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Roundabouts

15 REPLIES 15
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Message 1 of 16
whalen.jon
874 Views, 15 Replies

Roundabouts

Hi there. I have a question, however, not related to Civil 3D. It's more a general question regarding roundabout design. When it comes time to create your entry curves, what steps do you guys generally follow? The US DOT (FHA) guide talks about the splitter island entry curve being tangential to the central island, and the outside entry curve being tangential to the ICD (as do many other guides I've looked at). Of any of you who have designed roundabouts before, do you aim to keep the two said entry curves concentric with each other? If so, how do you keep them tangential and concentric when your entry width (5.3m) is not the same width as your circulatory width (6.3m) on an ICD of 40m? This is a single-lane, four-legged roundabout. I've never designed one before, and I'm having a lot of fun with it. The approaches are 50km/h. Capacity isn't a big issue, as they're local roads (very low volume of traffic).

Thanks,

Jon
15 REPLIES 15
Message 2 of 16
castled071049
in reply to: whalen.jon

You can't have them concentric and tangential with different incidental curves. Forget concentricness. Make them tangential. The roundabout needs to have travel lanes wider than the approach lanes. Do this and it will work out fine.
Message 3 of 16
whalen.jon
in reply to: whalen.jon

Thanks. I figured that...
Suppose you have different radii for your inner and outer curves (tangential and not concentric) - do you aim for a nice even entry/exit width (of say 5.3m exactly)? Or do you take what you end up with so long as it accommodates your design vehicle, meets your capacity requirements and meets safety requirements? Or do you work with different radii's/flaring so you do indeed end up with your desired entry/exit width?
I must apologize if I'm asking 'rookie' questions, but I'm a very detailed oriented person 😉 .

Thanks again!
Message 4 of 16
Anonymous
in reply to: whalen.jon

Hi whalen,

The best approach to this issue is to use a program like Autotrack to
drive your design vehicle through the roundabout. You can then adopt
any combination of curves which meet the requirements of:

Being easy to draw
Being easy to set out
Having a smooth appearance from a driver's viewpoint
Meet any design parameter requirements of an approval Authority

This way the functional requirements of the design will be met, rather
than a compliance with a difficult to specify and interpret set of rules
about relative radii, widths at certain locations etc.

Regards


Laurie Comerford

whalen.jon@gmail.com wrote:
> Thanks. I figured that... Suppose you have different radii for your
> inner and outer curves (tangential and not concentric) - do you aim for
> a nice even entry/exit width (of say 5.3m exactly)? Or do you take what
> you end up with so long as it accommodates your design vehicle, meets
> your capacity requirements and meets safety requirements? Or do you work
> with different radii's/flaring so you do indeed end up with your desired
> entry/exit width? I must apologize if I'm asking 'rookie' questions, but
> I'm a very detailed oriented person 😉 . Thanks again!
Message 5 of 16
castled071049
in reply to: whalen.jon

Sorry to take so long to respond. Have been very busy lately. Basically, I don't get too fancy with it. I use whatever radii are necessary to make them tangential with the concentric circles of the roundabout (paying attention, of course, to recommended lane sizes and roundabout diameters from the guide books). Then I use AutoTurn to drive the biggest expected vehicles through the roundabout to make sure that it functions properly. If it works and looks pretty, then it's a go for me.
Message 6 of 16
MikeEvansUK
in reply to: whalen.jon

Interesting: Does the US design of roundabouts not use traffic flow analysis at the entries and exits of the roundabouts to obtain required geometry values.

The UK design relies on these widths to reduce or increase the flow of vehicles through a roundabout and thus safety.

Design elements such as tapers and widening at the entries and exits are fixed by calculations made in software which evaluates the traffic flows from each leg and then gives the required geometry constraints, entry/exit curve radius, flare lengths and tapering widths.

If not I want to design roundabouts in the US : )
Mike Evans

Civil3D 2022 English
Windows 7 Professional 64-bit
Intel(R) Core(TM) i7-3820 CPU @ 3.60GHz (8 CPUs), ~4.0GHz With 32768MB RAM, AMD FirePro V4900, Dedicated Memory: 984 MB, Shared Memory: 814 MB

Message 7 of 16
dlmanning
in reply to: whalen.jon

http://www.civil3d.com/2008/10/3d-models-replaced-by-cones/

I think this answers your questions about the states.
Message 8 of 16
whalen.jon
in reply to: whalen.jon

Thanks all for the replies.

Having read through volumes of guides, I am simply curious what steps others take from a detailed design point of view for clarification of finer details that the numerous guides don't specifically state.

