Does anyone have a table that can be used to determine the amount of vehicles by approach that a roundabout can handle?  Preferably the table would break it down by the LOS that can be expected with certain volumes.

THANKS!

Jennifer Butcher, PE, PTOE

Savant Group Inc.

1700 Pacific, Suite 1240

Dallas, TX 75201

(214) 468-8200

Fax: (214) 468-8266

Jennifer@savantgroupinc.com

Jennifer,

Attached are a few images that we use in NY.  We looks at each leg to the roundabout separately since each leg really has it's own limitation.

 I am assuming that you are looking for a "ballpark" idea regarding LOS based on volumes - since it is nice to say "It will likely be LOS _"

based on a few minutes of adding up turn counts.  One of the programs should be run to verify the guestimate.  Here are LOS grades I would assume just based on adding up turn counts per leg and per lane

crossing: - Please note that we drop these numbers by 100 when 1 lane has to cross 2 lanes since some efficiency is lost when needing both circulating lanes to be clear at the same time...

0 - 750 A

750 - 850 A/B

850 - 950 B/C

950 - 1050 C/D

1050 - 1150 D/E

1150 - 1400 E/F

I look forward to hear what others think of this idea - and to hear if these numbers seem to be matching what others are seeing at their roundabouts.

Please feel free to contact me if you want any others opinions regarding roundabouts - they are one of my favorite topics.

Howard

Howard McCulloch

 Roundabout Design Unit

NYSDOT Design Services Bureau

50 Wolf Rd.  POD 24

Albany, NY 12232

518-485-7503 voice

518-457-2916 fax