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About roundabouts

K-Projekt AS
About roundabouts was posted on February 13th, 2014 at 5:44 AM EST

Hi, I have a 2 lane single-point roundabout with diamater of 120m. Since diameter of the roundabout is larger than most of the "conventional" roundabouts, the auditor claims that according to HCM 2000 one could calculate the diverging and merging on the roundabout itself as freeway weaving segments.

Thus, the question is could one assume the roundabout to be equvilant to a straight line between the ramps and calculate the results?

(Edited February 13th, 2014 at 3:14 AM EST)
Erik Ruehr
VRPA Technologies
RE: About roundabouts was posted on February 24th, 2014 at 8:22 PM EST

I would say that neither the 2000 or the 2010 versions of the HCM would support using freeway weaving analysis as a way of analyzing roundabouts. The two types of facilities are too different in their characteristics. If you have enough knowledge of the capacity procedures for both types of facilities, you could use freeway weaving analysis as a "point of reference", but you would have to be very careful in drawing conclusions based on that type of analysis.

Gustavo Riente de Andrade
TECTRAN - T├ęcnicos em Transportes ltda
RE: About roundabouts was posted on February 26th, 2014 at 11:42 PM EST

Although roundabouts do not function exactly as freeway weaving and ramp, those methods have been used as a proxy for large roundabouts that function as intersections, when a HCM analysis is desired or required. In that case, you should try to adjust carefully the free flow speed of each element according to the roundabout geometry.

K-Projekt AS
RE: About roundabouts was posted on March 21st, 2014 at 4:58 AM EDT

Thanks for the replies

(Edited March 21st, 2014 at 4:59 AM EDT)

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