5000 VPD the added delay cost per year is about $100,000 (assuming $10/hour cost of time lost in delays).  This is quite a lot less than the $3 million estimated economic value of each life lost (calculated using hedonic pricing methods), of the same order of magnitude as the $500,000 capital cost of the roundabout conversion, and much cheaper than $1 million to $2 million for an isolated grade separation and about $10 million to $15 million per mile for the Cadillac solution of full freeway conversion.