Oval Shape Roundabout

[SHOOTZ]

Am Designing a roundabour for a dual carriageway road, due to space limitation am thinking of designing an oval shaped roundabout can some one give me a guide,literature or any usefull information that will help me in designing this round about. the biggest size of truck in this road is wb50 truck

 

[Debaser]

I'm sure there's plenty of US guidance about, but you can always fall back on TD16/07 of the UK Design Manual for Roads and Bridges...The original, and still the best (possibly).

http://www.dft.gov.uk/ha/standards/dmrb/vol6/section2/td1607.pdf

 

[Compositepro]

I've never seen an oval roundabout and it seems a terrible idea. Changing curvature of the road will require much greater attention and care by the driver when his attention is on merging traffic. Just use the largest circle that will fit. Lessening the curvature of the roundabout in spots where it is possible, is a detriment to smooth traffic flow, not an improvement.

 

[GoldDredger]

I think roundabouts are a fabulous idea. I've seen them in action in a few places and find them more efficient than a four way stop. Much more traffic seems to be able to navigate them as well, as opposed to a long line of stopped cars.

 

[miningman]

Oval roundabout, bad idea. Well designed conventional roundabouts are the best idea since sliced bread!!! However I have yet to see an efficient one in North America. If you are unbiased and want to see how effective these can be, spend a few weeks in England... but be prepared to leave you North American pre conceptions behind!! And of course be aware that it might be the experience of driving on the "wrong" side of the road that might be giving you a negative impression. Pull over, park up and watch the locals go thru intersections at 50 mph +, that would otherwise need four way stops.

 

[TD2K]

I'm seeing more and more of them installed in WA state and BC.

I like them, I find they are far more efficient than 4 way stops. We had a 4 way stop near a college that was always a backup point with the 4 way stop signs that used to be there. Since they have put in a roundabout, most of the time you just drive through. Every so often, a few cars might back up waiting for a chance to enter but no where near the backup that used to regularly exist.

Some people do find them challenging though and from the letters in the paper every so often, some hate them.

 

[fel3]

Does the OP mean oval or elliptical? These are different shapes.

I'm more of a water systems guy, so I don't have a lot of road design experience and none when it comes to roundabouts. However, I think elliptical would be a bad idea because drivers seem to handle circular horizontal curves better than varying curves. That's probably why spiral curves for highway ramps have fallen out of favor here. I suspect an oval would be less of a problem for car control. I doubt either shape makes sense for traffic control.

BTW, there are a handful of residential neighborhoods in my city that have oval roundabouts. Basically they are long, fairly wide, landscaped medians that allow the main local street to pass through the neighborhood (one way each side), but block the several side streets from crossing the main street. In another case, the oval was so wideand long that it actually functioned as a park. The local residents petitioned the city to change the one-way traffic lanes on the main road to two-way traffic and eliminate curb parking to gain the necessary width.

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"Is it the only lesson of history that mankind is unteachable?"
--Winston S. Churchill

 

[civilman72]

Oval roundabouts are certainly a possibility. I used to drive through one in Avon, CO all the time.

Look up Avon, CO on Google Earth - there are five back-to-back roundabouts, including a teardrop and oval shape.