At this particular intersection, the size of the roundabout will handle the current and projected traffic flows (residential area). I'm using suggested minimum radii's to start and an I-Bus as my design vehicle (14m from TAC - btw, I'm in Canada). As far as the values for the rest of the components, I'm following what the guides suggest, and in the end will obviously ensure a safe and operational roundabout.

My prelim design has since been peer reviewed by an experienced firm, and the changes they suggested are minor, so I know I'm on the right track.

MIKEEVANS, may I ask what software package you are referring to? Is it RODEL?

Thanks everyone,

Jon
Message 9 of 16
Anonymous
in reply to: whalen.jon

ARCADY is the standard roundabout capacity calculation software in the UK.

http://www.trlsoftware.co.uk/products/detail.asp?aid=1&c=1&pid=66

I believe TRL in the UK were the originators of the maths behind RODEL and
the two are still somewhat related, though if I understand it correctly
ARCADY has had the greater amount of ongoing development and is a full
Windows program, whereas I think RODEL is still DOS based? (might be wrong
there)

Regards

Ian

EMIA Product Manager
Autodesk AEC Division


wrote in message
news:6114093@discussion.autodesk.com...
Thanks all for the replies. Having read through volumes of guides, I am
simply curious what steps others take from a detailed design point of view
for clarification of finer details that the numerous guides don't
specifically state. At this particular intersection, the size of the
roundabout will handle the current and projected traffic flows (residential
area). I'm using suggested minimum radii's to start and an I-Bus as my
design vehicle (14m from TAC - btw, I'm in Canada). As far as the values for
the rest of the components, I'm following what the guides suggest, and in
the end will obviously ensure a safe and operational roundabout. My prelim
design has since been peer reviewed by an experienced firm, and the changes
they suggested are minor, so I know I'm on the right track. MIKEEVANS, may I
ask what software package you are referring to? Is it RODEL? Thanks
everyone, Jon
Message 10 of 16
MikeEvansUK
in reply to: whalen.jon

Yep, Arcady is the one I was referring to although I believe we have used Rodel recently. It does fully work from through the command line in WinXP. Thanks Ian, I couldn't remember the name.

I don't actually use it now but have done before, we normally sub to someone else to give us the details.

PS: Does anyone know how I can change my name to lower case or Sentence case. It seems to have got stuck on upper case since I logged on a while ago with caps lock on. : )
Mike Evans

Civil3D 2022 English
Windows 7 Professional 64-bit
Intel(R) Core(TM) i7-3820 CPU @ 3.60GHz (8 CPUs), ~4.0GHz With 32768MB RAM, AMD FirePro V4900, Dedicated Memory: 984 MB, Shared Memory: 814 MB

Message 11 of 16
bester_paul
in reply to: whalen.jon

Jon,

I am in Canada too and we are increasingly required to evaluate the feasibility of roundabouts at intersections. By the way I received a newsletter from Transoftsolutions (the developers of Autoturn vehicle simulation software) saying that they are launching a new CAD software for roundabout design. Please see more information at http://www.transoftsolutions.com/PressRelease.aspx#detail if you are interested.

bester
Message 12 of 16
mike.barkasi
in reply to: whalen.jon

Attached is a document concerning roundabout design. Thes tools are part of all Bentleys Civil Applications. The article appeared in CAD user publication.

http://ftp2.bentley.com/dist/collateral/docs/press/in-a-roundabout-way_cad-user.pdf


Regards,

Michael Barkasi
Bentley Civil
Professional Services
Message 13 of 16
bester_paul
in reply to: whalen.jon

Hello Mike,

How does your tool cut iteration time? Do I still have to run autoturn on the curb geometry? This is the part i do not enjoy the most...adjusting geometry..run truck..adjust a little more..run truck, now it does work...go back to square one. Am I doing something wrong? Do you have some tutorials?
Message 14 of 16
mike.barkasi
in reply to: whalen.jon

Attached is a link to a video showing the tool operation. You will find the components of the RAB tie together, so modificatioon to one part will effect the entire design.

Also RAB libraries are provided and can be developed similar to Dgnlibs, to store specific RAB criteria.

The video is run on MX but the same tool works in Inroads, GEOPAK, and PowerCivil.

ftp://ftp.geopak.com/pub/outgoing/FULL_roundabout_180108.avi

PS The video will only be available for a few days.

Mike
Message 15 of 16
bester_paul
in reply to: whalen.jon

Thank you Mike for the video...the product looks quite good. I was wondering whether it runs in the AutoCAD environment as well?
Message 16 of 16
mike.barkasi
in reply to: whalen.jon

Inroads will run in the AutoCAD environment, however the RAB tool will not. You can however work in Dwg in Microstation and if Im not mistaken 3D Map can import the Microstation Dgn graphics also. So any resulting graphics can be moved to AutoCAD if necessary.

Mike

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